Estimates of Ground-Water Recharge from

Precipitation to Glacial-Deposit and Bedrock

Aquifers on Lopez, San Juan, Orcas, and

Shaw Islands, San Juan County, Washington

Prepared in cooperation with the

SAN JUAN COUNTY HEALTH AND COMMUNITY SERVICES

U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4114
U.S. GEOLOGICAL SURVEY

Water-Resources Investigations Report 02-4114

Estimates of Ground-Water Recharge from 

Precipitation to Glacial-Deposit and Bedrock 

Aquifers on Lopez, San Juan, Orcas, and 

Shaw Islands, San Juan County, Washington

Prepared in cooperation with the

SAN JUAN COUNTY HEALTH AND 

COMMUNITY SERVICES

By Laura A. Orr, Henry H. Bauer, and J.A. Wayenberg

Tacoma, Washington

2002
U.S. DEPARTMENT OF THE INTERIOR

GALE A. NORTON, Secretary

U.S. GEOLOGICAL SURVEY

Charles G. Groat, Director

For additional information write to:

District Chief

U.S. Geological Survey

1201 Pacific Avenue – Suite 600

Tacoma, Washington 98402

http://wa.water.usgs.gov

Copies of this report can be purchased

from:

U.S. Geological Survey

Information Services

Building 810

Box 25286, Federal Center

Denver, CO 80225-0286

Any use of trade, product, or firm names in this publication is for descriptive purposes only and does not imply 

endorsement by the U.S. Government.

District Chief

U.S. Geological Survey

1201 Pacific Avenue – Suite 600

Tacoma, Washington 98402

http://wa.water.usgs.gov
Contents iii

CONTENTS

Abstract ................................................................................................................................................................ 1

 Introduction ......................................................................................................................................................... 2

Purpose and Scope ...................................................................................................................................... 2

Previous Studies.......................................................................................................................................... 4

Well-Numbering System............................................................................................................................. 4

Acknowledgments....................................................................................................................................... 5

Description of Study Area.................................................................................................................................... 5

Climate and Precipitation............................................................................................................................ 5

Hydrogeology.............................................................................................................................................. 5

Recharge and Evapotranspiration ............................................................................................................... 9

Estimates of Ground-Water Recharge.................................................................................................................. 10

Near-Surface Water-Balance Method......................................................................................................... 10

Data Requirements............................................................................................................................. 11

Data Collection and Processing ......................................................................................................... 13

Precipitation .............................................................................................................................. 13

Precipitation Throughfall.......................................................................................................... 17

Solar Shortwave Radiation and Meteorological Measurements............................................... 18

Soil and Subsoil Properties ....................................................................................................... 18

Land Cover and Vegetation ...................................................................................................... 22

Land-Surface Altitude............................................................................................................... 22

Streamflow................................................................................................................................ 24

Model Calibration .............................................................................................................................. 27

Estimating Island-Wide Recharge for Lopez, San Juan, Orcas, and Shaw Islands 

Using Deep Percolation Model and Results from Study Basins........................................... 30

Sources of Uncertainty in the DPM Recharge Estimates .................................................................. 40

Chloride Mass-Balance Method.................................................................................................................. 41

 Data Collection ................................................................................................................................. 42

Recharge Estimates and Sources of Uncertainty Using Chloride Mass-Balance Method................. 42

Summary .............................................................................................................................................................. 49

References Cited .................................................................................................................................................. 51
iv Contents

FIGURES

Figure 1. Map showing location of Lopez, San Juan, Orcas, and Shaw Islands and the 

six study basins in San Juan County, Washington............................................................................. 3

Figure 2. Diagram showing well-number system used in Washington............................................................. 4

Figure 3. Map showing topography of Lopez, San Juan, Orcas, and Shaw Islands, 

San Juan County, Washington ........................................................................................................... 6

Figure 4. Map showing mean annual precipitation for Lopez, San Juan, Orcas, and 

Shaw Islands, San Juan County, Washington, 1961-90 .................................................................... 7

Figure 5. Map showing generalized surficial geology and data-collection sites for Lopez, 

San Juan, Orcas, and Shaw Islands, San Juan County, Washington ................................................. 8

Figure 6. Graphs showing cumulative precipitation and throughfall for three sites on 

Lopez, Orcas, and Shaw Islands, San Juan County, Washington...................................................... 19

Figure 7. Map showing distribution of soil groupings derived from Soil Conservation 

Service data for the Deep Percolation Model, on Lopez, San Juan, Orcas, and 

Shaw Islands, San Juan County, Washington.................................................................................... 20

Figure 8. Map showing areal distribution of land cover reclassified for the Deep Percolation 

Model for Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington .................... 23

Figure 9. Graphs showing streamflow for the six study basins on Lopez, San Juan, 

Orcas, and Shaw Islands, San Juan County, Washington, water years 1997-98 ............................... 25

Figure 10. Graphs showing monthly water-budget components for the six study basins on 

Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington, 

water years 1997-98........................................................................................................................... 31

Figure 11. Maps showing areal distribution of simulated average annual recharge for 

Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington, 

water years 1997-98........................................................................................................................... 35

Figure 12. Graph showing relation between chloride concentrations and well-bottom altitudes 

and distances from shore for all wells tapping glacial-deposit aquifers that were 

sampled during spring 1997 on Lopez Island, San Juan County, Washington, 

water years 1997-98........................................................................................................................... 46

Figure 13. Map showing locations and chloride concentrations for wells used in the chloride 

mass-balance method for estimating ground-water recharge, Lopez Island, 

San Juan County, Washington, spring 1997 ...................................................................................... 47
Contents v

TABLES

Table 1. Principal characteristics of the six study basins on Lopez, San Juan, Orcas, and 

Shaw Islands, San Juan County, Washington, water years 1997-98 ................................................. 11

Table 2. Summary of type, frequency, and location of data collected at sites on Lopez, 

San Juan, Orcas, and Shaw Islands, San Juan County, Washington, water years 1997–98 .............. 12

Table 3. Percentages of total basin area assigned soil types for use in the Deep Percolation 

Model for the six study basins, Lopez, San Juan, Orcas, and Shaw Islands, 

San Juan County, Washington ........................................................................................................... 14

Table 4. Percentages of total basin area assigned land cover for use in the Deep Percolation 

Model for the six study basins, Lopez, San Juan, Orcas, and Shaw Islands, 

San Juan County, Washington ........................................................................................................... 16

Table 5. Grid characteristics for the six modeled basins and Lopez, San Juan, Orcas, and 

Shaw Islands, San Juan County, Washington.................................................................................... 17

Table 6. Reclassification of original land-use data to land-cover categories used by the 

Deep Percolation Model (DPM) for Lopez, San Juan, Orcas, and Shaw Islands, 

San Juan County, Washington ........................................................................................................... 22

Table 7. Summary of streamflow measured for the six study basins on Lopez, San Juan, 

Orcas, and Shaw Islands, water years 1997-98.................................................................................. 24

Table 8. Summary of annual water-budget components using the Deep Percolation Model for 

the six study basins on Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, 

Washington, water years 1997-98...................................................................................................... 29

Table 9. Soil types assigned to Lopez, San Juan, Orcas, and Shaw Islands for use in the 

Deep Percolation Model, San Juan County, Washington.................................................................. 33

Table 10. Land-cover groups assigned to Lopez, San Juan, Orcas, and Shaw Islands for use 

in the Deep Percolation Model, San Juan County, Washington........................................................ 34

Table 11. Summary of annual water-budget components using the Deep Percolation 

Model for Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington, 

water years 1997-98........................................................................................................................... 39

Table 12. Summary of chloride concentrations in precipitation and dry chloride deposition observed 

at three locations on Lopez Island during October 1996 through September 1998........................... 43

Table 13. Summary of chloride concentrations and selected physical and hydrologic data 

for wells used in the chloride mass-balance method for Lopez Island, San Juan County, 

Washington, spring 1977 ................................................................................................................... 48

Table 14. Precipitation and throughfall in a predominantly evergreen forest located 

at the south end of Lopez Island, San Juan County, Washington, water years 1997-98 ................... 54

Table 15. Precipitation and throughfall in a predominantly evergreen forest located 

in Moran State Park, Orcas Island, San Juan County, Washington, water years 1997-98 ................ 74

Table 16. Precipitation and throughfall in a predominantly evergreen forest located 

on Shaw Island, San Juan County, Washington, water years 1997-98.............................................. 76

Table 17. Monthly water-budget components for the L1 study basin, Lopez Island, 

San Juan County, Washington, water years 1997-98 ........................................................................ 94

Table 18. Monthly water-budget components for the L2 study basin, Lopez Island, 

San Juan County, Washington, water years 1997-98 ........................................................................ 96

Table 19. Monthly water-budget components for the L3 study basin, Lopez Island, 

San Juan County, Washington, water year1997-98........................................................................... 98
vi Contents

Table 20. Monthly water-budget components for the SJ1 study basin, San Juan Island, 

San Juan County, Washington, water years 1997-98 ........................................................................100

Table 21. Monthly water-budget components for the OR1 study basin, Orcas Island, 

San Juan County, Washington, water years 1997-98 ........................................................................102

Table 22. Monthly water-budget components for the SH1 study basin, Shaw Island, 

San Juan County, Washington, water years 1997-98 ........................................................................104

Table 23. Monthly water-budget components for Lopez Island, San Juan County, 

Washington, water years 1997-98......................................................................................................106

Table 24. Monthly water-budget components for San Juan Island, San Juan County, 

Washington, water years 1997-98......................................................................................................108

Table 25. Monthly water-budget components for Orcas Island, San Juan County, 

Washington, water years 1997-98......................................................................................................110

Table 26. Monthly water-budget components for Shaw Island, San Juan County, 

Washington, water years 1997-98......................................................................................................112
Conversion Factors vii

CONVERSION FACTORS AND VERTICAL DATUM

Temperature in degrees Fahrenheit (oF) may be converted to degrees Celsius (oC) as follows:

oC=(oF-32)/1.8

Sea level: In this report, “sea level” refers to the National Geodetic Vertical Datum of 1929 (NGVD 

of 1929)—a feodetic datum derived from a general adjustment of the first-order level nets of both the 

United States and Canada, formerly called Sea Level Datum of 1929.

Altitude, as used in this report, refers to distance above or below sea level.

Concentrations of chemical constituents in water are given either in milligrams per liter (mg/L) or 

micrograms per liter (μg/L).

Multiply By To obtain

Length

inch (in) 25.4 millimeter

foot (ft) 0.3048 meter

mile (mi) 1.609 kilometer

Area

acre 4,047 square meter

square mile (mi2) 2.590 square kilometer

Flow rate

cubic foot per second (ft3/s) 0.02832 cubic meter per second
Abstract 1

Estimates of Ground-Water Recharge from

Precipitation to Glacial-Deposit and Bedrock 

Aquifers on Lopez, San Juan, Orcas, and 

Shaw Islands, San Juan County, Washington

By Laura A. Orr, Henry H. Bauer, and J.A. Wayenberg

ABSTRACT

An important source of fresh water on 

Lopez, San Juan, Orcas, and Shaw Islands in San 

Juan County off the northwestern coast of 

Washington is glacial-deposit and bedrock 

aquifers. Two methods were used to estimate 

recharge from precipitation to the water tables on 

the islands. A daily near-surface water-balance 

method, the Deep Percolation Model (DPM), was 

used to simulate water budgets for the period 

October 1, 1996, through September 30, 1998 

(water years 1997-98) for six small drainage 

basins—three on Lopez Island and one each on 

San Juan, Orcas, and Shaw Islands. The calibrated 

soil and subsoil parameters from the DPM for each 

small basin were then used in island-wide 

applications of the DPM where the direct runoff 

component (which is not available on an islandwide basis) was simulated, rather than input, and 

calibration was not required. A spatial distribution 

of annual recharge was simulated for each island, 

with island averages of: Lopez Island, 2.49 inches 

per year; San Juan Island, 1.99 inches per year; 

Orcas Island, 1.46 inches per year; and Shaw 

Island, 1.44 inches per year.

A chloride mass-balance method that 

requires measurements of atmospheric chloride 

deposition, precipitation, streamflow, and chloride 

concentrations in ground water was used to 

estimate recharge to the glacial-deposit aquifers of 

Lopez Island. Only average recharge could be 

estimated using this method rather than areaspecific recharge. Average recharge for Lopez 

Island estimated by this method was only 0.63 

inch per year. The range of chloride concentrations 

in ground-water samples from selected wells 

indicates that the average recharge in areas of 

glacial deposits is between 0.29 and 1.95 inches 

per year. Recharge simulated using the DPM for 

two drainage basins on Lopez Island overlain by 

glacial deposits are 2.76 and 2.64 inches per year. 

Sources of chloride in ground water other than 

from the atmosphere would cause the recharge 

estimated by the chloride mass-balance method to 

be less than the actual recharge, therefore these 

estimates may represent lower limits which are, at 

least, consistent with the higher simulated 

recharge from the DPM.

The average island-wide recharge is most 

closely related to the amount of area overlain by 

glacial deposits. Thus, even though Lopez Island 

receives the least precipitation, it has the most 

recharge per square mile because it proportionally 

has the largest area overlain by glacial deposits. 

Recharge simulated by the DPM for areas of 

shallow to outcropping bedrock generally was less 

than 1.5 inches per year, but recharge simulated in 

areas of glacial deposits ranged from less than 

0.5 to 3 inches per year, with recharge as high as 

9 inches per year in some small areas.
2 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

 INTRODUCTION

The islands that make up San Juan County, 

Washington, are located off the northwestern 

Washington coast (fig. 1). The islands are noted for 

their scenic beauty and low rainfall, and therefore are a 

popular location for residence and recreation. On the 

four largest islands—Lopez, San Juan, Orcas, and 

Shaw—the population and development are growing 

rapidly, and because an important source of fresh water 

for the islands is the glacial-deposit and bedrock 

aquifers, there is growing concern about the quality and 

availability of ground water. This is of particular 

concern on Lopez Island, which has the least 

precipitation, the lowest water levels, and, therefore, 

the greatest susceptibility to seawater intrusion. A key 

issue in assessing ground-water availability is to 

determine the amount of recharge to the aquifers from 

precipitation. Recharge is extremely difficult and costly 

to measure directly, and only very generalized and 

incomplete estimates of recharge are available for San 

Juan County.

In 1997, the U.S. Geological Survey (USGS), in 

cooperation with the San Juan County Health and 

Community Services, began a study of the quality and 

availability of ground water on Lopez, San Juan, Orcas, 

and Shaw Islands. The objective of the first phase of 

the study was to use chloride concentrations as an 

indicator to determine the present-day extent of 

possible seawater intrusion on Lopez Island (Orr, 2000) 

and then compare these findings with those from two 

previous USGS studies (Whiteman and others, 1983 

and Dion and Sumioka, 1984).

The objective of the second phase of the study 

was to estimate recharge from precipitation to the 

glacial-deposit and bedrock aquifers on each of the 

four islands. Indirect recharge estimates can be subject 

to large errors, and therefore more than one method 

was used. The most direct, reliable method, assuming 

ground-water recharge is equal to ground-water 

discharge, is to measure the discharge. However, as 

indicated by ground-water levels (Whiteman and 

others, 1983), most ground water in the San Juan 

Islands probably discharges through the seabed, thus 

this method could not be used. Therefore, two indirect 

methods were used: a near-surface water-balance 

method and a chloride mass-balance method.

Purpose and Scope

The purpose of this report is to document 

estimates of ground-water recharge from precipitation 

to glacial-deposit and bedrock aquifers on Lopez, San 

Juan, Orcas, and Shaw Islands for water years 1997-98 

using a near-surface water-balance method and a 

chloride mass-balance method. 

The study included four steps: 

1. Recharge was simulated using the Deep 

Percolation Model, a near-surface water-balance 

method, for six small drainage basins on the 

islands; 

2. Calibration results from water-balance simulations 

from the near-surface water-balance method in the 

six small drainage basins were used to simulate 

ground-water recharge for the entire areas of the 

four islands;

3. Recharge was estimated using a chloride massbalance method for the glacial-deposit aquifers of 

Lopez Island; and

4. Recharge estimates from the chloride massbalance method were used to ascertain the 

reasonableness of the results from the near-surface 

water-balance method. 

The near-surface water balance was simulated on 

a daily basis using a hydrometeorological model 

known as the Deep Percolation Model (DPM) (Bauer 

and Vaccaro, 1987; Bauer and Mastin, 1997) and the 

chloride mass-balance method used techniques 

documented by Eriksson and Khunakasem (1969) to 

estimate ground-water recharge. Since then, others 

(see, for example, Vacher and Ayers, 1980; Claassen 

and others, 1986; Dettinger, 1989; and Prych, 1998) 

have used this method for many different types of areas 

ranging from small oceanic islands to mountainous 

drainage basins that range in size from tens to 

thousands of square miles. Data needed to apply the 

methods were obtained from existing databases and 

collected as part of this study.

Data collected during water years 1997-98 

included streamflow, precipitation, precipitation 

throughfall, solar shortwave radiation, temperature, and 

atmospheric-chloride deposition. Chloride 

concentrations in ground water were determined at 

selected locations throughout the study area in the 

spring of 1997 during the first phase of this study (Orr, 

2000).
Introduction 3

123° 122°45'

48°37'30''

48°30'

UNITED STATES

UNITED STATES

 CANADA

CANADA

WHATCOM COUNTY

SAN JUAN COUNTY

SAN JUAN COUNTY

SKAGIT COUNTY

 LOPEZ

ISLAND

STUART

ISLAND

ORCAS

ISLAND

WALDRON

ISLAND

BLAKELY

 ISLAND

DECATUR

 ISLAND

SAN JUAN

 ISLAND

Friday 

Harbor

Deer 

Harbor

Shaw

Island

Roche

Harbor

Port

Stanley

Doebay

Thatcher

Rosario

Decatur

Lopez

Orcas

Prevost

Waldron

West

Sound

WASHINGTON

Location of 

study area

EAST SOUND

WEST SOUND

LOPEZ SOUND

Olympic

Mountains

0 2 4 6 8 10 MILES

0 2 4 6 8 10 KILOMETERS

Modified from University of Washington 

Digital Elevation Maps, 2001.

SHAW

ISLAND

EXPLANATION

STUDY BASIN AND

DESIGNATION

L3

L1

SH1

SJ1

OR1

L2

L2

Figure 1. Location of Lopez, San Juan, Orcas, and Shaw Islands and the six study basins in San Juan County, 

Washington.
4 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Previous Studies

The Washington State Department of Ecology 

inventoried the geology and surface- and ground-water 

resources of the islands of San Juan County in 1974 

(Russell, 1975). In 1978, the USGS conducted a 

reconnaissance of seawater intrusion in coastal 

Washington, including San Juan County (Dion and 

Sumioka, 1984). Whiteman and others (1983) assessed 

the occurrence, quality, and use of ground water on 

Lopez, San Juan, Orcas, and Shaw Islands, including a 

description of the ground-water flow system and 

measurements of chloride concentrations in wells. The 

geology of the islands is described by Russell (1975) 

and Brandon and others (1988). 

Well-Numbering System

The U.S. Geological Survey assigns numbers to 

wells and springs in Washington that identify their 

location in a township, range, and section. Well number 

34N/01W-18K01 indicates, successively, the township 

(T. 34 N.) and range (R. 01 W.) north and west of the 

Willamette Base Line and Meridian (fig. 2). The first 

number following the hyphen indicates the section (18) 

within the township, and the letter following the 

section number gives the 40-acre subdivision of the 

section. The number (01) following the letter is the 

sequence number of the well within the 40-acre 

subdivision. This number indicates that the well was 

the first one inventoried by USGS personnel in that 40-

acre tract. An "S" following the sequence number 

indicates that the site is a spring, a "D1" after the 

sequence indicates that the original reported depth of

Willamette Meridian

Willamette Base Line

SECTION 18

34N/01W-18K01

D C B A

EFGH

M L K J

NPQR

R. 01 W.

T.

34

 N.

6 5 4 3 2 1

7 12

18 13

19 24

30 25

31 32 33 34 35 36

W A S H I N G T O N

Study area

Lopez

Island

Figure 2. Well-number system used in Washington.
Description of Study Area 5

the well has been changed once, and successive 

numbers indicate the number of changes in the well 

depth.

Acknowledgments

The authors wish to express their gratitude to the 

many people in San Juan County who allowed access 

to their property for data collection for this study: Paul 

Atlas, David and Mary Fox, Walter Lease, Stanley 

Reitan, Sr., Charles Walker, Philip Weinheimer, John 

Willis, Laurence Wilmot, and Robert Winter, and a 

special thanks to Howard Cole, Gary Sale, Mother 

Therese and Mother Hildegard and their students at 

Our Lady of the Rock Priory, and Jan Helsell for the 

often difficult task of collecting the throughfall and(or) 

precipitation data. We also thank all USGS staff who 

collected data, and are especially grateful for the 

contributions of Karen Payne and C.G. Laird in 

processing the atmospheric chloride data. 

DESCRIPTION OF STUDY AREA

San Juan County covers an area of 265 mi2 off 

the coast of northwestern Washington State (fig. 1). 

About 172 mi2 of the county is composed of islands 

that are part of the San Juan archipelago. The four 

largest islands make up 87 percent (149.4 mi2) of the 

land area: Lopez, 18,847 acres (29.4 mi2), San Juan, 

35,448 acres (55.4 mi2), Orcas, 36,432 acres (56.9 

mi2), and Shaw, 4,928 acres (7.7 mi2). The population 

of the county in 2000 was 14,077, an increase of more 

than 40 percent since 1990 and the second largest 

population increase of counties in Washington (U.S. 

Census Bureau, 2001). The topography of individual 

islands varies (fig. 3). Orcas Island has the greatest 

relief, with land-surface altitudes ranging from sea 

level to 2,409 feet above sea level with seven peaks 

higher than 1,000 feet above sea level. One peak on 

San Juan Island is more than 1,000 feet above sea level 

and, along with Shaw Island, has a generally low, 

rolling landscape. Lopez Island is mostly flat or gently 

rolling, with a maximum altitude of 535 feet above sea 

level. The islands are composed of varying thicknesses 

of glacial deposits overlying bedrock that contain 

ground water that supplies most of the county's water 

needs. Most streams are intermittent and are usually 

dry between June and late October or November. 

Climate and Precipitation

The maritime climate of San Juan County is 

typified by cool, dry summers and mild, moderately 

wet winters. At the National Oceanic and Atmospheric 

Administration (NOAA) weather station on Orcas 

Island, average temperatures for January and August 

were 39.5 and 60.2oF for 1961-90 (U.S. Department of 

Commerce, 1999). The islands lie in a rainshadow on 

the leeward side of the Olympic Mountains (fig. 1), 

resulting in much less precipitation than in other parts 

of western Washington. The rainshadow effect 

influences the distribution of precipitation across the 

islands as well. Mean annual precipitation (1961-90) 

at low to moderate altitudes ranges from about 26 

inches in the southern part of the county to about 35 

inches in the north, and is about 48 inches at the highest 

land-surface altitudes on Orcas Island (fig. 4). 

November is usually the wettest month and July is 

usually the driest month (Oregon Climate Service, 

1999).

Hydrogeology

 Unconsolidated glacial deposits overlie, to 

varying extents, a complex of sedimentary and volcanic 

bedrock that is metamorphosed in many areas of the 

islands (Russell, 1975, and Brandon and others, 1988). 

The glacial deposits, where saturated, generally yield 

large quantities of water to wells, but the bedrock 

generally yields only small quantities, usually 

sufficient only for single-family domestic use. Most of 

the bedrock is nonporous, and water occurs primarily 

in joints and fractures, often referred to as secondary 

permeability. Because most areas are not overlain by 

sufficient thicknesses of glacial deposits (fig. 5), most 

wells produce water from the bedrock.

About 80 percent of Lopez Island is overlain by 

saturated glacial deposits with thicknesses of as much 

as 250 feet. About 40 percent of San Juan Island is 

overlain by glacial deposits, but only as thin, 

discontinuous sheets, with thicknesses generally less 

than 30 feet. Although much of the glacial deposits on 

San Juan Island is not saturated, the extreme southern 

part is overlain by relatively thick saturated glacial 

deposits, as much as 100 feet.
6 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

123° 122°45'

48°

37'

30''

48°

30'

LOPEZ SOUND

EXPLANATION

200

400

600

800

1000

1200

1400

1600

1800

2000

2200

2400

WHATCOM COUNTY

SAN JUAN COUNTY

BLAKELY

 ISLAND

CONTOURS–show altitude of land surface.

 National Geodetic Vertical Datum of 1929.

 Contour interval is 100 feet.

STUDY BASIN

0 2 4 6 8 10 MILES

0 2 4 6 8 10 KILOMETERS

UNITED 

STATES

CANADA

SHAW

ISLAND

SAN JUAN

 ISLAND

EAST SOUND

WEST SOUND

SAN JUAN COUNTY

SKAGIT COUNTY

 LOPEZ

ISLAND

ORCAS

ISLAND

WALDRON

ISLAND

DECATUR

 ISLAND

Figure 3. Topography of Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington.
Description of Study Area 7

123° 122°45'

48°37'30''

 CANADA

 LOPEZ

ISLAND

 SHAW

ISLAND

ORCAS

ISLAND

SAN JUAN

 ISLAND

EAST SOUND

WEST SOUND

48°30'

UNITED STATES

WHATCOM COUNTY

SAN JUAN COUNTY

SAN JUAN COUNTY

SKAGIT COUNTY

0 2 4 6 8 10 MILES

0 2 4 6 8 10 KILOMETERS

EXPLANATION

STUDY BASINS

PRECIPITATION, IN INCHES

No data

Less than 26

26 to less than 28

28 to less than 30

30 to less than 32

32 to less than 34

34 to less than 36

36 to less than 38

38 to less than 40

40 to less than 42

42 to less than 44

44 to less than 46

46 to less than 48

Equal to or greater than 48

LOPEZ SOUND

Figure 4. Mean annual precipitation for Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington, 

1961-90. 
8 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Study basins

123° 122°45'

48°37'30''

48°30'

UNITED STATES

UNITED STATES

 CANADA

 CANADA

WHATCOM COUNTY

SAN JUAN COUNTY

SAN JUAN COUNTY

SKAGIT COUNTY

 LOPEZ

ISLAND

SHAW

ISLAND

ORCAS

ISLAND

SAN JUAN

 ISLAND Friday 

Harbor

Deer 

Harbor

Shaw

Island

Port

Stanley

Doebay

Rosario

Lopez

Orcas

West

Sound

Atmospheric chloride deposition 

instrumentation

Micrometeorological station, including hourly 

precipitation and storage precipitation gages

Hourly precipitation gage

Precipitation storage gage

USGS streamflow gaging station and number

Stream discharge gage

EAST SOUND

WEST SOUND

LOPEZ SOUND

EXPLANATION

SURFICIAL GEOLOGY

STUDY BASIN AND DESIGNATION

Bedrock

Glacial deposits

No data

Roche

Harbor

0 2 4 6 8 10 MILES

0 2 4 6 8 10 KILOMETERS

L3

L1

SH1

C3

SJ1

P2

M2

OR1

S2 T3

S1

L2

P1

T1

M1

C2

C1

BLAKELY

 ISLAND

DECATUR

 ISLAND

DATA-COLLECTION SITES AND NUMBERS 

12200762

12200762

12200737

12200733

12200728

12200730

12200750

Figure 5. Generalized surficial geology and data-collection sites for Lopez, San Juan, Orcas, and Shaw Islands, 

San Juan County, Washington.

Surficial geology is modified from Jones (1999). Data-collection sites are summarized in table 2. 
Description of Study Area 9

About 15 percent of Orcas Island (many small areas) is 

overlain by glacial deposits with thicknesses of as 

much as 300 feet at the northern end and in the central 

part, west of East Sound. Less than 10 percent of Shaw 

Island (only one small area) is overlain by glacial 

deposits. Additional information on the thicknesses of 

the glacial deposits on the islands is presented in 

Whiteman and others (1983).

Recharge and Evapotranspiration

Direct recharge to ground water from 

precipitation results from the infiltration of 

precipitation into the soil and below the root zone, 

hereafter referred to as "deep percolation": generally, 

the greater the precipitation, the greater the deep 

percolation and recharge. Factors that control 

evapotranspiration, namely temperature, solar 

shortwave radiation, wind, soil type, vegetation type, 

and land-surface slope, also directly affect deep 

percolation. The quantity of deep percolation in many 

areas is further limited by low-permeability materials 

underlying the soils. For a period of time during and 

following a storm, rainwater infiltrating the soil 

encounters low-permeability bedrock, glacial till, or 

clay, and some moves short distances horizontally 

through the soil to local drainages and discharges as 

surface water directly to the ocean, and thus is not 

available for recharging the ground-water system. 

Furthermore, not all of the deep percolation necessarily 

recharges the uppermost saturated zone from which 

water can be effectively withdrawn. For example, a thin 

saturated zone may exist above the zone(s) generally 

tapped by wells, and water in this thin zone may, in 

part, flow laterally and discharge to a stream or spring. 

Deep percolation and subsequent ground-water 

recharge from precipitation in San Juan County 

probably is less than in most of western Washington 

State because the rainshadow of the Olympic 

Mountains results in less precipitation. 

Potential evapotranspiration (PET) is estimated 

to be about 25 inches per year (Russell, 1975). If soilmoisture holding capacities and root-zone depths are 

sufficiently large, potential recharge (rainwater not 

evapotranspired) could, in places, be nearly zero. 

Additionally, results from recent USGS studies in 

coniferous forested areas in the Puget Sound Lowland 

of western Washington have shown that measured daily 

evaporation frequently exceeds daily PET computed by 

traditional methods because large amounts of advective 

evaporation of intercepted precipitation (as much as 10 

to 18 inches, annually) are not accounted for in the 

traditional methods (Bauer and Mastin, 1997; W.R. 

Bidlake, U.S. Geological Survey, written commun., 

1998). In these areas, the quantity of recharge could be 

even less than would be expected using normal 

assumptions. 

Ground-water recharge should not be equated 

with ground-water availability. Under natural 

conditions, ground-water recharge is balanced by 

subsurface flow to the ocean, to the lower reaches of 

streams, and, in areas of shallow water tables, to the 

roots of phreatophytes (these areas are collectively 

called discharge areas). Removal of ground water by 

wells will lower ground-water levels and diminish the 

outflow to one or more of these discharge areas. Where 

discharge to the ocean is diminished, seawater intrusion 

into wells may be induced. Diminished ground-water 

discharge to streams will reduce dry-season low flows, 

which could affect fish, wildlife, and surface-water 

right holders. Lowered water tables could transform 

wetlands and phreatophyte areas into drier 

environments. If all recharge were consumptively used, 

there would be no discharge to any of these areas.

Removal of ground water in rural and suburban 

non-irrigated areas generally is not all consumptive, but 

is accompanied by the return of a large fraction of this 

water as wastewater to the subsurface and eventually to 

the aquifers. Water-quality problems may therefore 

occur before significant problems in water levels or in 

ground-water discharge areas develop. These issues are 

most readily addressed using ground-water models for 

which the recharge estimates presented in this report 

will be essential.
10 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

ESTIMATES OF GROUND-WATER 

RECHARGE

Near-Surface Water-Balance Method

The primary method for estimating ground-water 

recharge from precipitation for this study was the nearsurface water-balance method. A deep-percolation 

model (DPM), developed for eastern Washington 

(Bauer and Vaccaro, 1987) and modified for western 

Washington (Bauer and Mastin, 1997), was selected to 

estimate deep percolation from precipitation for this 

study. The DPM uses a daily water- budget approach to 

simulate deep percolation. In this method, the model 

computes daily fluxes of water into and out of a volume 

extending from the top of foliage to the bottom of the 

root zone and accounts for changes in water content. In 

most environments, deep percolation is destined to 

recharge the saturated systems that are tapped by wells. 

In some cases, ground-water recharge is less than deep 

percolation, and this is discussed later in the section 

"Sources of Uncertainty in the DPM Recharge 

Estimates." In this study, deep percolation is 

considered to be the best estimate of recharge.

Time-series data required for this application of 

the DPM include daily values of precipitation, 

precipitation throughfall, minimum and maximum air 

temperature, solar shortwave radiation, and "direct 

runoff." Direct runoff is herein defined as surface-water 

runoff plus water that drains from temporarily saturated 

soils to local drainage features. Spatial data required 

for the DPM include land-surface altitude, properties of 

soils, and land cover (vegetation type, surface water, or 

impervious surfaces). Areal variation in soils, 

vegetation, and land cover is accounted for in the DPM 

by dividing a drainage area into cells or polygons of 

any size and shape. Each cell is characterized by a 

single altitude (and optionally, surface slope and 

aspect), land cover, soil type, subsoil infiltration 

capacity, and climate regime. Areal variation in 

precipitation, air temperature, and solar shortwave 

radiation are accounted for by interpolation of data to 

each cell from data collected in or near the study 

basins.

Evapotranspiration depletes soil moisture and 

depends on soil-moisture content and meteorological 

conditions. Therefore, evapotranspiration and soil 

moisture must be calculated at sufficiently frequent 

intervals to accurately simulate changes. 

The DPM uses a daily time step, primarily because 

daily meteorological data generally are available. A 

daily time step is sufficiently short to ensure that soilmoisture variations are small enough to avoid 

significant error in the evapotranspiration calculations. 

For each day of a DPM simulation, deep percolation 

for each cell is computed as the residual of 

precipitation minus evapotranspiration minus direct 

runoff minus the change in soil moisture in the root 

zone.

Direct runoff for each cell is difficult to 

determine. Although the total direct runoff for the 

drainage basin can be readily estimated from 

streamflow measurements, the contributions from 

individual cells in the basin can vary greatly, depending 

on the soil and subsoil properties. For example, during 

a storm, a cell with a thick soil underlain by a 

permeable sand-and-gravel glacial outwash deposit 

may not contribute direct runoff, whereas a cell with 

thin soil overlying poorly permeable glacial till will 

contribute a large quantity of direct runoff. The DPM 

disaggregates the daily total measured direct runoff to 

the cells in proportion to a simulated daily direct runoff 

for each cell (for details, see Bauer and Mastin, 1997). 

A specified infiltration capacity beneath the root zone 

for each cell, based on the soil and subsoil properties, is 

incorporated into these calculations. By adjusting this 

parameter, a water balance (or calibration) is achieved. 

If the infiltration capacities are set mostly too large, too 

little water will be available to support the measured 

total direct runoff. This is indicated as a "negative 

deficit" in the DPM output; conversely, a "positive 

deficit" results when the infiltration capacities are 

mostly set too small.

Three steps were used to estimate recharge for all 

four islands using the DPM in this study: (1) the spatial 

data needed for applying the DPM to the entire study 

area were assembled, checked for accuracy, and 

divided into uniform cells; (2) the DPM was calibrated 

for each of the six study basins; and (3) the DPM was 

applied to each entire island using results of the 

calibrations of the six study basins.

In step 3, island-wide direct runoff data were not 

available. The DPM was, therefore, operated in a mode 

in which the simulated direct runoff for each cell is 

used in place of the disaggregated measured runoff. 
Estimates of Ground-Water Recharge 11

During the calibration process of step 2, the simulated 

direct runoff was made to match the measured direct 

runoff as closely as possible so that the simulated 

island-wide direct runoff, using the calibrated input 

values and parameters from the study basins, produce a 

reasonable representation of the actual island-wide 

direct runoff.

Data Requirements

Data needed to estimate recharge were collected 

for water years 1997-98 from six surface drainage areas 

(herein called study basins) — one each on San Juan, 

Orcas, and Shaw Islands and three on Lopez Island 

(fig. 5). The criteria used to select each of the six 

study basins were based on 

1. representativeness of the geologic materials;

2. ability to accurately gage streamflow; and

3. all or most of the streamflow in the basin was 

direct runoff (overland flow, or shallow subsurface 

flow through the soil) so that the amount of direct 

surface-water runoff to the ocean could be readily 

quantified. This was indicated by dry streambed or 

very small flow during field reconnaissance in late 

summer.

The principal characteristics of the study basins 

are summarized in table 1. In addition to the 

streamflow measurements, other data also were 

collected at various sites on the islands (see fig. 5). Two 

temporary micrometeorological stations were 

established to measure hourly precipitation, solar 

shortwave radiation, air temperature, wind speed, and 

relative humidity—one at the southeastern tip of Orcas 

Island and one at the southeastern end of Lopez Island. 

Precipitation throughfall data were collected on Orcas, 

Shaw, and Lopez Islands. Additional hourly 

precipitation data were collected on Lopez Island just 

south of the L2 study basin, and stored precipitation 

data were collected on Lopez, Orcas, and Shaw Islands. 

Atmospheric-chloride deposition data were collected at 

three sites on Lopez Island. Table 2 summarizes the 

type of data, frequencies of measurement, location of 

data, and landowners for the data-collection sites 

shown on figure 5.

Table 1. Principal characteristics of the six study basins on Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, 

Washington, water years 1997-98

[Study basin: Location of study basins are shown in figure 5. USGS streamflow-gaging station: Data are retrievable from Web-served U.S. Geological Survey 

data base. Streamflow statistics are summarized in table 7. Predominant soil group: Letter corresponds to composite soil group shown in a tabular explanation 

in figure 7. Predominant DPM land cover: Classification of land use from original land-use data to the land-use categories used by the Deep Percolation Model 

(DPM) are shown in table 6. Long-term average annual precipitation: Data from Oregon Climate Service (1999). Water years 1997 and 1998: Interpolated 

from temporary USGS precipitation gages installed for the study. Abbreviations: USGS, U.S. Geological Survey; mi2, square mile; in/yr, inch per year]

Island

Study

basin

(fig. 5)

USGS

streamflowgaging

station No.

Drainage

area

(mi2)

Geologic

material

beneath

the soils

(fig. 5)

Predominant

soil group

(fig. 7)

Predominant

DPM

land cover

(table 6)

Precipitation (in/yr)

 Water

year 

1997

 Water

year 

1998

Long-term

average

annual

(1961–90)

Lopez L1 12200733 0.45 Glacial 

deposits

B, E Pasture/hay and 

evergreen forest

30.04 20.54 28

L2 12200730 1.63 Glacial 

deposits

A, E Pasture/hay, grassland 

and evergreen forest

30.37 20.88 27.5

L3 12200728 0.66 Bedrock G Evergreen forest 28.98 20.07 27

San Juan SJ1 12200750 0.50 Bedrock G, H Evergreen forest 38.31 23.54 33

Orcas OR1 12200762 0.57 Bedrock D, H Evergreen forest 34.90 21.44 34

Shaw SH1 12200737 0.26 Bedrock B, G Evergreen forest 31.96 20.84 29
12 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Table 2. Summary of type, frequency, and location of data collected at sites on Lopez, San Juan, Orcas, and Shaw Islands, San 

Juan County, Washington, water years 1997–98

[Data-collection site No: Location of data-collection sites are shown in figure 5]

Island

Datacollection 

site No.

(fig. 5)

Land owner

USGS streamflowgaging station

No. or data 

location

Types of data collected Frequency of 

measurement

Lopez L1 Walter Lease 12200733 Streamflow Hourly

L2 Paul Atlas 12200730 Streamflow Hourly

L3 Laurence Wilmot 12200728 Streamflow Hourly

M1 Howard Cole Project archives Precipitation, solar shortwave radiation, 

air temperature, wind speed, humidity. 

Stored precipitation

Hourly

Approximately 

monthly

P1 Paul Atlas 12200730 Precipitation Hourly

S1 Charles Walker Project archives Stored precipitation Approximately 

monthly

T1 Howard Cole Appendix A Throughfall Daily

C1 Charles Walker 483208122532401 Atmospheric chloride deposition, wet, 

dry, and composite

Approximately 

monthly

C2 Howard Cole 482614122501701 Atmospheric chloride deposition, wet, 

dry, and composite

Approximately 

monthly

C3 Philip Weinheimer 483044122532001 Atmospheric chloride deposition,

composite only

Approximately 

monthly

San Juan SJ1 Town of Friday 

Harbor

12200750 Streamflow Hourly

Orcas OR1 Robert Winter 12200762 Streamflow Hourly

M2 John Willis Project archives Precipitation, solar radiation, air 

temperature, wind speed, 

humidity, stored precipitation

Hourly

Approximately 

monthly

S2 Jan Helsel Project archives Stored precipitation Approximately 

monthly

T3 Environmental 

Learning Center 

Moran State 

Park

Appendix A Throughfall Multi-day to 

multi-week

Shaw SH1 Our Lady of the 

Rock Priory

12200737 Streamflow Hourly

T2 Our Lady of the 

Rock Priory

Appendix A Throughfall Daily
Estimates of Ground-Water Recharge 13

Data Collection and Processing 

In step 1 of the process, each of the six study 

basins was divided into a uniform grid of cells, each 

98.4 feet (30 meters) on a side and with an area of 

0.222 acre (900 square meters). This cell size was 

selected to match the resolution of the land-cover data, 

which was the lowest resolution of all the GIS 

coverages used. Each cell was assigned the 

predominant soil type and land cover that occurred in 

the cell. The percentage of total area assigned each 

predominant soil type and land cover for use in the 

DPM for each study basin are shown in table 3 and 

table 4. When the model was applied to the four 

islands, cell size was increased to 295 feet (90 m) on a 

side (about 2 acres) in order to reduce the number of 

cells to accommodate file-size limitations in the preand post-processing software. Grid characteristics for 

the six modeled study basins and islands are shown in 

table 5.

Daily values of precipitation, throughfall, solar 

shortwave radiation, air temperature, and streamdischarge data were collected by the USGS during 

water years 1997-98. Most properties of soils, 

vegetation, and land cover were compiled from 

published data or previous studies of San Juan County. 

DPM model parameters defining maximum clear-sky 

shortwave radiation, soil-limiting transpiration, and 

snowmelt and sublimation were compiled from values 

used in two previous applications of the DPM to areas 

of western Washington. Bauer and Mastin (1997) 

estimated recharge in till-covered areas, and W.R. 

Bidlake (U.S. Geological Survey, written commun., 

1998) estimated recharge in areas covered by till and 

glacial outwash. These two studies used locally 

measured meteorological data and extensive calibration 

data, including direct stream runoff, soil-water content, 

soil saturation levels, and ground-water levels. Using 

parameter values from these previous two studies in 

this study is considered reasonable because all three 

study areas have a similar climate, vegetation cover, 

geology, and topography. The application of these 

parameters in the DPM is described in Bauer and 

Mastin (1997).

Precipitation

Three commercially available tipping-buckettype precipitation gages were installed—one on Orcas 

Island and two on Lopez Island—and data were 

collected for water years 1997-98. The gages were 

connected to microloggers installed in clear areas at 

locations where precipitation is typical of the study 

basins (fig. 4 and fig. 5). Each bucket tip, representing 

0.01 inch of precipitation, was counted and the total 

amounts were recorded in the data logger at 60-minute 

intervals. Data were retrieved from the data loggers at 

approximately 1-month intervals. Two of the tippingbucket precipitation gages, the one at the southern end 

of Lopez Island and the one on Orcas Island, were part 

of two temporary micrometeorological stations that 

also collected air temperature, solar shortwave 

radiation, wind speed, and relative humidity data.

Several storage-type precipitation gages also 

were installed at various locations in the study area. A 

storage gage is a simple and reliable means of 

collecting precipitation that falls onto a funnel and 

directing it into a container where it is stored and later 

manually measured. Blowover and evaporation errors 

were minimized by placing the containers 

approximately flush with the ground surface where 

wind speed would be at a minimum and humidity at a 

maximum. A storage precipitation gage was installed at 

two of the tipping-bucket sites (see fig. 5 and table 2; 

sites M1 and M2) and the resulting data were used to 

provide correction factors to the hourly tipping-bucket 

data (see fig. 5 and table 2). Storage- precipitation data 

also were collected at two of the chloride-deposition 

data sites (see fig. 5; sites C1 and C2) and at the 

precipitation throughfall data-collection sites (see 

fig. 5; sites T1, T2, and T3). One of the data sets was 

used to provide correction factors to the tipping-bucket 

data used in the DPM for study basin SH1. Similarly, 

but not located within or adjacent to SH1, a storage 

precipitation gage was installed at study basin OR1 to 

provide correction factors to the tipping bucket data at 

M2 (see fig. 5) used for OR1.

Daily precipitation data, collected by Roche 

Harbor Water Systems (a privately owned company) 

and published weekly in the local newspaper "Journal 

of the San Juan Islands," were used to calculate a 

correction factor to the M2 tipping-bucket data used for 

drainage basin SJ1.
14 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Table 3. Percentages of total basin area assigned soil types for use in the Deep Percolation Model for the six 

study basins, Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington

[Soil group: Letter corresponds to composite soil group shown in a tabular explanation in figure 7. All values rounded to two significant 

factors: Because of rounding, area totals may not agree exactly with other tables and percent values may not total 100 percent; 

Abbreviations: mi2, square mile]

 Soil group 

(fig. 7)

L1 L2 L3

Area

(mi2)

Percentage 

of total

basin area

Area

(mi2)

Percentage

of total 

basin area

Area

(mi2)

Percentage 

of total 

basin area

Bedrock

A 0.00 0.00 0.00 0.00 0.00 6.2

B 0.00 0.00 0.00 0.00 0.04 6.2

C 0.00 0.00 0.00 0.00 0.00 0.00

D 0.00 0.00 0.00 0.00 0.00 0.00

E 0.00 0.00 0.00 0.00 0.12 18

F 0.00 0.00 0.00 0.00 0.00 0.00

G 0.00 0.00 0.00 0.00 0.48 74

H 0.00 0.00 0.00 0.00 0.00 0.00

I 0.00 0.00 0.00 0.00 0.00 0.00

J 0.00 0.00 0.00 0.00 0.00 0.00

K 0.00 0.00 0.00 0.00 0.01 1.5

Glacial Deposits

A 0.01 2.2 0.82 50 0.00 0.00

B 0.14 31 0.07 4.3 0.00 0.00

C 0.00 0.00 0.07 4.3 0.00 0.00

D 0.00 0.00 0.00 0.00 0.00 0.00

E 0.27 60 0.44 27 0.00 0.00

F 0.02 4.4 0.04 2.5 0.00 0.00

G 0.00 0.00 0.00 0.00 0.00 0.00

H 0.00 0.00 0.00 0.00 0.00 0.00

I 0.00 0.00 0.00 0.00 0.00 0.00

J 0.00 0.00 0.12 7.4 0.00 0.00

K 0.01 2.2 0.07 4.3 0.00 0.00

Totals 0.45 1.63 0.65
Estimates of Ground-Water Recharge 15

Table 3. Percentages of total basin area assigned soil types for use in the Deep Percolation Model for the six 

study basins, Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington—Continued

Soil group

(fig. 7)

SJ1 OR1 SH1

Area

(mi2)

Percentage 

of total 

basin area

Area

(mi2)

Percentage

of total 

basin area

Area

(mi2)

Percentage 

of total 

basin area

Bedrock

A 0.00 0.00 0.00 0.00 0.00 0.00

B 0.00 0.00 0.00 0.00 0.11 41

C 0.00 0.00 0.00 0.00 0.00 0.00

D 0.00 0.00 0.47 82 0.00 0.00

E 0.00 0.00 0.01 1.8 0.00 0.00

F 0.00 0.00 0.00 0.00 0.00 0.00

G 0.29 57 0.00 0.00 0.15 56

H 0.22 43 0.09 16 0.00 0.00

I 0.00 0.00 0.00 0.00 0.00 0.00

J 0.00 0.00 0.00 0.00 0.01 3.7

K 0.00 0.00 0.00 0.00 0.00 0.00

Glacial Deposits

A 0.00 0.00 0.00 0.00 0.00 0.00

B 0.00 0.00 0.00 0.00 0.00 0.00

C 0.00 0.00 0.00 0.00 0.00 0.00

D 0.00 0.00 0.00 0.00 0.00 0.00

E 0.00 0.00 0.00 0.00 0.00 0.00

F 0.00 0.00 0.00 0.00 0.00 0.00

G 0.00 0.00 0.00 0.00 0.00 0.00

H 0.00 0.00 0.00 0.00 0.00 0.00

I 0.00 0.00 0.00 0.00 0.00 0.00

J 0.00 0.00 0.00 0.00 0.00 0.00

K 0.00 0.00 0.00 0.00 0.00 0.00

Totals 0.51 0.57 0.27
16 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Table 4. Percentages of total basin area assigned land cover for use in the Deep Percolation Model for the six study basins, 

Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington

[Land cover: Distribution of land cover is shown on figure 8. All values rounded to two significant factors: Because of rounding, area totals may not agree 

exactly with other tables and percent values may not exactly total 100 percent. Abbreviations: mi2, square mile]

Land cover

(fig. 8)

L1 L2 L3

Area

(mi2)

Percentage 

of total

basin area

Area

(mi2)

Percentage 

of total 

basin area

Area

(mi2)

Percentage 

of total 

basin area

Evergreen forest 0.25 54 0.33 20 0.49 75

Grassland 0.04 8.7 0.43 26 0.02 3.0

Orchard and deciduous 

forest

0.04 8.7 0.10 6.1 0.06 9.2

Pasture/hay 0.12 26 0.67 41 0.08 12

Row crops 0.00 0.00 0.01 0.61 0.00 0.00

Wheat 0.01 2.2 0.08 4.9 0.00 0.00

Surface water 0.00 0.00 0.01 0.61 0.00 0.00

Totals 0.46 1.63 0.65

Land cover

(fig. 8)

SJ1 OR1 SH1

Area

(mi2)

Percentage of 

total 

basin area

Area

(mi2)

Percentage of 

total 

basin area

Area

(mi2)

Percentage of 

total 

basin area

Evergreen forest 0.47 92 0.55 98 0.20 77

Grassland 0.00 0.00 0.00 0.00 0.00 0.00

Orchard and deciduous 

forest

0.03 5.9 0.00 0.00 0.05 19

Pasture/hay 0.00 0.00 0.00 0.00 0.00 0.00

Row crops 0.00 0.00 0.00 0.00 0.00 0.00

Wheat 0.00 0.00 0.00 0.00 0.00 0.00

Surface water 0.01 2.0 0.01 1.8 0.01 3.9

Totals 0.51 0.56 0.26
Estimates of Ground-Water Recharge 17

Precipitation Throughfall

In forested areas of the Puget Sound Lowland, 

evaporation of precipitation intercepted and stored on 

the foliage, often referred to as interception loss, 

proceeds at considerably faster rates than transpiration, 

especially during the winter months, and annually has 

been determined to be from about 20 to 50 percent of 

the total precipitation (Bauer and Mastin, 1997 and 

Bidlake and Payne, 2001). During this investigation, 

throughfall (that part of precipitation not evaporated 

from foliage) was measured at three sites: a 15-to-30-

year-old evergreen forest near the southern end of 

Lopez Island (site T1), an old-growth evergreen forest 

on Orcas Island (site T3), and a 50-to-100-year-old 

native evergreen forest on Shaw Island (site T2) (see 

fig. 5 for location of throughfall sites). At each 

throughfall data-collection site, several storage-type 

precipitation gages were installed at randomly selected 

locations within the forest and one was installed in an 

adjacent clear area. Following Hewlett (1982), seven 

gages were installed in forested areas at the sites on 

Shaw and Lopez Islands and six were installed in the 

forested area at the site on Orcas Island. Throughfall as 

a fraction of precipitation was calculated for the 

periods between site visits as the average of the forest 

gage totals divided by the clearing gage totals.

All sites were monitored for the USGS by local 

residents. Daily measurements were collected at the 

Lopez and Shaw Island sites and approximately weekly 

measurements were collected at the Orcas Island site.

At the site on Orcas Island, data were not 

available for the periods October 1 to November 6, 

1996; January 31 to May 13, 1998; and July 17 to 

September 30, 1998, because of the unavailability of 

gages or observers during those times. Therefore, data 

for those periods were estimated. All collected and 

estimated throughfall data are shown in tables 14-16 (at 

back of report).

Throughfall varied greatly from day to day 

primarily due to varying quantities, intensities, and 

durations of precipitation from day to day. Because 

measurement times were variable, a consistent basis 

was required to produce 24-hour values of throughfall 

for each site. This was done by calculating the average 

throughfall as a fraction of precipitation for the Shaw 

and Lopez Island sites for each rainy period, defined 

herein as a period of precipitation that is separated 

from the next rainy period by a period of 1 or more 

days of project-area-wide non-precipitation. For each 

site, the throughfall fraction for each rainy period was 

assumed to be the same for each of the days during the 

wet period.

Table 5. Grid characteristics for the six modeled basins and Lopez, San Juan, Orcas, and Shaw Islands, 

San Juan County, Washington

[Area modeled: Area modeled does not necessarily exactly equal the area of the basin because of model cell size. Cell size used for 

gridding data: Cell size means length of square cell. Abbreviations: mi2, square mile]

Study

basin or

island

(fig. 5)

Area

modeled

(mi2)

Cell size used for 

gridding data Number

of gridded

cells

Number of aggregated 

cells used in 

DPM simulation (feet) (meters)

L1 0.45 98.4 30 1,293 14

L2 1.63 98.4 30 4,683 not aggregated

L3 0.65 98.4 30 1,879 not aggregated

SJ1 0.50 98.4 30 1,451 not aggregated

OR1 0.57 98.4 30 1,637 7

SH1 0.26 98.4 30 761 not aggregated

Lopez Island 29.26 295 90 9,356 not aggregated

San Juan Island 55.01 295 90 17,589 not aggregated

Orcas Island 57.33 295 90 18,331 not aggregated

Shaw Island 7.54 295 90 2,410 not aggregated
18 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

This calculation could not be done for the Orcas site 

because of the long intervals between measurements. 

Therefore, daily throughfall data for the Orcas site 

were estimated by multiplying daily values from the 

Shaw site by correction factors based on the Orcas data.

Cumulative throughfall and precipitation at each 

of the three sites is shown in figure 6. For the 2-year 

period, the total throughfall was 86, 75, and 59 percent 

of precipitation, respectively, for the Lopez Island, 

Orcas Island, and Shaw Island sites. This large 

variability in throughfall probably is due mostly to the 

differences in the forest canopy. The Lopez Island site 

had the shortest trees, which therefore had the least 

storage capacity and the least advective evaporation. 

The "old growth" site on Orcas Island had the tallest 

trees, but they were more widely spaced than the 

"second growth" site on Shaw Island, thereby allowing 

greater quantities of precipitation to pass through the 

canopy without being intercepted by the foliage than 

the Shaw Island site. Interception loss in Puget 

Lowland forests was investigated in greater detail by 

Bidlake and Payne (2001), and Bauer and Mastin 

(1997).

Solar Shortwave Radiation and Meteorological 

Measurements

In addition to precipitation, daily incoming solar 

shortwave radiation, air temperature, relative humidity, 

and wind speed were measured during water years 

1997-98 at the two temporary micrometeorological 

stations (see fig. 5). These stations were installed in 

pasture areas at least 500 feet from wooded areas. A 

pyranometer positioned about 10 feet above the ground 

measured incoming shortwave radiation. The 

pyranometer, air temperature, wind speed, and relative 

humidity probes were connected along with the 

precipitation gage to a micrologger, which sampled 

output from the sensors every 15 seconds and recorded 

the averages every 60 minutes.

Soil and Subsoil Properties

 The soil properties needed for the DPM are 

depth, available water-holding capacity, horizontal 

hydraulic conductivity, specific yield, and texture. Only 

vertical hydraulic conductivity values were available in 

the soil surveys, and they were used only to estimate 

values of the horizontal conductivities. The soil cover 

information for the four islands and six study basins 

was obtained from the Washington State Department of 

Natural Resources Geographic Information System 

Division in the form of a digital coverage. The data 

were derived from the Private Forest Land Grading 

system (PFLG) and subsequent soil surveys, such as 

the U.S. Department of Agriculture Soil Conservation 

Service (SCS; the Soil Conservation Service is now 

known as the Natural Resources Conservation Service, 

but SCS is used in this report). The Geographic 

Information System (GIS) coverage was completed in 

1990, and data from the coverage were checked against 

the most recent published soil survey of the area (Soil 

Conservation Service, 1962). The GIS coverage was 

in the form of variable size and shape polygons where 

each polygon represents an area covered by a particular 

SCS soil series mapped on a 1:24,000 scale.

The 65 soil series defined by SCS in the study 

area were grouped according to abundance and to 

properties important in DPM simulation. Most of the 

soil types occupied 4 percent or more of the study area 

(main soil series) or 2 percent or less (minor soil 

series). Eleven composite soil groups were formed 

from the main soil series on the basis of similarities of 

depths and available water-holding capacities (fig. 7). 

Areas of minor soil types were included into the major 

soil types according to closest similarity of available 

water-holding capacity and soil depth. Properties of 

each soil group were computed as area-weighted 

averages of the properties of the soil series in the 

group. Ranges of the properties of the soils composing 

the 11 composite soil groups are 0.06 to 0.36 inch per 

inch for available water capacity, 0.05 to 21 feet per 

day for hydraulic conductivity, 14 to 84 inches for 

depth, and silt loam to gravelly sandy loam for soil 

texture (see figure 7 explanation).

An important and usually unknown parameter 

used in the DPM is the infiltration capacity (or vertical 

hydraulic conductivity) of the subsoil, the geologic 

material underlying the soil. The values used to 

calibrate DPM simulations in Bauer and Mastin (1997) 

ranged from 4.0 to 40.0 inches per year for three 

glacial-till-covered drainage basins, and the values 

used to calibrate DPM simulations in Bidlake and 

Payne (2001) were 26.28 inches per year for glacial till 

and 876 inches per year for glacial outwash and other 

coarse-grained deposits. Determination of the values 

for this study area are presented in the section 

"Calibration of Deep Percolation Model for the Study 

Basins."
Estimates of Ground-Water Recharge 19

25

50

75

0

Precipitation

Measured throughfall

Lopez Island A 15-to 30-year old everegreen forest (site T1)

0

25

50

75

CUMULATIVE AMOUNT, IN INCHES

Precipitation

Measured throughfall

Orcas Island An old-growth evergreen forest (site T3)

25

50

75

0

OND J FMAMJ J AS JFMAMJ J AS OND

1996 1997 1998

Precipitation

Measured throughfall

Shaw Island A 50-100-year old evergreen forest (site T2)

Figure 6. Cumulative precipitation and throughfall for three sites on Lopez, Orcas, and Shaw Islands, San Juan County, 

Washington. 

(See figure 4 for location of throughfall sites.)
20 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Figure 7. Distribution of soil groupings derived from Soil Conservation Service data for the Deep Percolation Model, on Lopez, 

San Juan, Orcas, and Shaw Islands, San Juan County, Washington.
Estimates of Ground-Water Recharge 21

Soil group A 

Bellingham clay loam 0.707 60 0.19 0.21

Bow gravelly silt loam 11.136 60 0.17 0.12

Soil group B 

Bellingham silt loam 1.794 51 0.18 0.13

Bow silt loam 5.586 50 0.19 0.16

Bow stony silt loam 2.672 50 0.15 0.52

Cloveland silt loam 0.972 48 0.19 0.27

Soil group C 

Coastal beaches 0.413 17 0.07 --

Everett gravelly sandy loam 3.576 24 0.08 18

Hovede loam 0.003 14 0.07 21

Neptune gravelly sandy loam 0.065 17 0.07 20

Tidal marsh 0.211 17 0.07 --

Soil group D 

Coveland gravelly silt loam 2.726 45 0.17 0.3

Coveland stony silt loam 1.087 45 0.14 0.5

Indianola-Roche complex 1.507 62 0.10 14

Norma loam 0.590 60 0.09 2

Norma loam, moderately deep 0.309 45 0.15 1.4

Pickett-Rock outcrop complex 27.962 40 0.13 3.3

San Juan gravelly sandy loam 2.890 36 0.15 1.6

San Juan loam 0.370 45 0.16 1.2

San Juan stony loam 0.362 50 0.12 1.2

Soil group E 

Alderwood gravelly sandy loam 0.931 50 0.08 5

Alderwood gravelly loam 1.392 42 0.10 3.7

Roche gravelly loam 14.430 48 0.08 0.18

Roche loam 0.791 48 0.08 0.33

Roche stony sandy loam 0.084 55 0.07 0.61

San Juan stony sandy loam 0.735 50 0.08 20

Soil group F 

Alderwood stony loam 2.366 45 0.08 1.2

Everett stony sandy loam 0.144 48 0.07 18

Roche gravelly sandy loam 0.451 48 0.07 0.52

Roche stony loam 10.250 60 0.06 0.14

Soil group G 

Roche-Rock outcrop complex 33.977 40 0.06 0.14

Soil group H 

Rock land, rolling and steep 8.016 40 0.06 0.14

Soil group I 

Active dune land 0.200 60 0.08 21

Indianola sandy loam 0.587 54 0.09 19

San Juan gravelly sandy loam 7.239 60 0.08 20

Soil group J 

Orcas peat 0.071 84 0.26 3.3

Semiahmoo muck 1.695 72 0.36 3.6

Soil group K 

Semiahmoo muck, shallow 0.565 60 0.22 0.05

Tanwax peat, alkaline variant 0.103 84 0.23 0.81

1

 Source: Soil Conservation Service, 1962, and digital coverages from the Washington State Department of Natural Resources Geographic Information 

System Division.

2 When soil consists of more than one layer, the average property for the entire soil column is computed by weighting the property of each layer by the 

thickness of the layer.

Groupings and physical properties of Soil Conservation Service (SCS) soil series occurring on Lopez, Orcas, Shaw, and San 

Juan Islands, Washington

[--, not applicable]

Depth Thickness-weighted Weighted averfrom average available water- age vertical

Soil group Area surface holding capacity 2 permeability

and SCS soil series1 (square mile) (inches) (inch per inch) (feet per day)

Figure 7.—Continued.
22 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Land Cover and Vegetation

Land-cover information for the study area was 

obtained from GIS coverages prepared by the USGS 

National Mapping Division for the Puget Sound 

NAWQA program. The coverages were developed 

from Landsat Thematic Mapper satellite data collected 

at a 30-meter resolution during the early 1990s 

(Vogelmann and others, 1998). There are 19 categories 

of land cover in the GIS data. Fourteen of those occur 

in the study area.

The DPM, however, does not allow all these 

categories. Therefore, each of the 14 GIS categories 

was approximated with seven of the most similar DPM 

categories (table 6 and fig. 8). 

The DPM contains default values of maximum foliar 

cover and maximum root depth, but these can be 

replaced with more appropriate values by the user 

(Bauer and Vaccaro, 1987). A 100-percent foliar 

cover value was used for all land uses, and 

maximum root depths were set at 5 feet for all nonagricultural, native vegetation land uses, 5 feet for 

alfalfa, and 3 feet for grasses and annual crops. The 

5-foot depth for native vegetation and alfalfa 

generally corresponds with the deepest reported soil 

depths of the predominant soils, the 3-foot depth for 

grasses is from Bauer and Mastin (1997) and the 3-

foot depth for annual crops is from James and others 

(1988). Where maximum root depths exceed the soil 

depth, the DPM automatically truncates the 

maximum root depth to the soil depth.

Land-Surface Altitude

Land-surface altitude data for the study basins 

were in the form of USGS 10-meter-resolution 

digital elevation models (DEMs) obtained from the 

University of Washington (2001). The DEMs were 

then converted into contour maps using GIS. The 

contour maps were checked for data reliability 

against USGS 7.5-minute quadrangle maps of the 

area. Average land-surface slope and aspect for 

model cells were not used in this application of the 

DPM.

Two other land-surface parameters that are 

used in the model for simulating direct runoff are a 

measure of the distance between the smallest 

drainage channels in the basin, and the slope 

between such channels and the drainage divides 

separating them (Bauer and Mastin, 1997). Values 

for these parameters were taken from Bauer and 

Mastin (1997) in their study in western Washington 

because both areas were subject to the last glaciation 

and their topographical features are similar.

Table 6. Reclassification of original land-use data to landcover categories used by the Deep Percolation Model (DPM) 

for Lopez, San Juan, Orcas, and Shaw Islands, San Juan 

County, Washington

[Original classification of land-use categories: Land-use data from GIS 

coverages derived from Landsat Thematic Mapper satellite data (Vogelmann 

and others, 1998)] 

Original classification of 

land-use categories

Grouped land-cover 

categories used for DPM

Evergreen forest Evergreen forest

Forest Evergreen forest

Low intensity residential Grassland

Natural grasslands Grassland

Grasses, other (parks, lawns, 

golf courses)

Grassland

Wetlands (woody wetlands) Grassland

Grass Grassland

Deciduous forest Orchard and deciduous forest

Natural shrubland, deciduous Orchard and deciduous forest

Maple trees etc. Orchard and deciduous forest

Grasses, pasture/hay Pasture/hay

Row crops Row crops

Small grains Wheat

Surface water, developed 

commercial/industrial, 

transitional, quarries/strip 

mines/gravel pits, bare, 

rock/sand, planted, bare soil

Surface water1

1Land-cover categories allowed in DPM described in Bauer and 

Vaccaro (1987). The DPM computationally treats impervious surfaces the 

same as surface water.
Estimates of Ground-Water Recharge 23

Figure 8. Areal distribution of land cover reclassified for the Deep Percolation Model for Lopez, San Juan, Orcas, 

and Shaw Islands, San Juan County, Washington.
24 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Streamflow

Streamflow was measured during water years 

1997-98 at the mouth of each of the six study basins 

using flow-control structures that provided accurate 

and constant stage-discharge relations. The streamflow 

measurements are summarized in table 7.

For basins L1, L3, OR1, and SH1, the flowcontrol structures consisted of pre-existing road 

culverts. For basin L2, a temporary V-notch weir was 

constructed by the USGS. For basin SJ1, a permanent 

V-notch weir was constructed by the Town of Friday 

Harbor Utilities Department according to specifications 

provided by the USGS. The V-notch weir for the SJ1 

basin was not completed until December 1996, so the 

early 1997 water-year data for the basin were estimated 

using a regression relation developed from the 

available SJ1 data and data collected at the OR1 basin 

(streamflow pattern in OR1 basin is similar to that of 

SJ1).

The streamflow hydrographs reflect the distinct 

characteristics of the study basins (fig. 9). Basins L1 

and L2 are entirely overlain by glacial deposits and 

total streamflow per unit area is less and streams are 

dry for longer periods than in the other four basins, 

which are underlain by bedrock just beneath the soil 

cover and have some exposed bedrock at the surface 

(see table 1). The characteristics of the basins with 

glacial deposits reflect, in part, the fact that the glacial 

deposits allow greater quantities of deep vertical 

infiltration of soil water that subsequently recharges the 

aquifers beneath the basin and flows out of the basin 

through the aquifers. Soils generally are thicker and 

have higher available water-holding capacities. As a 

result, more of the precipitation is temporarily stored in 

these soils, which subsequently results in greater 

amounts of evapotranspiration, which also causes less 

direct stream runoff.

Table 7. Summary of streamflow measured for the six study basins on Lopez, San Juan, Orcas, and Shaw Islands, water 

years 1997-98

[Study basin: Location of study basins are shown in figure 5. Discharge: Expressed as depth of water over the area of the study basin. Annual discharge and 

mean daily discharge: Values in these columns do not exactly agree with 1997 and 1998 values published by Wiggins and others (1998; 1999) due to 

refinements of study basin drainage area measurements made after 1996. Abbreviations: USGS, U.S. Geological Survey; mi2, square mile]

Study

basin

(fig. 5)

USGS

streamflowgaging 

station No.

Basin 

area

(mi2)

Water

year

Annual

discharge

(inch)

Mean discharge Highest daily

mean discharge

inch

per day

cubic foot

per second

inch

per day

cubic foot

per second

L1 12200733 0.45 1997 5.43 0.0149 0.18 0.760 9.2

1998 0.51 0.0014 0.017 0.036 0.43

L2 12200730 1.63 1997 7.42 0.0203 0.89 0.386 16.9

1998 0.57 0.0016 0.068 0.024 1.05

L3 12200728 0.66 1997 9.67 0.0265 0.47 1.465 26.0

1998 2.47 0.0068 0.12 0.885 1.57

SJ1 12200750 0.50 1997 16.03 0.0439 0.59 1.101 14.8

1998 7.61 0.0208 0.28 0.209 2.81

OR1 12200762 0.57 1997 16.20 0.0444 0.68 1.566 24.0

1998 4.77 0.0131 0.20 0.134 2.06

SH1 12200737 0.26 1997 6.79 0.0186 0.13 0.744 5.20

1998 2.40 0.0066 0.046 0.080 0.56
Estimates of Ground-Water Recharge 25

Basin L1

(Glacial deposits)

Basin L2

(Glacial deposits)

Basin L3

(Bedrock)

0.0001

0.001

0.01

0.1

1.0

0.0001

0.001

0.01

0.1

1.0

0.0001

0.001

0.01

0.1

1.0

MEAN DAILY DISCHARGE, IN INCHES PER DAY

O N D J FMAMJ J A S ON DJ FMA M J J A S

1996 1997 1998

Figure 9. Streamflow for the six study basins on Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington, 

water years 1997-98.

Because of a lack of data, streamflow in basin SJ1 was estimated for October 1–November 31, 1996.
26 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Figure 9.—Continued

0.0001

0.001

0.01

0.1

1.0

0.0001

0.001

0.01

0.1

1.0

MEAN DAILY DISCHARGE, IN INCHES PER DAY0.0001

0.001

0.01

0.1

1.0

O N D J FM A M J J A SO N D J F M A M J J A S

1996 1997 1998

Basin SH1

(Bedrock)

Basin OR1

(Bedrock)

Basin SJ1

(Bedrock)
Estimates of Ground-Water Recharge 27

Of the basins underlain by bedrock, L3 and SH1 

have no streamflow during the driest months of the 

year, whereas basins SJ1 and OR1 have streamflow all 

year (fig. 9). Basins SJ1 and OR1 lie at higher altitudes 

than the other basins, have more rugged topography, 

and receive more precipitation. The more deeply 

incised stream channels for these two basins probably 

are draining part of the water table. Such drainage is 

commonly referred to as baseflow, which is defined as 

that part of streamflow coming from ground-water 

seepage into a stream (U.S. Geological Survey, 2001). 

Daily baseflow quantities for SJ1 and OR1 were 

estimated and used in the DPM as one of the timeseries data inputs.

Baseflow was estimated by constructing a 

baseflow hydrograph from the hydrograph of the total 

streamflow. Total streamflow was assumed to be equal 

to baseflow during the summer seasons when 

precipitation was scarce and the soils were below field 

capacity, as evidenced by precipitation producing little 

or no streamflow response. A smooth baseflow curve 

was drawn for this period and then extended backward 

in time, using minimum wet-season flows from the 

total-flow hydrograph as maximum allowable baseflow 

values. The baseflow curve also was constrained to 

merge smoothly into the streamflow hydrograph of the 

previous dry season. Daily values were then read from 

the constructed baseflow curve.

Model Calibration

After the data were compiled, checked for 

accuracy, and assigned to the cells, the DPM was 

operated for each of the six study basins. For each 

study basin, various DPM parameters and an initial 

condition were adjusted in order to achieve a balance 

between the measured and simulated daily flows and 

fluxes of water (see "Near-Surface Water-Balance 

Method" section). Such a balance was achieved 

primarily by adjusting values assigned to the vertical 

hydraulic conductivity of the subsoil and less 

significantly to the soil properties and initial moisture 

conditions. Glacial deposits contain areas of three 

hydraulically distinct materials; clay, glacial till, and 

glacial outwash. All bedrock was assumed to be 

hydraulically similar. Soils underlain by bedrock or 

clay material generally allow less recharge because 

they have lower vertical hydraulic conductivities than 

soils underlain by glacial-deposit material. 

The subsoil material of each of the basins and islands 

was determined from the Soil Conservation Service 

(1962) and Jones (1999). Study basins L3, SJ1, OR1, 

and SH1 are underlain by bedrock beneath generally 

thin soils, whereas study basins L1 an L2 are underlain 

by glacial till, glacial outwash, and clay beneath thick 

soils.

The vertical hydraulic conductivities of subsoils 

composed of glacial till, glacial outwash, and clay were 

adjusted to 10, 100 and 4 inches per year, respectively. 

For bedrock, the vertical conductivity was adjusted to 1 

inch per year except for study basin SH1, which 

required a value of 3 inches per year. The value used 

for till falls within the range used by Bauer and Mastin 

(1997). The value of 100 inches per year used for 

glacial outwash is smaller than typical published values 

for similar materials. Assuming a 100:1 anisotropy, the 

value used lies at the lower hydraulic conductivity 

range for a clean sand (Freeze and Cherry, 1979). 

However, if values for outwash materials 

commensurate with published values were used, a 

poorer DPM calibration resulted because simulated 

direct runoff would be zero for such areas, when, in 

fact, there was some runoff during periods of heavy 

precipitation. Probably, the overlying soils, which have 

smaller hydraulic conductivities than the subsoils in 

these areas, limit the downward movement of water, 

rather than the subsoil, and produce runoff during 

periods of heavy precipitation. Because this process is 

not explicitly simulated in the DPM, the assignment of 

an artificially lower infiltration rate to the subsoil was 

required to produce an equivalent result. The hydraulic 

conductivity used for bedrock is at the low end of 

typical published values for fractured igneous and 

metamorphic rocks (Freeze and Cherry, 1979). This is 

reasonable, considering that the uppermost few inches 

of fractures in the bedrock probably are filled with fine 

particulate material that would decrease the overall 

hydraulic conductivity of the near-surface bedrock.

Additional adjustments required to achieve 

calibration were as follows.

• Soil depths for the study basins with shallow 

bedrock generally decreased by as much as 25 

percent from reported values. This adjustment also 

produced a better overall match between the 

quantities and timing of simulated and measured 

direct runoff.
28 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

• The horizontal hydraulic conductivities of the 

soils generally were set to as much as two orders 

of magnitude greater than the reported vertical 

hydraulic conductivities.

• To run the DPM, initial water contents of the soils 

must be specified. The amount of soil water is 

expressed as a fraction of the available waterholding capacity (unsaturated soil) and, for very 

wet conditions, as a fraction of specific yield 

(saturated soil). The start of the simulation for the 

six basins was October 1, 1996. In western 

Washington, non-irrigated soils are usually 

extremely dry by the first of October, and 

therefore, the initial soil moisture was first set to 

zero for all study basins. However, reasonable 

matches could not be obtained between the onset 

of simulated and measured direct stream runoff. 

The first simulated direct runoff for a basin 

typically would not occur until about a month after 

the first measured direct runoff. Inspection of 

precipitation records prior to October revealed that 

September had about twice the normal 

precipitation, suggesting that a non-dry initial soil 

moisture be used. A few trial-and-error DPM 

simulations revealed that an average initial 

unsaturated soil moisture of about 30 percent of 

available water-holding capacity gave a more 

reasonable match between the onset of simulated 

and measured direct stream runoff. Initial 

conditions errors may cause errors in the water 

budget, however such errors diminish as the 

simulation progresses. Tests have shown that after 

1 year of simulation time, there are no subsequent 

errors due to incorrect initial conditions. 

Therefore, when parameter adjustments were 

made that could not satisfy the water balance of 

both water years, preference was given to the 1998 

water year.

• A period of freezing temperatures limited 

infiltration of precipitation from December 26, 

1996, to January 2, 1997, and for a short period 

before the ground thawed. To simulate these 

conditions, the hydraulic conductivity of the 

subsoils was set to 0 inches per year during that 

time. The freezing temperatures and a subsequent 

heavy snow storm also adversely affected the 

quality of the data during this period. This also 

was cause for bias toward the 1998 water year 

during calibration.

For two of the study basins, L1 and OR1, the 

water budgets (including the "deficit" term) simulated 

by the DPM did not achieve an accurate mass balance, 

due to accumulation of computational roundoff errors. 

Therefore, all cells with identical properties were 

aggregated into single cells for these two study basins, 

thereby reducing the number of cells to 18 and 7 for 

study basins L1 and OR1, respectively. Because 

proportionately fewer computations are executed, the 

mass-balance error was reduced to an insignificant 

amount. Each of these larger cells represents many of 

the original cells that may or may not be connected. 

The locations for the larger cells were computed by 

averaging the location of the smaller cells that they 

represent. Because of the small size of the study basin, 

any error resulting from the more approximate 

interpolation of weather station data to the cells was 

assumed to be insignificant. 

After calibration, the average simulated annual 

deep percolation values for the six study basins from 

October 1996 to September 1998 were as follows.

The simulated annual water-budget components 

and the 2-year averages for each basin for the datacollection period are summarized in table 8. The output 

summary tables of the DPM simulations for the study 

basins, which present a more detailed breakdown of the 

simulated water-budget components on a monthly 

basis, are shown in tables 17-22 (at back of report).

L1 2.67 inches per year

L2 2.78 inches per year

L3 0.35 inch per year

SJ1 0.45 inch per year

OR1 0.27 inch per year

SH1 1.27 inches per year
Estimates of Ground-Water Recharge 29

As previously discussed, calibrating the water 

budgets for the study basins involves minimizing the 

soil-saturation deficit, which is the difference between 

precipitation and the sum of the other water-budget 

components (last column on tables 17-22). A zero 

deficit for all years for all basins was not possible to 

achieve because changing a parameter that is common 

to multiple basins often improves the water budget for 

one basin but worsens it in another. Similarly, 

improvement in one year often worsens the next or 

previous year. A considerable degree of "hydrologic 

judgment" is used during the calibration process, and 

results would probably vary slightly from one 

hydrologist to another.

Table 8. Summary of annual water-budget components using the Deep Percolation Model for the six study basins on Lopez, 

San Juan, Orcas, and Shaw Islands, San Juan County, Washington, water years 1997-98

[Study basin–geologic material: Location of study basins are shown in figure 5. Interception loss: May include small amounts of simulated snow 

evaporation. Components of water budget: Sum of interception loss, transpiration, direct runoff, deep percolation, change in soil moisture, and soil 

saturation deficit may not exactly equal precipitation because of roundoff errors]

Study 

basin – 

geologic 

material

Water

year

Precipitation Components of water budget (all values in inches)

Inches

Percentage 

of long-term 

average

Interception loss

Simulated 

transpiration

Direct

runoff

Simulated 

deep

percolation

Simulated 

change

in soil

moisture

Soilsaturation

deficit

L1, 1997 30.04 107 7.13 14.38 5.53 3.29 -0.33 0.00

Glacial 1998 20.54 73 5.99 13.17 0.52 2.06 -1.20 0.02

deposits avg 25.29 90 6.56 13.77 3.02 2.67 -0.77 0.01

L2, 1997 30.37 110 6.63 13.46 7.61 2.71 0.40 -0.50

Glacial 1998 20.88 76 5.48 13.14 0.58 2.86 -1.18 0.01

deposits avg 25.63 93 6.06 13.30 4.10 2.78 -0.39 -0.24

L3, 1997 28.98 107 6.82 12.88 9.76 0.31 -0.08 -0.73

Bedrock 1998 20.07 74 6.12 11.92 2.54 0.40 -0.93 0.00

avg 24.53 91 6.47 12.40 6.15 0.35 -0.50 -0.37

SJ1, 1997 38.31 124 10.70 10.20 15.90 0.43 0.25 0.54

Bedrock 1998 23.54 76 8.36 8.90 6.60 0.47 -0.88 -0.13

avg 30.92 100 9.53 9.55 11.25 0.45 -0.31 0.21

OR1 1997 34.90 116 9.73 12.26 14.60 0.28 -0.47 -1.84

Bedrock 1998 21.44 71 7.48 10.70 3.88 0.26 -0.94 -0.17

avg 28.17 94 8.60 11.48 9.24 0.27 -0.70 -1.01

SH1 1997 31.96 110 11.23 12.69 6.64 1.49 -0.25 0.15

Bedrock 1998 20.84 72 8.45 10.09 2.36 1.04 -1.08 -0.01

avg 26.40 91 9.84 11.39 4.50 1.27 -0.66 0.07
30 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

The average annual absolute deficit for the two 

glacial drift study basins for water years 1997-98 is 

0.12 inch, which compares favorably with the average 

simulated deep percolation 2.73 inches, suggesting an 

average uncertainty of about 4 percent.

The average annual absolute deficit for the four 

bedrock study basins for both years is 0.42 inch, which 

compares with an average annual deep percolation of 

0.59 inch for these basins. Even though the values of 

these deficits are small in comparison to the main 

water-budget components, an uncertainty in deep 

percolation of about 72 percent is suggested. Given the 

accuracy of the data components and the small 

magnitude of the simulated deep percolation, however, 

it probably is not possible to achieve better accuracy 

using this method. Sources of error are discussed more 

fully in the section "Sources of Uncertainty in the DPM 

Recharge Estimates."

Recharge in relation to the other water-budget 

components on a monthly basis for each of the six 

study basins is shown in figure 10. Deep percolation 

primarily occurs from November through March, with 

minor amounts sometimes occurring into April and 

May. Although precipitation is relatively high in 

October, deep percolation does not occur because the 

soils absorb most of this moisture due to their dried out 

condition from the previous dry months.

During April through August, evapotranspiration 

greatly exceeds precipitation, thereby depleting the 

moisture in soils. The relation between runoff and deep 

percolation also is evident. After the soils accumulate 

sufficient moisture in the autumn, a small amount of 

deep percolation usually precedes the onset of runoff. 

Thereafter, a greater rate of monthly deep percolation 

ensues but remains steady even though the runoff may 

vary greatly. For example, the monthly deep 

percolation in study basin L1 is about the same from 

January through March 1997, but the monthly runoff 

varies by a factor of more than six. This is due to the 

fact that the infiltration capacity of the subsoil imposes 

an upper limit on the deep percolation rate. This 

process is even more pronounced for study basins L3, 

OR1, SJ1, and SH1, where soils are underlain by 

bedrock. The bedrock imposes an even smaller upper 

limit on the deep percolation rate, which remains 

nearly constant from November through March or 

April.

Estimating Island-Wide Recharge for Lopez, San 

Juan, Orcas, and Shaw Islands Using Deep 

Percolation Model and Results from Study Basins

After the DPM was calibrated for the six study 

basins, the modified input values and parameters were 

used in the DPM simulations of the entire areas of each 

of the four islands in the study area: Lopez, San Juan, 

Orcas, and Shaw Islands. Except for streamflow data 

(see “Near-Surface Water-Balance Method” section), 

input data for the island-wide DPM simulations were 

compiled in much the same manner as for the studybasin simulations. The 11 soil groups and seven landuse categories described earlier were used in the DPM 

in the distributions for each island shown in table 9 and 

table 10 and fig. 7 and fig. 8. On an island-wide basis, 

distance-interpolated precipitation from data collected 

would not be fully representative of certain areas, 

especially in the high, mountainous terrain of Orcas 

Island. However, if average annual precipitation values 

for cells and for data-collection sites are input, the 

DPM makes an additional correction to each daily 

distance-interpolated cell value based on the ratios of 

the average annual cell precipitation to the average 

annual precipitation data at the sites. Therefore, 

average annual precipitation data for the cells were 

estimated from the annual precipitation data averaged 

over the most recent climate normal period, 1961- 90 

(Oregon Climate Service, 1999). Daily precipitation 

values were interpolated from the three tipping-bucket 

gages. Daily throughfall values were interpolated from 

all three data-collection sites, and daily solar shortwave 

radiation and air temperature values were interpolated 

from the temporary micrometeorological data stations 

on Lopez and Orcas Islands. The distance 

interpolations of these data across all cells are 

performed by the DPM. Calibrated vertical hydraulic 

conductivities of the subsoil, soil depth, and lateral 

permeability of the soil were taken from the six study 

basins for the corresponding subsoil materials and soil 

types.
Estimates of Ground-Water Recharge 31

OND J J FM AM A SO N D J FM AM A S J J J

WATER YEAR 1997 WATER YEAR 1998

AM0UNTS OF WATER, IN INCHES PER MONTH

0

2

6

4

0

2

6

4

0

2

6

8

4

Precipitation

Recharge

Runoff

Evapotranspiration

Basin L1

Basin L2

Basin L3

Figure 10. Monthly water-budget components for the six study basins on Lopez, San Juan, Orcas, and Shaw Islands, 

San Juan County, Washington, water years 1997-98.
32 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington AM0UNTS OF WATER, IN INCHES PER MONTH

0

2

8

10

6

4

OND J J FM AM A SO N D J FM AM A S J J J

WATER YEAR 1997 WATER YEAR 1998

0

2

6

8

4

0

2

6

4

Precipitation

Evapotranspiration

Recharge

Runoff

Basin SH1

Basin SJ1

Basin OR1

Figure 10.—Continued.
Estimates of Ground-Water Recharge 33

Table 9. Soil types assigned to Lopez, San Juan, Orcas, and Shaw Islands for use in the Deep Percolation Model, 

San Juan County, Washington

[Soil type: Letter corresponds to composite soil group shown in a tabular explanation in figure 7. All values rounded to two significant figures: 

Because of rounding, area totals may not agree exactly with other tables and percentage of values may not total exactly 100 percent. 

Abbreviations: mi2, square mile]

Soil type

Lopez Island San Juan Island Orcas Island Shaw Island

Area

(mi2)

Percentage 

of total 

basin area

Area

(mi2)

Percentage 

of total

basin area

Area

(mi2)

Percentage 

of total

basin area

Area

(mi2)

Percentage

of total 

basin area

Bedrock

A 0.48 1.6 0.49 0.89 1.2 2.02 1.2 16

B 0.45 1.5 1.4 2.6 0.82 1.44 1.2 16

C 0.14 0.48 0.26 0.47 0.75 1.33 0.04 0.53

D 0.28 0.95 1.6 2.9 27 48 0.06 0.79

E 1.0 3.5 2.3 4.1 2.0 3.5 0.00 0.00

F 0.76 2.6 3.9 7.1 1.4 2.4 0.05 0.66

G 3.8 13 14 25 7.0 12 3.8 50

H 0.68 2.3 4.9 8.9 2.8 4.9 0.00 0.00

I 0.22 0.75 0.41 0.78 0.02 0.04 0.00 0.00

J 0.00 0.00 0.12 0.22 0.02 0.04 0.02 0.26

K 0.00 0.00 0.01 0.02 0.07 0.12 0.01 0.13

Glacial Deposits

A 4.6 16 2.0 3.7 1.7 3.0 0.30 4.0

B 4.0 14 5.8 11 2.6 4.5 0.68 9.00

C 1.7 5.9 0.52 0.95 0.75 1.3 0.04 0.53

D 0.83 2.8 4.0 7.3 2.4 4.2 0.01 0.13

E 6.2 21 3.7 6.7 3.3 5.7 0.00 0.00

F 2.6 8.9 4.7 8.6 1.4 2.4 0.00 0.00

G 0.59 2.00 2.9 5.3 1.4 2.5 0.14 1.8

H 0.08 0.27 0.08 0.15 0.04 0.07 0.00 0.00

I 0.16 0.55 1.1 2 0.10 0.18 0.00 0.00

J 0.41 1.4 1.1 2 0.09 0.16 0.02 0.26

K 0.32 1.1 0.05 0.09 0.20 0.35 0.01 0.13

Totals 29.19 54.88 57.19 7.52
34 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

The simulated average annual recharge for each 

island in the study area for water years 1997-98 was 

The areal distribution of the simulated average 

annual recharge for each island (fig. 11) reflects not 

only the variation in the amount of precipitation (fig. 4) 

but also the different underlying materials, bedrock or 

glacial deposits (fig. 5). Recharge generally is greater 

in areas of glacial deposits than in areas of bedrock. 

Lopez Island, which receives the least precipitation, 

has the greatest amount of recharge per square mile 

because of the predominance of glacial deposits. 

Simulated reacharge in areas of shallow to outcropping 

bedrock generally is less than 1.5 inches per year. The 

DPM-simulated recharge on the glacial-deposit areas 

generally ranges from less than 0.5 to about 3 inches 

per year, but in some small areas where shallow sandy 

soils overlie permeable outwash deposits recharge is as 

high as 9 inches per year. This compares with generally 

greater estimates of recharge for glacial-deposit areas 

in the San Juan Islands presented in Vaccaro and others 

(1998, fig. 13) as broad ranges of values-from 1 to 11 

inches per year.

In order to assess the validity of the island-wide 

simulations, the study-basin recharge quantities were 

compared with the island-wide recharge quantities in 

the comparable areas. The following is a comparison 

of the 2-year average recharge values from the studybasin DPM simulations and for the study-basin areas 

within the island-wide DPM simulations.

From these comparisons, recharge values from 

the island-wide recharge simulations appear to be 

somewhat greater than those from the study basins; 

about 23 and 1 percent, on average, for the glacial 

deposits and bedrock areas, respectively.

Lopez Island 2.49 inches per year;

San Juan Island 1.99 inches per year;

Orcas Island 1.46 inches per year;

Shaw Island 1.44 inches per year.

Study 

basin

Average annual recharge 

for water years 1997-98, 

in inches

Study basin 

simulated 

recharge

Study basin 

recharge from 

island-wide 

simulation

L1 2.67 3.35

L2 2.78 3.70

L3 0.35 0.86

SJ1 0.45 0.58

OR1 0.27 0.34

SH1 1.27 0.58

Table 10. Land-cover groups assigned to Lopez, San Juan, Orcas, and Shaw Islands for use in the Deep Percolation Model, 

San Juan County, Washington

[Land cover: Distribution of land cover is shown on figure 8. All values rounded to two significant figures. Because of rounding, area totals may not agree 

exactly with other tables and percent values may not total exactly 100 percent. Abbreviations: mi2, square mile]

Land cover

(fig. 8)

Lopez Island San Juan Island Orcas Island Shaw Island

Area 

(mi2)

Percentage 

of total 

basin area

Area

(mi2)

Percentage 

of total

basin area

Area

(mi2)

Percentage 

of total

basin area

Area

(mi2)

Percentage 

of total

basin area

Evergreen forest 17 58 29 52 46 79 6.2 81

Grassland 3.3 10 3.1 5.5 1.4 2.3 0.43 5.6

Deciduous forest and 

shrubland

3.1 10 8.9 16 6.1 10 0.59 7.7

Pasture/hay 5.2 18 11 21 2.6 4.6 0.25 3.2

Row crops 0.08 0.27 0.42 0.76 0.09 0.16 0.00 0.00

Wheat 0.19 0.64 0.26 0.47 0.12 0.21 0.01 0.13

Surface water 0.81 2.7 2.3 4.2 1.8 3.2 0.18 2.4

Totals 30 55 58 8.7
Estimates of Ground-Water Recharge 35

EXPLANATION

AVERAGE ANNUAL RECHARGE, 

 IN INCHES 

STUDY BASIN

Surface-water body 

 or recharge equals 0

Less than 0.5

0.5 to less than 1

1 to less than 1.5

1.5 to less than 2

2 to less than 2.5

2.5 to less than 3

3 to less than 3.5

3.5 to less than 4

4 to less than 4.5

4.5 to less than 5

5 to less than 5.5

5.5 to less than 6

6 to less than 6.5

7.5 to less than 8

8 to less than 8.5

8.5 to less than 9

9 to less than 9.5

Equal to or greater than 9.5

Lopez Island

122°56'45" 122°48'45"

48°33'45''

48°26'15''

0 1 2 3 MILES

0 1 2 3 KILOMETERS

Figure 11. Areal distribution of simulated average annual recharge for Lopez, San Juan, Orcas, and Shaw Islands, 

San Juan County, Washington, water years 1997-98.
36 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

123°07'30" 123°01'15"

48°

37'

30''

48°

30'

0 1 2 3 4 5 MILES

0 1 2 3 4 5 KILOMETERS

EXPLANATION

AVERAGE ANNUAL 

 RECHARGE, 

 IN INCHES 

Surface-water body

 or recharge equals 0

Less than 0.5

0.5 to less than 1

1 to less than 1.5

1.5 to less than 2

2 to less than 2.5

2.5 to less than 3

3 to less than 3.5

3.5 to less than 4

4 to less than 4.5

4.5 to less than 5

5 to less than 5.5

5.5 to less than 6

6 to less than 6.5

6.5 to less than 7

7 to less than 7.5

7.5 to less than 8

8 to less than 8.5

8.5 to less than 9

San Juan Island

STUDY BASIN

Figure 11.—Continued
E

stimatesofGround-WaterRecharge37

123° 122°45'

48°

32'

30''

48°

36'

15''

0 1 2 3 4 5 MILES0 1 2 3 4 5 KILOMETERS

Orcas Island

Figure 11.—Continued
38 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington EXPLANATION AVERAGE ANNUAL RECHARGE, IN INCHES Surface-water body or recharge equals 0 Less than 0.5 0.5 to less than 1 1 to less than 1.5 1.5 to less than 2 2 to less than 2.5 3.5 to less than 4 4 to less than 4.5 4.5 to less than 5 5 to less than 5.5 5.5 to less than 6 6 to less than 6.5 6.5 to less than 7

7 to less than 7.5

123° 122°56'15"

48°

32'

30"

48°

35'

0 1 2 3 MILES0 1 2 3 KILOMETERS

Shaw Island

STUDY BASIN

Figure 11.—Continued
Estimates of Ground-Water Recharge 39

The DPM simulated water-budget components 

for the 1997 and 1998 water years for each of the four 

main islands are summarized in table 11. Because 

water year 1997 was much wetter (from 9.6 to 14.8 

inches more) than water year 1998, the DPM simulated 

recharge was greater on all islands for water year 1997 

than for water year 1998. The differences in recharge 

were greater for Lopez and San Juan Islands (1.09 and 

0.49 inches difference, respectively) than for Orcas and 

Shaw Islands (0.27 and 0.37 inches difference, 

respectively) because the mostly bedrock subsoils of 

Orcas and Shaw Islands impose smaller upper limits on 

the amount of deep percolation that can occur for a 

given period (see the section "Model Calibration" for 

discussion on limits on infiltration).

The question arises about how different the longterm recharge may be from this 2-year average 

recharge due to the difference in long-term 

precipitation from the 2-year average precipitation? 

The 2-year average precipitation for the four islands 

was only 6 to 10 percent less than the long-term 

average. If the ratio of the differences in recharge to the 

differences in precipitation from water year 1997 to 

water year 1998 is applied to the differences between 

long-term precipitation and the average 2-year 

precipitation for each of the main islands, then the 

long-term average annual recharge would be 0.26 inch 

(10 percent), 0.0 inch (0 percent), 0.04 inch (3 percent), 

and 0.01 inch (1 percent) more than the 2-year recharge 

values for Lopez, San Juan, Orcas, and Shaw Islands, 

respectively.

The output summary tables of the island-wide 

DPM simulations, which present a more detailed 

breakdown of the water-budget components on a 

monthly basis, are shown in tables 23-26 (at back of 

report).

Table 11. Summary of annual water-budget components using the Deep Percolation Model for Lopez, 

San Juan, Orcas, and Shaw Islands, San Juan County, Washington, water years 1997-98

[Components of water budget: Sum of interception loss, transpiration, direct runoff, deep percolation, change in soil moisture, and 

soil saturation deficit may not exactly equal precipitation because of roundoff errors. Interception loss: May include small amounts 

of simulated snow evaporation] 

Island Water

year

Precipitation,

inches

Water-budget components (all values in inches)

Interception

loss

Simulated 

transpiration

Simulated

direct

runoff

Simulated 

deep

percolation

Simulated 

change

in soil

moisture

Lopez 1997 30.65 6.73 14.22 5.59 3.03 0.68

1998 21.05 5.86 12.20 2.15 1.94 -1.46

avg 25.85 6.29 13.21 3.87 2.49 -0.39

San Juan 1997 34.99 8.24 13.40 9.77 2.24 0.48

1998 23.59 6.73 11.65 4.10 1.75 -1.39

avg 29.29 7.49 12.52 6.93 1.99 -0.46

Orcas 1997 40.37 9.64 13.48 14.50 1.60 0.59

1998 25.53 7.62 11.61 6.08 1.33 -1.65

avg 32.95 8.60 12.54 10.29 1.46 -0.53

Shaw 1997 34.12 10.79 13.06 8.52 1.62 -0.10

1998 22.47 8.40 10.64 3.11 1.25 -1.14

avg 28.29 9.59 11.85 5.81 1.44 -0.62
40 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Sources of Uncertainty in the DPM Recharge 

Estimates

Although uncertainties in recharge estimates 

using the DPM could not be quantified, sources of 

uncertainty fall into three main groups: 

1. errors in data and estimated parameters that affect 

reliability of estimates of downward drainage 

beneath the root zone as simulated by the DPM; 

2. assumptions concerning equivalency of downward 

drainage from the root zone and recharge to 

ground water; and 

3. assumptions involved with scaling up results from 

study basins to estimate annual recharge for the 

entire study area.

These are discussed as follows:

1. Several sources of error are associated with fielddata collection of water-budget components for the 

study basins.

• Precipitation can vary greatly from one location to 

another for any particular storm. Therefore, an 

error in the water budget can develop when 

precipitation and throughfall data at one or two 

measuring points are used to represent the 

precipitation and throughfall for a drainage basin. 

Moreover, forest throughfall data are subject to 

additional error because of the wide variety of 

vegetation, age, density, and species in forested 

areas. The data-collection sites selected may or 

may not be fully representative of the larger 

forested areas.

• The best streamflow data, using the methods in 

this study, are considered accurate to only about 5 

percent, and due to the small streamflow values 

measured in this study, probably only a 10-percent 

accuracy was achieved.

• A reliable means for computing direct runoff from 

total streamflow is not available, and subjective 

estimates of baseflow were used. This source of 

error only occurs for study basins SJ1 and OR1, 

which have baseflow. For the glacial-deposit study 

basins L1 and L2, there was no baseflow during 

the period of the study. This is because the water 

table on Lopez Island is mostly just a few feet 

above sea level (Orr, 2000, table 1), whereas landsurface altitudes of these study basins range 

upwards from about 120 feet above sea level. 

Baseflow for the bedrock study basins L3 and SH1 

was assumed to be zero because total streamflow 

during the summer months was zero as for study 

basins L1 and L2.

• Errors in assignments to DPM parameters used to 

characterize soil and plant properties could have 

caused errors in the modeled partitioning of the 

water budget and ultimately recharge.

• Little published information exists concerning 

evapotranspiration in western Washington with 

which to verify the estimates in this study. 

Simulated transpiration in this study accounted for 

a substantial percentage (from 31 to 54 percent) of 

precipitation on an average annual basis. However, 

during the dormant winter periods, transpiration 

error relative to precipitation is small because 

transpiration is small. Moreover, even though 

daily simulations of evapotranspiration may 

contain error, the total seasonal evapotranspiration error probably is small during 

summer and early autumn because nearly all 

precipitation and available soil moisture is 

transpired during this time. Error in transpiration 

during times when soil moisture is at field 

capacity during the growing season would result in 

the greater errors in simulated recharge. 

Therefore, the greater potential for error in 

simulated recharge is during the months of March 

through June.

2. Equating recharge to ground water to downward 

flow beneath the root zone also could lead to errors 

in recharge. In most environments, water that 

percolates below a few meters from the soil 

surface is destined to recharge a saturated system 

(arid environments can be an exception). However, 

a hydrogeologic system can contain multiple 

unsaturated zones that are separated by watersaturated zones. The arrangement and thicknesses 

of saturated and unsaturated zones in glacialdeposit areas may be complex. As a result, not all 

water that percolates downward beneath a root 

zone necessarily becomes recharge to the 

uppermost saturated zone that has been identified 

in the hydrogeologic framework. For example, 

water percolating through predominantly 

unsaturated materials beneath a root zone, upon 

meeting a layer of fine-grained sediments with low 

hydraulic conductivity, could recharge a thin 

saturated zone not tapped by wells, flow laterally, 

and discharge to a stream or spring. 
Estimates of Ground-Water Recharge 41

The water in this example might not reach the 

saturated ground-water system that is used as a 

source of water to wells.

3. Error may result from extending the recharge 

results from the study basins to estimating the 

island-wide recharge. Parameters that control 

recharge and direct runoff were assumed to be 

identical for similar geologic, soil, land-cover, and 

precipitation conditions. Without measurements of 

streamflow for all drainage basins, this assumption 

could lead to errors, especially with regard to 

mapped geologic conditions, which generally are 

extrapolated from only a few observable locations. 

For example, an area that may be mapped as 

glacial till for the surficial deposits may, in part, be 

underlain by a channel deposit of clean sand and 

gravel. This would result in local recharge errors 

approximately comparable to the range in recharge 

depicted on figure 11. 

Chloride Mass-Balance Method

The chloride mass-balance method was used as a 

second, independent means of estimating recharge in 

the study area. This method was used to estimate 

recharge only for Lopez Island, because the required 

chloride concentration data in ground water were not 

available for the other three islands. The chloride massbalance method for estimating recharge is based on the 

principle that a known fraction of chloride in 

precipitation and dry atmospheric deposition is 

transported to the water table by the downward flow of 

liquid water. As water percolates downward, some 

evaporates directly or is taken up and transpired by 

plants. Where this occurs, the concentration of chloride 

in soil water increases with depth because little or no 

chloride is lost by these processes. At greater depths, 

where evapotranspiration does not occur, the chloride 

concentration should be uniform if climate, soil, and 

other conditions near the surface have been steady for a 

sufficiently long time.

The chloride mass-balance method uses the 

assumption that precipitation is the only source of 

chloride in ground water and in surface-water runoff. 

Human sources such as septic systems and animal 

sources such as cow manure contribute minimal 

amounts of chloride to the water in the study area, and 

natural sources such as evaporite rocks or connate 

seawater are not present in the hydrogeologic units 

above sea level. A mass balance of chloride in 

precipitation, surface runoff, and ground water is 

expressed in the following equation (Maurer and 

others, 1996; Prych, 1998):

, (1)

where

Rearranging the terms in equation 1 and solving 

for gives:

.

(2)

Implicit in the derivation and uses of equation 2 

is the assumption of "plug flow" for which it is 

assumed that (1) the direction of water flow and 

chloride transport is vertical and downward, (2) areal 

distributions of the rate of percolation of water and of 

chloride on the local scale (a few tenths of a meter) are 

uniform (no preferred pathways), (3) all chloride is 

dissolved in soil water, and the distribution of the 

dissolved chloride in the soil water is relatively 

uniform within a pore (no solid chloride phase, 

sorption by soil, or anion exclusion), and (4) advection 

is the dominant mode of chloride transport, and 

dispersion is relatively unimportant. Additional 

assumptions are that (5) minerals in the soil are not a 

source of chloride-the only sources are precipitation 

and dry atmospheric deposition, (6) measured chloride 

concentrations are at depths great enough that seasonal 

variations in concentration are small, and (7) chloride 

concentrations in surface-water runoff are the same as 

those in precipitation. The method is still valid if 

chloride is taken up by growing vegetation as long as it 

is also released by decaying vegetation at the same rate.

P is annual precipitation, in inches;

Cp is concentration of chloride in 

precipitation, in milligrams per liter;

GWR is annual ground-water recharge, in 

inches;

Cg is concentration of chloride in ground 

water; and 

SWR is annual surface-water runoff, in 

inches.

P Cp × GWR Cg ( ) × SWR Cp = + ( ) ×

GWR

P Cp ( ) × SWR Cp – ( ) ×

Cg

= --------------------------------------------------------
42 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

 Data Collection

Chloride concentrations from the atmosphere 

(precipitation and dry deposition), the water table, 

and(or) the unsaturated-zone soil moisture were 

determined from precipitation and dry atmospheric 

deposition samples collected during water years 1997-

98, and from ground-water samples collected in spring 

1997 on Lopez Island during phase 1 of the study (Orr, 

2000) Three atmospheric-chloride depositioncollection sites were established on Lopez Island-one 

at the northern end of the island, one near study basin 

L1 near the center of the island, and one at the southern 

end at the location of a precipitation-throughfall datacollection site and a temporary micrometeorological 

station (see fig. 5). Wet- and dry-atmospheric chloride 

deposition samplers were installed at the northern and 

southern sites. The sampler consists of two buckets 

mounted on an electromechanical device that senses 

precipitation and automatically places a cover on one 

or the other of the buckets. During periods of 

precipitation the "dry" bucket is covered while the 

"wet" bucket collects precipitation. When it is not 

raining, the "wet" bucket is covered to prevent any 

influx from the dry atmosphere (including insects, bird 

droppings, and wind-blown ground debris) and to 

minimize evaporation. At the same time, the dry bucket 

is open to collect microscopic crystals of chloride salts 

that fall from the atmosphere. In addition to the wet and 

dry sampler at the northern and southern Lopez Island 

sites, one permanently open bucket was installed at 

each of these sites to collect a "composite" of the wet 

and dry deposition. At the central Lopez Island site, 

only a permanently open bucket was installed. The 

permanently open buckets were subject to more 

contamination from birds, insects, and so forth, and 

samples from them were used only to approximately 

check the values from the wet and dry samples. Data 

from these buckets also were used to estimate certain 

missing values from the wet and dry samples.

The sampling buckets were collected and 

replaced with clean buckets on a monthly basis. All 

bucket samples were weighed and filtered alloquots 

were sent to the USGS Central Laboratory for 

determination of low-level chloride concentrations. 

Alloquots from the dry buckets were collected by first 

rinsing with a known quantity of distilled water and 

sampling the rinse water.

 Chloride concentrations in ground-water 

samples were determined colorimetrically using ferric 

thiocyanate (Friedman and Erdmann, 1982) at the 

Tacoma Field Services Unit of the USGS.

Recharge Estimates and Sources of Uncertainty 

Using Chloride Mass-Balance Method

In equation 2, all atmospheric chloride in soil 

water is assumed to be deposited by precipitation (wet 

deposition). However, about 37 percent of the total 

chloride deposition occurs as dry deposition. 

Equation 2 was therefore modified for this study to 

account for atmospheric chloride in terms of the total 

of the wet and dry chloride fluxes rather than just the 

concentration of chloride in precipitation. A summary 

of chloride concentrations in precipitation and dry 

deposition is shown in table 12.

The term P × Cp in equation 2, which represents 

the wet chloride deposition, is replaced by FWD, the 

total flux (mg/m2) of the wet and dry chloride 

deposition. The term SWR × Cp, which represents the 

outflow of atmospheric chloride through direct stream 

runoff, is replaced with the term SWR × FWD/P, where 

FWD/P is the chloride concentration in stream water. 

This follows the assumption that the chloride in the 

stream water is a composite of the wet plus dry 

chloride deposition because precipitation, after falling 

on the ground, also dissolves and transports the 

chloride from the dry deposition as it moves to the 

stream channel. Equation 2 then becomes

(3)

expressed in consistent units. In this study, FWD is 

expressed in mg/m2, Cg in mg/L, and GWR, SWR, and 

P, in inches. Equation 3 then becomes

 . (4)

GWR FWD( ) 1 – SWR ⁄ P Cg = ⁄

GWR 0.0394FWD( ) 1 – SWR/P /Cg =
Estimates of Ground-Water Recharge 43

Table 12. Summary of chloride concentrations in precipitation and dry chloride deposition observed at three locations on Lopez 

Island during October 1996 through September 1998—Continued

Observation period

(month-day-year)

Chloride concentration

(milligrams per liter)

Atmospheric chloride flux

(milligrams per square meter)

From To Location Wet

bucket

Composite

bucket

In

precipitation

(wet)

As dry

deposition

(dry)

Total of

wet+dry

Total

from

composite

bucket

10-03-96 11-06-96 C1 1.9 4.8 205.59 7.68 213.27 521.61

C2 11.0 2.4 1285.77 21.08 306.85 188.33

C3 — 2.2 — — — 174.83

11-06-96 12-04-96 C1 1.4 1.7 158.30 48.44 206.74 203.89

C2 2.1 2.9 222.05 68.00 290.05 306.83

C3 — 2.0 — — — 191.07

12-04-96 12-31-96 C1 0.95 0.98 49.65 98.24 147.90 132.00

C2 1.8 2.19 121.20 50.88 172.08 158.40

C3 — 1.3 — — — 88.92

12-31-96 02-03-97 C1 0.82 1.0 95.51 28.32 123.83 127.34

C2 1.70 2.08 170.68 49.51 220.19 209.03

C3 — 1.0 — — — 97.07

02-03-97 03-20-97 C1 0.87 1.36 104.23 38.33 142.56 166.70

C2 1.5 2.43 141.80 106.08 247.89 230.21

C3 — 1.7 — — — 139.74

03-20-97 04-30-97 C1 1.07 1.66 48.44 30.13 78.56 76.71

C2 2.80 7.30 73.74 160.75 234.49 192.62

C3 — 3.45 — — — 83.72

04-30-97 06-02-97 C1 0.542 0.902 28.87 9.81 38.68 48.98

C2 0.668 1.31 22.71 24.93 47.64 44.43

C3 — 0.675 — — — 30.65

06-02-97 07-10-97 C1 0.372 1.29 10.81 14.87 25.69 40.52

C2 0.756 1.66 44.05 30.03 74.08 97.88

C3 — 4.098 — — — 68.03

07-10-97 08-14-97 C1 (

2—) 1.394 27.81 19.99 27.80 28.07

C2 (

2—) 4.231 215.62 43.61 59.23 87.73

C3 — 4.098 — — — 84.42

08-14-97 09-08-97 C1 0.12 0.59 1.62 5.20 6.82 7.72

C2 0.17 0.81 2.63 16.52 19.15 12.25

C3 — 0.23 — — — 3.43

Table 12. Summary of chloride concentrations in precipitation and dry chloride deposition observed at three locations on Lopez 

Island during October 1996 through September 1998

[Location: Location of precipitation throughfall sites are shown in figure 5. C1, site at north end of island; C2, site at south end of island; and C3, site at center 

of island. Wet bucket: Only composite samples were collected at site H. Composite bucket: Concentrations are affected by evaporation because the buckets 

remained uncovered at all times. In order to consistently compare composite and wet sample concentrations, the values presented are calculated assuming no 

evaporation; in other words, the calculated concentration is the concentration of the sample as if diluted by the difference in water content between the wet and 

composite buckets. Atmospheric chloride flux in precipitation and total of wet+dry: Only composite samples were collected at site H. — , no data]
44 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Table 12. Summary of chloride concentrations in precipitation and dry chloride deposition observed at three locations on 

Lopez Island during October 1996 through September 1998—Continued

Observation period

(month-day-year)

Chloride concentration

(milligrams per liter)

Atmospheric chloride flux

(milligrams per square meter)

From To Location Wet

bucket

Composite

bucket

In

precipitation

(wet)

As dry

deposition

(dry)

Total of

wet+dry

Total

from

composite

bucket

09-08-97 10-08-97 C1 0.189 0.48 12.01 0.77 12.78 30.32

C2 0.342 1.48 23.90 4.91 28.80 103.58

C3 — 0.641 — — — 22.86

10-08-97 11-04-97 C1 1.434 1.80 92.73 49.85 142.58 118.31

C2 (

2—) (2—) 2128.89 195.44 324.33 (1—)

C3 — 2.397 — — — 114.10 l

11-04-97 12-02-97 C1 0.709 1.12 28.50 19.34 47.85 47.02

C2 1.029 1.81 39.58 27.39 66.98 69.47

C3 — 1.596 — — — 52.99

12-02-97 01-08-98 C1 1.051 1.37 95.43 47.61 143.05 136.38

C2 2.616 3.82 188.71 143.15 331.86 282.07

C3 — 1.867 — — — 139.90

01-08-98 02-05-98 C1 1.615 2.28 72.25 24.02 96.27 103.25

C2 2.945 4.25 86.19 61.03 147.22 125.33

C3 — 3.702 — — — 98.72

02-05-98 03-11-98 C1 1.712 0.858 65.97 133.32 99.29 26.83

C2 2.533 (

1—) 72.78 156.42 129.20 (1—)

C3 — 0.516 — — — 13.69

03-11-98 04-22-98 C1 0.511 1.37 14.72 10.37 25.10 39.69

C2 0.729 1.78 26.39 25.45 51.84 64.34

C3 — (

1—) — — — (1—)

04-22-98 06-02-98 C1 3.202 0.90 139.61 16.18 155.80 39.11

C2 0.583 2.049 15.09 41.61 56.70 65.43

C3 — 1.158 — — — 32.04

06-02-98 07-20-98 C1 0.223 2.37 8.36 22.47 30.83 89.30

C2 0.425 (

1—) 15.41 34.97 50.39 (1—)

C3 — 3.216 — — — 87.48

07-20-98 09-09-98 C1 0.40 27.44 0.13 6.98 7.12 9.15

C2 (

2—) 3.951 25.45 53.83 59.28 51.10

C3 — 0.828 — — — 10.81

09-09-98 10-06-98 C1 1.28 2.04 6.16 3.60 9.76 9.77

C2 1.70 3.34 9.52 7.51 17.04 18.71

C3 — 0.732 — — — 10.39

1Samples lost or destroyed or value deemed unreasonable. Value estimated by methods described in text, no estimates made for composite buckets. 2Very little or no water in wet bucket during this period. Chloride flux determined in same manner as for dry bucket.
Estimates of Ground-Water Recharge 45

For the 2-year data-collection period, FWD for 

the northern and southern Lopez Island sites was 1,782 

and 2,935 mg/m2 ( table 12). These 2-year totals 

include a few estimated values where data were 

missing. Missing values were estimated by comparison 

with known values at the same site or with known 

values at the other site. Same-site comparison estimates 

were made by assuming that the wet-plus-dry value 

equaled the composite value. Different-site comparison 

estimates were made by assuming that the ratio of 

individual values between sites were the same as the 

ratio of the sums of all non-missing data values 

between sites. If data values were missing at both sites, 

an average deposition rate, determined from the other 

data values, was used to calculate missing values. For 

basins L1 and L2, the two basins lying within glacial 

deposits, SWR for this 2-year period totaled 6.05 and 

8.19 inches, respectively. Precipitation for this period 

measured at three locations on Lopez Island (locations 

M1, P1, C1; fig. 5 and table 2) ranged from 44.85 to 

50.69 inches.

For determining Cg in equation 4, ground-water 

samples must be from wells where the only source of 

chloride in the aquifer is from the atmosphere. 

Therefore, samples from any wells that may be 

intruded by seawater could not be used. One 

requirement that assures that there would be no 

seawater intrusion is that the bottoms of the wells be 

above sea level. For such wells, the water levels cannot 

be drawn down by pumping to below sea level, and 

therefore no potential gradient from seawater to the 

well could develop. The only potential migration of 

chloride from seawater would be by diffusion, which 

would only occur over distances that are small 

compared with distances to seawater. However, only 10 

of the wells completed in the glacial deposits sampled 

on Lopez Island during 1977 met this bottom-altitude 

requirement. For those wells, the chloride 

concentrations ranged from 24 to 150 mg/L (Orr, 2000, 

table 1). In order to obtain a larger sample, wells also 

were selected from among those whose bottoms were 

below sea level but which did not appear to be intruded 

by seawater. Chloride concentrations in relation to 

well-bottom altitudes and distance from shore for all 

wells tapping glacial-deposit aquifers that were 

sampled during the spring of 1997 are shown in 

figure 12. Using figure 12, two conservative criteria 

were used in this selection. The wells had to be more 

than 2,000 feet from the shoreline and the well bottoms 

had to be higher than 15 feet below sea level. 

This produced a sample size of 27, all of which had 

chloride concentrations of less than 150 mg/L. The 

average chloride concentration for these wells is 63.6 

mg/L. Locations of these wells and the chloride 

concentrations are shown on figure 13.

When the average values for the variables 

discussed above are used in equation 4, the average 

recharge is 1.25 inches for the 2-year period (0.63 inch 

annually), about 23 percent of the recharge estimated 

using the DPM. No attempt was made to estimate the 

distribution of recharge from the data used for this 

method. For any particular sampling point in the 

aquifer, ground water generally has a predominantly 

horizontal flow component. Therefore, any groundwater sample consists of an unknown mixture of water, 

consisting of water percolating vertically downward 

from recharge at the surface and from other upgradient 

areas. Recharge values calculated from chloride 

concentrations in single samples of ground water 

would therefore represent upgradient composite values.

Equation 4 and the data collected can be used to 

estimate certain limiting values of recharge. For 

example, areas with highly permeable subsoils would 

not produce direct runoff and therefore would have the 

largest amount of recharge and the lowest chloride 

concentrations. Selecting the lowest three chloride 

concentrations in ground water (approximately 

representing the lowest decile) from table 13, and 

setting SWR = 0 in equation 4, and maintaining the 

average value of atmospheric chloride deposition, 

yields a recharge value of 3.89 inches for the 2 years 

(1.95 inches annually). Conversely, using the three 

highest chloride concentrations from table 13 and using 

the larger of the two direct runoff values results in a 

recharge value of 0.58 inch for the 2 years (0.29 inch 

annually).

In the above analysis, it was assumed that there 

are no other sources of chloride to the aquifer, when in 

fact there are likely some anthropogenic chloride in the 

aquifers originating from septic systems and 

application of fertilizers, pesticides, and herbicides. 

Quantification of these sources was beyond the scope 

of this study, but such sources are thought to be 

minimal because of the low population density inland 

of 2,000 feet from the shore.
46 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

CHLORIDE CONCENTRATIONS, 

 IN MILLIGRAMS PER LITER 

Less than 50

50 to less than 100

100 to less than 250

250 to 420

EXPLANATION

-350

-300

-250

-200

-150

-100

-50

0

50

100

1000 2000 3000 4000 5000 6000 7000 8000 9000

DISTANCE FROM SHORE, IN FEET

 ALTITUDE OF BOTTOM OF WELL, IN FEET ABOVE SEA LEVEL

Figure 12. Relation between chloride concentrations and well-bottom altitudes and distances from shore for all wells 

tapping glacial-deposit aquifers that were sampled during spring 1997 on Lopez Island, San Juan County, Washington, 

water years 1997-98.
Estimates of Ground-Water Recharge 47

 11J01

 13D01

 11F01

 12D02

 13E01

 13M01 14E01 14F01

 14M01

 14N01

 16D01

 17D02

 18K01

 18P02

 21E01

 23K02

 24H01

 25Q01

 26B01

 26G01

35D01

 27J01

 33R02

 34F01

 34K01

 03J01

 14M02

0 1 2 3 MILES

0 1 2 3 KILOMETERS

EXPLANATION

WELL AND SEQUENCE NUMBER, 

 AND CHLORIDE CONCENTRATIONS, 

 IN MILLIGRAMS PER LITER 

 Less than 50

50 to less than 100

100 to less than 250

1

1

T.36 N.

T.35 N.

See table 13 for complete well number

122°55' 122°50'

48°

32'

30"

48°

27'

30"

SHAW ISLAND

LOPEZ ISLAND

DECATUR 

ISLAND

Base modified from U.S. Geological Survey

digital data, 1:2,000,000, 1972

T.35 N.

T.34 N.

R.2 W R.1 W.

 11F01

 14N01

 13D01

Figure 13. Locations and chloride concentrations for wells used in the chloride mass-balance method for 

estimating ground-water recharge, Lopez Island, San Juan County, Washington, spring 1997. 
48 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Table 13. Summary of chloride concentrations and selected physical and hydrologic data for wells used in the chloride 

mass-balance method for Lopez Island, San Juan County, Washington, spring 1977

[Well No.: The well-numbering system in Washington is described on page 4. Altitude of land surface: Estimated from 7.5-minute U.S. Geological 

Survey topographic maps. All listed wells are finished in glacial materials on Lopez Island and were sampled in spring 1997. Altitude refers to sea level, 

referenced to the National Geodetic Vertical Datum of 1929. Chloride rounded to two significant digits; all other data rounded to nearest foot. —, no data]

Well

No.

Altitude

of land

surface

(feet)

Altitude

of well

bottom

(feet)

Well depth

(feet below

land

surface)

Waterlevel

altitude

(feet)

Chloride

concentration

(milligrams per

liter)

34N/01W-16D01 150 38 112 — 72

34N/01W-17D02 220 68 152 205 150

34N/01W-18K01 110 95 15 108 48

34N/01W-18P02 60 8 52 43 94

34N/01W-21E01 80 50 30 77 110

34N/02W-03J01 170 -11 181 — 100

35N/02W-11F01 130 -13 143 — 34

35N/02W-11J01 170 -15 185 4 34

35N/02W-12D02 90 -5 95 8 30

35N/02W-13D01 115 -10 125 6 78

35N/02W-13E01 100 -14 114 3 40

35N/02W-13M01 100 -14 114 3 48

35N/02W-14E01 100 -13 113 0 50

35N/02W-14F01 135 -7 142 10 32

35N/02W-14M01 110 -3 113 10 52

35N/02W-14M02 180 25 155 45 50

35N/02W-14N01 170 33 137 48 120

35N/02W-23K02 205 -6 211 5 30

35N/02W-24H01 120 20 100 110 130

35N/02W-25Q01 125 65 60 84 82

35N/02W-26B01 218 -2 220 9 64

35N/02W-26G01 265 -15 280 10 20

35N/02W-27J01 230 -11 241 102 28

35N/02W-33R02 190 0 190 16 24

35N/02W-34F01 180 -14 194 -1 68

35N/02W-34K01 190 -13 203 4 100

35N/02W-35D01 205 25 191 22 28
Summary 49

Another possible source of chloride is residual 

chloride from early post-ice-age seawater that may 

have intruded the glacial materials while the island was 

below sea level from the time after the glaciers 

retreated and before the island isostatically rebounded 

to above sea level. In areas of the northern Puget Sound 

region, there is evidence that chloride from this source 

has not yet been flushed from the aquifers (Halstead, 

1986). Chloride concentrations in those areas, however, 

are much higher than those used in this analysis.

The net effect of sources of chloride other than 

from the atmosphere would be that the recharge values 

using the chloride mass-balance method are less than 

the actual recharge. This is evident from equation 3, in 

which the calculated recharge is inversely proportional 

to the chloride concentration in ground water, if the 

other variables remain unchanged. Therefore, the 

recharge estimates of from 0.29 to 1.95 inches per year 

calculated by the chloride-mass balance method may 

represent lower limits, which is consistent with the 

generally higher simulated recharge using the DPM 

(2.67 and 2.64 inches per year for the study basins L1 

and L2).

The two methods also are representative of two 

different periods, which could be another cause for 

different results. The DPM simulations are for a 

specific 2-year period, but the chloride mass-balance 

method uses chloride concentrations in ground water 

that are the composite result of an unknown number of 

previous years during which chloride deposition, on 

average, may have been different from that measured 

during this study. The difference in annual chloride 

deposition between the 2 years that data were collected 

is about 32 percent of the annual average for the 2 

years. This suggests that the uncertainty from this 

source in recharge estimated by this method could be of 

this magnitude.

SUMMARY

On Lopez, San Juan, Orcas, and Shaw Islands, 

the largest of the islands that make up San Juan County, 

Washington, population and development are growing 

rapidly. There is growing concern about the quality and 

availability of ground water because an important 

source of fresh water for the islands is the glacialdeposit and bedrock aquifers.

The amount of recharge available to the aquifers from 

precipitation, a key element in assessing ground-water 

availability, is extremely difficult and costly to measure 

directly, and only very generalized and incomplete 

estimates of recharge are available for San Juan 

County. In 1997, the U.S. Geological Survey, in 

cooperation with San Juan County Health and 

Community Services, began a study of the quality and 

availability of ground water on Lopez, San Juan, Orcas, 

and Shaw Islands.

Ground-water recharge from deep percolation of 

precipitation to the water tables on Lopez, San Juan, 

Orcas, and Shaw Islands was estimated using two 

independent methods. The first technique used a daily 

water and energy budgeting model, the Deep 

Percolation Model (DPM), to compute, simulate, and 

allocate daily moisture fluxes of precipitation, 

evapotranspiration, direct runoff, and deep percolation 

for any number of unique areas in a drainage basin. The 

DPM requires precipitation, streamflow, solar 

shortwave radiation, air temperature, soil-property, and 

vegetation-cover data. Precipitation throughfall data 

also were used for forested areas. The DPM was 

operated for six small study basins: three on Lopez 

Island and one each on San Juan, Orcas, and Shaw 

Islands. Various soil and subsoil parameters were 

estimated for the different geologic and soil conditions 

represented by each of the six study basins during a 

calibration process for each study basin. The process 

involved adjusting model parameters until the 

quantities and timing of measured precipitation, 

measured direct runoff (derived from streamflow data), 

measured evaporation (derived from throughfall 

measurements), computed transpiration, and computed 

vertical movement of soil water out of the bottom of 

the root zone (deep percolation) were reconciled into a 

water budget that minimized total water-balance error. 

The calibrated soil and subsoil parameters were then 

used in island-wide applications of the DPM where the 

direct-runoff component (which is not available on an 

island-wide basis) is simulated rather than input, and 

calibration is not required. A spatial distribution of 

recharge was simulated for each island.

The second technique used a chloride massbalance method that requires measurements of 

atmospheric chloride deposition, precipitation, 

streamflow, and chloride concentrations in ground 

water.
50 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Atmospheric chloride deposition data were collected as 

part of this study. Precipitation and streamflow data 

were available from the near-surface-water balance 

method used in this study and ground-water chloride 

concentration data were available from the earlier 

seawater-intrusion investigation phase of this project. 

Samples of atmospheric chloride deposition were 

collected at three sites on Lopez Island for the same 2-

year period as for the time-series data collected for the 

near-surface water-balance method in this study. 

Recharge using this method was estimated only for the 

glacial deposits of Lopez Island and only average, 

rather than area-specific, values of recharge could be 

determined.

The study-basin recharge values estimated using 

the DPM for the two basins located on glacial deposits 

on Lopez Island were:

averaged over the 2-year period. This compares with an 

average value of only 0.63 inch per year based on the 

results of the chloride mass-balance method. The range 

of chloride concentrations in ground-water samples 

from the selected wells when used in the final equation 

indicates that average recharge ranges from 0.29 to 

1.95 inches per year.

Sources of chloride in ground water other than 

from the atmosphere would cause the recharge 

estimated by the chloride mass-balance method to be 

less than the actual recharge. Therefore, the chloride 

mass-balance recharge estimates represent lower limits 

which are, at least, consistent with the higher recharge 

values from the DPM.

The other four study basins are all located on 

areas of shallow and outcropping bedrock, one on each 

of the four islands. Average recharge estimates using 

the DPM for these basins were:

The island-wide recharge estimates using the 

DPM were

The average island-wide recharge is most closely 

related to the amount of area covered by glacial 

deposits. Thus Lopez Island, with the most extensive 

area covered with glacial deposits, has the most 

recharge per square mile, even though it also has the 

least precipitation.

According to the DPM simulations, recharge in 

areas of shallow and outcropping bedrock generally is 

less than 1.5 inches per year. In areas underlain by 

glacial deposits, the DPM-simulated recharge generally 

ranges from less than 0.5 to about 3 inches per year, but 

in some small areas of sandy soils with highly 

permeable subsoils recharge is as great as 9 inches per 

year.

Ground-water recharge should not be equated 

with ground-water availability. Under natural 

conditions ground-water recharge is balanced by 

subsurface flow to the ocean, to the lower reaches of 

streams, and, in areas of shallow water tables, to the 

roots of phreatophytes. Removal of ground water by 

wells will lower ground-water levels and diminish the 

outflow to one or more of these discharge areas, 

inducing seawater intrusion into wells, reducing dryseason low flows in streams or transforming wetlands 

and phreatophyte areas into drier environments. If all 

recharge were consumptively used, there would be no 

discharge to any of these areas.

Removal of ground water in rural and suburban 

non-irrigated areas generally is not all consumptive, but 

a large fraction of this water is returned as wastewater 

to the subsurface and eventually to the aquifers. Waterquality problems may occur before significant 

problems in water levels or in ground-water discharge 

areas develop. These issues are most readily addressed 

using ground-water models for which the recharge 

estimates presented in this report will be essential.

L1 2.67 inches per year

L2 2.64 inches per year

L3 (Lopez Island) 0.35 inch per year

SJ1 (San Juan Island) 0.45 inch per year

OR1 (Orcas Island) 0.27 inch per year

SH1 (Shaw Island) 1.27 inches per year

Lopez Island 2.49 inches per year

San Juan Island 1.99 inches per year

Orcas Island 1.46 inches per year

Shaw Island 1.44 inches per year
References Cited 51

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D.M., 1998, Regional land cover characterization using 

Landsat thematic mapper data and ancillary data 

sources: Environmental Monitoring and Assessment, v. 

51, p. 415-428.

Whiteman, K.J., Molenaar, Dee, Bortleson, G.C., and 

Jacoby, J.M., 1983, Occurrence, quality, and use of 

ground water in Orcas, San Juan, Lopez, and Shaw 

Islands, San Juan County, Washington: U.S. Geological 

Survey Water-Resources Investigations Report 83-

4019, 12 sheets.

Wiggins, W.D., Ruppert, G.P., Smith, R.R., Reed, L.L., and 

Courts, M.L., 1998, Water resources data, Washington, 

water year 1997: U.S. Geological Survey Water-Data 

Report WA-97-1, 528 p.

Wiggins, W.D., Ruppert, G.P., Smith, R.R., Hubbard, L.E., 

and Courts, M.L., 19998, Water resources data, 

Washington, water year 1998: U.S. Geological Survey 

Water-Data Report WA-98-1, 508 p.
Tables 14 through 26 53

Tables 14 through 26
54 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)

09-13-96 0000 — — — — — — — —

09-14-96 1212 0.17 0.09 0.10 0.17 0.16 0.06 0.06 0.11

09-15-96 1630 0.52 0.38 0.63 0.53 0.77 0.53 0.41 0.40

09-16-96 1335 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-17-96 1250 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-18-96 1145 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-19-96 1900 0.18 0.21 0.17 0.13 0.20 0.08 0.25 0.15

09-20-96 1600 0.03 0.00 trace 0.01 trace trace 0.01 trace

09-21-96 1615 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

09-22-96 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-23-96 1645 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-24-96 1345 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-25-96 1745 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-26-96 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-27-96 1330 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-28-96 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-29-96 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-30-96 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-01-96 1845 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-02-96 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-03-96 1700 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-04-96 1645 0.53 0.36 0.82 0.67 0.75 0.65 0.49 0.50

10-05-96 1800 0.005 0.015 0.05 0.01 0.02 0.01 0.02 0.02

10-06-96 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-07-96 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-08-96 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-09-96 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-10-96 1730 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-11-96 1930 0.18 0.07 0.03 0.24 0.23 0.14 0.15 0.13

10-12-96 1445 0.01 0.00 0.00 trace trace 0.00 0.005 trace

10-13-96 1830 0.10 0.04 0.02 0.11 0.07 0.03 0.04 0.05

10-14-96 1745 0.15 0.10 0.15 0.30 0.15 0.16 0.15 0.20

10-15-96 1700 0.05 0.02 0.12 0.07 0.06 0.02 0.03 0.02

10-16-96 1715 0.01 trace trace trace trace trace trace trace

10-17-96 1730 0.17 0.05 0.05 0.05 trace 0.00 0.04 0.00

10-18-96 1800 0.22 0.16 0.32 0.31 0.20 0.21 0.12 0.23

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98

[Values represent cumulative amounts from the data and time of the prior record to that of the current record. —, no data]
Tables 14 through 26 55

10-19-96 1815 0.03 0.00 0.00 trace trace trace trace trace

10-20-96 1430 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-21-96 1800 0.10 0.05 0.05 0.15 0.09 0.13 0.10 0.10

10-22-96 1745 0.26 0.20 0.55 0.30 0.25 0.22 0.18 0.23

10-23-96 1700 0.10 0.04 0.02 0.10 0.07 0.05 0.08 0.05

10-24-96 1800 0.11 0.04 0.04 0.14 0.07 0.07 0.08 0.08

10-25-96 1800 0.15 0.05 0.02 0.09 0.12 0.04 0.05 0.02 

10-26-96 1630 trace 0.00 0.00 trace trace 0.03 trace trace

10-27-96 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-28-96 1700 0.85 0.65 1.38 1.25 1.02 0.89 1.00 1.00

10-29-96 1700 trace trace trace trace trace trace trace trace

10-30-96 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

10-31-96 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-01-96 1800 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-02-96 1630 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

11-03-96 1730 0.17 0.10 0.12 0.22 0.15 0.10 0.15 0.15

11-04-96 1700 0.18 0.07 0.03 0.16 0.15 0.05 0.13 0.10

11-05-96 1610 0.03 0.01 trace 0.03 0.02 0.01 0.02 0.01

11-06-96 1730 0.15 0.03 0.03 0.20 0.10 0.02 0.04 0.08

11-07-96 1530 0.01 trace 0.00 0.00 0.00 0.00 0.01 trace

11-08-96 1515 0.21 0.10 0.13 0.24 0.18 0.13 0.18 0.19

11-09-96 1610 0.01 0.00 0.00 trace 0.00 trace trace trace

11-10-96 1515 trace 0.00 0.00 0.00 0.00 trace trace trace

11-11-96 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

11-12-96 1545 0.03 0.00 0.00 0.01 trace 0.00 trace 0.00

11-13-96 1600 0.55 0.44 0.77 0.71 0.67 0.37 0.57 0.47

11-14-96 1500 0.05 0.05 0.02 0.13 0.10 0.05 0.14 0.05

11-15-96 1530 0.05 0.03 0.03 0.02 0.02 0.02 0.02 0.03

11-16-96 1630 0.13 0.03 0.02 0.09 0.11 0.04 0.05 0.02

11-17-96 1545 0.61 0.50 0.93 0.82 0.70 0.46 0.76 0.47

11-18-96 1500 trace trace trace trace 0.00 trace trace trace

11-19-96 1515 trace 0.00 0.00 0.00 trace trace 0.00 0.00

11-20-96 1615 0.19 0.18 0.26 0.22 0.32 0.22 0.25 0.35

11-21-96 1600 0.05 trace 0.01 0.01 0.01 0.01 0.03 0.01

11-22-96 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-23-96 1415 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
56 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

11-24-96 1430 0.03 0.01 trace 0.04 0.02 0.02 0.04 trace

11-25-96 1545 0.27 0.12 0.23 0.29 0.22 0.12 0.22 0.20

11-26-96 1330 0.05 0.03 trace 0.07 0.06 0.01 0.08 0.03

11-27-96 1745 1.42 1.15 2.72 1.87 1.37 1.30 2.17 1.45

11-28-96 1630 0.35 0.17 0.20 0.25 0.32 0.21 0.20 0.17

11-29-96 1630 0.01 trace trace 0.01 trace trace 0.01 trace

11-30-96 1615 0.05 0.02 0.01 0.04 0.02 0.02 0.01 0.02

12-01-96 1600 0.28 0.05 0.08 0.26 0.19 0.10 0.12 0.12

12-02-96 1845 0.15 0.05 0.08 0.18 0.15 0.06 0.09 0.12

12-03-96 1845 trace 0.00 trace trace trace trace trace trace

12-04-96 1600 0.32 0.18 0.37 0.35 0.22 0.27 0.23 0.30

12-05-96 1630 0.04 0.00 trace 0.01 trace trace trace trace

12-06-96 1530 0.05 0.02 0.01 0.05 0.03 0.02 0.02 0.03

12-07-96 1600 0.03 0.01 0.01 0.02 0.01 trace 0.01 trace

12-08-96 1545 0.05 0.01 trace 0.04 0.04 0.02 0.02 0.01

12-09-96 1745 trace trace trace trace trace trace trace trace

12-10-96 1430 0.02 0.00 trace 0.01 0.00 trace 0.01 0.00

12-11-96 1545 0.10 0.03 0.02 0.12 0.09 0.03 0.06 0.04

12-12-96 1445 0.02 trace trace 0.03 0.02 trace trace 0.01

12-13-96 1515 0.10 0.01 0.02 0.07 0.03 0.02 0.02 0.02

12-14-96 1530 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-15-96 1630 0.02 0.00 0.00 trace 0.00 trace 0.01 trace

12-16-96 1530 0.03 0.01 0.01 0.03 0.02 0.02 0.03 0.02

12-17-96 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

12-18-96 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-19-96 1500 0.35 0.25 0.62 0.42 0.33 0.27 0.42 0.30

12-20-96 1530 0.38 0.22 0.80 0.51 0.32 0.31 0.39 0.34

12-21-96 1530 trace trace 0.01 trace trace 0.01 trace trace

12-22-96 1430 0.04 0.02 0.01 0.02 0.01 0.01 0.03 0.01

12-23-96 1600 0.43 0.03 0.17 0.07 0.05 0.10 0.03 0.11

12-24-96 1545 0.35 0.42 0.56 0.30 0.45 0.23 0.26 0.23

12-25-96 1630 0.18 0.17 0.25 0.10 0.30 0.02 0.08 0.08

12-26-96 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-03-97 1530 12.47 12.50 12.03 13.25 11.38 11.65 13.03 12.65

01-04-97 1500 trace trace trace trace trace trace trace trace

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 57

01-05-97 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-06-97 1500 0.06 0.02 0.01 0.06 0.02 0.03 0.02 0.02

01-07-97 1600 0.75 0.48 1.25 1.12 1.05 0.50 0.58 0.76

01-08-97 1615 0.03 0.01 0.01 0.01 0.01 0.01 0.02 0.01

01-09-97 1330 0.13 0.10 0.10 0.18 0.10 0.06 0.13 0.10

01-10-97 1615 0.02 0.01 0.01 0.01 trace 0.00 0.01 0.01

01-11-97 1700 0.01 0.01 trace 0.01 0.01 trace 0.01 trace

01-12-97 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

01-13-97 1613 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-14-97 1545 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-15-97 1600 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-16-97 1645 0.01 0.02 0.02 0.07 0.03 0.03 0.10 0.02

01-17-97 1500 0.16 0.08 0.09 0.20 0.10 0.10 0.17 0.12

01-18-97 1400 0.52 0.54 0.94 0.70 0.49 0.40 0.95 0.43

01-19-97 1530 0.20 0.16 0.27 0.35 0.16 0.12 0.14 0.20

01-20-97 1435 0.73 0.63 1.61 1.05 0.72 0.89 0.96 0.61

01-21-97 1515 trace trace trace trace trace trace trace trace

01-22-97 1615 0.12 0.16 0.10 0.22 0.20 0.15 0.20 0.10

01-23-97 1430 0.15 0.03 0.04 0.16 0.10 0.04 0.04 0.09

01-24-97 1530 trace trace trace trace trace trace trace trace

01-25-97 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-26-97 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-27-97 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-28-97 1730 0.04 0.01 0.01 0.03 0.01 0.01 0.03 0.01

01-29-97 1700 0.10 0.06 0.01 0.14 0.08 0.06 0.15 0.08

01-30-97 1600 0.72 0.42 0.98 0.89 0.45 0.46 0.41 0.62

01-31-97 1400 trace trace trace trace trace trace trace trace

02-01-97 1445 0.16 0.11 0.07 0.17 0.12 0.10 0.17 0.12

02-02-97 1605 0.05 0.02 0.01 0.07 0.04 0.07 0.03 0.02

02-03-97 1700 0.04 0.02 0.01 0.05 0.04 0.02 0.04 0.02

02-04-97 1645 0.00 0.00 trace trace 0.00 trace trace trace

02-05-97 1730 trace 0.00 0.00 0.00 0.00 trace 0.00 0.00

02-06-97 1530 trace 0.00 0.00 0.00 0.00 0.00 0.00 trace

02-07-97 1700 0.05 0.02 trace 0.04 0.05 0.03 0.03 0.02

02-08-97 1600 trace trace 0.00 trace trace 0.00 trace trace

02-09-97 1430 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
58 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

02-10-97 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-11-97 1530 0.23 0.19 0.27 0.30 0.20 0.13 0.28 0.21

02-12-97 1730 0.38 0.25 0.52 0.57 0.37 0.25 0.40 0.27

02-13-97 1630 0.07 0.03 0.02 0.08 0.05 0.02 0.04 0.04

02-14-97 1600 0.51 0.41 0.93 0.87 0.49 0.35 0.53 0.54

02-15-97 1600 0.68 0.53 1.50 1.44 0.63 0.42 0.67 0.65

02-16-97 1530 trace trace trace trace trace trace trace trace

02-17-97 1600 0.06 0.01 trace 0.04 0.04 0.01 0.01 0.01

02-18-97 1715 0.03 0.01 trace 0.01 trace 0.005 trace trace

02-19-97 1700 0.23 0.06 0.12 0.19 0.19 0.10 0.12 0.18

02-20-97 1545 0.09 0.03 0.03 0.12 0.06 0.03 0.03 0.05

02-21-97 1815 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-22-97 1600 trace trace trace trace trace trace trace trace

02-23-97 1615 trace trace trace trace trace trace trace trace

02-24-97 1600 trace 0.00 0.00 trace trace 0.00 trace trace

02-25-97 1715 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-26-97 1645 0.22 0.21 0.10 0.27 0.22 0.20 0.20 0.13

02-27-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-28-97 1700 trace trace trace trace trace trace trace trace

03-01-97 1500 0.05 trace trace trace trace trace 0.01 0.01

03-02-97 1645 0.02 0.00 trace 0.02 trace trace trace trace

03-03-97 1400 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-04-97 1730 0.02 0.00 0.00 0.01 trace trace 0.00 0.00

03-05-97 1700 0.02 0.00 trace 0.005 0.00 trace trace 0.00

03-06-97 1345 0.03 trace trace 0.03 trace 0.01 0.01 trace

03-07-97 1630 0.10 0.03 0.04 0.13 0.07 0.05 0.05 0.07

03-08-97 1615 0.00 0.00 trace trace trace 0.00 trace .06

03-09-97 1730 0.01 0.00 0.00 trace 0.00 trace 0.00 0.00

03-10-97 1530 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

03-11-97 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-12-97 1700 0.36 0.28 0.25 0.40 0.34 0.22 0.30 0.22

03-13-97 1730 trace 0.00 trace trace 0.00 0.00 trace trace

03-14-97 1730 trace 0.00 trace 0.00 0.00 0.00 0.00 0.00

03-15-97 1630 0.58 0.53 0.47 0.76 0.55 0.48 0.74 0.54

03-16-97 1630 0.02 0.03 0.03 0.02 0.02 0.02 0.02 0.02

03-17-97 1830 0.18 0.15 0.12 0.25 0.17 0.13 0.15 0.14

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 59

03-18-97 1700 0.31 0.20 0.41 0.46 0.21 0.24 0.19 0.29

03-19-97 1645 0.22 0.13 0.20 0.29 0.16 0.11 0.12 0.15

03-20-97 1630 0.02 0.02 0.01 0.02 0.02 0.01 0.02 0.02

03-21-97 1745 trace 0.00 trace trace 0.00 0.00 trace 0.00

03-22-97 1730 0.04 trace 0.00 0.01 0.00 trace trace 0.00

03-23-97 1730 0.01 0.00 0.00 trace 0.00 0.00 trace 0.00

03-24-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-25-97 1800 0.12 0.07 0.02 0.14 0.12 0.05 0.09 0.07

03-26-97 1645 0.13 0.08 0.09 0.14 0.10 0.07 0.10 0.09

03-27-97 1645 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-28-97 1700 0.03 0.00 trace 0.02 trace trace trace trace

03-29-97 1530 0.01 0.00 0.00 trace 0.00 0.00 0.00 0.00

03-30-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-31-97 1745 0.10 0.00 0.00 0.02 trace 0.01 trace trace

04-01-97 1700 trace 0.00 0.00 trace trace 0.00 0.00 0.00

04-02-97 1650 trace trace 0.00 0.00 0.00 0.00 0.00 0.00

04-03-97 1700 0.05 0.02 0.01 0.04 0.05 0.03 0.04 0.04

04-04-97 1645 trace 0.00 0.00 trace 0.00 0.00 trace 0.00

04-05-97 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

04-06-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-07-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-08-97 1650 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-09-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-10-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-11-97 1930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-12-97 1610 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-13-97 1700 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-14-97 1800 0.07 0.03 0.01 0.05 0.04 0.02 0.04 0.02

04-15-97 1815 0.02 trace 0.00 0.02 0.01 trace trace trace

04-16-97 1800 0.08 0.01 trace 0.03 0.03 0.01 0.01 trace

04-17-97 1730 0.01 0.00 0.00 trace 0.00 0.00 trace 0.00

04-18-97 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

04-19-97 1800 0.17 0.10 0.10 0.20 0.14 0.12 0.16 0.15

04-20-97 1530 0.46 0.40 0.53 0.50 0.42 0.40 0.50 0.51

04-21-97 1745 trace trace 0.00 0.00 trace 0.00 trace trace

04-22-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
60 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

04-23-97 1700 0.05 trace trace 0.04 0.01 trace trace 0.01

04-24-97 1615 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-25-97 1600 0.02 trace 0.00 0.01 trace trace trace 0.00

04-6-97 1700 0.01 0.00 0.00 trace 0.00 0.00 trace 0.00

04-27-97 1730 0.38 0.24 0.12 0.26 0.34 0.23 0.23 0.12

04-28-97 1745 0.09 0.03 trace 0.07 0.05 0.03 0.06 0.03

04-29-97 1800 0.03 trace 0.00 0.02 0.01 trace 0.01 trace

04-30-97 1715 0.02 0.00 0.00 0.01 trace trace 0.01 0.00

05-01-97 1745 0.07 0.02 0.00 0.03 0.04 0.02 0.02 0.01

05-02-97 1815 0.00 0.00 0.00 0.00 0.00 0.00 trace 0.00 

05-03-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-04-97 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-05-97 1830 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-06-97 1845 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-07-97 2020 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-08-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-09-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-10-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-11-97 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-12-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-13-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-14-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-15-97 1800 0.01 0.00 0.00 trace 0.00 0.00 0.00 0.00

05-16-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-17-97 1845 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-18-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-19-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-20-97 1745 0.05 trace 0.00 0.03 0.01 0.00 0.01 0.00

05-21-97 2015 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-22-97 1930 0.02 trace 0.00 0.01 0.02 0.01 0.01 0.00

05-23-97 2000 0.09 0.03 0.00 0.06 0.07 0.03 0.03 0.02

05-24-97 2000 trace 0.00 0.00 trace trace 0.00 trace 0.00

05-25-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

05-26-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

05-27-97 1900 0.15 0.10 0.05 0.13 0.13 0.08 0.11 0.10

05-28-97 1700 0.12 0.09 0.02 0.12 0.10 0.06 0.12 0.07

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 61

05-29-97 1830 0.28 0.25 0.28 0.40 0.32 0.25 0.31 0.35

05-30-97 1800 0.24 0.20 0.15 0.27 0.21 0.16 0.28 0.21

05-31-97 1800 0.33 0.27 0.42 0.43 0.32 0.21 0.34 0.42

06-01-97 1700 0.23 0.20 0.32 0.31 0.22 0.20 0.29 0.28

06-02-97 1800 0.01 trace trace trace trace trace trace trace

06-03-97 1745 0.20 0.16 0.12 0.20 0.19 0.15 0.25 0.18

06-04-97 1830 0.01 trace trace trace trace trace trace trace

06-05-97 1630 0.03 trace 0.00 0.01 0.01 trace 0.01 trace

06-06-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-07-97 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-08-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-09-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-10-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-11-97 1945 0.14 0.07 0.02 0.14 0.11 0.06 0.08 0.09

06-12-97 1915 0.03 0.03 0.01 0.04 0.03 0.01 0.03 0.05

06-13-97 1910 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

06-14-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-15-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-16-97 1700 trace trace trace trace trace trace trace trace

06-17-97 1800 0.16 0.05 0.01 0.12 0.11 0.05 0.09 0.05

06-18-97 1930 0.02 0.00 0.00 trace trace 0.00 trace trace

06-19-97 1915 0.01 0.00 0.00 trace 0.00 0.00 0.00 0.00

06-20-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

06-21-97 1930 0.35 0.30 0.30 0.41 0.39 0.38 0.32 0.27 

06-22-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-23-97 1900 0.01 0.01 trace 0.03 0.04 trace 0.01 0.01

06-24-97 1830 trace trace 0.00 trace trace trace trace trace

06-25-97 1900 trace 0.00 0.00 0.00 trace trace 0.00 0.00

06-26-97 1800 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-27-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-28-97 1930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-29-97 1630 0.52 0.36 0.63 0.68 0.55 0.30 0.36 0.60

06-30-97 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-01-97 1930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-02-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
62 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

07-03-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-04-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-05-97 1900 0.32 0.22 0.22 0.35 0.28 0.15 0.20 0.25

07-06-97 1600 0.05 0.02 trace 0.03 0.01 0.01 0.02 trace

07-07-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-08-97 1830 0.32 0.25 0.32 0.41 0.35 0.25 0.40 0.31

07-09-97 1930 0.16 0.08 0.05 0.16 0.14 0.06 0.08 0.09

07-10-97 2045 0.16 0.09 0.13 0.20 0.17 0.10 0.14 0.14

07-11-97 1845 0.01 trace trace trace trace trace trace trace

07-12-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-13-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-14-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-15-97 1930 0.02 0.00 0.00 0.01 trace 0.00 0.00 0.00

07-16-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-17-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-18-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-19-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-20-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-21-97 1900 0.01 0.00 0.00 trace 0.00 0.00 0.00 0.00

07-22-97 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-23-97 1930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-24-97 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-25-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-26-97 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-27-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-28-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-29-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-30-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-31-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-01-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-02-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-03-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-04-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-05-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-06-97 2000 0.02 0.00 0.00 trace 0.00 0.00 trace 0.00

08-07-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 63

08-08-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-09-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-10-97 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-11-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-12-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-13-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-14-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-15-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-16-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-17-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-18-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-19-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-20-97 1900 0.06 0.01 0.00 0.05 0.03 0.01 0.02 0.01

08-21-97 1900 0.01 0.01 0.00 0.01 0.01 trace trace trace

08-22-97 1945 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-23-97 2030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-24-97 1900 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-25-97 2130 0.06 0.02 0.00 0.05 0.03 0.01 0.04 trace

08-26-97 1930 0.49 0.37 0.77 0.51 0.41 0.39 0.55 0.48

08-27-97 1615 0.04 0.04 0.09 0.05 0.04 0.03 0.04 0.03

08-28-97 1800 0.01 trace trace 0.00 trace trace 0.00 0.00

08-29-97 1800 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-30-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-31-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-01-97 2000 0.05 0.02 0.00 0.04 0.03 0.01 0.02 0.01

09-02-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-03-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-04-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-05-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-06-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-07-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-08-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-09-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-10-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-11-97 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-12-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
64 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

09-13-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-14-97 1600 0.16 0.10 0.06 0.18 0.14 0.09 0.17 0.12

09-15-97 1630 0.08 0.01 0.00 0.05 0.05 0.01 0.07 0.07

09-16-97 1815 0.18 0.06 0.08 0.16 0.12 0.11 0.18 0.11

09-17-97 1800 0.14 0.08 0.15 0.15 0.12 0.12 0.16 0.11

09-18-97 1800 0.14 0.07 0.09 0.14 0.12 0.09 0.12 0.10

09-19-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-20-97 1700 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-21-97 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-22-97 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-23-97 1830 trace trace trace 0.00 0.00 0.00 trace trace

09-24-97 1845 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-25-97 1830 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-26-97 1800 0.51 0.25 0.51 0.51 0.51 0.37 0.43 0.42

09-27-97 1730 0.26 0.19 0.40 0.36 0.29 0.20 0.20 0.22

09-28-97 1730 trace 0.00 trace trace trace trace trace trace

09-29-97 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-30-97 1830 0.20 0.09 0.11 0.30 0.24 0.14 0.14 0.15

10-05-97 2400 21.17 21.08 21.60 21.99 21.53 21.05 21.41 21.37

10-17-97 2400 21.10 20.57 20.84 21.05 20.81 20.55 20.74 20.72

10-23-97 2400 20.13 20.08 20.11 20.14 20.11 20.07 20.10 20.10

10-31-97 2400 21.44 20.94 21.39 21.73 21.33 20.91 21.23 21.19

11-01-97 1745 0.01 trace trace trace trace trace trace trace

11-02-97 1700 trace 0.00 0.00 trace 0.00 0.00 0.00 0.00

11-03-97 1630 0.15 0.06 0.07 0.18 0.07 0.08 0.07 0.12

11-04-97 1645 trace trace trace trace trace trace trace trace

11-05-97 1600 trace 0.00 0.00 0.00 0.00 0.00 trace 0.00

11-06-97 1430 0.42 0.32 0.65 0.57 0.37 0.42 0.37 0.51

11-07-97 1400 0.01 0.01 0.01 0.01 trace trace trace 0.01

11-08-97 1600 0.06 0.04 0.02 0.06 0.04 0.02 0.06 0.03

11-09-97 1530 trace trace trace trace trace trace trace trace

11-10-97 1630 trace 0.00 0.00 0.00 0.00 trace 0.00 0.00 

11-11-97 1615 trace 0.00 trace 0.00 0.00 0.00 0.00 trace

11-12-97 1645 trace 0.00 0.00 0.00 0.00 trace 0.00 trace

11-13-97 1745 trace 0.00 0.00 0.00 0.00 trace 0.00 trace

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 65

11-14-97 1845 trace 0.00 trace trace 0.00 trace 0.00 trace

11-15-97 1700 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-16-97 1445 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-17-97 1700 0.23 0.18 0.21 0.03 0.15 0.14 0.16 0.19

11-18-97 1730 0.10 0.08 0.08 0.16 0.09 0.04 0.06 0.09

11-19-97 1630 0.04 trace trace 0.03 trace 0.05 0.03 0.10

11-20-97 1630 0.32 0.17 0.31 0.45 0.25 0.17 0.20 0.33

11-21-97 1630 trace trace trace trace trace trace trace trace 

11-22-97 1615 0.05 0.05 0.01 0.04 0.02 0.01 0.03 0.01

11-23-97 1730 0.08 0.02 0.01 0.07 0.04 0.02 0.03 0.01

11-24-97 1630 0.04 0.005 0.01 0.06 0.02 trace 0.01 0.01

11-25-97 1600 0.12 0.07 0.05 0.15 0.07 0.07 0.08 0.09

11-26-97 1630 trace trace trace trace trace trace trace trace

11-27-97 1700 0.05 0.01 0.01 0.05 0.02 0.01 0.02 0.02

11-28-97 1600 0.36 0.22 0.37 0.50 0.34 0.21 0.19 0.36

11-29-97 1530 0.01 trace trace trace trace trace 0.01 trace

11-30-97 1530 0.05 0.02 0.01 0.05 0.03 0.01 0.02 0.02

12-01-97 1645 trace trace trace trace trace trace trace trace

12-02-97 1615 0.00 0.00 trace 0.00 0.00 0.00 0.00 0.00

12-03-97 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-04-97 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-05-97 1645 trace 0.00 trace trace 0.00 0.00 0.00 trace

12-06-97 1700 0.005 0.00 0.00 trace 0.00 0.00 0.00 trace

12-07-97 1615 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-08-97 1630 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-09-97 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-10-97 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-11-97 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-12-97 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-13-97 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-14-97 1600 0.05 trace 0.01 0.01 0.02 0.01 0.01 0.02

12-15-97 1615 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-16-97 1615 0.45 0.38 0.07 0.75 0.45 0.41 0.32 0.60

12-17-97 1615 0.11 0.04 0.03 0.05 0.09 0.02 0.04 0.09

12-18-97 1600 0.02 trace trace trace trace .005 trace trace

12-19-97 1745 0.05 0.02 0.01 0.03 0.01 0.02 0.03 0.01

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
66 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

12-20-97 1645 0.12 0.03 0.02 0.08 0.04 0.02 0.02 0.04

12-21-97 1545 0.26 0.18 0.08 0.17 0.21 0.15 0.15 0.11

12-22-97 1445 trace trace trace trace trace trace trace trace

12-23-97 1600 0.18 0.10 0.15 0.22 0.15 0.10 0.12 0.16

12-24-97 1500 0.03 0.02 0.02 0.05 0.03 0.02 0.03 0.03

12-25-97 1630 trace trace trace trace trace 0.00 0.00 trace

12-26-97 1615 0.20 0.15 0.20 0.39 0.17 0.26 0.22 0.26

12-27-97 1530 0.04 0.04 0.06 0.05 0.03 0.03 0.02 0.03

12-28-97 1600 0.31 0.20 0.35 0.42 0.20 0.23 0.28 0.29

12-29-97 1700 0.07 0.05 0.04 0.10 0.05 0.04 0.04 0.06

12-30-97 1715 trace trace trace trace trace trace trace trace

12-31-97 1645 trace 0.00 trace trace 0.00 trace trace trace

01-01-98 1630 0.54 0.50 0.32 0.65 0.50 0.42 0.46 0.42

01-02-98 1645 0.32 0.31 0.65 0.55 0.32 0.27 0.28 0.37

01-03-98 1645 trace trace trace trace trace trace trace trace

01-04-98 1715 0.05 0.01 trace 0.04 0.02 0.01 0.02 trace

01-05-98 1630 0.22 0.10 0.18 0.30 0.15 0.10 0.10 0.20

01-06-98 1600 0.22 0.14 0.15 0.32 0.17 0.09 0.14 0.20

01-07-98 1830 0.05 0.07 0.08 0.10 0.05 0.03 0.04 0.06

01-08-98 1700 trace trace trace trace trace trace trace trace

01-09-98 1645 trace trace trace trace trace trace trace trace

01-10-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-11-98 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-12-98 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-13-98 1615 0.45 0.43 0.75 0.58 0.60 0.40 0.72 0.55

01-14-98 1800 0.13 0.05 0.05 0.15 0.07 0.06 0.05 0.10

01-15-98 1745 0.23 0.13 0.15 0.36 0.20 0.07 0.08 0.24

01-16-98 1700 0.05 0.02 0.01 0.03 0.01 .015 0.02 0.02

01-17-98 1630 0.10 0.03 0.02 0.05 0.04 0.03 0.03 0.02 

01-18-98 1630 0.01 0.00 trace trace trace trace trace trace

01-19-98 1700 trace trace trace trace trace trace trace trace

01-20-98 1800 0.13 0.07 0.05 0.16 0.10 0.06 0.08 0.08

01-21-98 1715 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-22-98 1645 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-23-98 1745 0.09 0.03 0.03 0.08 0.04 0.05 0.07 0.04

01-24-98 1745 0.011 0.03 0.02 0.11 0.07 0.04 0.03 0.07

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 67

01-25-98 1630 0.14 0.10 0.18 0.23 0.14 0.10 0.11 0.15

01-26-98 1745 0.06 0.03 0.02 0.06 0.03 0.04 0.02 0.02

01-27-98 1715 trace 0.00 0.00 0.00 trace 0.00 trace trace

01-28-98 1700 0.05 0.02 0.01 0.03 0.01 0.01 0.03 0.01

01-29-98 1730 0.09 0.04 0.02 0.10 0.05 0.03 0.04 0.03

01-30-98 1645 0.01 0.01 trace 0.02 0.02 trace 0.01 0.02

01-31-98 1645 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-01-98 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-02-98 1645 0.01 0.00 0.00 0.005 trace 0.00 0.00 0.00

02-03-98 1715 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-04-98 1645 0.09 0.06 0.01 0.08 0.06 0.03 0.05 0.02

02-05-98 1730 trace trace 0.00 trace trace trace trace trace

02-06-98 1645 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-07-98 1715 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-08-98 1515 0.005 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-09-98 1715 0.09 0.04 0.03 0.10 0.08 0.03 0.04 0.06

02-10-98 1730 0.01 0.00 0.03 0.01 0.08 0.00 trace trace

02-11-98 1915 0.01 0.00 trace trace trace 0.00 0.00 0.00

02-12-98 1915 0.07 0.02 0.02 0.05 0.03 0.02 0.02 0.01

02-13-98 1915 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-14-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-15-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-16-98 1700 0.05 0.02 trace 0.02 0.02 0.01 0.02 trace

02-17-98 1700 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-18-98 1400 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-19-98 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-20-98 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-21-98 1500 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-22-98 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-23-98 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-24-98 1530 0.16 0.05 0.07 0.16 0.13 0.05 0.06 0.14

02-25-98 1400 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-26-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-27-98 1800 0.10 0.05 0.03 0.10 0.03 0.04 0.06 0.05

02-28-98 1700 0.09 0.03 0.03 0.08 0.03 0.05 0.06 0.03

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
68 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

03-01-98 1600 0.29 0.17 0.27 0.35 0.23 0.18 0.23 0.25

03-02-98 1600 0.12 0.17 0.27 0.35 0.23 0.18 0.23 0.25

03-03-98 1700 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-04-98 1600 0.21 0.12 0.06 0.20 0.16 0.09 0.12 0.11

03-05-98 1600 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-06-98 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-07-98 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-08-98 1600 0.08 0.05 0.04 0.09 0.07 0.04 0.04 0.06

03-09-98 1600 0.16 0.10 0.19 0.21 0.15 0.09 0.10 0.17

03-10-98 1600 0.14 0.09 0.09 0.13 0.10 0.07 0.10 0.08

03-11-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-12-98 1600 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-13-98 1500 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-14-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-15-98 1530 0.07 0.03 0.02 0.09 0.04 0.03 0.04 0.03

03-16-98 1730 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-17-98 1530 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-18-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-19-98 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-20-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-21-98 1400 0.12 0.05 0.06 0.12 0.09 0.05 0.07 0.07

03-22-98 1600 0.40 0.16 0.30 0.38 0.30 0.11 0.18 0.29

03-23-98 1430 0.20 0.18 0.11 0.19 0.16 0.11 0.24 0.16

03-24-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-25-98 1700 0.26 0.18 0.12 0.29 0.26 0.12 0.16 0.16

03-26-98 1430 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-27-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-28-98 1930 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-29-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-30-98 1800 0.28 0.12 0.07 0.29 0.18 0.11 0.19 0.14

03-31-98 1500 0.25 0.17 0.29 0.33 0.26 0.15 0.24 0.21

04-01-98 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-02-98 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-03-98 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-04-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-05-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 69

04-06-98 1845 0.00 trace trace trace trace trace trace trace

04-07-98 1730 trace 0.00 0.00 trace 0.00 trace trace 0.00

04-08-98 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-09-98 1800 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-10-98 1800 0.08 0.02 0.00 0.07 0.05 0.02 0.05 trace

04-11-98 1700 0.11 0.05 0.03 0.12 0.09 0.03 0.06 0.07

04-12-98 1500 0.06 0.01 trace 0.04 0.04 trace 0.02 0.02

04-13-98 1730 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-14-98 1800 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-15-98 1800 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-16-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-17-98 1830 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-18-98 1600 0.09 0.03 trace 0.08 0.06 0.03 0.06 0.02

04-19-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-20-98 1900 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-21-98 1700 trace 0.00 0.00 trace 0.00 0.00 0.00 0.00

04-22-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-23-98 1900 0.09 trace 0.00 0.06 0.03 trace 0.01 trace

04-24-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-25-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-26-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-27-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-28-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

04-29-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-30-98 1930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-01-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-02-98 1700 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-03-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-04-98 1900 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-05-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-06-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-07-98 1600 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-08-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-09-98 1700 0.06 trace 0.00 0.06 0.03 0.00 trace 0.02

05-10-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-11-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
70 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

05-12-98 1700 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-13-98 1900 0.06 0.00 0.00 0.03 0.01 0.00 trace trace

05-14-98 1830 0.22 0.08 0.03 0.23 0.18 0.08 0.15 0.09

05-15-98 1700 0.27 0.21 0.27 0.34 0.29 0.20 0.29 0.29

05-16-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-17-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-18-98 1930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-19-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-20-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-21-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-22-98 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-23-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-24-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-25-98 1800 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-26-98 1700 0.67 0.47 0.78 0.88 0.82 0.30 0.51 0.51

05-27-98 1800 0.27 0.14 0.06 0.27 0.26 0.09 0.14 0.16

05-28-98 2100 0.81 0.77 1.35 1.19 1.11 0.55 0.88 1.09

05-29-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-30-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-31-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-01-98 2030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-02-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-03-98 1930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-04-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-05-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-06-98 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-07-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-08-98 1900 0.03 0.00 0.00 0.01 0.00 0.00 0.00 0.00

06-09-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-10-98 2030 0.36 0.24 0.30 0.46 0.49 0.22 0.34 0.30

06-11-98 1930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-12-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-13-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-14-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-15-98 1700 0.08 trace 0.00 0.05 0.05 trace trace 0.01

06-16-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 71

06-17-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-18-98 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-19-98 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-20-98 1545 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-21-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-22-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-23-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-24-98 1700 0.34 0.19 0.20 0.51 0.37 0.24 0.36 0.26

06-25-98 1830 0.07 0.08 0.04 0.09 0.11 0.06 0.08 0.07

06-26-98 1900 0.03 trace 0.00 0.02 trace 0.00 0.00 0.00

06-27-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-28-98 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-29-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-30-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-01-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-02-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-03-98 2100 0.34 0.20 0.30 0.43 0.51 0.12 0.26 0.37

07-04-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-05-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-06-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-07-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-08-98 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-09-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-10-98 1900 0.00 0.01 0.02 0.01 0.02 0.00 0.00 0.00

07-11-98 1900 0.05 trace 0.00 0.01 0.01 0.00 0.00 0.00

07-12-98 1900 0.06 0.03 0.00 0.06 0.09 0.03 0.10 0.00

07-13-98 1900 0.01 0.00 0.00 trace trace 0.00 0.00 0.00

07-14-98 1900 0.24 0.18 0.04 0.27 0.24 0.15 0.24 0.17

07-15-98 1900 0.17 0.10 0.05 0.20 0.18 0.07 0.17 1.10

07-16-98 1800 trace trace trace trace trace trace trace trace

07-17-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-18-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-19-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-20-98 2100 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-21-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-22-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
72 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

07-23-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-24-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-25-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-26-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-27-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-28-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-29-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-30-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 trace trace

07-31-98 1800 0.01 0.00 0.00 0.01 0.00 0.00 0.00 0.00

08-31-98 2400 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-01-98 1730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-02-98 2030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-03-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-04-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-05-98 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-06-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-07-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-08-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-09-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-10-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-11-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-12-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-13-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-14-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-15-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-16-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-17-98 1700 0.12 0.26 0.00 0.10 0.07 0.03 0.06 0.03

09-18-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-19-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-20-98 1900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-21-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-22-98 1745 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-23-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-24-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-25-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-26-98 1830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 73

09-27-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-28-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-29-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-30-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-01-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-02-98 1730 0.15 0.03 0.03 0.06 0.12 0.02 0.04 0.05

10-03-98 1800 0.05 trace 0.00 0.02 0.01 trace trace trace

10-04-98 1730 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-05-98 1700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-06-98 1800 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

1Value subject to large error due to heavy snow storm during this period.

2Data not obtained. Value estimated from the average throughfall collected at the Shaw Island site for this period, multiplied by a factor equal to 

the sum of the throughfall quantities collected in this gage divided by the sum of the average throughfall collected in the Shaw Island gages over all 

periods with no missing data.

Table 14. Precipitation and throughfall in a predominantly evergreen forest located at the south end of Lopez Island, San Juan 

County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
74 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Table 15. Precipitation and throughfall in a predominantly evergreen forest located in Moran State Park, Orcas 

Island, San Juan County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7)

10-01-96 0000 — — — — — — —

11-06-96 1500 15.54 14.76 15.04 16.31 13.77 14.24 14.14

11-14-96 1600 1.60 1.00 1.34 1.60 1.10 1.03 1.10

11-20-96 1750 1.18 0.88 0.92 1.07 0.91 0.82 0.84

11-30-96 1700 3.00 2.80 2.07 2.86 2.00 2.70 2.29

12-03-96 1800 0.50 0.18 0.41 0.05 0.26 0.35 0.17

12-04-96 1400 0.50 0.33 0.31 0.50 0.35 0.18 0.37

12-06-96 1330 0.65 0.30 0.55 0.57 0.38 0.40 0.30

12-09-96 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-12-96 1600 0.25 0.06 0.20 0.24 0.03 0.12 0.04

12-15-96 1215 0.32 0.15 0.17 0.30 0.15 0.10 0.14

12-18-96 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-04-97 1030 22.56 23.57 22.76 23.70 22.81 23.26 22.44

01-09-97 1510 0.82 0.77 0.75 0.80 0.56 0.55 0.57

01-20-97 1030 2.30 2.15 1.79 2.30 1.50 1.39 1.62

01-31-97 0800 2.00 1.55 1.35 1.44 1.27 0.90 1.50

02-16-97 1200 3.32 3.03 2.26 3.30 2.25 2.07 2.13

02-28-97 1130 1.00 0.30 0.65 0.91 0.35 0.50 0.30

03-02-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-08-97 1200 0.67 0.32 0.44 0.68 0.26 0.30 0.27

03-21-97 0930 3.18 2.61 2.63 3.17 2.00 1.58 2.37

03-31-97 1200 0.45 0.12 0.45 0.50 0.20 0.32 0.18

04-01-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-04-97 0930 0.05 0.01 0.04 0.05 0.01 0.03 0.01

04-12-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-20-97 1410 1.31 1.13 0.89 1.36 0.67 0.77 0.84 

04-28-97 1730 0.80 0.43 0.70 0.86 0.36 0.55 0.42

05-07-97 1200 0.50 0.12 0.50 0.59 0.23 0.36 0.17

05-20-97 1430 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-02-97 1322 1.92 1.38 1.60 2.00 1.00 1.30 1.09

06-09-97 1945 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-14-97 1315 0.38 0.22 0.28 0.41 0.17 0.24 0.15

06-20-97 0910 0.41 0.24 0.23 0.43 0.16 0.22 0.21

06-30-97 0912 1.53 1.04 1.73 1.65 1.02 1.15 1.10

07-03-97 1740 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-10-97 1540 1.74 1.32 1.29 1.79 1.16 1.15 1.18

07-26-97 1600 0.05 0.03 0.06 0.08 0.02 0.05 0.04

07-31-97 1400 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 15. Precipitation and throughfall in a predominantly evergreen forest located in Moran State Park, Orcas 

Island, San Juan County, Washington, water years 1997-98

[Values represent cumulative amounts from the data and time of the prior record to that of the current record. —, no data]
Tables 14 through 26 75

08-01-97 0930 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-05-97 1640 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-08-97 1605 0.07 0.02 0.04 0.07 0.01 0.03 0.01

08-12-97 1545 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-17-97 1100 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-24-97 0945 0.06 0.03 0.04 0.07 0.00 0.06 0.01

08-30-97 1322 0.92 0.86 0.64 0.99 0.54 0.65 0.64

09-01-97 1015 0.05 0.01 0.02 0.05 0.00 0.02 0.00

09-06-97 0840 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-09-97 1045 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-30-97 1345 2.86 2.03 1.63 2.87 1.32 1.95 1.35

10-06-97 1615 0.79 0.48 0.80 0.81 0.00 0.57 0.44

10-13-97 1100 0.51 0.16 0.22 0.08 0.11 0.19 0.16

10-22-97 1730 0.67 0.50 0.50 30.70 0.32 0.50 0.40

10-30-97 1300 2.07 1.60 1.67 2.00 1.22 1.34 1.43

11-30-97 1900 3.50 2.10 2.40 3.40 1.50 2.00 31.83

12-01-97 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-05-97 1400 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-11-97 1300 0.16 0.05 0.08 0.17 0.02 0.03 0.02

01-15-98 1600 6.84 5.00 6.00 6.35 4.03 4.70 4.81

01-26-98 1330 1.57 0.76 1.00 1.54 0.59 0.70 0.65

01-31-98 1200 0.34 0.14 0.25 0.33 0.11 0.17 0.10

05-13-98 0910 15.37 14.29 14.56 15.65 13.38 13.49 14.19

05-19-98 0930 0.90 0.58 0.73 0.81 0.52 0.58 0.47

06-05-98 1320 2.84 2.06 2.56 2.72 1.92 2.02 2.25

06-18-98 1105 30.48 0.34 0.41 0.50 0.24 0.36 0.29

06-27-98 1415 31.06 0.95 0.81 1.11 0.70 0.72 0.81

07-07-98 1200 0.46 0.44 0.42 0.48 0.34 0.39 0.35

07-17-98 1030 0.52 0.23 0.49 0.64 0.31 0.44 0.29

09-30-98 2400 10.37 10.19 10.20 10.25 10.15 10.17 10.17

1Data not obtained. Value estimated from the average throughfall collected at the Shaw Island site for this period multiplied by a 

factor equal to the sum of the throughfall quantities collected in this gage divided by the sum of the average throughfall collected in the 

Shaw Island gages over all periods with no missing data. 2Value subject to large error due to heavy snow storm during this period.

3Data not obtained. Values estimated from the average throughfall collected in the other gages at this site, multiplied by a factor 

equal to the sum of throughfall quantities collected in this gage divided by the sum of the average throughfall collected in the other gages 

over all periods with no missing data.

Table 15. Precipitation and throughfall in a predominantly evergreen forest located in Moran State Park, Orcas 

Island, San Juan County, Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches)

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7)
76 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)

09-11-96 1100 — — — — — — — —

09-14-96 1005 0.31 0.15 0.08 0.13 0.18 0.18 0.27 0.12

09-15-96 0930 0.41 0.32 0.29 0.295 0.325 0.36 0.43 0.28

09-16-96 1005 0.01 0.00 0.00 0.00 0.00 trace 0.00 0.00

09-17-96 1015 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-18-96 1015 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-19-96 1015 0.22 0.16 0.10 0.13 0.15 0.15 0.27 0.11

09-20-96 1130 trace trace 0.00 0.00 0.00 trace trace trace

09-21-96 1030 trace 0.00 0.00 0.00 trace trace trace trace

09-22-96 0920 0.00 0.00 0.00 0.00 0.00 0.00 trace 0.00

09-23-96 0955 0.00 0.00 0.00 0.00 0.00 0.00 trace 0.00

09-24-96 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-25-96 0745 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-26-96 0710 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-27-96 0915 0.00 0.00 0.00 0.00 0.00 0.00 trace 0.00

09-28-96 0700 0.00 0.00 0.00 0.00 0.00 0.00 trace 0.00

09-29-96 0930 0.00 trace 0.00 0.00 0.00 0.00 trace 0.00

09-30-96 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-01-96 0915 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-02-96 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-03-96 1015 0.00 0.00 0.00 0.00 0.00 0.00 trace 0.00

10-04-96 1015 0.26 0.14 0.15 0.10 0.12 0.16 0.21 0.09

10-05-96 1015 0.22 0.17 0.25 0.18 0.22 0.23 0.23 0.20

10-06-96 0810 trace trace trace trace trace trace trace trace

10-07-96 0910 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-08-96 0735 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-09-96 0910 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-10-96 0720 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-11-96 1000 0.29 0.14 0.22 0.12 0.145 0.19 0.25 0.24

10-12-96 0910 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-13-96 0725 0.02 0.00 0.00 0.00 0.00 0.00 0.005 0.00

10-14-96 0900 0.12 0.01 0.01 0.00 0.02 0.02 0.05 0.01

10-15-96 0900 0.33 0.16 0.23 0.04 0.10 0.10 0.06 0.08

10-16-96 1620 0.16 0.08 0.05 0.06 0.07 0.11 0.14 0.07

10-17-96 0910 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-18-96 0920 0.57 0.26 0.36 0.11 0.22 0.20 0.18 0.19

10-19-96 1015 trace 0.00 trace 0.00 0.00 0.00 0.00 0.00

10-20-96 0945 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-21-96 1015 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-22-96 1030 0.48 0.33 0.34 0.20 0.33 0.29 0.28 0.26

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98

[Values represent cumulative amounts from the date and time of the prior record to that of the current record. —, no data] 
Tables 14 through 26 77

10-23-96 1030 0.10 0.03 0.02 0.02 0.03 0.02 0.06 trace

10-24-96 1030 0.15 0.03 0.05 trace 0.04 0.03 0.02 0.01

10-25-96 1030 0.10 0.10 trace 0.07 0.10 0.07 0.17 0.07

10-26-96 1030 0.03 0.02 0.02 0.03 0.03 0.02 0.02 0.02

10-27-96 1015 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-28-96 1030 1.50 1.00 1.20 1.10 1.50 1.00 0.90 2.00

10-29-96 1030 0.15 0.13 0.10 0.12 0.14 0.12 0.17 0.11

10-30-96 0930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-31-96 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-01-96 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-02-96 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-03-96 1000 0.19 0.15 0.09 0.09 0.13 0.15 0.20 0.10

11-04-96 0855 0.12 0.05 0.02 0.04 0.055 0.07 0.125 0.04

11-05-96 0930 0.04 0.03 trace 0.01 0.02 0.02 0.04 0.02

11-06-96 0850 0.05 0.00 trace 0.00 trace trace 0.02 0.00

11-07-96 0900 trace 0.00 0.00 0.00 0.00 0.00 trace 0.00

11-08-96 0915 0.33 0.085 0.12 0.04 0.09 0.07 0.11 0.06

11-09-96 1130 0.03 trace trace trace 0.002 trace 0.025 0.01

11-10-96 1015 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-11-96 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-12-96 1130 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-13-96 0920 0.38 0.27 0.28 0.28 0.31 0.30 0.41 0.32

11-14-96 1030 0.22 0.17 0.13 0.17 0.19 0.16 0.26 0.17

11-15-96 1030 0.00 0.00 0.00 0.00 0.00 0.00 trace 0.00

11-16-96 1030 0.16 0.06 0.10 0.05 0.08 0.07 0.11 0.04

11-17-96 0940 0.37 0.23 0.10 0.20 0.24 0.19 0.41 0.22

11-18-96 0910 0.02 0.05 0.06 0.13 0.10 0.04 0.07 0.06

11-19-96 0900 trace trace trace trace trace trace trace trace

11-20-96 1500 0.17 0.11 0.15 0.11 0.11 0.09 0.12 0.11

11-21-96 0915 trace trace trace trace trace trace trace 0.00

11-22-96 0900 trace trace 0.00 0.00 0.00 0.00 0.00 0.00

11-23-96 0915 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-24-96 1000 0.10 0.06 0.04 0.06 0.08 0.08 0.09 0.09

11-25-96 1000 0.15 0.10 0.05 0.07 0.09 0.08 0.09 0.10

11-26-96 1000 0.08 0.06 0.10 0.08 0.09 0.07 0.06 0.10

11-27-96 1000 1.00 0.83 0.70 0.72 0.72 0.70 1.00 1.02

11-28-96 1000 1.00 0.92 0.65 0.88 1.03 0.61 1.12 0.86

11-29-96 1000 0.00 0.00 0.00 0.00 trace trace 0.00 0.00

11-30-96 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
78 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

12-01-96 0930 0.28 0.06 0.09 0.03 0.08 0.08 0.16 0.05

12-02-96 0910 0.07 0.01 0.01 0.00 0.005 trace 0.02 0.005

12-03-96 0905 0.09 0.025 0.03 0.02 0.02 0.03 0.05 0.02

12-04-96 0905 0.16 0.05 0.10 0.02 0.05 0.04 0.01 0.04

12-05-96 0855 0.63 0.40 0.48 0.27 0.49 0.40 0.37 0.34

12-06-96 0955 0.12 0.10 0.04 0.055 0.07 0.07 0.125 0.055

12-07-96 0955 0.02 trace 0.005 0.00 trace trace trace trace

12-08-96 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-09-96 1000 0.09 0.02 0.02 0.01 0.02 0.03 0.05 0.02

12-10-96 1000 0.10 0.03 0.05 0.02 0.04 0.03 0.06 0.03

12-11-96 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-12-96 1000 0.05 0.00 0.00 0.00 0.00 trace 0.02 0.02

12-13-96 1000 0.08 0.00 0.02 0.00 0.03 0.00 0.02 0.01

12-14-96 1000 0.06 0.01 0.02 0.00 0.02 0.00 0.02 0.00

12-15-96 0925 trace trace 0.00 0.00 trace 0.00 0.00 0.00

12-16-96 0910 0.125 0.08 0.07 0.04 0.055 0.04 0.07 0.075

12-17-96 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-18-96 0855 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-20-96 0835 0.49 0.37 0.31 0.32 0.40 0.32 0.41 0.34

12-21-96 0845 0.03 trace 0.005 trace 0.01 trace 0.015 trace

12-22-96 1000 trace trace trace trace trace trace trace trace

12-23-96 1000 0.50 0.20 0.10 0.10 0.15 0.13 0.25 0.25

12-24-96 1000 0.20 0.10 0.05 0.05 0.08 0.07 0.15 0.12

12-25-96 1600 0.08 0.04 0.13 0.04 0.07 0.09 0.10 0.10

12-26-96 1100 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-27-96 1100 0.03 0.00 0.00 0.00 0.00 0.04 0.00 0.00

01-01-97 1605 14.31 12.22 11.45 11.82 12.28 11.73 12.94 13.12

01-02-97 1555 0.10 0.005 0.04 0.02 0.02 0.015 0.03 0.02

01-03-97 0945 0.025 0.02 trace 0.01 0.02 0.022 0.04 0.02

01-04-97 0920 0.38 0.33 0.275 0.34 0.34 0.365 0.39 0.38

01-05-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-06-97 1000 0.20 0.05 0.10 0.02 0.09 0.09 0.20 0.06

01-07-97 1000 0.21 0.06 0.11 0.05 0.10 0.10 0.10 0.06

01-08-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-09-97 1000 0.04 0.04 0.03 0.04 0.05 0.05 0.08 0.05

01-10-97 1000 0.11 0.03 0.02 0.04 0.05 0.03 0.08 0.04

01-11-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-12-97 0935 trace 0.00 trace 0.00 0.00 trace trace trace

01-13-97 1300 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-14-97 0910 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-15-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-16-97 0900 trace 0.00 0.00 0.00 0.00 trace 0.00 trace

01-17-97 0925 0.19 0.04 0.02 0.02 0.04 0.01 0.13 0.05

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 79

01-18-97 1540 1.00 0.91 0.63 0.92 0.94 0.63 1.04 0.81

01-19-97 1000 0.35 0.14 0.19 0.11 0.20 0.14 0.19 0.10

01-20-97 1000 0.47 0.38 0.31 0.40 0.39 0.35 0.50 0.36

01-21-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-22-97 1530 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-23-97 0910 0.16 0.09 0.06 0.07 0.085 0.10 0.14 0.07

01-24-97 1000 0.01 0.00 0.00 0.00 0.00 0.00 0.00 trace

01-29-97 1730 0.33 0.16 0.06 0.13 0.15 0.13 0.24 0.15

01-30-97 0930 1.03 0.79 0.91 0.55 0.85 0.65 0.52 0.54

01-31-97 0915 trace trace trace trace trace trace trace trace

02-01-97 0920 0.14 0.12 0.07 0.09 0.11 0.10 0.15 0.07

02-02-97 0945 0.16 0.09 0.09 0.06 0.09 0.10 0.15 0.06

02-03-97 1000 0.04 0.01 0.02 0.01 0.02 0.01 0.03 0.01

02-04-97 1000 0.05 0.00 0.01 0.01 0.02 0.01 0.02 0.00

02-05-97 1000 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-06-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-07-97 1000 0.06 0.02 0.00 trace 0.02 0.02 0.05 trace

02-08-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-09-97 0940 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-10-97 0945 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-11-97 1020 0.14 0.12 0.03 0.09 0.095 0.095 0.16 0.105

02-12-97 0905 0.63 0.35 0.45 0.25 0.41 0.33 0.27 0.29

02-13-97 0945 0.06 0.02 0.01 0.005 0.015 0.015 0.04 0.01

02-14-97 0915 0.35 0.25 0.29 0.23 0.28 0.25 0.24 0.20

02-15-97 1030 0.83 0.69 0.84 0.64 0.81 0.75 0.81 0.66

02-16-97 1000 0.00 0.00 trace 0.00 0.00 0.00 0.00 0.00

02-17-97 1000 0.13 0.07 0.06 0.05 0.09 0.01 0.13 0.06

02-18-97 1000 0.19 0.08 0.11 0.06 0.08 0.09 0.11 0.06

02-19-97 1000 0.19 0.08 0.12 0.06 0.09 0.08 0.11 0.07

02-20-97 1420 0.03 trace 0.01 trace trace 0.005 0.02 trace

02-21-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-22-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-23-97 1338 0.00 0.00 0.00 0.00 0.00 0.00 trace trace

02-24-97 1100 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-25-97 1430 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-26-97 0920 0.045 0.02 trace 0.01 0.02 0.02 0.05 0.02

02-27-97 0750 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-28-97 0915 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-01-97 1400 0.20 0.20 0.20 0.00 0.02 0.01 0.03 0.01

03-02-97 1000 0.00 0.02 0.03 0.00 0.01 0.01 0.02 0.01

03-03-97 1000 0.04 0.00 0.00 0.00 0.00 0.00 trace 0.00

03-04-97 1000 0.07 0.04 0.01 0.03 0.04 0.04 0.06 0.03

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
80 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

03-05-97 1100 0.02 0.00 trace 0.00 0.00 0.00 0.00 0.00

03-06-97 0935 0.13 0.01 0.04 trace 0.03 0.01 0.04 0.01

03-09-97 0920 0.18 0.04 0.09 0.03 0.06 0.06 0.09 0.03

03-10-97 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-11-97 1045 0.015 0.00 0.00 0.00 0.00 0.00 0.005 trace

03-13-97 0955 0.01 0.06 0.03 0.06 0.06 0.07 0.11 0.05

03-14-97 0910 0.005 trace trace trace trace trace 0.01 trace

03-15-97 1540 0.64 0.59 0.34 0.645 0.62 0.37 0.70 0.60

03-16-97 0945 0.12 0.14 0.13 0.14 0.14 0.11 0.155 0.12

03-17-97 0910 0.25 0.27 0.135 0.22 0.22 0.155 0.28 0.18

03-19-97 0915 0.80 0.31 0.44 0.17 0.33 0.25 0.25 0.19

03-20-97 0855 0.20 0.10 0.09 0.10 0.125 0.10 0.14 0.08

03-21-97 0935 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-23-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-24-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-25-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-26-97 1000 0.21 0.13 0.07 0.11 0.13 0.14 0.21 0.10

03-27-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-28-97 1000 0.02 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-29-97 1000 trace 0.00 0.00 0.00 0.00 0.00 trace 0.00

03-30-97 0905 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-01-97 1515 0.05 trace trace 0.00 trace 0.00 0.02 trace

04-02-97 0815 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

04-03-97 0940 0.13 0.025 0.07 0.02 0.05 0.06 0.10 0.03

04-04-97 0915 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-05-97 0905 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

04-06-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-07-97 0915 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-08-97 0830 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

04-09-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-10-97 0945 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-11-97 0905 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-12-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-13-97 0900 0.02 0.00 0.00 0.00 trace 0.00 0.00 trace

04-14-97 0910 trace 0.00 0.00 0.00 0.00 0.00 trace 0.00

04-15-97 1630 0.08 0.01 trace trace 0.02 trace 0.05 0.015

04-16-97 1640 0.07 0.015 trace trace 0.02 0.01 0.04 0.01

04-17-97 1400 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-18-97 0905 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-19-97 0900 0.02 trace 0.00 0.00 trace 0.00 0.02 trace

04-20-97 0710 0.87 0.74 0.68 0.55 0.72 0.70 0.65 0.57

04-21-97 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 81

04-22-97 0915 0.005 trace trace trace trace trace trace trace

04-23-97 1000 0.21 0.03 0.09 0.02 0.04 0.05 0.05 0.03

04-24-97 1445 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-26-97 0855 0.07 0.02 0.00 trace 0.02 0.01 0.05 0.015

04-27-97 0900 0.22 0.16 0.12 0.16 0.15 0.17 0.24 0.14

04-28-97 0940 0.08 0.04 trace 0.02 0.03 0.02 0.09 0.02

04-30-97 0900 0.09 0.005 0.005 trace 0.01 trace 0.05 0.01

05-01-97 1100 0.13 0.10 0.06 0.07 0.08 0.10 0.14 0.07

05-02-97 1005 0.01 0.005 0.00 trace 0.005 trace 0.01 trace

05-03-97 0900 0.03 trace 0.00 0.00 0.01 trace 0.02 0.01

05-04-97 0930 0.04 trace 0.005 0.00 trace trace trace trace

05-05-97 0855 trace 0.00 0.00 0.00 trace 0.00 0.00 0.00

05-06-97 1010 0.15 0.08 0.05 0.07 0.10 0.08 0.16 0.06

05-07-97 0910 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-08-97 1015 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

05-09-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-10-97 0910 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-11-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-12-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-13-97 0700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-14-97 0740 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-15-97 0645 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-16-97 1005 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-17-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-18-97 0905 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-19-97 0735 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-20-97 1800 0.15 0.09 0.07 0.05 0.10 0.01 0.14 0.06

05-21-97 1810 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-22-97 2035 0.37 0.27 0.26 0.29 0.43 0.35 0.40 0.33

05-23-97 0700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

05-24-97 1855 0.10 0.04 0.02 0.03 0.05 0.06 0.08 0.04

05-25-97 0910 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-26-97 0715 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-27-97 0730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-28-97 1005 0.14 0.07 0.03 0.06 0.09 0.09 0.12 0.07

05-29-97 0720 0.44 0.36 0.21 0.32 0.37 0.31 0.40 0.33

05-30-97 1015 0.10 0.11 0.09 0.07 0.11 0.10 0.09 0.05

05-31-97 1220 0.49 0.41 0.23 0.34 0.44 0.35 0.40 0.32

06-01-97 0940 0.35 0.36 0.19 0.30 0.33 0.25 0.30 0.25

06-02-97 0720 0.00 0.00 0.00 0.00 trace 0.00 trace 0.00

06-03-97 0715 0.03 0.02 0.00 0.01 0.03 0.01 0.04 0.02

06-04-97 2130 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
82 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

06-05-97 1900 0.24 0.14 0.03 0.12 0.14 0.11 0.17 0.12

06-06-97 1920 0.01 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-07-97 0900 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-08-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-09-97 0725 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-10-97 0700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-11-97 0730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-12-97 0725 0.12 0.07 0.01 0.04 0.07 0.05 0.06 0.03

06-13-97 0730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-14-97 0720 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-15-97 0905 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-16-97 0720 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-17-97 0930 0.24 0.10 0.09 0.09 0.09 0.10 0.17 0.07

06-18-97 1205 0.18 0.05 0.12 0.05 0.09 0.08 0.16 0.05

06-19-97 1840 0.01 0.00 0.00 0.00 0.00 0.00 trace 0.00

06-20-97 0755 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-21-97 1010 0.30 0.30 0.20 0.26 0.27 0.26 0.37 0.24

06-22-97 0730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

06-24-97 0925 0.08 0.02 0.02 0.02 0.03 0.04 0.07 0.02

06-25-97 0630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

06-26-97 1900 0.15 0.09 0.02 0.07 0.08 0.06 0.15 0.05

06-27-97 0740 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

06-28-97 0730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

06-29-97 1520 0.56 0.43 0.48 0.34 0.46 0.48 0.675 0.32

06-30-97 0630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-01-97 0730 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-02-97 0700 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-03-97 0650 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-04-97 0745 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-05-97 0740 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-06-97 2050 0.42 0.26 0.18 0.22 0.29 0.25 0.47 0.17

07-07-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-08-97 1840 0.40 0.20 0.16 0.20 0.25 0.21 0.35 0.15

07-09-97 1840 0.11 0.09 0.07 0.08 0.10 0.09 0.13 0.06

07-10-97 2050 0.03 0.01 0.005 trace 0.02 trace 0.02 0.01

07-11-97 2030 0.01 trace 0.00 trace trace 0.00 0.01 0.00

07-12-97 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-13-97 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-14-97 2000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-15-97 0720 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-16-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-17-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 83

07-18-97 0740 0.005 0.00 0.00 0.00 trace 0.00 trace 0.00

07-19-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-20-97 0840 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-21-97 0705 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-22-97 0720 0.04 0.005 trace 0.00 0.02 0.01 0.03 trace

07-23-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-24-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-25-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-26-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-27-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-28-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-29-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-30-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-31-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-01-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

08-02-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-03-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-04-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-05-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-06-97 0945 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-07-97 1000 0.05 0.01 trace trace 0.025 trace 0.04 trace

08-08-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-09-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-10-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-11-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-12-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-13-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-14-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-15-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-16-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-17-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-18-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-19-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-20-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-21-97 1000 0.03 0.005 0.00 0.00 0.015 trace 0.02 0.00

08-22-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-23-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-25-97 1700 0.13 .055 trace 0.04 0.07 0.05 0.08 0.04

08-26-97 1300 0.16 0.08 0.04 0.065 0.08 0.08 0.18 0.08

08-27-97 1400 0.37 0.24 0.30 0.24 0.30 0.28 0.35 0.17

08-29-97 1400 0.02 .012 trace trace trace trace trace 0.01

08-30-97 1300 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-31-97 1400 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
84 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

09-01-97 1400 0.015 trace trace trace trace trace 0.01 trace

09-02-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-03-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-04-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-05-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-06-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-07-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-08-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-09-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-10-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-11-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-12-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-13-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-14-97 1400 0.29 0.21 0.10 0.17 0.17 0.20 0.26 0.13

09-15-97 1500 0.13 0.03 0.03 .025 0.05 0.06 0.09 0.045

09-16-97 1500 0.11 0.02 0.04 trace 0.02 0.01 0.02 0.05

09-17-97 1500 0.25 0.07 0.10 0.06 0.10 0.09 0.14 0.10

09-18-97 1500 0.08 0.03 0.03 0.04 0.03 0.03 0.06 0.05

09-19-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-20-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-21-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-22-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-23-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-24-97 1200 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-25-97 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-26-97 1500 0.45 0.30 0.20 0.26 0.33 0.33 0.48 0.25

09-27-97 1600 0.37 0.22 0.22 0.20 0.29 0.25 0.32 0.18

09-28-97 1600 0.14 0.02 0.02 0.02 0.05 0.05 0.07 0.02

09-29-97 1500 trace trace trace trace trace trace trace trace

09-30-97 1530 0.25 0.14 0.14 0.13 0.14 0.20 0.24 0.12

10-01-97 1545 0.08 0.05 0.02 0.02 0.05 0.05 0.06 0.025 

10-03-97 1500 0.23 0.02 0.05 0.02 0.04 0.04 0.08 0.03

10-04-97 1530 0.05 0.28 0.22 0.22 0.35 0.30 0.42 0.20

10-05-97 1500 0.20 0.11 0.10 0.10 0.14 0.15 0.20 0.10

10-06-97 1500 trace trace trace trace trace trace trace trace

10-07-97 1500 0.02 trace trace trace 0.01 trace 0.01 trace

10-08-97 1500 0.14 0.02 0.04 0.01 0.03 0.02 0.03 0.01

10-09-97 1500 0.11 0.03 0.05 trace 0.03 0.01 0.01 0.02

10-10-97 1530 0.02 trace trace trace trace trace 0.01 trace

10-11-97 1530 0.05 0.01 0.02 trace 0.01 0.02 0.03 0.01

10-12-97 1530 0.02 trace trace trace 0.01 trace 0.02 0.02

10-13-97 1530 0.17 0.15 0.10 0.15 0.15 0.11 0.20 0.15

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 85

10-14-97 1530 0.11 0.08 0.03 0.09 0.09 0.05 0.14 0.08

10-15-97 1500 0.01 0.04 0.02 0.00 0.01 0.01 0.01 0.01

10-16-97 1430 0.08 0.05 0.02 0.02 0.03 0.03 0.10 0.03

10-17-97 1630 trace 0.00 0.00 0.00 0.00 0.00 0.01 0.00

10-18-97 1530 0.00 trace trace trace trace trace trace trace

10-19-97 1530 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-20-97 1530 trace trace 0.00 trace trace 0.00 0.00 0.00

10-21-97 1530 0.06 0.02 0.04 0.05 0.03 0.03 0.05 0.03

10-22-97 1530 0.02 trace trace 0.00 0.00 0.00 trace trace

10-23-97 1530 trace trace trace 0.00 0.00 0.00 0.00 trace

10-24-97 1630 0.00 0.00 0.00 0.00 trace 0.00 0.00 trace

10-25-97 1530 0.05 0.02 trace 0.03 0.03 0.01 0.06 0.02

10-26-97 1530 0.03 0.01 trace trace trace 0.01 trace trace

10-27-97 1530 0.07 0.01 0.02 trace 0.01 0.01 0.06 0.02

10-29-97 1530 1.50 1.25 1.25 0.75 0.75 0.85 0.75 0.75

10-30-97 1530 0.17 0.10 0.07 0.05 0.10 0.12 0.12 0.07

11-01-97 1430 0.02 trace trace trace trace trace 0.01 0.02

11-02-97 1500 0.00 0.00 0.00 0.00 0.00 trace 0.00 trace

11-03-97 1400 0.16 0.05 0.04 0.01 0.02 0.03 0.05 0.05

11-04-97 1430 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-05-97 1530 0.01 trace 0.00 0.00 trace 0.00 0.01 0.01

11-06-97 1530 0.15 0.05 0.06 0.00 0.06 0.06 0.14 0.07

11-07-97 1530 0.10 0.05 0.08 0.06 0.06 0.05 0.11 0.01

11-08-97 1530 trace 0.00 0.00 0.00 trace 0.00 0.00 trace

11-09-97 1600 trace 0.00 0.00 0.00 0.00 0.00 trace trace

11-10-97 1530 trace trace 0.00 0.00 0.00 trace trace trace

11-11-97 1630 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-12-97 1500 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-13-97 1530 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

11-14-97 1530 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

11-15-97 1530 trace trace 0.00 0.00 0.00 0.00 trace trace

11-16-97 1530 trace 0.00 0.00 0.00 0.00 0.00 trace trace

11-17-97 1400 0.15 0.07 0.06 0.03 0.02 0.03 0.10 0.08

11-18-97 1530 0.08 0.03 0.04 0.04 0.06 0.04 0.11 0.05

11-20-97 1530 0.36 0.05 0.08 0.04 0.04 0.04 0.15 0.06

11-21-97 1530 0.01 trace 0.00 0.00 trace 0.00 trace trace

11-24-97 1330 0.48 0.25 0.17 0.20 0.27 0.25 0.48 0.22

11-25-97 1415 0.10 0.07 0.01 0.05 0.07 0.05 0.10 0.06

11-27-97 1530 0.09 0.07 0.06 0.06 0.05 0.05 0.08 0.05

11-28-97 0930 0.32 0.14 0.18 0.21 0.15 0.24 0.30 0.17

11-29-97 1330 0.17 0.03 0.05 0.05 0.04 0.04 0.09 0.03

11-30-97 1400 trace 0.00 0.00 0.00 0.00 0.00 trace trace

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
86 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

12-01-97 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-02-97 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-03-97 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-04-97 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-05-97 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-06-97 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-07-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-08-97 1030 0.07 trace 0.02 trace 0.05 0.01 0.03 0.01

12-09-97 1630 trace 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-10-97 1000 0.045 0.01 0.01 trace 0.01 trace 0.01 trace

12-11-97 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-12-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-13-97 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-14-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-15-97 1000 0.13 0.05 0.01 0.04 0.05 0.09 0.11 0.06

12-16-97 1000 0.77 0.44 0.54 0.36 0.52 0.45 0.36 0.38

12-17-97 1000 0.50 0.36 0.33 0.32 0.40 0.38 0.48 0.33

12-18-97 1000 0.03 0.01 0.01 trace 0.02 0.02 0.03 0.01

12-19-97 1400 0.07 0.02 0.02 0.01 0.01 0.01 0.02 0.02

12-20-97 1530 0.12 0.03 0.06 trace 0.04 0.02 0.05 0.02

12-21-97 1400 0.17 0.15 0.10 0.13 0.15 0.15 0.16 0.12

12-22-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-23-97 1400 0.09 0.01 0.025 0.01 0.025 0.015 0.02 0.02

12-24-97 1100 trace trace trace trace trace trace trace trace

12-25-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-26-97 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-27-97 1000 0.24 0.16 0.17 0.14 0.18 0.15 0.15 0.16

12-28-97 0900 0.27 0.19 0.23 0.16 0.23 0.20 0.24 0.19

12-29-97 1100 0.05 0.01 0.025 0.05 0.015 0.01 0.03 0.005

12-30-97 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

12-31-97 1100 0.01 trace trace trace trace trace trace trace

01-01-98 1500 0.53 0.50 0.33 0.50 0.50 0.42 0.51 0.48

01-02-98 1000 0.06 0.05 0.05 0.05 0.05 0.05 0.05 0.05

01-03-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-04-98 1500 0.23 0.13 0.09 0.24 0.18 0.21 0.32 0.17

01-05-98 1000 0.29 0.10 0.18 0.07 0.14 0.11 0.14 0.09

01-06-98 1000 0.51 0.35 0.29 0.40 0.44 0.37 0.51 0.40

01-07-98 1000 0.15 0.08 0.09 0.08 0.11 0.10 0.16 0.08

01-08-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-09-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-10-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-11-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-12-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 87

01-14-98 1000 0.68 0.50 0.40 0.49 0.55 0.50 0.55 0.51

01-15-98 1000 0.57 0.19 0.28 0.13 0.28 0.26 0.35 0.19

01-16-98 1000 0.18 0.06 0.07 0.04 0.09 0.08 0.11 0.06

01-17-98 1000 0.29 0.09 0.05 0.05 0.08 0.15 0.14 0.07

01-18-98 1030 0.03 0.02 0.015 0.01 0.01 0.01 0.01 0.01

01-19-98 1430 0.09 0.01 0.01 0.02 0.02 0.01 0.05 0.02

01-20-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-21-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

01-22-98 1500 0.01 trace trace trace trace trace trace trace

01-24-98 1400 0.20 0.05 0.05 0.03 0.09 0.04 0.11 0.06

01-25-98 1530 0.25 0.11 0.17 0.09 0.13 0.14 0.18 0.13

01-26-98 1000 0.09 0.03 0.03 trace 0.015 trace 0.02 0.02

01-27-98 1000 0.04 0.01 trace 0.02 0.02 0.02 0.03 0.02

01-30-98 1000 0.23 0.12 0.09 0.11 0.13 0.08 0.21 0.12

01-31-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-01-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-02-98 0930 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-03-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-04-98 1000 0.14 0.07 0.02 0.04 0.05 0.06 0.11 0.03

02-05-98 1400 0.01 trace trace trace trace trace trace trace

02-06-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-07-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-08-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-09-98 1000 0.10 0.02 0.05 0.01 0.03 0.04 0.07 0.02

02-10-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-11-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-12-98 1200 0.03 trace trace trace trace trace trace trace

02-13-98 1400 0.19 0.035 0.06 0.035 0.04 0.05 0.10 0.03

02-14-98 1330 0.04 trace trace 0.01 trace trace 0.02 0.01

02-15-98 0900 0.06 0.03 0.01 0.02 0.02 0.03 0.05 0.02

02-16-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-18-98 1000 0.05 trace 0.01 0.00 0.01 trace 0.02 trace

02-19-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-20-98 1000 0.045 0.01 trace 0.01 0.02 0.02 0.03 0.01

02-21-98 1030 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-22-98 0900 0.04 0.00 0.00 0.00 0.10 trace trace 0.01 

02-23-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-24-98 1000 0.05 0.01 0.02 0.00 0.02 0.01 0.03 0.01

02-25-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-26-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

02-27-98 1000 0.01 0.00 0.00 0.00 0.00 0.00 0.005 0.00

02-28-98 0900 0.09 0.04 0.03 0.04 0.04 0.08 0.06 0.04

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
88 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

03-01-98 0900 0.38 0.17 0.18 0.14 0.18 0.15 0.24 0.18

03-03-98 1000 0.23 0.09 0.08 0.08 0.10 0.10 0.19 0.08

03-04-98 1130 0.16 0.11 0.09 0.10 0.10 0.085 0.17 0.15

03-05-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-06-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-07-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-08-98 0900 0.085 0.02 0.03 trace 0.02 0.01 0.02 0.015

03-09-98 1100 0.05 0.01 0.015 trace 0.015 0.015 0.01 0.005

03-10-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-11-98 1000 0.17 0.03 0.04 0.04 0.05 0.04 0.10 0.15

03-12-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-13-98 1000 0.08 0.02 0.02 0.02 0.03 0.03 0.07 0.04 

03-14-98 1000 0.03 0.02 0.02 0.03 0.02 0.03 0.02 0.02

03-15-98 0900 0.04 0.02 trace 0.01 0.02 0.02 0.04 0.02

03-16-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-17-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-18-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-19-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-20-98 1000 0.03 0.01 0.01 trace trace 0.01 .015 trace

03-21-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-22-98 0900 0.26 0.12 0.10 0.11 0.13 0.14 0.24 0.11

03-23-98 1000 0.23 0.10 0.03 0.09 0.13 0.09 0.23 0.11

03-24-98 1000 0.08 0.04 0.02 0.03 0.03 0.03 0.05 0.04

03-25-98 1000 0.02 0.01 trace 0.01 0.02 0.01 0.03 0.01

03-26-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-27-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-28-98 1000 0.24 0.13 0.10 0.11 0.14 0.18 0.22 0.15

03-29-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-30-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

03-31-98 0730 0.28 0.12 0.09 0.13 0.14 0.16 0.225 0.15

04-01-98 1000 0.05 0.03 0.04 0.03 0.04 0.03 0.05 0.03

04-02-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-03-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-04-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-05-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-06-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-07-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-08-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

04-09-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-10-98 1000 0.07 0.02 trace 0.01 0.02 0.02 0.07 0.01

04-11-98 1000 0.08 0.01 0.01 0.01 0.02 0.01 0.05 0.02

04-12-98 0900 0.05 0.02 0.01 trace 0.05 0.01 0.03 0.01

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 89

04-13-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-14-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-15-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-16-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-17-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-18-98 1000 0.07 0.04 0.01 0.03 0.04 0.04 0.07 0.03

04-19-98 1000 0.04 0.02 trace 0.01 0.01 0.02 0.03 0.02

04-20-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-21-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-22-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-23-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-24-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-25-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-26-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-27-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-28-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-29-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

04-30-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-01-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-02-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-03-98 9000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-04-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-05-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-06-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-07-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-08-98 1000 0.16 0.09 0.03 0.05 0.06 0.08 0.15 0.06

05-09-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-10-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-11-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-12-98 1000 0.02 trace trace trace trace trace 0.01 trace

05-14-98 1000 0.16 0.02 0.02 0.02 0.03 0.03 0.10 0.03

05-15-98 1000 0.14 0.08 0.07 0.06 0.06 0.10 0.12 0.07

05-16-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-17-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-18-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-19-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-20-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-21-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-22-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-23-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-25-98 1000 0.67 0.44 0.80 0.50 0.31 0.45 0.66 0.44

05-26-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-27-98 1000 1.28 0.75 0.83 0.64 0.62 0.94 1.26 0.64

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
90 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

05-28-98 1000 0.05 0.02 0.02 0.02 0.03 0.03 0.05 0.01

05-29-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-30-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

05-31-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-01-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

06-02-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-03-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-04-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-05-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

06-06-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-07-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-08-98 1000 0.02 trace 0.01 trace trace 0.01 0.02 0.01

06-09-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-10-98 1000 0.41 0.28 0.25 0.28 0.14 0.27 0.41 0.21

06-11-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-12-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-13-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-14-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-15-98 1000 0.04 0.01 trace trace trace 0.01 0.03 0.01

06-16-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-17-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-18-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-19-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-20-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-21-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-22-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-23-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-25-98 1000 0.44 0.22 0.22 0.29 0.17 0.31 0.34 0.29

06-26-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-27-98 1000 0.04 0.02 trace trace 0.02 0.03 0.03 0.02

06-28-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-29-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

06-30-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-01-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-02-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-04-98 1000 0.46 0.20 0.32 0.25 0.17 0.32 0.37 0.17

07-05-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00 

07-06-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-07-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-08-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-09-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-10-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 91

07-11-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-12-98 0900 0.15 0.11 0.07 0.09 0.08 0.12 0.13 0.06

07-13-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-14-98 1000 0.13 0.08 0.04 0.06 0.04 0.08 0.10 0.05

07-15-98 1000 0.11 0.05 0.03 0.03 0.02 0.07 0.07 0.02

07-16-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-17-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-18-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-19-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-20-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-21-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-22-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-23-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-24-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-25-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-26-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-27-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-28-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-29-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

07-30-98 1000 0.015 trace 0.00 0.00 0.00 0.00 0.00 0.00

07-31-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-01-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-02-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-03-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-04-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-05-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-06-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-07-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-08-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-09-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-10-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-11-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-12-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-13-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-14-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-15-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-16-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-17-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-18-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-19-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-20-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
92 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington

08-21-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-22-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-23-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-24-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-25-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-26-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-27-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-28-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-29-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-30-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

08-31-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-01-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-02-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-03-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-04-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-05-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-06-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-07-98 1000 0.04 trace 0.00 trace 0.00 0.00 0.02 trace 

09-08-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-09-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-10-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-11-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-12-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-13-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-14-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-15-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-16-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-17-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-18-98 1000 0.19 0.10 0.05 0.08 0.10 0.10 0.16 0.09

09-19-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-20-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-21-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-22-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-23-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-24-98 1000 0.05 0.01 0.01 0.02 0.03 0.01 0.04 0.02

09-25-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-26-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-27-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-28-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-29-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

09-30-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
Tables 14 through 26 93

10-01-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-02-98 1000 0.14 0.04 0.03 0.05 0.06 0.07 0.10 0.04

10-03-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-04-98 0900 0.08 0.04 trace 0.02 0.03 0.02 0.05 0.02

10-05-98 1000 0.08 0.04 trace 0.02 0.03 0.02 0.05 0.02

10-06-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-07-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-08-98 1000 0.04 0.03 0.00 trace 0.03 trace 0.03 0.01

10-09-98 1000 0.08 0.04 0.01 0.03 0.04 0.025 0.05 0.02

10-10-98 1000 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-11-98 0900 0.00 0.00 0.00 0.00 0.00 0.00 0.00 0.00

10-12-98 1000 0.21 0.04 0.03 0.025 0.06 0.03 0.14 0.03

10-13-98 1000 0.09 0.01 0.01 trace 0.02 0.01 0.03 0.01

10-14-98 0900 0.30 0.15 0.19 0.16 0.18 0.20 0.26 0.15

1Value subject to large error due to heavy snow storm during this period.

Table 16. Precipitation and throughfall in a predominantly evergreen forest located on Shaw Island, San Juan County, 

Washington, water years 1997-98—Continued

Date Time

Precipitation

(inches) 

(#1)

Throughfall under forest canopy at indicated gage number (inches)

(#2) (#3) (#4) (#5) (#6) (#7) (#8)
94 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 17. Monthly water-budget components for the L1 study basin, Lopez Island, San Juan County, Washington, water years 1997-98—

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 

Month Year Water Year 1997 October 1996 3.48 1.26 0.00 0.00 0.00 0.00 0.00 0.00 0.71 0.68 2.11 0.69 0.00 

November 1996 4.59 0.44 0.02 0.00 0.04 0.00 0.00 0.00 0.10 0.10 3.84 0.59 0.00 December 1996 3.45 0.32 0.00 0.36 0.44 0.00 0.00 0.08 0.02 0.02 1.75 0.79 0.00 January 1997 3.94 0.40 -0.01 3.28 0.76 0.00 0.00 0.00 0.07 0.07 -0.77 0.61 0.00 February 1997 2.91 0.73 -0.01 1.33 0.76 0.00 0.00 0.00 0.31 0.31 0.02 0.50 0.00 March 1997 2.60 1.36 0.00 0.54 0.83 0.00 0.00 0.00 0.63 0.63 -0.17 0.77 0.00 April 1997 1.75 2.89 0.00 0.02 0.29 0.01 0.01 0.00 1.87 1.86 -1.10 0.68 0.00 May 1997 2.06 4.45 0.01 0.00 0.11 0.00 0.00 0.00 3.17 2.91 -1.57 0.60 0.00 June 1997 1.72 4.96 -0.01 0.00 0.02 0.00 0.00 0.00 3.66 2.89 -1.71 0.53 0.00 July 1997 0.98 5.53 0.00 0.00 0.02 0.00 0.00 0.00 4.43 2.69 -2.06 0.32 0.00 August 1997 0.60 5.05 0.00 0.00 0.01 0.00 0.00 0.00 4.20 1.44 -1.03 0.18 0.00 September 1997 1.96 3.15 0.02 0.00 0.01 0.01 0.00 0.00 2.18 0.78 0.35 0.79 0.00 

Totals 30.04 30.54 0.02 5.53 3.29 0.03 0.02 0.08 21.36 14.38 -0.33 7.05 0.00 

Month Year Water Year 1998 October 1997 4.16 1.28 -0.01 0.00 0.01 0.00 0.00 0.00 0.48 0.48 2.68 1.00 0.00 

November 1997 2.02 0.65 0.01 0.00 0.01 0.00 0.00 0.00 0.26 0.26 1.08 0.65 0.00 December 1997 2.79 0.35 -0.01 0.01 0.11 0.00 0.00 0.00 0.12 0.12 2.01 0.55 0.00 January 1998 3.09 0.40 -0.01 0.38 0.52 0.00 0.00 0.00 0.06 0.06 1.51 0.63 0.00 February 1998 0.72 0.70 0.03 0.00 0.40 0.00 0.00 0.00 0.32 0.32 -0.44 0.41 0.00 March 1998 2.60 1.60 0.00 0.10 0.61 0.00 0.00 0.00 0.81 0.81 0.14 0.93 0.00 April 1998 0.37 3.23 -0.02 0.02 0.21 0.01 0.00 0.00 2.41 2.37 -2.49 0.27 0.00 May 1998 2.17 3.65 0.00 0.00 0.12 0.00 0.00 0.00 2.63 2.39 -0.98 0.63 0.00 June 1998 1.11 4.77 0.00 0.00 0.03 0.00 0.00 0.00 3.69 2.72 -2.00 0.36 0.00 July 1998 1.28 5.21 0.00 0.00 0.02 0.00 0.00 0.00 4.16 2.18 -1.31 0.38 0.00 August 1998 0.06 5.46 0.00 0.00 0.01 0.01 0.00 0.00 4.61 1.10 -1.10 0.05 0.00 September 1998 0.18 3.65 0.00 0.00 0.01 0.01 0.00 0.00 3.02 0.36 -0.32 0.13 0.00 

Totals 20.54 30.95 -0.02 0.52 2.06 0.03 0.02 0.00 22.57 13.17 -1.20 5.99 0.00 

Table 17. Monthly water-budget components for the L1 study basin, Lopez Island, San Juan County, Washington, water years 1997-98[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHG

foliage (zero for cells with land cover for which throughfall data are used); RUNOFF; measured or estimated direct runoff; RECHRG; soil water that percolates below th

potential soil evaporation over bare soil areas (none in this investigation); ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage

transpiration; APLTR, actual plant transpiration; CHGSM, change in soil moisture; EVINT, interception loss computed from input precipitation throughfall, and DPM-

use is not evergreen forest; CHGSNW, change in snowpack; AVTMP, average temperature; DEFCIT, if the following is negative: rain + snowmelt + starting soil moistu

holding capacity - evaporation and transpiration components - observed direct runoff; if the following is positive: rain + snowmelt - (available water-holding capacity + spe

- observed direct runoff - recharge. All values in inches of water except AVTMP, which is in degrees Farenheit. All values rounded to two significant figures. Because of equal the sum of the shown monthly values]
Tables 14 through 26 95

Month Average monthly values

October 3.82 1.27 0.00 0.00 0.00 0.00 0.00 0.00 0.59 0.58 2.39 0.85 0.00 November 3.31 0.54 0.02 0.00 0.02 0.00 0.00 0.00 0.18 0.18 2.46 0.62 0.00 December 3.12 0.33 -0.01 0.19 0.28 0.00 0.00 0.04 0.07 0.07 1.88 0.67 0.00 January 3.51 0.40 -0.01 1.83 0.64 0.00 0.00 0.00 0.07 0.07 0.37 0.62 0.00 February 1.81 0.72 0.01 0.67 0.58 0.00 0.00 0.00 0.32 0.32 -0.21 0.45 0.00 March 2.60 1.48 0.00 0.32 0.72 0.00 0.00 0.00 0.72 0.72 -0.01 0.85 0.00 April 1.06 3.06 -0.01 0.02 0.25 0.01 0.01 0.00 2.14 2.11 -1.79 0.48 0.00 May 2.12 4.05 0.00 0.00 0.11 0.00 0.00 0.00 2.90 2.65 -1.27 0.61 0.00 June 1.41 4.87 0.00 0.00 0.02 0.00 0.00 0.00 3.68 2.80 -1.85 0.44 0.00 July 1.13 5.37 0.00 0.00 0.02 0.00 0.00 0.00 4.29 2.44 -1.68 0.35 0.00 August 0.33 5.25 0.00 0.00 0.01 0.00 0.00 0.00 4.40 1.27 -1.06 0.12 0.00 September 1.07 3.40 0.01 0.00 0.01 0.01 0.00 0.00 2.60 0.57 0.02 0.46 0.00 

Totals 25.29 30.74 0.00 3.02 2.67 0.03 0.02 0.04 21.97 13.77 -0.77 6.52 0.00 

Table 17. Monthly water-budget components for the L1 study basin, Lopez Island, San Juan County, Washington, water years 1997-98—

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 
96 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 18. Monthly water-budget components for the L2 study basin, Lopez Island, San Juan County, Washington, water years 1997-98—

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 

Month Year Water Year 1997 October 1996 3.51 1.56 0.00 0.00 0.00 0.00 0.00 0.00 0.89 0.73 2.10 0.67 0.00 

November 1996 4.54 0.52 0.04 0.00 0.24 0.00 0.00 0.00 0.10 0.10 3.67 0.49 0.00 December 1996 2.98 0.34 -0.01 0.42 0.59 0.00 0.00 0.01 0.01 0.01 1.49 0.47 0.00 January 1997 4.71 0.43 -0.02 3.92 0.73 0.00 0.00 0.00 0.03 0.03 -0.43 0.51 0.00 February 1997 2.87 0.84 -0.02 2.06 0.58 0.00 0.00 0.00 0.33 0.33 -0.52 0.48 0.00 March 1997 2.52 1.57 0.00 0.97 0.40 0.00 0.00 0.00 0.74 0.74 -0.03 0.72 0.00 April 1997 1.78 3.41 0.00 0.22 0.02 0.01 0.00 0.00 2.31 2.21 -1.21 0.66 0.00 May 1997 2.26 5.45 0.00 0.02 0.02 0.00 0.00 0.00 3.99 2.78 -1.24 0.70 0.00 June 1997 1.75 6.10 0.00 0.00 0.04 0.00 0.00 0.00 4.66 2.61 -1.50 0.60 0.00 July 1997 0.90 6.87 0.00 0.00 0.04 0.00 0.00 0.00 5.80 2.20 -1.65 0.31 0.00 August 1997 0.53 6.38 0.00 0.00 0.04 0.00 0.00 0.00 5.67 1.06 -0.75 0.19 0.00 September 1997 2.02 3.96 0.03 0.00 0.02 0.01 0.00 0.00 2.99 0.67 0.48 0.82 0.00 

Totals 30.37 37.42 0.03 7.61 2.71 0.03 0.02 0.02 27.52 13.46 0.40 6.61 0.00 

Month Year Water Year 1998 October 1997 4.27 1.59 -0.02 0.00 0.02 0.00 0.00 0.00 0.57 0.54 2.65 1.07 0.00 

November 1997 .00 0.82 0.02 0.00 0.11 0.00 0.00 0.00 0.31 0.31 1.00 0.56 0.00 December 1997 2.98 0.41 -0.03 0.00 0.36 0.00 0.00 0.00 0.12 0.12 2.13 0.40 0.00 January 1998 3.03 0.47 -0.01 0.15 0.56 0.00 0.00 0.00 0.05 0.05 1.78 0.49 0.00 February 1998 0.68 0.86 0.04 0.15 0.41 0.00 0.00 0.00 0.41 0.41 -0.71 0.39 0.00 March 1998 .67 1.88 -0.01 0.25 0.55 0.00 0.00 0.00 1.00 0.99 0.08 0.80 0.00 April 1998 0.34 3.84 -0.03 0.03 0.30 0.01 0.00 0.00 2.96 2.67 -2.92 0.29 0.00 May 1998 2.05 4.44 0.00 0.00 0.23 0.00 0.00 0.00 3.31 2.29 -1.02 0.55 0.00 June 1998 1.11 5.86 0.00 0.00 0.21 0.00 0.00 0.00 4.73 2.33 -1.74 0.31 0.00 July 1998 1.47 6.50 0.00 0.00 0.04 0.00 0.00 0.00 5.45 1.97 -0.94 0.39 0.00 August 1998 0.07 6.82 0.00 0.00 0.04 0.01 0.00 0.00 6.17 1.06 -1.10 0.07 0.00 September 1998 0.21 4.56 0.00 0.00 0.04 0.01 0.00 0.00 4.09 0.40 -0.40 0.17 0.00 

Totals 20.88 38.06 -0.03 0.58 2.86 0.03 0.01 0.00 29.14 13.14 -1.18 5.48 0.00 

Table 18. Monthly water-budget components for the L2 study basin, Lopez Island, San Juan County, Washington, water years 1997-98[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHGfoliage (zero for cells with land cover for which throughfall data are used); RUNOFF; measured or estimated direct runoff; RECHRG; soil water that percolates below th

potential soil evaporation over bare soil areas (none in this investigation); ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage

transpiration; APLTR, actual plant transpiration; CHGSM, change in soil moisture; EVINT, interception loss computed from input precipitation throughfall, and DPM-

use is not evergreen forest; CHGSNW, change in snowpack; AVTMP, average temperature; DEFCIT, if the following is negative: rain + snowmelt + starting soil moistu

holding capacity - evaporation and transpiration components - observed direct runoff; if the following is positive: rain + snowmelt - (available water-holding capacity + s

moisture) - observed direct runoff - recharge. All values in inches of water except AVTMP, which is in degrees Farenheit. All values rounded to two significant figures. Bexactly equal the sum of the shown monthly values]
Tables 14 through 26 97

Month Average monthly values

October 3.89 1.58 -0.01 0.00 0.01 0.00 0.00 0.00 0.73 0.64 2.38 0.87 0.00 November 3.27 0.67 0.03 0.00 0.17 0.00 0.00 0.00 0.20 0.20 2.34 0.52 0.00 December 2.98 0.38 -0.02 0.21 0.47 0.00 0.00 0.01 0.07 0.07 1.81 0.43 0.00 January 3.87 0.45 -0.01 2.04 0.64 0.00 0.00 0.00 0.04 0.04 0.68 0.50 0.00 February 1.78 0.85 0.01 1.10 0.49 0.00 0.00 0.00 0.37 0.37 -0.62 0.43 0.00 March 2.60 1.73 0.00 0.61 0.48 0.00 0.00 0.00 0.87 0.87 0.02 0.76 0.00 April 1.06 3.63 -0.02 0.13 0.16 0.01 0.00 0.00 2.64 2.44 -2.06 0.47 0.00 May 2.16 4.94 0.00 0.01 0.12 0.00 0.00 0.00 3.65 2.53 -1.13 0.62 0.00 June 1.43 5.98 0.00 0.00 0.12 0.00 0.00 0.00 4.69 2.47 -1.62 0.46 0.00 July 1.19 6.68 0.00 0.00 0.04 0.00 0.00 0.00 5.63 2.09 -1.30 0.35 0.00 August 0.30 6.60 0.00 0.00 0.04 0.00 0.00 0.00 5.92 1.06 -0.93 0.13 0.00 September 1.12 4.26 0.01 0.00 0.03 0.01 0.00 0.00 3.54 0.53 0.04 0.50 0.00 

Totals 25.63 37.74 0.00 4.10 2.78 0.03 0.01 0.01 28.33 13.30 -0.39 6.05 0.00 

Table 18. Monthly water-budget components for the L2 study basin, Lopez Island, San Juan County, Washington, water years 1997-98—

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 
98 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 19. Monthly water-budget components for the L3 study basin, Lopez Island, San Juan County, Washington, 1997-98—Continued DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 

Month Year Water Year 1997 October 1996 3.33 3.00 0.00 0.00 0.00 0.00 0.00 0.00 2.51 1.03 1.76 0.54 0.00 

November 1996 4.56 0.97 0.01 0.36 0.04 0.00 0.00 0.00 0.53 0.33 3.16 0.65 0.00 December 1996 3.49 0.54 0.00 1.46 0.08 0.00 0.00 0.06 0.16 0.14 0.80 0.95 0.00 January 1997 3.34 0.77 -0.01 5.43 0.07 0.00 0.00 0.00 0.43 0.39 -2.85 0.50 0.00 February 1997 2.85 1.64 0.00 1.51 0.04 0.00 0.00 0.00 1.22 0.94 0.33 0.43 0.00 March 1997 2.54 3.07 0.00 0.78 0.07 0.00 0.00 0.00 2.28 1.25 -0.37 0.81 0.00 April 1997 1.69 6.49 0.00 0.17 0.01 0.00 0.00 0.00 5.40 1.84 -0.90 0.65 0.00 May 1997 1.95 10.26 0.00 0.03 0.00 0.00 0.00 0.00 8.87 2.11 -0.72 0.55 0.00 June 1997 1.71 11.42 0.00 0.01 0.00 0.00 0.00 0.00 10.03 2.06 -0.80 0.44 0.00 July 1997 0.99 12.85 0.00 0.00 0.00 0.00 0.00 0.00 11.58 1.60 -0.91 0.30 0.00 August 1997 0.61 11.95 0.00 0.00 0.00 0.00 0.00 0.00 10.92 0.55 -0.09 0.15 0.00 September 1997 1.93 7.42 0.00 0.00 0.00 0.00 0.00 0.00 6.41 0.61 0.53 0.78 0.00 

Totals 28.98 70.37 0.00 9.76 0.31 0.02 0.01 0.06 60.33 12.88 -0.08 6.76 0.00 

Month Year Water Year 1998 October 1997 4.12 3.06 0.00 0.00 0.01 0.00 0.00 0.00 2.34 0.86 2.40 0.86 0.00 

November 1997 1.98 1.60 0.00 0.01 0.06 0.00 0.00 0.00 1.18 0.54 0.67 0.69 0.00 December 1997 2.65 0.77 0.00 0.18 0.06 0.00 0.00 0.00 0.52 0.33 1.47 0.60 0.00 January 1998 3.01 0.85 0.00 1.16 0.07 0.00 0.00 0.00 0.42 0.33 0.77 0.68 0.00 February 1998 0.69 1.69 0.00 0.57 0.06 0.00 0.00 0.00 1.31 0.76 -1.12 0.41 0.00 March 1998 2.53 3.63 0.00 0.49 0.07 0.00 0.00 0.00 2.75 1.07 -0.16 1.06 0.00 April 1998 0.38 7.29 0.00 0.12 0.06 0.01 0.00 0.00 6.37 1.94 -2.01 0.26 0.00 May 1998 2.20 8.36 0.00 0.02 0.00 0.00 0.00 0.00 7.18 1.89 -0.47 0.76 0.00 June 1998 1.07 10.95 0.00 0.00 0.00 0.00 0.00 0.00 9.71 2.10 -1.38 0.34 0.00 July 1998 1.23 12.15 0.00 0.00 0.00 0.00 0.00 0.00 10.96 1.47 -0.55 0.30 0.00 August 1998 0.06 12.73 0.00 0.00 0.00 0.00 0.00 0.00 11.66 0.47 -0.46 0.05 0.00 September 1998 0.17 8.57 0.00 0.00 0.00 0.01 0.00 0.00 7.82 0.14 -0.08 0.11 0.00 

Totals 20.07 71.64 0.00 2.54 0.40 0.02 0.01 0.00 62.21 11.92 -0.93 6.12 0.00 

Table 19. Monthly water-budget components for the L3 study basin, Lopez Island, San Juan County, Washington, water year 1997-98[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHGfoliage (zero for cells with land cover for which throughfall data are used); RUNOFF; measured or estimated direct runoff; RECHRG; soil water that percolates below th

potential soil evaporation over bare soil areas (none in this investigation); ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage

transpiration; APLTR, actual plant transpiration; CHGSM, change in soil moisture; EVINT, interception loss computed from input precipitation throughfall, and DPM-

use is not evergreen forest; CHGSNW, change in snowpack; AVTMP, average temperature; DEFCIT, if the following is negative: rain + snowmelt + starting soil moistu

holding capacity - evaporation and transpiration components - observed direct runoff; if the following is positive: rain + snowmelt - (available water-holding capacity + s

moisture) - observed direct runoff - recharge. All values in inches of water except AVTMP, which is in degrees Farenheit. All values rounded to two significant figures. B

exactly equal the sum of the shown monthly values]
Tables 14 through 26 99

Month Average monthly values

October 3.73 3.03 0.00 0.00 0.00 0.00 0.00 0.00 2.42 0.94 2.08 0.70 0.00 November 3.27 1.28 0.00 0.18 0.05 0.00 0.00 0.00 0.85 0.44 1.92 0.67 0.00 December 3.07 0.66 0.00 0.82 0.07 0.00 0.00 0.03 0.34 0.24 1.14 0.77 0.00 January 3.17 0.81 0.00 3.30 0.07 0.00 0.00 0.00 0.43 0.36 -1.04 0.59 0.00 February 1.77 1.66 0.00 1.04 0.05 0.00 0.00 0.00 1.26 0.85 -0.40 0.42 0.00 March 2.53 3.35 0.00 0.63 0.07 0.00 0.00 0.00 2.51 1.16 -0.27 0.94 0.00 April 1.03 6.89 0.00 0.15 0.04 0.00 0.00 0.00 5.88 1.89 -1.46 0.46 0.00 May 2.07 9.31 0.00 0.03 0.00 0.00 0.00 0.00 8.03 2.00 -0.60 0.66 0.00 June 1.39 11.18 0.00 0.01 0.00 0.00 0.00 0.00 9.87 2.08 -1.09 0.39 0.00 July 1.11 12.50 0.00 0.00 0.00 0.00 0.00 0.00 11.27 1.54 -0.73 0.30 0.00 August 0.34 12.34 0.00 0.00 0.00 0.00 0.00 0.00 11.29 0.51 -0.27 0.10 0.00 September 1.05 7.99 0.00 0.00 0.00 0.00 0.00 0.00 7.11 0.38 0.22 0.45 0.00 

Totals 24.53 71.00 0.00 6.15 0.35 0.02 0.01 0.03 61.27 12.40 -0.50 6.44 0.00 

Table 19. Monthly water-budget components for the L3 study basin, Lopez Island, San Juan County, Washington, 1997-98—Continued

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 
100 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 20. Monthly water-budget components for the SJ1 study basin, San Juan Island, San Juan County, Washington, water years 199

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 

Month Year Water Year 1997 October 1996 4.76 1.16 0.00 0.01 0.03 0.02 0.02 0.00 0.64 0.64 2.83 1.22 0.00 

November 1996 5.28 0.41 0.00 1.06 0.08 0.01 0.01 0.00 0.12 0.12 1.80 0.92 0.00 December 1996 5.40 0.31 0.00 2.20 0.08 0.00 0.00 0.08 0.05 0.05 0.47 2.01 0.00 January 1997 5.44 0.41 0.00 7.22 0.08 0.01 0.01 0.00 0.11 0.11 -2.98 1.26 0.00 February 1997 3.67 0.78 0.00 2.40 0.07 0.01 0.01 0.00 0.38 0.38 0.26 0.77 0.00 March 1997 3.63 1.43 0.00 2.22 0.08 0.02 0.02 0.00 0.63 0.63 -0.66 1.32 0.00 April 1997 2.22 2.89 0.00 0.56 0.01 0.05 0.02 0.00 1.71 1.71 -0.46 0.84 0.00 May 1997 2.13 4.09 0.00 0.13 0.00 0.02 0.00 0.00 2.71 2.00 -0.41 0.52 0.00 June 1997 1.71 4.52 0.00 0.07 0.00 0.00 0.00 0.00 3.12 2.03 -0.72 0.40 0.00 July 1997 1.24 4.89 0.00 0.03 0.00 0.00 0.00 0.00 3.56 1.47 -0.62 0.38 0.00 August 1997 0.90 4.31 0.00 0.00 0.00 0.03 0.01 0.00 3.14 0.38 0.26 0.24 0.00 September 1997 1.93 2.73 0.00 0.00 0.00 0.04 0.01 0.00 1.73 0.69 0.47 0.74 0.00 

Totals 38.31 27.94 0.00 15.90 0.43 0.22 0.10 0.08 17.91 10.20 0.25 10.62 0.00 

Month Year Water Year 1998 October 1997 4.02 1.16 0.00 0.09 0.01 0.02 0.02 0.00 0.55 0.55 2.27 1.10 0.00 

November 1997 2.52 0.57 0.00 0.33 0.08 0.01 0.01 0.00 0.28 0.28 0.71 1.09 0.00 December 1997 3.18 0.33 0.00 1.37 0.08 0.01 0.01 0.00 0.13 0.13 0.66 0.92 0.00 January 1998 4.13 0.39 0.00 3.25 0.08 0.01 0.01 0.00 0.07 0.07 -0.57 1.26 0.00 February 1998 1.25 0.68 0.00 0.71 0.08 0.01 0.01 0.00 0.30 0.30 -0.64 0.77 0.00 March 1998 2.90 1.63 0.00 0.55 0.08 0.03 0.02 0.00 0.78 0.78 0.18 1.25 0.00 April 1998 0.39 3.17 0.00 0.18 0.05 0.05 0.01 0.00 2.20 2.19 -2.26 0.23 0.00 May 1998 2.56 3.41 0.00 0.04 0.00 0.02 0.00 0.00 2.25 1.63 0.10 0.80 0.00 June 1998 1.50 4.34 0.00 0.02 0.00 0.00 0.00 0.00 3.02 1.78 -0.82 0.52 0.00 July 1998 0.92 4.57 0.00 0.05 0.00 0.00 0.00 0.00 3.31 0.99 -0.39 0.32 0.00 August 1998 0.01 4.78 0.00 0.01 0.00 0.04 0.00 0.00 3.54 0.14 -0.13 0.01 0.00 September 1998 0.17 3.20 0.00 0.00 0.00 0.05 0.00 0.00 2.29 0.06 0.01 0.09 0.00 

Totals 23.54 28.22 0.00 6.60 0.47 0.23 0.08 0.00 18.72 8.90 -0.88 8.36 0.00 

Table 20. Monthly water-budget components for the SJ1 study basin, San Juan Island, San Juan County, Washington, water years 199[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHG

foliage (zero for cells with land cover for which throughfall data are used); RUNOFF; measured or estimated direct runoff; RECHRG; soil water that percolates below thpotential soil evaporation over bare soil areas (none in this investigation); ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage

transpiration; APLTR, actual plant transpiration; CHGSM, change in soil moisture; EVINT, interception loss computed from input precipitation throughfall, and DPM-

use is not evergreen forest; CHGSNW, change in snowpack; AVTMP, average temperature; DEFCIT, if the following is negative: rain + snowmelt + starting soil moistu

holding capacity - evaporation and transpiration components - observed direct runoff; if the following is positive: rain + snowmelt - (available water-holding capacity + spe

- observed direct runoff - recharge. All values in inches of water except AVTMP, which is in degrees Farenheit. All values rounded to two significant figures. Because of equal the sum of the shown monthly values]
Tables 14 through 26 101

Month Average monthly values

October 4.39 1.16 0.00 0.05 0.02 0.02 0.02 0.00 0.59 0.59 2.55 1.16 0.00 November 3.90 0.49 0.00 0.69 0.08 0.01 0.01 0.00 0.20 0.20 1.26 1.01 0.00 December 4.29 0.32 0.00 1.79 0.08 0.00 0.00 0.04 0.09 0.09 0.56 1.47 0.00 January 4.78 0.40 0.00 5.24 0.08 0.01 0.01 0.00 0.09 0.09 -1.78 1.26 0.00 February 2.46 0.73 0.00 1.55 0.07 0.01 0.01 0.00 0.34 0.34 -0.19 0.77 0.00 March 3.27 1.53 0.00 1.39 0.08 0.02 0.02 0.00 0.71 0.71 -0.24 1.29 0.00 April 1.31 3.03 0.00 0.37 0.03 0.05 0.01 0.00 1.96 1.95 -1.36 0.53 0.00 May 2.34 3.75 0.00 0.09 0.00 0.02 0.00 0.00 2.48 1.82 -0.15 0.66 0.00 June 1.60 4.43 0.00 0.04 0.00 0.00 0.00 0.00 3.07 1.91 -0.77 0.46 0.00 July 1.08 4.73 0.00 0.04 0.00 0.00 0.00 0.00 3.44 1.23 -0.50 0.35 0.00 August 0.45 4.54 0.00 0.01 0.00 0.03 0.00 0.00 3.34 0.26 0.07 0.13 0.00 September 1.05 2.96 0.00 0.00 0.00 0.05 0.01 0.00 2.01 0.37 0.24 0.42 0.00 

Totals 30.92 28.08 0.00 11.25 0.45 0.23 0.09 0.04 18.31 9.55 -0.31 9.49 0.00 

Table 20. Monthly water-budget components for the SJ1 study basin, San Juan Island, San Juan County, Washington, water years 199

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 
102 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 21. Monthly water-budget components for the OR1 study basin, Orcas Island, San Juan County, Washington, water years 1997-9

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 

Month Year Water Year 1997 October 1996 4.33 1.15 0.00 0.01 0.00 0.03 0.02 0.00 0.64 0.64 2.47 1.17 0.00 

November 1996 4.81 0.40 0.00 1.08 0.05 0.01 0.01 0.00 0.12 0.12 2.62 0.86 0.00 December 1996 4.92 0.31 0.00 2.10 0.08 0.01 0.01 0.08 0.05 0.05 0.41 1.91 0.00 January 1997 4.95 0.41 0.00 6.44 0.04 0.01 0.01 0.00 0.11 0.11 -1.49 1.19 0.00 February 1997 3.35 0.79 0.00 2.56 0.05 0.02 0.02 0.00 0.40 0.40 -0.28 0.71 0.00 March 1997 3.31 1.45 0.00 1.78 0.05 0.03 0.03 0.00 0.67 0.67 -0.37 1.16 0.00 April 1997 2.02 2.93 0.00 0.40 0.00 0.06 0.03 0.00 1.75 1.75 -0.54 0.73 0.00 May 1997 1.94 4.08 0.00 0.16 0.00 0.03 0.00 0.00 2.73 2.60 -1.07 0.39 0.00 June 1997 1.56 4.52 0.00 0.05 0.00 0.00 0.00 0.00 3.13 2.71 -1.48 0.32 0.00 July 1997 1.13 4.87 0.00 0.01 0.00 0.00 0.00 0.00 3.50 1.92 -1.12 0.32 0.00 August 1997 0.82 4.24 0.00 0.00 0.00 0.04 0.01 0.00 3.04 0.63 -0.05 0.23 0.00 September 1997 1.76 2.71 0.00 0.00 0.00 0.06 0.02 0.00 1.71 0.64 0.44 0.65 0.00 

Totals 34.90 27.87 0.00 14.60 0.28 0.29 0.15 0.08 17.85 12.26 -0.47 9.65 0.00 

Month Year Water Year 1998 October 1997 3.67 1.14 0.00 0.00 0.00 0.03 0.03 0.00 0.55 0.55 2.05 1.02 0.00 

November 1997 2.29 0.56 0.00 0.03 0.01 0.01 0.01 0.00 0.28 0.28 0.92 1.02 0.00 December 1997 2.90 0.33 0.00 0.68 0.03 0.01 0.01 0.00 0.13 0.13 1.28 0.81 0.00 January 1998 3.76 0.38 0.00 2.17 0.08 0.01 0.01 0.00 0.08 0.08 0.27 1.13 0.00 February 1998 1.14 0.68 0.00 0.53 0.04 0.01 0.01 0.00 0.32 0.32 -0.47 0.69 0.00 March 1998 2.64 1.65 0.00 0.25 0.08 0.04 0.03 0.00 0.82 0.82 0.30 1.14 0.00 April 1998 0.36 3.20 0.00 0.15 0.02 0.07 0.01 0.00 2.20 2.19 -2.15 0.19 0.00 May 1998 2.33 3.42 0.00 0.04 0.00 0.03 0.00 0.00 2.23 2.11 -0.47 0.67 0.00 June 1998 1.36 4.35 0.00 0.02 0.00 0.00 0.00 0.00 3.02 2.37 -1.45 0.43 0.00 July 1998 0.84 4.54 0.00 0.01 0.00 0.00 0.00 0.00 3.25 1.35 -0.81 0.29 0.00 August 1998 0.01 4.75 0.00 0.00 0.00 0.05 0.00 0.00 3.44 0.38 -0.38 0.01 0.00 September 1998 0.15 3.17 0.00 0.00 0.00 0.07 0.00 0.00 2.23 0.11 -0.04 0.07 0.00 

Totals 21.44 28.19 0.00 3.88 0.26 0.32 0.11 0.00 18.55 10.70 -0.94 7.48 0.00 

Table 21. Monthly water-budget components for the OR1 study basin, Orcas Island, San Juan County, Washington, water years 1997-9[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHG

foliage (zero for cells with land cover for which throughfall data are used); RUNOFF; measured or estimated direct runoff; RECHRG; soil water that percolates below th

potential soil evaporation over bare soil areas (none in this investigation); ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage

transpiration; APLTR, actual plant transpiration; CHGSM, change in soil moisture; EVINT, interception loss computed from input precipitation throughfall, and DPM-use is not evergreen forest; CHGSNW, change in snowpack; AVTMP, average temperature; DEFCIT, if the following is negative: rain + snowmelt + starting soil moistu

holding capacity - evaporation and transpiration components - observed direct runoff; if the following is positive: rain + snowmelt - (available water-holding capacity + spe

- observed direct runoff - recharge. All values in inches of water except AVTMP, which is in degrees Farenheit. All values rounded to two significant figures. Because of 

equal the sum of the shown monthly values]
Tables 14 through 26 103

Month Average monthly values

October 4.00 1.15 0.00 0.00 0.00 0.03 0.02 0.00 0.60 0.60 2.26 1.10 0.00 November 3.55 0.48 0.00 0.56 0.03 0.01 0.01 0.00 0.20 0.20 1.77 0.94 0.00 December 3.91 0.32 0.00 1.39 0.06 0.01 0.01 0.04 0.09 0.09 0.84 1.36 0.00 January 4.36 0.40 0.00 4.30 0.06 0.01 0.01 0.00 0.09 0.09 -0.61 1.16 0.00 February 2.24 0.73 0.00 1.55 0.05 0.02 0.02 0.00 0.36 0.36 -0.37 0.70 0.00 March 2.98 1.55 0.00 1.02 0.07 0.03 0.03 0.00 0.75 0.75 -0.04 1.15 0.00 April 1.19 3.07 0.00 0.27 0.01 0.07 0.02 0.00 1.98 1.97 -1.34 0.46 0.00 May 2.13 3.75 0.00 0.10 0.00 0.03 0.00 0.00 2.48 2.36 -0.77 0.53 0.00 June 1.46 4.44 0.00 0.03 0.00 0.00 0.00 0.00 3.07 2.54 -1.47 0.38 0.00 July 0.98 4.70 0.00 0.01 0.00 0.00 0.00 0.00 3.37 1.63 -0.96 0.31 0.00 August 0.41 4.50 0.00 0.00 0.00 0.05 0.00 0.00 3.24 0.51 -0.21 0.12 0.00 September 0.95 2.94 0.00 0.00 0.00 0.06 0.01 0.00 1.97 0.38 0.20 0.36 0.00 

Totals 28.17 28.03 0.00 9.24 0.27 0.31 0.13 0.04 18.20 11.48 -0.70 8.56 0.00 

Table 21. Monthly water-budget components for the OR1 study basin, Orcas Island, San Juan County, Washington, water years 1997-9

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 
104 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 22. Monthly water-budget components for the SH1 study basin, Shaw Island, San Juan County, Washington, water years 1997-9

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 

Month Year Water Year 1997 October 1996 3.83 1.08 0.00 0.00 0.00 0.00 0.00 0.00 0.60 0.60 1.92 1.30 0.00 

November 1996 4.60 0.39 0.01 0.30 0.14 0.00 0.00 0.00 0.09 0.09 2.93 1.14 0.00 December 1996 3.79 0.31 0.00 1.08 0.25 0.00 0.00 0.08 0.03 0.03 0.73 1.63 0.00 January 1997 4.75 0.39 0.00 2.84 0.25 0.00 0.00 0.00 0.08 0.08 -0.04 1.62 0.00 February 1997 3.04 0.70 0.00 1.19 0.22 0.00 0.00 0.00 0.33 0.33 0.29 0.95 0.00 March 1997 2.83 1.28 0.00 0.76 0.25 0.00 0.00 0.00 0.57 0.57 0.05 1.11 0.00 April 1997 1.86 2.64 0.00 0.30 0.24 0.00 0.00 0.00 1.57 1.57 -1.08 0.83 0.00 May 1997 2.09 3.84 0.00 0.09 0.11 0.00 0.00 0.00 2.59 2.58 -1.24 0.55 0.00 June 1997 1.64 4.28 -0.01 0.07 0.03 0.00 0.00 0.00 2.93 2.69 -1.64 0.51 0.00 July 1997 0.99 4.68 0.00 0.01 0.00 0.00 0.00 0.00 3.46 2.40 -1.80 0.39 0.00 August 1997 0.65 4.16 0.00 0.00 0.00 0.00 0.00 0.00 3.13 1.11 -0.72 0.27 0.00 September 1997 1.88 2.63 0.01 0.00 0.00 0.00 0.00 0.00 1.64 0.64 0.37 0.85 0.00 

Totals 31.96 26.38 0.01 6.64 1.49 0.00 0.00 0.08 17.03 12.69 -0.25 11.15 0.00 

Month Year Water Year 1998 October 1997 3.95 1.07 0.00 0.01 0.01 0.00 0.00 0.00 0.41 0.41 2.09 1.42 0.00 

November 1997 2.10 0.53 0.00 0.06 0.11 0.00 0.00 0.00 0.23 0.23 0.68 1.02 0.00 December 1997 2.90 0.33 0.00 0.35 0.16 0.00 0.00 0.00 0.11 0.11 1.28 1.00 0.00 January 1998 3.31 0.37 0.00 1.02 0.20 0.00 0.00 0.00 0.07 0.07 0.86 1.16 0.00 February 1998 0.87 0.62 0.01 0.38 0.19 0.00 0.00 0.00 0.28 0.28 -0.50 0.52 0.00 March 1998 2.62 1.47 0.00 0.36 0.23 0.00 0.00 0.00 0.73 0.73 0.07 1.22 0.00 April 1998 0.34 2.91 -0.01 0.12 0.10 0.00 0.00 0.00 2.05 2.02 -2.11 0.23 0.00 May 1998 2.15 3.19 0.00 0.06 0.03 0.00 0.00 0.00 2.15 1.73 -0.40 0.73 0.00 June 1998 1.21 4.12 0.00 0.01 0.01 0.00 0.00 0.00 2.94 2.06 -1.34 0.48 0.00 July 1998 1.17 4.39 0.00 0.00 0.00 0.00 0.00 0.00 3.22 1.57 -0.92 0.52 0.00 August 1998 0.04 4.60 0.00 0.00 0.00 0.00 0.00 0.00 3.52 0.67 -0.66 0.03 0.00 September 1998 0.18 3.06 0.00 0.00 0.00 0.00 0.00 0.00 2.27 0.20 -0.13 0.11 0.00 

Totals 20.84 26.66 -0.01 2.36 1.04 0.00 0.00 0.00 17.99 10.09 -1.08 8.45 0.00 

Table 22. Monthly water-budget components for the SH1 study basin, Shaw Island, San Juan County, Washington, water years 1997-9[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHG

foliage (zero for cells with land cover for which throughfall data are used); RUNOFF; measured or estimated direct runoff; RECHRG; soil water that percolates below thpotential soil evaporation over bare soil areas (none in this investigation); ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage

transpiration; APLTR, actual plant transpiration; CHGSM, change in soil moisture; EVINT, interception loss computed from input precipitation throughfall, and DPM-

use is not evergreen forest; CHGSNW, change in snowpack; AVTMP, average temperature; DEFCIT, if the following is negative: rain + snowmelt + starting soil moistuholding capacity - evaporation and transpiration components - observed direct runoff; if the following is positive: rain + snowmelt - (available water-holding capacity + spe

- observed direct runoff - recharge. All values in inches of water except AVTMP, which is in degrees Farenheit. All values rounded to two significant figures. Because of 

equal the sum of the shown monthly values]
Tables 14 through 26 105

Month Average monthly values

October 3.89 1.08 0.00 0.01 0.01 0.00 0.00 0.00 0.50 0.50 2.00 1.36 0.00 November 3.35 0.46 0.00 0.18 0.13 0.00 0.00 0.00 0.16 0.16 1.80 1.08 0.00 December 3.35 0.32 0.00 0.71 0.20 0.00 0.00 0.04 0.07 0.07 1.01 1.31 0.00 January 4.03 0.38 0.00 1.93 0.22 0.00 0.00 0.00 0.08 0.08 0.41 1.39 0.00 February 1.96 0.66 0.00 0.78 0.21 0.00 0.00 0.00 0.30 0.30 -0.11 0.74 0.00 March 2.73 1.37 0.00 0.56 0.24 0.00 0.00 0.00 0.65 0.65 0.06 1.16 0.00 April 1.10 2.77 -0.01 0.21 0.17 0.00 0.00 0.00 1.81 1.80 -1.59 0.53 0.00 May 2.12 3.52 0.00 0.08 0.07 0.00 0.00 0.00 2.37 2.15 -0.82 0.64 0.00 June 1.42 4.20 0.00 0.04 0.02 0.00 0.00 0.00 2.93 2.37 -1.49 0.49 0.00 July 1.08 4.53 0.00 0.01 0.00 0.00 0.00 0.00 3.34 1.99 -1.36 0.45 0.00 August 0.35 4.38 0.00 0.00 0.00 0.00 0.00 0.00 3.32 0.89 -0.69 0.15 0.00 September 1.03 2.84 0.01 0.00 0.00 0.00 0.00 0.00 1.96 0.42 0.12 0.48 0.00 

Totals 26.40 26.52 0.00 4.50 1.27 0.00 0.00 0.04 17.51 11.39 -0.66 9.80 0.00 

Table 22. Monthly water-budget components for the SH1 study basin, Shaw Island, San Juan County, Washington, water years 1997-9

DATE PRECP POTET CHGINT RUNOFF RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EVINT CHGSNW 
106 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 23. Monthly water-budget components for Lopez Island, San Juan County, Washington, water years 1997-98—Continued DATE PRECP POTET CHGINT SYM-RO RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EV

Month Year Water Year 1997 October 1996 3.54 2.35 0.00 0.02 0.00 0.02 0.02 0.00 1.85 0.73 2.17 0

November 1996 4.78 0.79 0.02 0.21 0.06 0.01 0.01 0.00 0.44 0.16 3.73 0December 1996 3.73 0.48 0.00 0.67 0.33 0.00 0.00 0.06 0.17 0.06 1.72 0January 1997 3.60 0.66 -0.01 1.40 0.53 0.01 0.01 0.00 0.34 0.16 0.96 0February 1997 3.00 1.31 0.00 1.46 0.52 0.01 0.01 0.00 0.92 0.45 0.11 0March 1997 2.70 2.43 0.00 1.08 0.56 0.02 0.02 0.00 1.71 0.75 -0.50 0April 1997 1.79 5.12 0.00 0.48 0.49 0.05 0.04 0.00 4.11 1.78 -1.65 0May 1997 2.04 8.05 0.00 0.16 0.23 0.05 0.05 0.00 6.80 2.54 -1.45 0June 1997 1.77 8.96 0.00 0.07 0.14 0.05 0.05 0.00 7.67 2.66 -1.61 0July 1997 1.04 10.07 -0.01 0.02 0.07 0.06 0.06 0.00 8.89 2.62 -2.02 0August 1997 0.65 9.33 0.00 -0.01 0.04 0.06 0.05 0.00 8.33 1.49 -1.08 0September 1997 2.00 5.80 0.01 0.02 0.05 0.04 0.03 0.00 4.82 0.84 0.32 0

Totals 30.65 55.34 0.02 5.59 3.03 0.38 0.35 0.07 46.07 14.22 0.68 6

Month Year Water Year 1998 October 1997 4.28 2.39 0.00 0.13 0.05 0.02 0.02 0.00 1.70 0.57 2.64 0

November 1997 2.08 1.26 0.01 0.16 0.08 0.01 0.01 0.00 0.88 0.31 0.86 0December 1997 2.78 0.64 -0.01 0.29 0.18 0.01 0.01 0.00 0.40 0.16 1.59 0January 1998 3.19 0.71 0.00 0.71 0.44 0.01 0.01 0.00 0.35 0.12 1.28 0February 1998 0.75 1.33 0.02 0.35 0.32 0.01 0.01 0.00 0.97 0.39 -0.76 0March 1998 2.65 2.87 0.00 0.38 0.42 0.03 0.02 0.00 2.09 0.84 0.03 0April 1998 0.39 5.75 -0.02 0.13 0.19 0.05 0.04 0.00 4.88 2.06 -2.28 0May 1998 2.30 6.57 0.00 0.05 0.11 0.04 0.04 0.00 5.52 1.97 -0.54 0June 1998 1.13 8.60 0.00 0.02 0.06 0.05 0.05 0.00 7.48 2.40 -1.74 0July 1998 1.26 9.51 0.00 0.01 0.05 0.05 0.05 0.00 8.40 2.00 -1.17 0August 1998 0.06 9.97 0.00 -0.04 0.03 0.06 0.05 0.00 8.94 1.01 -1.04 0September 1998 0.17 6.70 0.00 -0.03 0.01 0.05 0.04 0.00 5.95 0.37 -0.33 0

Totals 21.05 56.29 -0.02 2.15 1.94 0.39 0.34 0.00 47.57 12.20 -1.46 5

Table 23. Monthly water-budget components for Lopez Island, San Juan County, Washington, water years 1997-98[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHG

foliage (zero for cells with land cover for which throughfall data are used); SYM-RO, DPM-simulated direct runoff; small negative values should be interpreted as zero-n

error during summation for large number of cells; RECHRG; soil water that percolates below the root zone (recharge); SOLPEV, potential soil evaporation over bare soiACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage-type-dependent potential transpiration; APLTR, actual plant transpiratio

moisture; EVINT, interception loss computed from input throughfall, or DPM-simulated throughfall if not input; CHGSNW, change in snowpack; AVTMP, average temp

is negative: rain + snowmelt + starting soil moisture in excess of available water-holding capacity – evaporation and transpiration components – observed direct runoff; if 

snowmelt – (available water-holding capacity + specific yield – starting soil moisture) – observed direct runoff – recharge. All values in inches of water except AVTMP, wvalues rounded to two significant figures. Because of rounding totals may not exactly equal the sum of the shown monthly values]
Tables 14 through 26 107

Month Average monthly values

October 3.91 2.37 0.00 0.08 0.03 0.02 0.02 0.00 1.78 0.65 2.40 0November 3.43 1.02 0.01 0.19 0.07 0.01 0.01 0.00 0.66 0.23 2.30 0December 3.26 0.56 -0.01 0.48 0.25 0.00 0.00 0.03 0.28 0.11 1.65 0January 3.39 0.68 0.00 1.05 0.49 0.01 0.01 0.00 0.35 0.14 1.12 0February 1.87 1.32 0.01 0.90 0.42 0.01 0.01 0.00 0.95 0.42 -0.33 0March 2.67 2.65 0.00 0.73 0.49 0.02 0.02 0.00 1.90 0.80 -0.24 0April 1.09 5.44 -0.01 0.30 0.34 0.05 0.04 0.00 4.50 1.92 -1.96 0May 2.17 7.31 0.00 0.10 0.17 0.05 0.04 0.00 6.16 2.25 -1.00 0June 1.45 8.78 0.00 0.04 0.10 0.05 0.05 0.00 7.58 2.53 -1.68 0July 1.15 9.79 -0.01 0.02 0.06 0.05 0.05 0.00 8.65 2.31 -1.59 0August 0.36 9.65 0.00 -0.02 0.04 0.06 0.05 0.00 8.64 1.25 -1.06 0September 1.09 6.25 0.01 0.00 0.03 0.05 0.03 0.00 5.38 0.60 -0.01 0

Totals 25.82 55.82 0.00 3.87 2.49 0.38 0.34 0.03 46.82 13.21 -0.39 6

Table 23. Monthly water-budget components for Lopez Island, San Juan County, Washington, water years 1997-98—Continued

DATE PRECP POTET CHGINT SYM-RO RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EV
108 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 24. Monthly water-budget components for San Juan Island, San Juan County, Washington, water years 1997-98—Continued DATE PRECP POTET CHGINT SYM-RO RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EV

Month Year Water Year 1997 October 1996 4.10 1.14 0.00 0.06 0.00 0.04 0.04 0.00 0.59 0.57 2.57 0

November 1996 5.31 0.40 0.02 0.70 0.15 0.01 0.01 0.00 0.08 0.08 3.60 0December 1996 4.23 0.31 0.00 1.54 0.31 0.01 0.01 0.08 0.02 0.02 1.20 1January 1997 4.49 0.39 0.00 2.61 0.37 0.01 0.01 0.00 0.06 0.06 0.63 0February 1997 3.39 0.67 0.00 2.48 0.37 0.03 0.03 0.00 0.27 0.27 -0.34 0March 1997 3.09 1.23 0.00 1.63 0.40 0.05 0.05 0.00 0.49 0.49 -0.36 0April 1997 2.04 2.63 0.00 0.66 0.32 0.10 0.08 0.00 1.57 1.56 -1.36 0May 1997 2.31 4.05 0.00 0.20 0.17 0.11 0.09 0.00 2.81 2.69 -1.45 0June 1997 1.94 4.54 -0.01 0.03 0.10 0.10 0.10 0.00 3.24 2.90 -1.77 0July 1997 1.15 5.05 0.00 -0.06 0.03 0.10 0.10 0.00 3.96 2.73 -2.00 0August 1997 0.73 4.60 0.00 -0.07 0.00 0.11 0.09 0.00 3.68 1.26 -0.78 0September 1997 2.20 2.87 0.02 -0.01 0.00 0.09 0.07 0.00 1.86 0.77 0.54 0

Totals 34.99 27.88 0.02 9.77 2.24 0.77 0.68 0.08 18.62 13.40 0.48 8

Month Year Water Year 1998 October 1997 4.68 1.15 -0.01 0.11 0.03 0.04 0.04 0.00 0.37 0.37 3.01 1

November 1997 2.35 0.58 0.01 0.32 0.13 0.02 0.02 0.00 0.22 0.22 0.88 0December 1997 3.17 0.33 -0.01 0.71 0.24 0.01 0.01 0.00 0.09 0.09 1.47 0January 1998 3.64 0.38 -0.01 1.49 0.39 0.01 0.01 0.00 0.05 0.05 0.92 0February 1998 0.89 0.63 0.02 0.65 0.29 0.02 0.02 0.00 0.25 0.25 -0.81 0March 1998 2.97 1.45 0.00 0.78 0.37 0.06 0.05 0.00 0.67 0.67 0.06 1April 1998 0.42 2.94 -0.03 0.25 0.18 0.11 0.08 0.00 2.10 2.07 -2.43 0May 1998 2.53 3.33 0.00 0.03 0.08 0.09 0.07 0.00 2.33 2.14 -0.47 0June 1998 1.30 4.37 0.00 -0.05 0.03 0.09 0.09 0.00 3.30 2.64 -1.85 0July 1998 J1.38 4.76 0.00 -0.06 0.01 0.10 0.10 0.00 3.71 2.03 -1.13 0August 1998 0.06 5.00 0.00 -0.09 0.00 0.13 0.10 0.00 4.07 0.84 -0.84 0September 1998 0.20 3.32 0.00 -0.06 0.00 0.11 0.07 0.00 2.61 0.27 -0.21 0

Totals 23.59 28.23 -0.02 4.10 1.75 0.79 0.67 0.00 19.76 11.65 -1.39 6

Table 24. Monthly water-budget components for San Juan Island, San Juan County, Washington, water years 1997-98[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHGfoliage (zero for cells with land cover for which throughfall data are used); SYM-RO, DPM-simulated direct runoff; small negative values should be interpreted as zero-n

error during summation for large number of cells; RECHRG; soil water that percolates below the root zone (recharge); SOLPEV, potential soil evaporation over bare soi

ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage-type-dependent potential transpiration; APLTR, actual plant transpiratio

moisture; EVINT, interception loss computed from input throughfall, or DPM-simulated throughfall if not input; CHGSNW, change in snowpack; AVTMP, average tem

following is negative: rain + snowmelt + starting soil moisture in excess of available water-holding capacity – evaporation and transpiration components – observed direc

positive: rain + snowmelt – (available water-holding capacity + specific yield – starting soil moisture) – observed direct runoff – recharge. All values in inches of water ex

Farenheit. All values rounded to two significant figures. Because of rounding totals may not exactly equal the sum of the shown monthly values]
Tables 14 through 26 109

Month Average monthly values

October 0.39 1.14 0.00 0.09 0.02 0.04 0.04 0.00 0.48 0.47 2.79 0November 3.83 0.49 0.02 0.51 0.14 0.02 0.02 0.00 0.15 0.15 2.24 0December 3.70 0.32 -0.01 1.13 0.27 0.01 0.01 0.04 0.06 0.06 1.34 0January 4.06 0.38 0.00 2.05 0.38 0.01 0.01 0.00 0.06 0.06 0.78 0February 2.14 0.65 0.01 1.56 0.33 0.03 0.03 0.00 0.26 0.26 -0.58 0March 3.03 1.34 0.00 1.21 0.39 0.05 0.05 0.00 0.58 0.58 -0.15 0April 1.23 2.79 -0.01 0.46 0.25 0.10 0.08 0.00 1.83 1.82 -1.90 0May 2.42 3.69 0.00 0.12 0.12 0.10 0.08 0.00 2.57 2.42 -0.96 0June 1.62 4.45 -0.01 -0.01 0.06 0.09 0.09 0.00 3.27 2.77 -1.81 0July 1.27 4.90 0.00 -0.06 0.02 0.10 0.10 0.00 3.83 2.38 -1.57 0August 0.40 4.80 0.00 -0.08 0.00 0.12 0.10 0.00 3.87 1.05 -0.81 0September 1.20 3.10 0.01 -0.04 0.00 0.10 0.07 0.00 2.23 0.52 0.16 0

Totals 29.29 28.05 0.00 6.93 1.99 0.78 0.68 0.04 19.19 12.52 -0.46 7

Table 24. Monthly water-budget components for San Juan Island, San Juan County, Washington, water years 1997-98—Continued

DATE PRECP POTET CHGINT SYM-RO RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EV
110 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 25. Monthly water-budget components for Orcas Island, San Juan County, Washington, water years 1997-98—Continued DATE PRECP POTET CHGINT SYM-RO RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EV

Month Year Water Year 1997 October 1996 4.93 1.05 0.00 0.10 0.01 0.02 0.02 0.00 0.56 0.56 3.09 1

November 1996 5.75 0.39 0.00 1.71 0.13 0.01 0.01 0.00 0.10 0.10 2.94 0December 1996 5.50 0.31 0.00 2.71 0.21 0.01 0.01 0.08 0.04 0.04 0.64 1January 1997 5.47 0.39 0.00 3.98 0.24 0.01 0.01 0.00 0.09 0.09 0.04 1February 1997 3.89 0.71 0.00 3.25 0.23 0.02 0.02 0.00 0.34 0.34 -0.63 0March 1997 3.76 1.29 0.00 1.98 0.25 0.03 0.03 0.00 0.57 0.56 -0.15 1April 1997 2.34 2.61 0.00 0.49 0.18 0.06 0.06 0.00 1.52 1.52 -0.67 0May 1997 2.35 3.72 0.00 0.21 0.15 0.07 0.07 0.00 2.46 2.44 -0.94 0June 1997 1.94 4.15 -0.01 0.10 0.10 0.07 0.07 0.00 2.77 2.72 -1.48 0July 1997 1.32 4.51 0.00 0.01 0.06 0.08 0.08 0.00 3.21 2.74 -1.91 0August 1997 0.93 3.98 0.00 -0.04 0.03 0.08 0.07 0.00 2.87 1.46 -0.83 0September 1997 2.18 2.53 0.01 0.00 0.02 0.06 0.05 0.00 1.56 0.91 0.48 0

Totals 40.37 25.65 0.01 14.50 1.60 0.51 0.49 0.09 16.08 13.48 0.59 9

Month Year Water Year 1998 October 1997 0.59 1.04 0.00 0.15 0.04 0.02 0.02 0.00 0.45 0.45 2.83 1

November 1997 2.68 0.52 0.00 0.43 0.11 0.01 0.01 0.00 0.23 0.23 0.85 1December 1997 3.42 0.32 0.00 1.28 0.17 0.01 0.01 0.00 0.11 0.11 1.06 0January 1998 4.31 0.37 0.00 2.58 0.25 0.01 0.01 0.00 0.06 0.06 0.34 1February 1998 1.23 0.62 0.00 0.53 0.19 0.01 0.01 0.00 0.27 0.27 -0.43 0March 1998 3.16 1.48 0.00 0.93 0.23 0.03 0.03 0.00 0.71 0.71 0.08 1April 1998 0.44 2.86 -0.01 0.20 0.12 0.07 0.06 0.00 1.94 1.93 -2.10 0May 1998 2.78 3.11 0.00 0.09 0.08 0.06 0.06 0.00 2.00 1.96 -0.08 0June 1998 1.56 4.01 0.00 0.03 0.07 0.07 0.07 0.00 2.75 2.54 -1.58 0July 1998 1.14 4.23 0.00 -0.02 0.04 0.07 0.07 0.00 2.99 2.01 -1.34 0August 1998 0.03 4.44 0.00 -0.07 0.02 0.09 0.08 0.00 3.26 0.99 -1.01 0September 1998 0.19 2.94 0.00 -0.05 0.00 0.07 0.05 0.00 2.10 0.35 -0.27 0

Totals 25.53 25.94 -0.01 6.08 1.33 0.52 0.48 0.00 16.87 11.61 -1.65 7

Table 25. Monthly water-budget components for Orcas Island, San Juan County, Washington, water years 1997-98[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHGfoliage (zero for cells with land cover for which throughfall data are used); SYM-RO, DPM-simulated direct runoff; small negative values should be interpreted as zero-nerror during summation for large number of cells; RECHRG; soil water that percolates below the root zone (recharge); SOLPEV, potential soil evaporation over bare soi

ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage-type-dependent potential transpiration; APLTR, actual plant transpiration

moisture; EVINT, interception loss computed from input throughfall, or DPM-simulated throughfall if not input; CHGSNW, change in snowpack; AVTMP, average temp

is negative: rain + snowmelt + starting soil moisture in excess of available water-holding capacity – evaporation and transpiration components – observed direct runoff; if 

snowmelt – (available water-holding capacity + specific yield – starting soil moisture) – observed direct runoff – recharge. All values in inches of water except AVTMP, wvalues rounded to two significant figures. Because of rounding totals may not exactly equal the sum of the shown monthly values]
Tables 14 through 26 111

Month Average monthly values

October 4.76 1.04 0.00 0.12 0.02 0.02 0.02 0.00 0.50 0.50 2.96 1November 4.21 0.45 0.00 1.07 0.12 0.01 0.01 0.00 0.17 0.17 1.90 0December 4.46 0.32 0.00 2.00 0.19 0.01 0.01 0.04 0.08 0.08 0.85 1January 4.89 0.38 0.00 3.28 0.25 0.01 0.01 0.00 0.08 0.08 0.19 1February 2.56 0.67 0.00 1.89 0.21 0.02 0.02 0.00 0.30 0.30 -0.53 0March 3.46 1.38 0.00 1.46 0.24 0.03 0.03 0.00 0.64 0.63 -0.04 1April 1.39 2.74 0.00 0.35 0.15 0.06 0.06 0.00 1.73 1.72 -1.38 0May 2.57 3.42 0.00 0.15 0.11 0.07 0.06 0.00 2.23 2.20 -0.51 0June 1.75 4.08 0.00 0.06 0.08 0.07 0.07 0.00 2.76 2.63 -1.53 0July 1.23 4.37 0.00 -0.01 0.05 0.08 0.08 0.00 3.10 2.37 -1.62 0August 0.48 4.21 0.00 -0.05 0.02 0.08 0.07 0.00 3.07 1.23 -0.92 0September 1.19 2.73 0.00 -0.02 0.01 0.06 0.05 0.00 1.83 0.63 0.10 0

Totals 32.95 25.79 0.00 10.29 1.46 0.52 0.49 0.04 16.47 12.54 -0.53 8

Table 25. Monthly water-budget components for Orcas Island, San Juan County, Washington, water years 1997-98—Continued

DATE PRECP POTET CHGINT SYM-RO RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EV
112 Estimates of Ground-Water Recharge on Lopez, San Juan, Orcas, and Shaw Islands, Washington Table 26. Monthly water-budget components for Shaw Island, San Juan County, Washington, wter years 1997-98—Continued DATE PRECP POTET CHGINT SYM-RO RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EV

Month Year Water Year 1997 October 1996 4.06 1.11 0.00 0.03 0.02 0.01 0.01 0.00 0.61 0.61 2.16 

November 1996 5.06 0.40 0.01 0.40 0.16 0.00 0.00 0.00 0.09 0.09 3.30 December 1996 4.32 0.31 0.00 1.36 0.21 0.00 0.00 0.08 0.03 0.03 0.93 January 1997 4.47 0.40 0.00 2.07 0.26 0.00 0.00 0.00 0.09 0.09 0.71 February 1997 3.30 0.74 0.00 2.35 0.26 0.01 0.01 0.00 0.35 0.35 -0.56 0March 1997 3.08 1.35 0.00 1.56 0.29 0.01 0.01 0.00 0.60 0.60 -0.51 April 1997 1.98 2.76 0.00 0.72 0.28 0.02 0.02 0.00 1.64 1.64 -1.50 0May 1997 2.15 3.94 0.00 0.11 0.11 0.03 0.03 0.00 2.61 2.58 -1.20 0June 1997 1.80 4.37 -0.01 0.00 0.03 0.03 0.03 0.00 2.94 2.70 -1.44 0July 1997 1.12 4.75 0.00 -0.03 0.01 0.04 0.04 0.00 3.41 2.47 -1.76 0August 1997 0.74 4.19 0.00 -0.03 0.00 0.03 0.03 0.00 3.06 1.16 -0.69 0September 1997 2.04 2.66 0.01 -0.01 0.00 0.02 0.02 0.00 1.63 0.72 0.44 0

Totals 34.12 26.99 0.01 8.52 1.62 0.21 0.21 0.08 17.08 13.06 -0.10 10

Month Year Water Year 1998 October 1997 4.31 1.10 0.00 0.03 0.02 0.01 0.01 0.00 0.43 0.43 2.44 

November 1997 2.28 0.55 0.00 0.19 0.14 0.00 0.00 0.00 0.24 0.24 0.66 December 1997 3.02 0.33 0.00 0.41 0.18 0.00 0.00 0.00 0.12 0.12 1.37 0January 1998 3.58 0.38 0.00 1.10 0.26 0.00 0.00 0.00 0.07 0.07 1.02 February 1998 0.93 0.65 0.01 0.69 0.23 0.01 0.01 0.00 0.29 0.29 -0.84 0March 1998 2.81 1.55 0.00 0.61 0.27 0.01 0.01 0.00 0.76 0.76 -0.10 April 1998 0.40 3.03 -0.01 0.16 0.12 0.03 0.02 0.00 2.09 2.09 -2.23 0May 1998 2.42 3.29 0.00 0.01 0.02 0.03 0.02 0.00 2.15 1.84 -0.25 0June 1998 1.29 4.21 0.00 -0.02 0.01 0.03 0.03 0.00 2.92 2.21 -1.43 0July 1998 1.20 4.44 0.00 -0.03 0.00 0.03 0.03 0.00 3.18 1.70 -0.99 0August 1998 0.05 4.65 0.00 -0.03 0.00 0.04 0.03 0.00 3.45 0.67 -0.66 0September 1998 0.18 3.10 0.00 -0.02 0.00 0.03 0.02 0.00 2.25 0.20 -0.13 0

Totals 22.47 27.28 -0.01 3.11 1.25 0.22 0.21 0.00 17.97 10.64 -1.14 

Table 26. Monthly water-budget components for Shaw Island, San Juan County, Washington, water years 1997-98[PRECP, measured precipitation; POTET, potential evapotranspiration (may be less than sum of evaporation and transpiration components, as discussed in report); CHGfoliage (zero for cells with land cover for which throughfall data are used); SYM-RO, DPM-simulated direct runoff; small negative values should be interpreted as zero-nerror during summation for large number of cells; RECHRG; soil water that percolates below the root zone (recharge); SOLPEV, potential soil evaporation over bare soi

ACTSEV, actual bare-soil evaporation; SNWEVP, direct evaporation of snow; PPLTR, foliage-type-dependent potential transpiration; APLTR, actual plant transpiration

moisture; EVINT, interception loss computed from input throughfall, or DPM-simulated throughfall if not input; CHGSNW, change in snowpack; AVTMP, average temp

is negative: rain + snowmelt + starting soil moisture in excess of available water-holding capacity – evaporation and transpiration components – observed direct runoff; if 

snowmelt – (available water-holding capacity + specific yield – starting soil moisture) – observed direct runoff – recharge. All values in inches of water except AVTMP, wvalues rounded to two significant figures. Because of rounding totals may not exactly equal the sum of the shown monthly values]
Tables 14 through 26 113

Month Average monthly values

October 4.18 1.11 0.00 0.03 0.02 0.01 0.01 0.00 0.52 0.52 2.30 November 3.67 0.47 0.00 0.30 0.15 0.00 0.00 0.00 0.17 0.17 1.98 December 3.67 0.32 0.00 0.89 0.19 0.00 0.00 0.04 0.08 0.08 1.15 January 4.03 0.39 0.00 1.58 0.26 0.00 0.00 0.00 0.08 0.08 0.87 February 2.12 0.69 0.00 1.52 0.25 0.01 0.01 0.00 0.32 0.32 -0.70 0March 2.94 1.45 0.00 1.08 0.28 0.01 0.01 0.00 0.68 0.68 -0.30 April 1.19 2.90 0.00 0.44 0.20 0.02 0.02 0.00 1.87 1.86 -1.86 0May 2.29 3.61 0.00 0.06 0.07 0.03 0.03 0.00 2.38 2.21 -0.73 0June 1.54 4.29 0.00 -0.01 0.02 0.03 0.03 0.00 2.93 2.46 -1.43 0July 1.16 4.60 0.00 -0.03 0.01 0.03 0.03 0.00 3.30 2.09 -1.37 0August 0.39 4.42 0.00 -0.03 0.00 0.03 0.03 0.00 3.26 0.92 -0.68 0September 1.11 2.88 0.00 -0.01 0.00 0.02 0.02 0.00 1.94 0.46 0.16 0

Totals 28.29 27.13 0.00 5.81 1.44 0.22 0.21 0.04 17.52 11.85 -0.62 9

Table 26. Monthly water-budget components for Shaw Island, San Juan County, Washington, wter years 1997-98—Continued

DATE PRECP POTET CHGINT SYM-RO RECHRG SOLPEV ACTSEV SNWEVP PPLTR APLTR CHGSM EV
Estimates of Ground-Water Recharge from Precipitation to Glacial-Deposit and Bedrock Aquifers

on Lopez, San Juan, Orcas, and Shaw Islands, San Juan County, Washington

Orr, Bauer, and Wayenberg USGS WRIR 02-4114

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