Prepared in cooperation with the

TAHOE REGIONAL PLANNING AGENCY

Surface- and Ground-Water Characteristics in the

Upper Truckee River and Trout Creek Watersheds, 

South Lake Tahoe, California and Nevada, 

July-December 1996

U.S. Department of the Interior

U.S. Geological Survey

Water-Resources Investigations Report 00-4001
Surface- and Ground-Water Characteristics in the

Upper Truckee River and Trout Creek Watersheds, 

South Lake Tahoe, California and Nevada, 

July-December 1996

By Timothy G. Rowe and Kip K. Allander

U.S. Department of the Interior

U.S. Geological Survey

Water-Resources Investigations Report 00-4001

Prepared in cooperation with the

TAHOE REGIONAL PLANNING AGENCY

Carson City, Nevada

2000
U.S. DEPARTMENT OF THE INTERIOR

BRUCE BABBITT, Secretary

U.S. GEOLOGICAL SURVEY

CHARLES G. GROAT, Director

Any use of trade names in this publication is for descriptive purposes 

only and does not constitute endorsement by the U.S. Government

For additional information Copies of this report can be

contact: purchased from:

District Chief U.S. Geological Survey 

U.S. Geological Survey Branch of Information Services

333 West Nye Lane, Room 203 Box 25286

Carson City, NV 89706-0866 Denver, CO 80225-0286

email: GS-W-NVpublic-info@usgs.gov

http://nevada.usgs.gov
CONTENTS III

CONTENTS

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

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

Background ................................................................................................................................................................ 2

Purpose and Scope ..................................................................................................................................................... 4

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

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

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

Geology ...................................................................................................................................................................... 5

Vegetation................................................................................................................................................................... 7

Climate ....................................................................................................................................................................... 7

History........................................................................................................................................................................ 7

Upper Truckee River Watershed ................................................................................................................................ 7

Trout Creek Watershed............................................................................................................................................... 8

Inventory and Measurement Methods ................................................................................................................................... 8

Streamflow and Seepage............................................................................................................................................ 8

Wells and Ground-Water Levels ................................................................................................................................ 11

Water Quality ............................................................................................................................................................. 21

Surface- and Ground-Water Conditions ................................................................................................................................ 28

Streamflow and Seepage Estimates ........................................................................................................................... 28

Ground-Water Levels and Direction of Flow............................................................................................................. 30

Water Quality ............................................................................................................................................................. 33

Summary and Conclusions .................................................................................................................................................... 36

References Cited.................................................................................................................................................................... 38

PLATE

[Plate is in pocket at back of report]

1. Map showing ground-water level contours and stream sections of gaining and losing flow in Upper Truckee River 

and Trout Creek watersheds, California and Nevada, August-November 1996

FIGURES

1-4. Maps of the Upper Truckee River and Trout Creek watersheds showing:

1. Lake Tahoe Basin, California and Nevada............................................................................................................ 3

2. Locations of roads, streams, and general surficial geology .................................................................................. 6

3. Streamflow measurement sites, September 1996. ................................................................................................ 15

4. Location of well sites and general surficial geology, September 1996................................................................. 20

5-6. Boxplots showing summary statistics for surface- and ground-water sites, July-December 1996, for:

5. Water-quality field measurements......................................................................................................................... 25

6. Nutrient concentrations ......................................................................................................................................... 26

7. Hydrograph showing streamflow for the Upper Truckee River at South Lake Tahoe, California, and for

Trout Creek near Tahoe Valley, California, and daily precipitation below Fallen Leaf Lake, California, 

1996 water year................................................................................................................ .......................................... 29

8. Graph showing cumulative streamflow gains and losses for Upper Truckee River and Trout Creek, California,

September 1996 ......................................................................................................................................................... 30

9. Hydrographs showing water-level changes in wells 73 and 131 in Upper Truckee River and Trout Creek

watersheds, California ............................................................................................................................................... 32
IV Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

10-11. Graphs showing for sites on Upper Truckee River and Trout Creek, California:

10. Relation between distance from Lake Tahoe and specific conductance for surface-water-quality 

monitoring sites, September 1996. ................................................................................................................ 34

11. Field ground-water-quality measurements, July-December 1996.................................................................... 35

TABLES

1-7. Tables for Upper Truckee River and Trout Creek watersheds, California, listing:

1. Periods of record for daily streamflow, water-quality, and suspended sediment data at current and 

historical U.S. Geological Survey gaging stations and sampling sites.......................................................... 5

2. Streamflow measurement sites used for seepage estimates, September 1996...................................................... 9

3. Streamflow and water-quality data for streamflow sites, September 1996. ......................................................... 12

4. Streamflow measurement data and seepage estimates for designated main-stem reaches, September 1996....... 14

5. Selected characteristics of ground-water monitoring sites, July-November 1996................................................ 16

6. Water-quality data for selected streamflow sites, July-December 1996 ............................................................... 22

7. Water-quality data for ground-water monitoring sites, July-December 1996....................................................... 27

CONVERSION FACTORS, VERTICAL DATUM, AND ABBREVIATED WATER-QUALITY UNITS

Multiply By To obtain

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

cubic foot per second per mile (ft3/s/mi) 0.01760 cubic meter per second per kilometer

foot (ft) 0.3048 meter

inch (in.) 25.4 millimeter

mile (mi) 1.609 kilometer

square mile (mi2) 2.590 square kilometer

Temperature: Degrees Celsius (oC) can be converted to degrees Fahrenheit (oF) by using the formula oF = [1.8(o

C)]+32. Degrees Fahrenheit 

can be converted to degrees Celsius by using the formula oC = 0.556(oF-32).

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

Datum of 1929”), which is derived from a general adjustment of the first-order leveling networks of the United States and Canada.

Abbreviated Water-Quality Units Used in this Report

μg/L (microgram per liter)

mg/L (milligram per liter)

mL (milliliter)
Abstract 1

Abstract

The Upper Truckee River and Trout Creek 

watersheds, South Lake Tahoe, California and 

Nevada, were studied from July to December 1996 

to develop a better understanding of the relation 

between surface water and ground water. Base 

flows at 63 streamflow sites were measured in late 

September 1996 in the Upper Truckee River and 

Trout Creek watersheds. Most reaches of the main 

stem of the Upper Truckee River and Trout Creek 

had gaining or steady flows, with one losing reach 

in the mid-section of each stream. 

Twenty-seven of the streamflow sites measured in the Upper Truckee River watershed were 

on 14 tributaries to the main stem of the Upper 

Truckee River. Sixteen of the 40 streamflow sites 

measured in the Upper Truckee River watershed 

had no measurable flow. Streamflow in Upper 

Truckee River watershed ranged from 0 to 11.6 

cubic feet per second (ft3/s). The discharge into 

Lake Tahoe from the Upper Truckee River was 

11.6 ft3/s, of which, 40 percent of the flow was 

from ground-water discharge into the main stem, 

40 percent was from tributary inflows, and the 

remaining 20 percent was the beginning flow. 

Gains from or losses to ground water along 

streams ranged from a 1.4 cubic feet per second 

per mile (ft3/s/mi) gain to a 0.5 ft3/s/mi loss along 

the main stem.

Fourteen of the streamflow sites measured 

in the Trout Creek watershed were on eight tributaries to the main stem of Trout Creek. Of the 23 

streamflow sites measured in the Trout Creek 

watershed, only one site had no flow. Flows in the 

Trout Creek watershed ranged from zero to 23.0 

ft3/s. Discharge into Lake Tahoe from Trout Creek 

was 23.0 ft3/s, of which, about 5 percent of the 

flow was from ground-water discharge into the 

main stem, 75 percent was from tributary inflows, 

and the remaining 20 percent was the beginning 

flow. Ground-water seepage rates ranged from a 

1.4 ft3/s/mi gain to a 0.9 ft3/s/mi loss along the 

main stem. 

Specific conductances measured during 

the seepage run in September 1996 increased in 

a downstream direction in the main stem of the 

Upper Truckee River and remained relatively 

constant in the main stem of Trout Creek. Water 

temperatures measured during the seepage run 

also increased in a downstream direction in both 

watersheds.

Depths to ground water measured at 62 

wells in the study area were used with the results 

of the seepage run to produce a water-level map in 

the Upper Truckee River and Trout Creek watersheds. Ground-water levels ranged from 1.3 to 

69.8 feet below land surface. In the upper sections 

of the watersheds ground-water flow is generally 

toward the main stems of Upper Truckee River 

and Trout Creek, whereas in the lower sections, 

ground-water flow generally parallels the two 

streams and flows toward Lake Tahoe. The altitude of ground water between Lake Tahoe and 

Highway 50 was nearly the same as the lakesurface altitude from July to November 1996. 

This suggests ground-water discharge beneath the 

Upper Truckee River and Trout Creek drainages 

directly to Lake Tahoe was minimal and that much 

of the ground-water discharge was to the channels 

of the Upper Truckee River and Trout Creek 

upstream from Highway 50. Hydraulic gradients 

ranged from near zero to 1,400 feet per mile.

Surface- and Ground-Water Characteristics in the

Upper Truckee River and Trout Creek Watersheds, 

South Lake Tahoe, California and Nevada, 

July-December 1996 

By Timothy G. Rowe and Kip K. Allander
2 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

Samples were collected at six surfacewater-quality and eight ground-water-quality sites 

from July through mid-December 1996. Specific 

conductance of the ground-water-quality sites was 

higher than that of the surface-water-quality sites. 

Water temperature and pH median values were 

similar between ground-water-quality and surfacewater-quality sites but ground water had greater 

variation in pH and surface water had greater variation in water temperature. Ground-water nutrient 

concentrations were generally higher than those in 

streams except for bioreactive iron.

INTRODUCTION

Lake Tahoe is an outstanding natural resource and 

is known for its deep, clear water (fig. 1). Protection of 

this renowned clarity has become important in the past 

half century, as clarity has been decreasing by about 

1 ft each year (Goldman and others, 1986), mainly 

due to human activities.

Increased nutrient concentrations within Lake 

Tahoe are considered the leading cause of algal growth 

and loss of clarity in the lake. Within the Lake Tahoe 

Basin, both surface- and ground-water discharge are 

suspected of being significant mechanisms for nutrient 

transport to Lake Tahoe (Thodal, 1994, p. 2). 

Background

The Tahoe Regional Planning Agency (TRPA) 

is a bi-state resource management agency that has primary responsibility for the environmental protection of 

Lake Tahoe. TRPA’s principal mission is to reduce the 

loss of clarity in Lake Tahoe. TRPA oversees the 

monitoring of existing environmental conditions in the 

basin through a number of programs. The U.S. Geological Survey (USGS) began a tributary discharge and 

water-quality monitoring study in 1988 in cooperation 

with TRPA. TRPA and USGS also instituted a cooperative ground-water monitoring study during 1990-92. 

A revised ground-water study was reinstated in 1995. 

Both of these ongoing water-quality data-collection 

efforts include the involvement of the University of 

California-Davis, Tahoe Research Group (TRG) and 

are included in the Lake Tahoe Interagency Monitoring 

Program (LTIMP). LTIMP was formed in 1978 with 

12 State and Federal agencies and TRG (Goldman and 

others, 1986). Agencies currently participating in 

LTIMP include TRG; USGS; TRPA; U.S. Forest 

Service (USFS); U.S. Natural Resources Conservation 

Service (NRCS); U.S. Environmental Protection 

Agency (USEPA); Lahontan Regional Water Quality 

Control Board; California Department of Parks and 

Recreation; California Department of Fish and Game; 

California Tahoe Conservancy; Nevada Department 

of Environmental Protection; University of Nevada, 

Reno; Douglas County, Nev.; El Dorado County, Calif.; 

Washoe County, Nev.; and the City of South Lake 

Tahoe, Calif. 

The current USGS-TRPA networks include 

32 surface-water sites where suspended sediment, 

water-quality, and streamflow data are collected, and 

32 ground-water sites, where water-quality and waterlevel data are collected. These surface- and groundwater sites are located throughout the Lake Tahoe 

Basin. Both of these networks are described in more 

detail by Boughton and others (1997) and are shown on 

a map by Rowe and Stone (1997). From these two networks, six surface-water sites and eight ground-water 

sites were used from within the study area.

In 1996, TRPA developed the Lake Tahoe Federal 

Legislative Agenda, a public-private partnership of 

agencies in the Tahoe region (Tahoe Regional Planning 

Agency, 1996). The plan designated four Lake Tahoe 

watersheds as high priority for possible watershed 

restoration projects. TRPA included Third and Incline 

Creek watersheds in the north, Edgewood Creek watershed in the southeast, and the Upper Truckee River 

watershed in the south. 

In 1996, the Upper Truckee River watershed was 

chosen for a focused effort to improve water quality 

within one watershed of the Lake Tahoe Basin. An 

advisory group, the Upper Truckee River Watershed 

Focused Group, was formed as a subgroup of LTIMP.

The Upper Truckee River watershed is the largest 

of the 63 watersheds in the Lake Tahoe Basin. The 

Upper Truckee River also delivers the largest volume 

of surface water and may be providing some of the 

largest nutrient and sediment loads to the lake. Also, 

the Upper Truckee River watershed has the greatest 

human population of any watershed in the Lake Tahoe 

Basin, thus increasing the chances of negative human 

effects on water quality. The watershed also has several 

land-uses representative of many water-quality influences that occur throughout the Lake Tahoe Basin. 

Trout Creek is included in the study area because the 

watersheds are adjacent to each other and together 

comprise most of the South Lake Tahoe area. 
INTRODUCTION 3

88

89

4

89

431

89

267

207

28

80

395

50

50

50

395

50

89

0 10 MILES

0 10 KILOMETERS

Glenbrook

Sand

Harbor

Carson

City

Incline

Village

Crystal

Carnelian Bay

Bay

Kings

Beach

Tahoe

City

Homewood

Tahoe Pines

Meeks

Bay

Truckee

Stateline

Emerald

Bay

Meyers

Minden

Gardnerville South Lake

Tahoe

Zephyr

Cove

Cave

Rock

Meyers

NEVADA

CALIFORNIA

OREGON IDAHO

Area

of map San

Francisco

Los

Angeles

Reno

Las

Vegas

PLACER CO

EL DORADO CO

ALPINE CO

DOUGLAS CO

CARSON

CITY

WASHOE CO NEVADA CO Upper Truckee River

Lake

Tahoe

River

Carson

Washoe

Lake

Marlette

Lake

NEVADA

CALIFORNIA

West

Fork

Fork

Carson

Carson

River

River

East

 Fallen

Leaf

Lake

Cascade

Lake

Echo

Lake

Echo

Lake

Truckee

River

Martis

Creek

Donner

Lake

Martis Creek

Lake

Martis Creek

Lake

39° 15'

120° 15' 120° 00' 119° 45'

39° 00'

38° 45'

Base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000, 1969-85

Universal Transverse Mercator projection, Zone 11

SIERRA

NEVADA

CARSON

RANGE

EXPLANATION

Lake Tahoe Basin Hydrographic

 Area

Study area

Boundary of watershed

Upper

Truckee

River

Watershed

Trout

Creek

Watershed

Washoe

Valley

Eagle

Valley

Carson

Valley

Figure 1. Location of Lake Tahoe Basin and Upper Truckee River and Trout Creek watersheds, California and 

Nevada.
4 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

Purpose and Scope

This report presents a compilation of groundwater and surface-water data collected in the Upper 

Truckee River and Trout Creek watersheds during 

baseflow conditions from July to December 1996. 

The data are used to (1) determine ground-water levels 

and direction of ground-water flow in the watersheds, 

(2) determine the interaction between ground water 

and streamflow, and (3) compare the water quality of 

the ground- and surface-water systems during baseflow 

conditions.

USGS, in cooperation with TRPA, began a study 

in July 1996 to improve the understanding of the 

surface-water and ground-water systems and their 

interactions within the Upper Truckee River and 

Trout Creek watersheds. Principle efforts included 

(1) making streamflow measurements during baseflow 

conditions on the Upper Truckee River and Trout 

Creek and their tributaries; (2) inventorying existing 

wells on the basis of well drillers’ reports and canvassing local residents; (3) determining depth to water in 

located wells; (4) developing a map showing the altitude of the water table using depth-to-water measurements in wells and results of seepage estimates; and 

(5) collecting additional water-quality data.

Previous Studies

The USGS has been involved with surface-water 

studies in the Upper Truckee River and Trout Creek 

watersheds since 1960, when operation of streamflowgaging stations and surface-water-quality sampling 

sites first began. Periods of record of daily streamflow, 

water-quality, and suspended-sediment data are listed 

in table 1 for eight current and historical sites. Data 

from these eight sites have been published previously 

in USGS annual data reports by California and Nevada. 

Previous USGS surface-water studies in the Upper 

Truckee River and Trout Creek watersheds have 

included sediment discharge (Kroll, 1976); flood and 

related debris-flow hazards map for the South Lake 

Tahoe area (Katzer and Glancy, 1978); and suspendedsediment factors for the Lake Tahoe Basin (Hill and 

Nolan, 1988). Jeton (1999) has constructed a precipitation/runoff model for the Lake Tahoe Basin that 

includes Upper Truckee River and Trout Creek.

TRG has been involved with several studies and 

has collected physical and chemical data on Upper 

Truckee River and Trout Creek since the early 1970’s. 

These data are included in LTIMP annual reports. 

The most recent LTIMP report is by Byron and 

others (1989).

TRPA also has published annual water-quality 

reports since 1990 for the Lake Tahoe Basin. These 

reports have included USGS and TRG data on Upper 

Truckee River and Trout Creek. The most recent report 

is by Hill (1996).

USFS also has been involved with several 

studies collecting physical and chemical data on 

Upper Truckee River and Trout Creek. USFS has published a water-quality report on the Santa Fe erosion 

control project by Hoffman (1991); a water-quality 

report summarizing five baseline stations by Lowry 

and Meeker (1993); a monitoring report on Hell Hole 

Road water-quality improvement project by Norman 

(1996); a water-quality-monitoring report on spring 

runoff in the Grass Lake research natural area by Norman and Parsons (1997); and a monitoring report on 

Pope Marsh burn by Norman (1997).

U.S. Army Corps of Engineers (USCOE) published a report on flood-plain information for the Upper 

Truckee River, South Lake Tahoe, Calif. (U.S. Army 

Corps of Engineers, 1969). El Dorado County Department of Transportation has been involved in several 

studies and data collection efforts on the Upper Truckee River and Trout Creek. A recently published report 

on the Apache Erosion Control project was done by 

Robinson (1996).

Within the study area, ground water is the primary 

source for domestic and public water supplies. Historical wastewater disposal practices and current large 

municipal withdrawals of ground water within the 

Upper Truckee River and Trout Creek watersheds are 

the basis for several studies that focused on water quality and quantity. For example, the California Department of Water Resources has been monitoring water 

levels since 1958 for selected wells to identify longterm trends, if any, within the Lake Tahoe Basin. Two 

of these wells are within the study area. Thodal (1997) 

used data from 32 wells to characterize ground-water 

quality within the Lake Tahoe Basin. Six of these wells 

are within the study area. Scott and others (1978), 

Blum (1979), and Woodling (1987) report the results of 

hydrogeologic investigations in the study area. Results 

of investigations of ground-water nutrient flux of the 

Upper Truckee River and Trout Creek watersheds are 

included in reports by Loeb and Goldman (1979), Loeb 

(1987), and Thodal (1997).
DESCRIPTION OF STUDY AREA 5

Acknowledgments

This work was done in cooperation with the 

Tahoe Regional Planning Agency. Appreciation is 

extended to residents in the area who gave permission 

to access their wells. Many government and private 

agencies also are acknowledged for providing data and 

access to their wells: Agra Earth and Environmental; 

California Department of State Parks and Recreation; 

California Department of Water Resources; California 

Tahoe Conservancy; El Dorado County Department of 

Transportation; Lahontan Water Quality Control 

Board; South Tahoe Public Utility District; and U.S. 

Forest Service—Lake Tahoe Basin Management Unit.

DESCRIPTION OF STUDY AREA

The study area is in the southern part of the Lake 

Tahoe Basin Hydrographic Area1 and includes the 

entire Upper Truckee River and Trout Creek watersheds (figs. 1 and 2) in California. Additionally, samples were taken from wells and a spring adjacent to the 

study area in California and Nevada.

Historically, Trout Creek was tributary to Upper 

Truckee River in the Truckee Marsh area near the lake 

(fig. 2). But with development of the Tahoe Keys, the 

Upper Truckee River was channeled to the lake and 

currently the streamflow of the two tributaries combine 

only during high runoff. Because of this historical combination of the Upper Truckee River and Trout Creek 

on the surface, speculation is that their ground-water 

systems also may combine at some point. This is one 

reason that both watersheds are included in this study.

Geology

The main geologic units identified within the 

study area are granitic rocks and glacial deposits. 

Other units that are much less extensive are pluvial 

1

Formal hydrographic areas in Nevada were delineated systematically by the U.S. Geological Survey and Nevada Division of 

Water Resources in the late 1960’s (Rush, 1968; Cardinalli and 

others, 1968) for scientific and administrative purposes. The official hydrographic-area names, numbers, and geographic boundaries continue to be used in Geological Survey scientific reports 

and Division of Water Resources administrative activities.

Table 1. Periods of record for daily streamflow, water-quality, and suspended-sediment data at current and historical U.S. 

Geological Survey gaging stations and sampling sites for Upper Truckee River and Trout Creek watersheds, California

Water quality: NUT, instantaneous nutrient samples; SC, daily specific conductance; WT, daily water temperature.

Suspended sediment: DAILY, daily suspended sediment; INST, instantaneous suspended sediment discharge.

[Abbreviation: USFS, U.S. Forest Service]

Site 

no.

 (pl. 1)

Site name Station

number

Daily 

streamflow Water quality Suspended

sediment 

Upper Truckee River watershed

 6 Upper Truckee River at Hwy 50 at South 

Lake Tahoe (gage)

10336610 1972-74,77,

78,80-current

WT:1972-74,78,80-92

SC:1981-83

NUT:1993-current

DAILY:1972-74,78,80-92

INST: 1993-current

 17 Upper Truckee River at Hwy 50 above 

Meyers (gage)

103366092 1990-current NUT:1990-current INST:1990-current

 20 Upper Truckee River nr Meyers (inactive 

gage)

10336600 1961-86

 43 Upper Truckee River at S. Upper Truckee 

Rd (gage)

10336580 1990-current NUT:1990-current INST:1990-current

Trout Creek watershed

 49 Trout Creek at Hwy 50 at South Lake Tahoe 10336790 WT:1972-74,89-92

NUT:1993-current

DAILY: 1972-74,89-92

INST:1993-current

 52 Trout Creek at Martin Ave nr Tahoe Valley 

(gage)

10336780 1961-current WT:1972-74,78, 80-85,88

SC:1981-83

DAILY:1972-74,78,

80-85,88

 57 Trout Creek at Pioneer Trail nr South Lake 

Tahoe (gage)

10336775 1990-current NUT:1990-current INST:1990-current

 68 Trout Creek at USFS Rd 12N01 nr Meyers 

(gage)

10336770 1990-current NUT:1990-current INST:1990-current
6 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

0 1 2 3 MILES

0 1 2 3 KILOMETERS

Fallen

Leaf

Lake

Pope

Marsh

Truckee

Marsh

High

Meadows

Hell

Hole

Upper

Echo Lake

Lower

Echo Lake

 Angora

Lakes

Tamarack

Lake

Elbert

Lake

Dardanelles

Lake

Round

Lake

Ralston

Lake

Showers

Lake

Star

Lake

Freel

Peak

Red Lake

Peak

Lake Tahoe

Upper

Truckee

River

Cre e k

Tro u t

EL DORADO CO

ALPINE CO

Fallen

Leaf

Lake

Pope

Marsh

Truckee

Marsh

High

Meadows

Hell

Hole

Upper

Echo Lake

Lower

Echo Lake

 Angora

Lakes

Tamarack

Lake

Elbert

Lake

Dardanelles

Lake

Round

Lake

Ralston

Lake

Showers

Lake

Star

Lake

Freel

Peak

Red Lake

Peak

Lake Tahoe

Upper

Truckee River

Cre e k

Tro u t

NEVADA

CALIFORNIA

EL DORADO CO

ALPINE CO

38°55'

120°05' 120° 119°55'

38°50'

38°45'

Planimetric base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000, 1969–85

Universal Transverse Mercator Projection, Zone 11.

Shaded-relief base from 1:24,000 Digital Elevation Model; sun illumination from northwest at

30 degrees above horizon

Geology from Burnett (1971)

89

89

89

EXPLANATION

Basin fill deposits

Consolidated rocks

Wetlands

Study-area boundary

Hydrographic-area

 boundary

Lake Tahoe Basin

 boundary

Figure 2. Locations of roads, streams, and general surficial geology, Upper Truckee River and Trout Creek 

watersheds, California.
DESCRIPTION OF STUDY AREA 7

and alluvial deposits, volcanic rock, and metamorphic 

rock (Tahoe Regional Planning Agency and U.S. 

Forest Service, 1971, plate).

The geology of the study area can be characterized by lake and glacial deposits at the lower altitudes, 

flatlands, and low-lying hills; and by granitic rocks that 

make up the steep and high mountain slopes and peaks. 

The only volcanic rocks within the study area are in the 

extreme headwaters of the Upper Truckee River watershed, and the only metamorphic rocks are two small 

areas above Echo Lake and two small areas in the lowlying hill between the City of South Lake Tahoe and 

Fallen Leaf Lake. Lake deposits are evident in a few 

high-mountain meadows and along the lower stream 

channels in the Upper Truckee River and Trout Creek 

watersheds (Tahoe Regional Planning Agency and U.S. 

Forest Service, 1971, plate).

Landforms of the study area were principally 

shaped from tectonic and glacial processes. A combination of basin-and-range style fault-bounded blocks 

and glacial erosional and depositional action resulted in 

the formation of the present-day landforms. Four periods of major glaciation shaped these landforms (Tahoe 

Regional Planning Agency and U.S. Forest Service, 

1971). The major landforms attributed to glaciation are 

deep basin-fill deposits, steep mountain slopes adjacent 

to the upper reaches of the Upper Truckee River and 

Trout Creek, and large lateral moraines that divide the 

Trout Creek watershed from the Upper Truckee River 

watershed and the Upper Truckee River watershed 

from Fallen Leaf Lake (Tahoe Regional Planning 

Agency and U.S. Forest Service, 1971). 

The basin-fill deposits within the study area are 

comprised entirely of lake, stream, and glacial deposits. 

Also, the underlying basement rock is assumed to be 

entirely granitic. Thicknesses of the basin-fill deposits 

in the South Lake Tahoe area near Lake Tahoe may 

be as great as 1,600 - 1,900 ft (Blum, 1979). For the 

purposes of this report, the areas with basin-fill deposits will be referred to as unconsolidated areas and the 

areas that have exposed bedrock will be referred to as 

consolidated areas.

Vegetation

Vegetation in the Upper Truckee River and Trout 

Creek watersheds is primarily coniferous forest with 

lodgepole pine, ponderosa pine, Jeffrey pine, white fir, 

red fir, western white pine, mountain hemlock, and 

sugar pine. Alders, aspen, and willows are common 

along the stream zones (Cartier and others, 1993).

Climate

In the Upper Truckee River watershed, precipitation (mostly in the form of snow) ranges from nearly 

25 in. to greater than 60 in., with a general decrease 

from west to east (Twiss and others, 1971). In the Trout 

Creek watershed, precipitation ranges from nearly 20 

in. to about 40 in. with a general decrease from southwest to northeast. The National Weather Service 

reported above average annual precipitation during 

1996 at the long-term weather stations in Tahoe City 

and Glenbrook. The daily precipitation record for a 

nearby National Resource Conservation Service 

(NRCS) Snow Telemetry (SNOTEL) site near Lake 

Tahoe just north of Fallen Leaf Lake is shown in figure 

7. Most of the precipitation for 1996 (approximately 94 

percent) occurred between late November 1995 and 

mid-May 1996. Minor rainfall amounts were recorded 

at the end of June, mid-July, and mid-August of 1996. 

Summer thunderstorms, typical of the study area, were 

almost absent in 1996.

History

Historically, the land use of the Lake Tahoe Basin 

by humans first began with the Washoe Indian Tribe. 

Major changes in land use occurred with the discovery 

of the Comstock Lode in nearby Virginia City, Nev. 

Many trees in the Lake Tahoe Basin, including those 

within the study area, were harvested to provide shoring timbers for the Comstock mines (Crippen and 

Pavelka, 1972). When the Comstock era began to 

decline during the late 1800’s, the Lake Tahoe Basin 

began to emerge as a seasonal vacation area. By the end 

of World War II, the Lake Tahoe Basin had become an 

established year-round destination.

Upper Truckee River Watershed

The Upper Truckee River watershed is almost 

entirely within El Dorado County, Calif. (fig. 2). About 

3 mi2 of the southern tip is in Alpine County, Calif. 

This watershed is the largest in the Lake Tahoe Basin 

and occupies 56.5 mi2, which is 18 percent of the total 

land area tributary to Lake Tahoe (314 mi2

). Upper 

Truckee River has a drainage perimeter of 53.9 mi 

(Cartier and others, 1995). The Upper Truckee River 
8 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

main channel length is 21.4 mi. The land-surface 

altitudes range from lake level to 10,063 ft above 

sea level at Red Lake Peak (fig. 2).

The lowest land-surface altitude within the study 

area that is above water is determined by the surface 

of Lake Tahoe, which can fluctuate from a little below 

its natural rim of 6,221.9 ft (6,223.0 ft Bureau of 

Reclamation (BOR) datum) to slightly greater than 

its legal maximum altitude of 6,228.0 ft (6,229.1 ft 

BOR datum). For the period of this study, July through 

December, Lake Tahoe had a maximum lake-surface 

altitude in July of 6,227.9 ft, a minimum in November 

of 6,226.1 ft, and a mean of 6,227.0 ft (Bonner and 

others, 1998).

Percent slope, which describes the steepness 

of the topography within the watershed, ranges from 

approximately zero near Lake Tahoe and along the 

valley bottoms, to as much as 50 in the upper altitudes 

of the watershed (Cartier and others, 1993). Dominant 

aspect, which is the compass direction of a slope face, 

is generally east, west, southwest, and northwest facing 

slopes.

The main tributary drainages to the Upper 

Truckee River (pl. 1) include Grass Lake Creek (drainage area of 6.4 mi2

; table 2), Angora Creek (5.7 mi2), 

Echo Creek (5.4 mi2), and Big Meadow Creek (5.1 

mi2

). Major wetlands include Grass Lake, Osgood 

Swamp, Truckee Marsh, Benwood Meadow, and Big 

Meadow (pl. 1). Major lakes include Upper and Lower 

Echo Lakes and smaller lakes include Dardanelles, 

Round, Showers, Elbert, Tamarack, Ralston, and 

Angora Lakes (fig. 2). The only diversion from this 

watershed is to the American River Basin from Echo 

Lake, which has a storage capacity of 1,890 acre-ft 

(Bostic and others, 1997, p. 260). 

Trout Creek Watershed

The Trout Creek watershed is within El Dorado 

County, Calif., east of the Upper Truckee River watershed (fig. 2). The watershed is the second largest in the 

Lake Tahoe Basin and occupies 41.2 mi2

, which is 13 

percent of the total land area tributary to Lake Tahoe. 

Trout Creek has a drainage perimeter of 34.8 mi. Trout 

Creek has a main channel length of 12.1 mi. The landsurface altitudes range from lake level to 10,881 ft at 

Freel Peak (fig. 2). 

Percent slope ranges from approximately zero in 

the lower reach near Lake Tahoe, to 50 at higher altitudes (Cartier and others, 1993). Aspect is a mixture 

of generally west, east, north, northwest, and southwest 

facing slopes.

The main tributaries to Trout Creek include Cold 

Creek (drainage area of 12.8 mi2), Saxon Creek (8.2 

mi2

), Heavenly Valley Creek (3.0 mi2), and Hidden 

Valley Creek (1.7 mi2

; table 2, pl. 1). Major wetland 

areas include Truckee Marsh, High Meadows, and Hell 

Hole (pl. 1, fig. 2). The only lake in the Trout Creek 

watershed is Star Lake (fig. 2). The major basin diversion is ground-water withdrawal for municipal use.

INVENTORY AND MEASUREMENT 

METHODS

Streamflow and Seepage

Seepage estimates were determined for selected 

reaches in the Upper Truckee River and Trout Creek 

watersheds by measuring streamflow entering and 

leaving the reach and by measuring all tributary flows 

entering the reach during base-flow conditions. If 

streamflow leaving the reach exceeded all streamflow 

entering the reach by at least 5 percent, the difference 

was assumed to be ground-water seepage to the stream 

and the reach is referred to as a gaining reach. If flow 

leaving the reach was less than all inflow to the reach 

by at least 5 percent, then the streamflow was assumed 

lost to ground water and the reach is referred to as a losing reach. If flow leaving the reach was within 5 percent of all the inflow to the reach, then the difference 

was within standard measurement error and the reach is 

referred to as a steady reach with no losses or gains. 

This method for estimating seepage along the stream 

channels assumes no overland runoff, negligible evaporation directly from the stream, negligible evapotranspiration from riparian vegetation along the stream, and 

no storage changes along the stream channel.

Unit-runoff values were derived by dividing 

streamflow values by contributing drainage area. Unitrunoff values are defined as the average number of 

cubic feet per second flowing from each square mile 

of area drained by a stream, assuming that the runoff 

is distributed uniformly in time and space. Delineation 

of drainage areas used in this study are from Cartier 

and others (1995). 

Seventy streamflow measurement sites were 

established in the study area—45 in the Upper Truckee 

River watershed and 25 in the Trout Creek watershed. 
INVENTORY AND MEASUREMENT METHODS 9

.

Table 2. Streamflow measurement sites used for seepage estimates in the Upper Truckee River and Trout Creek watersheds, 

California, September 1996

Site

no.

(pl. 1)

Site name Station

number

Latitude

(degrees,

minutes,

seconds)

Longitude

(degrees,

minutes,

seconds)

Drainage

area

(square

miles)

Altitude

(feet)

River

mile, 

from 

mouth

(miles)

Upper Truckee River watershed

 1 Upper Truckee R. at mouth - W. channel-off Venice Dr 10336612 385604 1195957 56.5 6,228 0.5

 2 Upper Truckee R. at mouth - E. channel 103366117 385557 1195944 6,228 .9

 3 Upper Truckee R. abv marsh - W. channel-off Michael 103366113 385532 1195939 6,228 1.5

 4 Upper Truckee R. abv marsh - E. channel-off Michael 10336611 385531 1195937 6,228 1.5

 5 D St Drainage at Sky Meadows 103366107 385531 1195939 6,240 1.5

 6 Upper Truckee R. at Hwy 50 at S. Lake Tahoe (gage) 10336610 385522 1195925 54.0 6,229 1.9

 7 Upper Truckee R. blw SLT Airport - E. channel 1033660987 385447 1195911 6,240 2.8

 8 Upper Truckee R. blw SLT Airport - W. channel 1033660985 385453 1195926 6,240 3.1

 9 Upper Truckee R. at Hwy 50 blw Meyers 103366098 385231 1200016 50.1 6,280 6.5

 10 Sante Fe Trib at Country Club Rd nr Arapahoe St 103366095 385157 1200041 1.0 6,320 7.5

 11 Sante Fe Trib blw Hwy 50 off Sante Fe Rd 1033660947 385125 1200041 6,350 8.2

 12 Angora Ck. nr Sawmill Rd at Ranch Rd 103366096 385228 1200102 5.7 6,290 7.3

 13 Sawmill Pond Outlet at Sawmill Rd 1033660957 385319 1200132 6,340 8.7

 14 Angora Ck. at Lake Tahoe Blvd 1033660953 385252 1200221 6,360 8.9

 15 Upper Truckee R. abv Golfcourse off Country Club Dr 1033660943 385155 1200114 6,290 8.3

 16 Osgood Ck. at N. Upper Truckee Rd 103366094 385114 1200203 1.6 6,380 9.4

 17 Upper Truckee R. at Hwy 50 abv Meyers (gage) 103366092 385055 1200134 39.2 6,310 9.8

 18 Upper Truckee R. Trib at N. Upper Truckee Rd nr Hwy 50 103366091 385051 1200143 6,360 9.9

 19 Echo Ck. at S. Upper Truckee Rd nr Meyers 10336609 385045 1200135 5.4 6,350 10.0

 20 Upper Truckee R. nr Meyers (old gage) 10336600 385035 1200125 33.2 6,322 10.3

 21 Upper Truckee R. Trib nr Kekin St at S. Upper Truckee Rd 10336599 385020 1200124 6,380 10.6

 22 Upper Truckee R. Trib at Celio Ranch at S. Upper Truckee Rd 10336598 385008 1200119 6,380 11.1

 23 Upper Truckee R. Trib at Hwy 89 N. of Santa Claus Dr 10336597 384951 1200058 6,400 11.5

 24 Upper Truckee R. Trib at Hwy 89 S. of Santa Claus Dr 10336596 384923 1200059 6,410 12.3

 25 Upper Truckee R. blw Grass Lake Ck. (blw Portal Rd) 10336594 384858 1200101 6,410 12.8

 26 Upper Truckee R. N. Trib at Grass Lk Rd 1033659356 384826 1200052 6,480 13.6

 27 Upper Truckee R. S. Trib at Grass Lk. Rd (Grass Lk. Ck. Div) 1033659354 384813 1200052 6,480 13.7

 28 Grass Lake Ck. nr Meyers (off Grass Lake Rd) 10336593 384807 1200054 6.4 6,480 13.9

 29 Grass Lake Ck. at Hwy 89 (lower) 103365925 384753 1200030 6,880 14.3

 30 Grass Lake Ck. abv Big Meadow Ck. at Hwy 89 10336592 384740 1195935 7,440 15.3

 31 Grass Lake Ck. Trib W. abv Hwy 89 103365915 384750 1195847 7,640 15.9

 32 Grass Lake Ck. Trib MidWest abv Hwy 89 10336591 384751 1195840 7,650 16.2

 33 Grass Lake Ck. Trib MidEast abv Hwy 89 103365905 384752 1195805 7,720 16.8

 34 Grass Lake Ck. blw Grass Lake 10336590 384740 1195802 7,720 16.8

 35 Grass Lake Ck. Trib E. abv Hwy 89 10336588 384741 1195729 7,720 17.5
10 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

 36 Grass Lake Ck. Trib abv Hwy 89 nr Luther Pass 10336587 384738 1195715 7,720 17.8

 37 Big Meadow Ck. at mouth off Grass Lake Rd 1033659352 384803 1200050 5.1 6,480 14.0

 38 Big Meadow Ck. at Hwy 89 (lower) 103365935 384732 1200035 7,010 14.7

 39 Big Meadow Ck. abv Hwy 89 103365932 384711 1200011 7,160 15.4

 40 Benwood Meadows Trib N. at S. Upper Truckee Rd 10336584 384806 1200105 1.4 6,480 14.0

 41 Benwood Meadows Trib Middle at S. Upper Truckee Rd 10336583 384804 1200105 6,480 14.0

 42 Benwood Meadows Trib S. at S. Upper Truckee Rd 10336582 384803 1200103 6,480 14.0

 43 Upper Truckee R. at S. Upper Truckee Rd (gage) 10336580 384745 1200106 14.2 6,490 14.3

 44 Upper Truckee R. Trib abv Hawley Grade Rd 10336579 384727 1200110 6,600 14.7

 45 Upper Truckee R. abv Trib abv Hawley Grade Rd 10336578 384727 1200115 6,600 14.8

Trout Creek watershed

 46 Trout Ck. nr mouth - E. channel-off Bellevue/El Dorado Ave 10336795 385611 1195917 41.0 6,230 .7

 47 Trout Ck. nr mouth - middle channel-off Bellevue/El Dorado Ave 10336794 385607 1195920 6,230 .7

 48 Trout Ck. nr mouth - W. channel-off Bellevue/El Dorado 10336793 385605 1195922 6,230 1.1

 49 Trout Ck. at Hwy 50 at S. Lake Tahoe 10336790 385556 1195842 40.4 6,240 1.5

 50 Heavenly Valley Ck. at Black Bart nr Tahoe Valley 10336785 385517 1195813 3.0 6,260 2.8

 51 Heavenly Valley Ck. at Pioneer Trail 10336783 385504 1195730 6,300 3.8

 52 Trout Ck. at Martin Ave nr Tahoe Valley (gage) 10336780 385512 1195817 36.7 6,241 2.8

 53 Cold Ck. at mouth (off Plateau Dr) 10336779 385444 1195806 12.8 6,260 3.6

 54 Cold Ck. at Pioneer Trail 10336778 385432 1195739 6,300 4.1

 55 Cold Ck. Trib at Del Norte Dr 10336777 385427 1195712 6,440 4.7

 56 Cold Ck. off Del Norte Dr 10336776 385406 1195715 6,440 4.8

 57 Trout Ck. at Pioneer Trail nr S. Lake Tahoe (gage) 10336775 385413 1195804 23.0 6,270 4.3

 58 Trout Ck. Trib off Columbine nr USFS Rd 12N08 103367745 385346 1195751 6,280 5.1

 59 Trout Ck. Trib off Pioneer Trail at old RR grade 10336774 385324 1195816 6,280 5.7

 60 Trout Ck. blw Saxon Ck. off Powerline Rd 10336773 385302 1195836 6,280 6.3

 61 Saxon Ck. blw Landfill at Powerline Rd 103367726 385245 1195858 8.2 6,300 6.8

 62 Saxon Ck. at USFS Rd 12N01 10336772 385219 1195855 6,320 7.4

 63 Saxon Ck. Trib abv USFS Rd 12N01 103367718 385212 1195845 6,360 7.6

 64 Saxon Ck. abv Trib abv old RR grade 103367716 385206 1195853 6,360 7.7

 65 Trout Ck. abv Saxon Ck. at Powerline Rd 103367708 385247 1195847 6,300 6.7

 66 Hidden Valley Ck. at Trail Crossing 103367706 385220 1195727 1.7 7,000 8.4

 67 Trout Ck. Trib blw gage at USFS Rd 12N01 103367702 385151 1195733 1.4 6,940 8.8

 68 Trout Ck. at USFS Rd 12N01 nr Meyers (gage) 10336770 385148 1195726 7.4 6,850 8.8

 69 Hell Hole Meadow Trib nr mouth 10336768 385117 1195654 2.8 7,520 9.6

 70 Trout Ck. abv Hell Hole Trib at Horsetrail Crossing 10336769 385126 1195646 7,500 9.6

Table 2. Streamflow measurement sites used for seepage estimates in the Upper Truckee River and Trout Creek watersheds, 

California, September 1996—Continued

Site

no.

(pl. 1)

Site name Station

number

Latitude

(degrees,

minutes,

seconds)

Longitude

(degrees,

minutes,

seconds)

Drainage

area

(square

miles)

Altitude

(feet)

River

mile, 

from 

mouth

(miles)
INVENTORY AND MEASUREMENT METHODS 11

Streamflow was determined at 63 of the streamflow 

measurement sites—40 in the Upper Truckee River 

watershed and 23 in the Trout Creek watershed. These 

sites were selected to estimate seepage and unit-runoff 

values along selected reaches in the main stems and 

tributaries (tables 3 and 4, pl. 1, fig. 3). Of the 40 sites 

in the Upper Truckee River watershed with streamflow 

measurements, 13 are main-stem sites and 27 are tributary sites. The main stem of the Upper Truckee River 

was divided into 10 reach segments. Of the 23 sites in 

the Trout Creek watershed with streamflow measurements, 9 are main-stem sites and 14 are tributary sites. 

The main stem of Trout Creek was divided into six 

reach segments. Existing streamgage locations and 

water-quality sampling sites were selected along with 

sites at the confluence of all inflowing tributaries with 

the main-stem streams. Additional sites along the 

major tributaries were selected in each watershed. The 

selection of these sites was made on the basis of accessibility. Measurements of streamflow were made on 

the same day within each watershed. Streamflow measurements in the Upper Truckee River watershed were 

made on September 23, 1996, and streamflow measurements in the Trout Creek watershed were made 

on September 26, 1996.

Streamflows were measured following USGS 

guidelines (Buchanan and Somers, 1969). Water and 

air temperatures were measured using calibrated field 

thermometers. 

River miles (distance from mouth of river to 

seepage measurement sites) along the main stems were 

calculated from the mouth of each watershed using a 

geographical information system (table 2, fig. 3). River 

miles on the tributaries were calculated by taking the 

river mile of the main channel at the tributary mouth 

and then adding the distance of the tributary channel 

going upstream. River miles were used in computing 

relative ground-water seepage rates along selected 

reaches of the Upper Truckee River and Trout Creek.

Wells and Ground-Water Levels

Well drillers’ logs in the study area were obtained 

from the California Department of Water Resources. 

These logs are used to locate existing domestic and 

public supply wells and to provide well-construction 

information such as well depth, screen interval, well 

diameter, and lithology. A field reconnaissance of 

existing wells was made from early August 1996 

through November 1996. Some wells were found 

after interviewing local residents in areas of known 

domestic withdrawals. When a well was found, its 

location was plotted on a 7.5-minute topographic map 

and its latitude and longitude coordinates were determined using a Precision Lightweight Global Positioning System Receiver (PLGR). The accuracy of these 

locations is ±100 ft, or approximately 1 second of 

latitude or longitude. 

Field information collected for each well 

included casing diameter, well depth, well-owner 

information, measuring-point height, land-surface 

altitude, well and water-use status, and water level 

(table 5). All land-surface altitudes were taken from 

USGS 7.5-minute topographic quadrangle maps except 

for those wells that already had land-surface altitudes 

determined by conventional surveying techniques. The 

accuracy of land-surface altitudes estimated from the 

maps is typically within 20 ft and often within 10 ft, 

depending on the topographic-contour interval (plus 

or minus one-half of the topographic-contour interval). 

For land-surface altitudes determined by surveying 

techniques, accuracies are within 0.1 ft. All water-level 

measurements were made using either a steel or electric 

tape. Because water levels were determined by subtracting depth to water from land-surface altitudes, 

they carry the same uncertainties as the land-surface 

altitudes. Domestic wells were frequently used for yard 

irrigation during the late summer and early fall when 

data were collected. Water levels from these pumping 

wells are not representative of static conditions (table 

5). Data for wells presented in this report are stored in 

the USGS National Water Information System (NWIS) 

data base.

Between July 16 and November 8, 1996, USGS 

staff inventoried 94 wells and 1 spring. Of the 94 wells, 

79 are within the study-area boundaries. The other 15 

wells and 1 spring are adjacent to the study area. Most 

of the sites adjacent to the study area were included in 

this study to help interpret water-level contours and 

hydraulic gradients at the study area boundaries. The 

remainder of these sites were included because the 

information from them is previously unpublished. 

Of the 79 wells within the study area, water levels 

were measured at 62 wells. Seventeen wells were not 

measured because they were either flowing, inaccessible, or pumping almost continuously. Thirteen of the 

wells measured had been pumped recently (identified 

with an R on table 5), and may not represent a static 

water level. Two of the wells measured were pumping; 

these water levels are not representative of static levels 
12 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

Table 3. Streamflow and water-quality data for streamflow sites in the Upper 

Truckee River and Trout Creek watersheds, California, September, 1996—Continued

Site no.

(pl. 1)

 Flow

(ft3/s)

Specific

conductance 

(μS/cm)

Air 

temperature

(degrees Celsius)

Water 

temperature

(degrees Celsius)

Unit runoff

(ft3/s/mi2)

Upper Truckee River watershed

 1 -- 99 -- -- --

 2 0 -- -- -- --

 3 11.6 98 16.0 12.0 0.21

 4 0 -- -- -- --

 5 0 -- -- -- 0

 6 11.2 96 -- 13.5 .21

 7 10.1 98 14.0 12.0 --

 8 0 -- -- -- --

 9 10.3 98 18.5 11.5 .21

 10 0 -- -- -- 0

 11 0 -- -- -- 0

 12 .8 72 14.5 6.5 .14

 13 0 -- -- -- 0

 14 .2 39 3.5 4.5 --

 15 10.4 99 18.5 12.0 --

 16 .1 31 5.0 5.5 .06

 17 8.5 91 14.5 9.5 .22

 18 0 -- -- -- 0

 19 .1 148 15.5 9.0 .02

 20 7.7 84 14.0 10.5 .23

 21 0 -- -- -- 0

 22 0 -- -- -- 0

 23 0 -- -- -- 0

 24 0 -- -- -- 0

 25 6.4 75 20.0 11.0 --

 26 0 -- -- -- 0

 27 .9 73 19.5 8.5 --

 28 1.1 73 16.5 7.5 .31

 29 -- -- -- -- --

 30 2.6 65 18.5 8.5 --

 31 .1 36 17.0 9.5 --

 32 .3 43 17.5 7.5 --

 33 .2 -- -- -- --

 34 1.0 43 18.0 11.5 --

 35 -- -- -- -- --

Table 3. Streamflow and water-quality data for streamflow sites in the Upper

Truckee River and Trout Creek watersheds, California, September 1996

[Abbreviations and symbol: ft3/s, cubic feet per second; μS/cm, microsiemens per centimeter at 25 degrees 

Celsius; ft3

/s/mi2, cubic feet per second per square mile; --, not measured]
INVENTORY AND MEASUREMENT METHODS 13

 36 -- -- -- -- --

 37 0.9 69 10.0 7.5 0.18

 38 -- -- -- -- --

 39 .5 50 18.5 8.0 --

 40 0 -- -- -- 0

 41 0 -- -- -- --

 42 0 -- -- -- --

 43 3.1 51 10.0 6.0 .22

 44 .6 50 14.5 7.0 --

 45 2.6 50 25.0 9.0 --

Trout Creek watershed

 46 11.8 50 17.0 11.5 .56

 47 8.4 50 15.5 10.5 --

 48 2.8 50 15.5 11.5 --

 49 22.6 50 14.0 7.0 .56

 50 .2 52 20.5 7.0 .07

 51 .4 50 11.0 7.0 --

 52 20.6 52 -- 10.5 .56

 53 11.2 43 27.0 8.0 .88

 54 11.3 44 30.0 7.0 --

 55 0 -- -- -- 0

 56 -- -- -- -- --

 57 10.8 54 14.5 10.5 .47

 58 .1 92 17.0 9.0 --

 59 .1 75 16.0 9.0 --

 60 -- -- -- -- --

 61 2.4 55 15.5 6.5 .29

 62 2.5 46 19.0 7.5 --

 63 .2 54 19.5 7.5 --

 64 2.0 45 18.0 7.5 --

 65 9.8 52 18.5 6.0 --

 66 .8 51 18.0 7.0 .47

 67 1.4 44 17.0 6.0 1.00

 68 6.2 53 9.5 5.0 .84

 69 1.0 54 11.5 6.0 .36

 70 4.7 49 12.0 7.0 --

Table 3. Streamflow and water-quality data for streamflow sites in the Upper 

Truckee River and Trout Creek watersheds, California, September, 1996—Continued

Site no.

(pl. 1)

 Flow

(ft3/s)

Specific

conductance 

(μS/cm)

Air 

temperature

(degrees Celsius)

Water 

temperature

(degrees Celsius)

Unit runoff

(ft3/s/mi2)
14 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

but do give a lower boundary for the water surface 

(water level in parentheses in table 5). The water-use 

distribution for the 79 wells within the study area is as 

follows: 11 wells are used for public supply; 45 wells 

are used for domestic purposes; and 23 wells are used 

for monitoring purposes (fig. 4).

Well locations and associated water-level altitudes were used along with seepage estimates to 

develop a water-level map of the study area (pl. 1). 

Directions of ground-water flow in the study area 

were determined from the water levels on plate 1.

Hydraulic gradients in the study area were 

determined also from water levels shown on plate 1. 

Because of the uncertainties in water-level altitudes, 

an inherent uncertainty is associated with the hydraulic 

gradients. These uncertainties are generally greatest in 

the middle part of the study area (Tahoe Paradise area) 

and the least in the steeply sloping area above Christmas Valley along Luther Pass.

The 94 wells inventoried for this study are a sample of the entire population of wells in and adjacent to 

the study area. How many wells make up the entire well 

population is unknown due to inconsistent reporting 

of well drilling in the past as well as undocumented 

destruction of wells. The sample distribution of wells 

is assumed to be representative of the total well distribution. This results in clusters of wells in areas of 

current domestic withdrawals and areas of environmental ground-water monitoring. Three major clusters 

are apparent on plate 1. The largest cluster is in the 

south end of Christmas Valley, where the residential 

population is still on domestic-well systems. Another 

cluster is on the south side of Twin Peaks, where the 

Table 4. Streamflow measurement data and seepage estimates for designated main-stem reaches in the 

Upper Truckee River and Trout Creek, California, September 1996

[Abbreviations and symbol: ft3/s, cubic feet per second; ft3/s/mi, cubic feet per second per mile; nd, streamflow not determined; --, not applicable]

Reach

number

(pl. 1)

Reach

segment

(between

site numbers)

Flow at

beginning

of reach

(ft3/s)

Tributary

flows

(ft3/s)

Flow out

of reach

(ft3/s)

Percent

change

in flow 1

1 Percent change in flow determined as difference between flow out of reach and sum of flow at beginning of reach and all tributary flows.

Estimated

ground-water

seepage

(ft3/s) 2

2 Ground-water seepage is difference between flow out of reach and sum of flow at beginning of reach and all tributary flows. 

Reach

designation 3

3 If percent change in flow is greater than 5 percent, then reach is designated as gaining (gaining flow from ground-water seepage into reach). 

If percent change in flow is less than -5 percent, then reach is designated as losing (losing flow to ground-water seepage out of reach). If percent 

change in flow is greater than -5 percent and less than 5 percent, then reach is designated as steady (no change in flow due to ground-water seepage).

Estimated gain (+) 

or loss (-) per

unit length 

(ft3/s/mi) 4

4 Gain (+) or loss (-) is estimated ground-water seepage divided by length of reach (see table 2 for river mile designations).

Upper Truckee River

 1 1 to 3 11.6 0 nd -- -- -- --

 2 3 to 6 11.2 0 11.6 +3.6 -- Steady --

 3 6 to 7 10.1 0 11.2 +11 +1.1 Gaining +1.2

 4 7 to 9 10.3 0 10.1 -1.9 -- Steady --

 5 9 to 15 10.4 .8 10.3 -8.0 -0.9 Losing -0.50

 6 15 to 17 8.5 .1 10.4 +21 +1.8 Gaining +1.2

 7 17 to 20 7.7 .1 8.5 +9.0 +0.7 Gaining +1.4

 8 20 to 25 6.4 0 7.7 +20 +1.3 Gaining +0.52

 9 25 to 43 3.1 2.9 6.4 +6.7 +0.4 Gaining +0.27

 10 43 to 45 2.6 .6 3.1 -3.1 -- Steady --

Trout Creek

 11 46 to 49 22.6 0 23.0 +1.8 -- Steady --

 12 49 to 52 20.6 .2 22.6 +8.7 +1.8 Gaining +1.4

 13 52 to 57 10.8 11.2 20.6 -6.4 -1.4 Losing -0.93

 14 57 to 65 9.8 2.6 10.8 -13 -1.6 Losing -0.67

 15 65 to 68 6.2 2.2 9.8 +17 +1.4 Gaining +0.67

 16 68 to 70 4.7 1.0 6.2 +8.8 +0.5 Gaining +0.62
0 1 2 3 MILES

0 1 2 3 KILOMETERS

Fallen

Leaf

Lake

Pope

Marsh

Truckee

Marsh

Upper

Echo Lake

Tamarack

Lake

Elbert

Lake

Dardanelles

Lake

Round

Lake

Ralston

Lake

Showers

Lake

Star

Lake

Freel

Peak

Red Lake

Peak

Lake Tahoe

Upper

Truckee

River

Cre e k

Tro u t

EL DORADO CO

ALPINE CO

High

Meadows

Hell

Hole

Lower

Echo Lake

 Angora

Lakes

Fallen

Leaf

Lake

Pope

Marsh

Truckee

Marsh

Upper

Echo Lake

Tamarack

Lake

Elbert

Lake

Dardanelles

Lake

Round

Lake

Ralston

Lake

Showers

Lake

Star

Lake

Freel

Peak

Red Lake

Peak

Lake Tahoe

Upper

Truckee River

Cre e k

Tro u t

NEVADA

CALIFORNIA

EL DORADO CO

ALPINE CO

High

Meadows

Hell

Hole

Lower

Echo Lake

 Angora

Lakes

38°55'

38°50'

38°45'

Planimetric base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000, 1969–85

Universal Transverse Mercator Projection, Zone 11.

Shaded-relief base from 1:24,000 Digital Elevation Model; sun illumination from northwest at

30 degrees above horizon

89

89

89

1

2 3

4 5

6

7

8

9

10

21

22

23

24

25

26 27

28

29

30

31 32 33

34

35

36

37

38

39

40

41

42

43

44 45

46

47

48 49

50

52 51

53 54 55

57 56

58

59

60

61

62

63

64

65

66

67 68

69

70 11

12

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17 18

19 20

1

2 3

4 5

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9

10

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25

26 27

28

29

30

31 32 33

34

35

36

37

38

39

40

41

42

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44 45

46

47

48 49

50

52 51

53 54 55

57 56

58

59

60

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65

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67 68

69

70 11

12

13

14

15

16

17 18

19 20

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4 3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄43⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄43⁄4

3⁄4

3⁄4

3⁄4 3⁄4 3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4 3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄43⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄4

3⁄43⁄4

3⁄4

3⁄4

3⁄4 3⁄4 3⁄4

3⁄4

1

1 1

2

3

4

5

6 7

8

9

10

2

3

4

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7 8

9

13

11

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14 15

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14

15

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17

1

1 1

2

3

4

5

6

7

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9

10

2

3

4

5

6

7

7

8

9

13

11

12

14 15

16

14

15

16

17

INVENTORY AND MEASUREMENT METHODS 15

Figure 3. Streamflow measurement sites, Upper Truckee River and Trout Creek watersheds, California, 

September 1996.
16 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe Table 5. Well information for ground-water monitoring sites in Upper Truckee River and Trout Creek watersheds, California and Nevada, 

Continued Well no. (pl. 1) U.S. Geological Survey site identification number 1 Local identification number 2 Station name Land- surface altitude (feet above sea level) Land- surface altitude uncertainty (+ or - feet) Well casing 

 Diameter (inches) Depth (feet below land surface) Open interval (feet below land surface) 

me

Upper Truckee River watershed 71 385613120014801 90 N13 E18 06ABBC1 USGS TM-2A 3 6,235 6 2 20.45 15.45 - 20.45 11-

72 385559120001301 90 N12 E18 05AADD1 KEYS 1 3 6,230 6 -- 318 -- 11-

73 385519120004601 90 N12 E18 05CAAD1 LOPEZ 6,257.6 .1 8 60 36 - 60 10-74 385518119593801 90 N12 E18 04CAAD1 LITTLE TRUCKEE MOBILE PARK 6,240 10 -- -- -- 09-75 385517119593901 90 N12 E18 04CAAD2 SWEATT 6,240 10 6 68 56 - 66 10-76 385511119593301 90 N12 E18 04DBCB1 EDS AUTO BODY 6,240 10 6 72 47 - 71 10-77 385507119593002 90 N12 E18 04DBCA2 HELEN 2 3 6,240 6 12 150 90 - 150 07-78 385504119595201 90 N12 E18 04CACC1 MATTERHORN MOTEL 6,250 10 8 125 -- 09-79 385428120001101 90 N12 E18 08AAAD1 HURLEY 6,285 20 6 68 44 - 64 10-80 385423119593601 90 N12 E18 09ABC 1 AIRPORT 2 3 6,240 10 12 380 186 - 366 07-81 385318120000301 90 N12 E18 16BCCA1 MCGEE 6,300 20 6 412 -- 11-82 385251120022601 90 N12 E18 18CCCB1 ANGORA CR SED BASIN 1 6,340 20 1.5 8 -- 10-83 385251120022401 90 N12 E18 18CCCB2 ANGORA CR SED BASIN 2 6,340 20 1.5 8 -- 10-84 385245120001601 90 N12 E18 20AAAB1 BROWN ABANDONED HOUSE 6,330 20 6 -- -- 08-85 385234120002401 90 N12 E18 20ADBB2 LOEFLER 6,280 20 6 70 -- 08-86 385232120002401 90 N12 E18 20ADBB1 GUARNERO 6,270 10 6 -- -- 08-87 385232120002301 90 N12 E18 20ADBD2 YANT1 6,270 10 8 -- -- 08-88 385231120004001 90 N12 E18 20ACBD1 SKALBERG 6,310 20 6 425 -- 08-

89 385231120001901 90 N12 E18 20ADBD1 FRAZIER 6,265 10 8 58 -- 08-90 385227120004601 90 N12 E18 20BDDA1 ANGORA CREEK 10 6,270 10 2 4 -- 10-91 385227120003701 90 N12 E18 20ACCA2 ANGORA CREEK 18 6,270 10 2 4 -- 10-92 385226120003701 90 N12 E18 20ACCA1 ANGORA CREEK 15 6,270 10 2 4 -- 10-93 385225120004801 90 N12 E18 20BDDB1 ANGORA CREEK 2 6,270 10 2 5 -- 10-94 385223120004601 90 N12 E18 20BDDD1 ANGORA CREEK 4 6,270 10 2 3 -- 10-95 385210120012502 90 N12 E18 19DADC2 WASHOE MEADOW STATE PARK 2 6,300 20 4 6 -- 10-

Table 5. Selected characteristics of ground-water monitoring sites in Upper Truckee River and Trout Creek watersheds, California and NLand-surface altitude uncertainties: ±0.1 foot, altitudes determined from surveying techniques; ±6, 10, and 20 feet, altitudes determined from map with uncertainty be

interval. Topographic contour interval for this region is 40 feet for altitudes greater than 6,280 feet with a supplementary contour interval of 20 feet for altitudes less than of 6,228 feet. Contour interval for altitudes less than 6,240 feet is 12 feet.Site status: D, dry well; F, flowing well, but head was not measured; P, well being pumped; R, well pumped recently; S, site is a spring, water level is at land-surface; 

measurement. If no status is indicated, reported water level measurement represents static level. Water level may represent local conditions only.Method: S, steel tape; T, electric tape; O, observed in field.[Symbols: --, unknown; <, less than; >, greater than]
INVENTORY AND MEASUREMENT METHODS 17

96 385210120012501 90 N12 E18 19DADC1 WASHOE MEADOW STATE PARK 1 6,300 20 4 5 -- 1097 385118120010601 90 N12 E18 29CBD 1 ARROWHEAD 2 3 6,340 20 20 268 218 - 268 07

98 385110120010701 90 N12 E18 29CCAD1 CHRIS CAFE 6,335 20 1.5 8 -- 1099 384917120004401 90 N11 E18 08BAAA1 SHIELDS 6,620 20 6 86 16 - 70 08

100 384837120010501 90 N11 E18 08CCAB1 MYERS 6,440 20 6 48 24 - 48 08101 384832120011001 90 N11 E18 08CCBD1 CHARSHAFIAN 6,470 20 6.63 80 41 - 76 08102 384832120010501 90 N11 E18 08CCAC1 PAULING 6,440 20 6 -- -- 08103 384831120011001 90 N11 E18 08CCCA1 AMUNDSON 6,470 20 6 -- -- 08

104 384828120010501 90 N11 E18 08CCDB1 WILKIE 6,460 20 6 40 -- 08105 384828120005301 90 N11 E18 08CDCA1 BAGINSKI 6,460 20 6 73 53 - 73 08106 384826120010801 90 N11 E18 08CCCD1 PAULSON 6,470 20 6 60 40 - 60 08107 384825120005201 90 N11 E18 08CDCD1 CAPELLA 6,470 20 6 91 71 - 91 08108 384824120010901 90 N11 E18 17BBBA1 RENNISON 6,480 20 6 130 -- 08109 384823120005301 90 N11 E18 17BABA1 MOSBACHER 1 6,460 20 6 80 -- 08

110 384822120005201 90 N11 E18 17BABA2 FEVES 6,470 20 6 60 40 - 60 08

111 384821120010801 90 N11 E18 17BBAB1 RECORD 6,480 20 6 65 45 - 65 08

112 384821120010602 90 N11 E18 17BBAB3 HOSMAN 2 6,470 20 6 300 60 - 300 08113 384821120010601 90 N11 E18 17BBAB2 HOSMAN 1 6,470 20 6.63 100 94 - 100 08114 384821120010001 90 N11 E18 17BBAA1 ULRICH 6,450 20 8 72 -- 08115 384820120005002 90 N11 E18 17BAAC2 ZAIGER 2 6,470 20 6 -- -- 08116 384820120005001 90 N11 E18 17BAAC1 ZAIGER 1 6,470 20 6 -- -- 08117 384818120010201 90 N11 E18 17BBAD1 YURE 6,460 20 6.63 54 40 - 53 08118 384817120010501 90 N11 E18 17BBDB1 WILLIAMS 6,470 20 6 190 63 - 190 08119 384817120005201 90 N11 E18 17BACA1 MOSBACHER 2 6,450 20 6 -- -- 08

120 384814120005301 90 N11 E18 17BACD1 ROMAN 6,460 20 6.63 80 62 - 70 08

Table 5. Well information for ground-water monitoring sites in Upper Truckee River and Trout Creek watersheds, California and Nevada

Continued

Well

 no. 

(pl. 1)

U.S. Geological

 Survey site

 identification

number 1

Local 

identification number 2 Station name

Landsurface

 altitude 

(feet above

 sea level)

Landsurface

altitude

uncertainty

 (+ or - feet)

Well casing 

 Diameter

(inches)

Depth

 (feet

below

land

 surface)

Open

 interval

(feet 

below 

land 

surface)

m
18 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe 121 384813120010701 90 N11 E18 17BBDC1 GINOTTI 6,480 20 6 200 160 - 180 08

122 384813120010601 90 N11 E18 17BBDC1 ALI 6,470 20 6 -- -- 09123 384813120010301 90 N11 E18 17BBDD2 RADEKAN 1 6,470 20 6 100 -- 08124 384813120010101 90 N11 E18 17BBDD3 RADEKAN 2 6,470 20 8 44 -- 08125 384812120005301 90 N11 E18 17BACD2 JETT-PEARCE 6,460 20 6 49 29 - 40 08126 384811120010201 90 N11 E18 17BBDD1 SHEA 6,470 20 6 -- -- 08127 384811120005501 90 N11 E18 17BDBA1 CHILCOTES 6,460 20 6 31 -- 08128 384810120010301 90 N11 E18 17BCAA1 ROBERSON 6,470 20 6 60 20 - 60 08129 384807120005801 90 N11 E18 17BDBC1 AGEE 6,460 20 6 -- -- 08130 384721119595901 90 N11 E18 21BDBB1 USFS BIG MEADOW TRAILHEAD 7,260 20 6.63 108 65 - 105 08

Trout Creek watershed 131 385624119592401 90 N13 E18 32CCCC1 SCHWABL 6,235 6 6 40 24 - 40 10

132 385609119590701 90 N12 E18 04AAAD1 HARCOTUNIAN 6,240 6 8.62 77 63 - 73 10133 385602119584201 90 N12 E18 03BACD1 EPPLER 6,260 10 6 78 54 - 74 09134 385549119590301 90 N12 E18 03BCBB1 GERKEN 6,245 10 8 76 52 - 76 11135 385538119585001 90 N12 E18 03BCC 1 SKY LAKE LODGE 6 6,260 10 -- -- -- 11

136 385535119585801 90 N12 E18 03ACCA1 SILVER DOLLAR MOTEL 6,255 10 8 65 -- 09137 385522119580204 90 N12 E18 03DAAB4 USGS TCF-4 3 6,260 10 2 135 130 - 135 10138 385514119581601 90 N12 E18 03DBAD1 BLACK BART 6,250 10 1.5 7 -- 10139 385432119574201 90 N12 E18 11BBAA1 LAKE CHRISTOPHER WELL 6,275 10 1.5 7 -- 10140 385413119580801 90 N12 E18 10ADCA1 GOLDEN BEAR 6,270 10 1.5 6 -- 10141 385235119590701 90 N12 E18 21AADC1 MEYERS LANDFILL 10 6,335.1 .1 2 24 9 - 23 11142 385231119590901 90 N12 E18 21ADAB1 MEYERS LANDFILL 4 6,376.3 .1 2.5 44 -- 11143 385231119590301 90 N12 E18 22BCBB1 MEYERS LANDFILL 9 3 6,340.5 .1 2 27 12 - 26 11144 385229119591102 90 N12 E18 21ADAC2 MEYERS LANDFILL M-5 6,380.8 .1 4 71 -- 11145 385229119591101 90 N12 E18 21ADAC1 MEYERS LANDFILL M-3 6,380.3 .1 4 39 -- 11

Table 5. Well information for ground-water monitoring sites in Upper Truckee River and Trout Creek watersheds, California and Nevada

Continued Well no. (pl. 1) U.S. Geological Survey site identification number 1 Local identification number 2 Station name Land- surface altitude (feet above sea level) Land- surface altitude uncertainty (+ or - feet) Well casing 

 Diameter (inches) Depth (feet below land surface) Open interval (feet below land surface) 

m
INVENTORY AND MEASUREMENT METHODS 19

146 385226119591201 90 N12 E18 21ADCA1 MEYERS LANDFILL 2 6,380.1 .1 2.5 37 -- 11147 385225119591601 90 N12 E18 21ADCB1 MEYERS LANDFILL 1 6,374.2 .1 4 22 -- 11148 385224119591901 90 N12 E18 21ADCC1 MEYERS LANDFILL M-7 6,400.4 .1 2 35 30 - 35 11149 385224119590701 90 N12 E18 21ADDC1 MEYERS LANDFILL 8 6,352.5 .1 2 32 16 - 31 11

Adjacent to study area

150 385627120034401 90 N13 E17 26DDBA1 USFS BALDWIN BEACH 1 6,235 6 8.63 100 70 - 100 11151 385824119550401 90 N13 E18 23CBB 1 FOLSOM SPRING 6,335 20 -- -- -- 11152 385816119563001 90 N13 E18 22DCA 1 EDGEWOOD4 6,260 10 2 24 -- 11153 385742119565701 90 N13 E18 27BDA 1 EDGEWOOD1 6,245 10 2 23 -- 10154 385736119563401 90 N13 E18 27DBBC1 TAHOE TROPICANA LODGE 6,276.7 .1 8 116 88 - 112 11155 385729119565101 90 N13 E18 27CACC1 STATION HOUSE INN 6,240 6 10 -- -- 09156 385708119564901 90 N13 E18 34BACA1 MIDWAY MOTEL ANNEX 6,260 10 -- 70 -- 09

157 385705119565601 90 N13 E18 34BBDA1 MI TIERRA 6,250 10 -- 58 -- 09158 385658119571001 90 N13 E18 34BCBC1 OSGOOD 4 6,235 6 4 8 -- 10159 385654119571401 90 N13 E18 33ADDA1 COPPER LANTERN MOTEL 6,240 6 6 77 -- 09160 385646119571901 90 N13 E18 33DAAB1 ALDER INN MOTEL 6,250 10 8 -- -- 09161 385644119574601 90 N13 E18 33CAD 1 BEVERLY LODGE 6 6,235 6 -- 76 -- 11

162 385636119583701 90 N13 E18 32DCAA1 TIMBERLAKE INN 6,250 10 8 97 -- 09

163 385618119572001 90 N12 E18 02ABBB1 ROEDER 6,270 10 6.63 117 97 - 117 09164 385651119581701 90 N12 E18 03ABA 1 AL TAHOE SCHOOL 6 6,260 10 12 125 -- 11

165 385557119572301 90 N12 E18 02BDDD1 EPPS 6,291.1 .1 6 76 44 - 72 11

1 Sites are identified by standard U.S. Geological Survey identification number, which is a unique number based on grid system of latitude and longitude of the si

denote degrees, minutes, and seconds of latitude; next seven denote degrees, minutes, and seconds of longitude; and last two digits (assigned sequentially) identify sites 385816119563001 refers to 38° 58′ 16′′ latitude and 119° 56′ 30′′ longitude, and is first site recorded in that 1-second grid. If more precise latitude and longitude subsequen

number is retained. 

2 Locations are assigned using a grid system referenced to Mount Diablo base line and meridian for official rectangular subdivision of public lands. Location consist

area number (Rush, 1968), Second unit is township, preceded by N or S to indicate location north or south of base line. Third unit is range, preceded by E to indicate locof section number and letters designating quarter section, quarter-quarter section, and so on (A, B, C, and D indicate northeast, northwest, southwest, and southeast quarindicating sequence in which site was recorded. For example, well 90 N11 E18 21BDBB1 is in the Lake Tahoe Basin (hydrographic area 90). It is the first site recorded iquarter (B) of the southeast quarter (D) of the northwest quarter (B) of section 21, Township 11 North, Range 18 East, Mount Diablo base line and meridian.

3 Ground-water-quality sites used in this study.4 Water levels in parenthesis are pumping levels and probably do not represent static water level. Pumping levels were used as a lower boundary for static water l

Table 5. Well information for ground-water monitoring sites in Upper Truckee River and Trout Creek watersheds, California and Nevada

Continued

Well

 no. 

(pl. 1)

U.S. Geological

 Survey site

 identification

number 1

Local 

identification number 2 Station name

Landsurface

 altitude 

(feet above

 sea level)

Landsurface

altitude

uncertainty

 (+ or - feet)

Well casing 

 Diameter

(inches)

Depth

 (feet

below

land

 surface)

Open

 interval

(feet 

below 

land 

surface)

m
20 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

Figure 4. Locations of well sites and general surficial geology, Upper Truckee River and Trout Creek watersheds, 

California, September 1996.

0 1 2 3 MILES

0 1 2 3 KILOMETERS

Fallen

Leaf

Lake

Pope

Marsh

Truckee

Marsh

Upper

Echo Lake

Tamarack

Lake

Elbert

Lake

Dardanelles

Lake

Round

Lake

Ralston

Lake

Showers

Lake

Star

Lake

Freel

Peak

Red Lake

Peak

Lake Tahoe

Upper

Truckee

River

Cre e k

Tro u t

EL DORADO CO

ALPINE CO

High

Meadows

Hell

Hole

Lower

Echo Lake

 Angora

Lakes

Fallen

Leaf

Lake

Pope

Marsh

Truckee

Marsh

Upper

Echo Lake

Tamarack

Lake

Elbert

Lake

Dardanelles

Lake

Round

Lake

Ralston

Lake

Showers

Lake

Star

Lake

Freel

Peak

Red Lake

Peak

Lake Tahoe

Upper

Truckee River

Cre e k

Tro u t

NEVADA

CALIFORNIA

EL DORADO CO

ALPINE CO

High

Meadows

Hell

Hole

Lower

Echo Lake

 Angora

Lakes

38°55'

120°05' 120° 119°55'

38°50'

38°45'

Planimetric base from U.S. Geological Survey digital data, 1:24,000 and 1:100,000, 1969–85

Universal Transverse Mercator Projection, Zone 11.

Shaded-relief base from 1:24,000 Digital Elevation Model; sun illumination from northwest at

30 degrees above horizon

Geology from Burnett (1971)

89

89

89

a

a

a

a

a

a

a

a

a

aaa aa a

aa

a aaaa

a

¢

¢

¢

¢

¢

¢

¢

¢ ¢

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¢

¢ ¢

¢

¢

¢

¢

¢

¢

¢

Á

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ÁÁÁÁÁ

Á

ÁÁÁ

ÁÁÁÁÁÁÁÁ

Á

EXPLANATION

Basin fill deposits

Consolidated rocks

Wetlands

Study-area boundary

Watershed boundary

 Domestic

Well—Solid fill indicates

 water-quality site

 Monitoring

 Public

Lake Tahoe Basin

 boundary

a

a

¢

¢

Á
INVENTORY AND MEASUREMENT METHODS 21

residential population still uses wells for domestic supply and where environmental monitoring of ground 

water is done in a nearby meadow. The third cluster is 

in the Trout Creek watershed at the old landfill near 

Meyers, Calif. This cluster of observation wells was 

established to monitor environmental effects of the 

landfill on the local ground water.

Water Quality

Samples were collected to determine specific 

conductance at each streamflow site at the time of 

measurement (table 3). Specific conductance is the 

ability of a substance to conduct an electric current at 

a specific temperature. In water, specific conductance 

is a good indicator of the concentration of dissolved 

solids. The greater the specific conductance, the greater 

the concentration of dissolved solids (Hem, 1985). 

Samples for specific-conductance measurements were 

collected by hand dipping a field-rinsed 250-mL polyethylene bottle in the center of flow at each site. Readings were then made within 24 hours of collection for 

each sample at the USGS Nevada District Laboratory 

using a calibrated specific conductance field meter 

adjusted to conductance at 25°C.

Six surface-water-quality sites (fig. 3; three on 

the Upper Truckee River and three on Trout Creek) 

were sampled periodically from July through December 1996 (table 6). These sites were sampled for total 

kjeldahl (ammonia plus organic nitrogen), total phosphorous, dissolved orthophosphorus, dissolved ammonia, dissolved nitrite plus nitrate, and total bioreactive 

iron. Field measurements of specific conductance, pH, 

water temperature, and dissolved oxygen were collected also. Historical USGS water-quality data, dating 

back to 1992, are available for all these sites. Standard 

USGS methods were used for sample collection. The 

method used for this study to collect water-quality 

samples was the equal-width increment (EWI) method, 

which is a depth- and width-integration method. This 

method involves collecting depth-integrated samples 

from equal-width segments of the cross section of a 

stream. The sample was then composited and mixed in 

a churn. The samples for measurements of total constituents were collected directly from the churn and the 

dissolved samples were filtered from the churn. These 

water-quality samples were then preserved (nutrients 

were chilled to 4°C and stored in the dark, and iron 

samples were acidified with concentrated nitric acid 

to a pH below 2) and shipped overnight to the UC 

Davis-TRG laboratories in Davis and Tahoe City, Calif. 

The samples were analyzed for iron and nutrients 

within 8 days according to procedures described by 

Hunter and others (1993). Specific-conductance and 

pH measurements were made from water taken from 

the churn after thoroughly mixing. The water temperature and dissolved oxygen were measured directly in 

the stream at the time of sampling. Specific conductance, pH, and dissolved oxygen were measured with 

field meters that were calibrated before each sample.

Summary statistics were computed for the combined samples of all six surface-water-quality sites on 

the Upper Truckee River and Trout Creek for July 

through December 1996 (figs. 5 and 6). For all 6 sites, 

only samples collected the same day or within 1 day 

were used in the analysis to compare with the summary 

statistics for the ground-water-quality sites.

Seven wells in the study area (five in the Upper 

Truckee River watershed and two in the Trout Creek 

watershed) and one well adjacent to the study area 

were sampled in July 1996 (table 7). These wells were 

sampled for dissolved nitrite plus nitrate, dissolved 

ammonia, dissolved kjeldahl (ammonia plus organic 

nitrogen), dissolved phosphorous, dissolved orthophosphorus, and dissolved bioreactive iron. Historical 

USGS water-quality data dating back to 1990 is available for these wells. These eight wells and well 143 

(table 7) were sampled in November and December 

1996. Seven of these are public supply wells and two 

are observation wells. The public-supply wells were 

sampled from the delivery system using existing 

pumps. For these wells, water was collected as close to 

the wellhead as possible to ensure that the sample was 

not affected by any treatment or storage of the water. 

Because these samples were collected from public-supply wells that are heavily used, it is assumed that the 

water is representative of the aquifer water. The two 

observation wells were sampled using a submersible 

pump. Because these wells are not pumped regularly, 

more than three casing volumes of water were pumped 

prior to sampling and specific conductance and water 

temperature were checked until stabilized, to assure 

that the water was representative of the aquifer water. 

These water-quality samples were filtered (through 

0.45-μm filter) in the field and then preserved (nutrients were chilled to 4°C and stored in the dark and 

iron samples were acidified with concentrated nitric 

acid to a pH below 2) and shipped to the UC DavisTRG laboratories in Davis and Tahoe City, Calif. The 

samples were analyzed for iron and for nutrients 

within 8 days according to the procedures described 

by Hunter and others (1993). Specific conductance, 
22 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe Table 6. Water-quality data for selected streamflow sites in Upper Truckee River and Trout Creek watersheds, California, July - December 

Date Time Discharge, instantaneous (ft3/s) Specific conductance (μs/cm) pH field (standard units) Air temper- ature (°C) Water temper- ature (°C) Oxygen, dissolved (mg/L) Nitrogen, NO2+NO3 dissolved (mg/L as N) Nitrogen, ammonia dissolved (mg/L as N) Nitrogen, ammonia + organic, total (mg/L as N) Phosphorus total (mg/L as P) 

Upper Truckee River watershed Site No. 6 - Upper Truckee River at South Lake Tahoe 07-03-96 1110 130 35 -- 23.5 13.5 -- 0.008 0.001 0.11 0.028 

07-19-96 1320 57 51 7.8 20.0 16.0 8.4 .003 <.001 .07 .038 08-16-96 1030 24 77 -- 23.0 17.0 -- .003 <.001 .05 .019 09-06-96 1115 11 96 7.8 14.0 12.0 9.4 .008 <.001 .13 .028 09-23-96 1147 11 96 -- -- 13.5 -- -- -- -- -- 10-01-96 1030 10 100 7.7 14.0 11.5 8.8 .011 .004 .15 .023 11-05-96 1240 12 90 -- 5.0 3.0 -- .009 .001 .33 .017 11-18-96 1530 627 27 -- 7.5 4.5 -- .020 .005 .27 .105 11-19-96 1335 200 25 -- 2.5 4.5 -- .018 .002 .28 .067 12-05-96 1315 770 39 -- 1.5 1.0 -- .011 .010 .08 .144 12-09-96 1430 70 57 -- 3.0 3.0 -- .017 .002 .19 .020 12-12-96 1400 700 43 -- 4.5 2.5 -- .010 .013 .20 .074 12-13-96 1300 200 40 -- 6.5 3.5 -- .006 .008 .17 .047 12-31-96 1545 200 40 -- 7.0 1.5 -- .012 .003 .34 .078 Site No. 17 - Upper Truckee River at Hwy 50 abv Meyers 07-03-96 1310 118 34 -- 24.0 13.0 -- .008 .001 .12 .021 07-19-96 1400 45 47 7.6 23.0 14.0 8.3 .007 <.001 .14 .037 07-31-96 0915 29 43 -- 19.0 13.0 -- -- -- -- -- 08-16-96 1230 19 71 -- 24.0 15.0 -- .010 <.001 .06 .019 09-06-96 1300 9.7 87 7.8 22.5 12.5 9.4 .002 <.001 .07 .033 09-23-96 1030 8.5 91 -- 14.5 9.5 -- -- -- -- -- 10-02-96 1630 7.1 101 -- 16.0 12.5 -- .010 .003 .51 .016 11-05-96 1350 8.8 82 -- 5.0 3.5 -- .012 .001 .16 .014 11-18-96 1610 445 22 -- 6.0 4.5 -- .016 .001 .15 .031 11-19-96 1605 277 21 -- 3.0 4.0 -- .012 <.001 .09 .016 12-12-96 1515 290 41 -- 2.0 2.0 -- .007 .005 .07 .032 

Table 6. Water-quality data for selected streamflow sites in Upper Truckee River and Trout Creek watersheds, California, July - December [Abbreviations: ft3/s, cubic feet per second; mg/L, milligrams per liter; μs/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius, USFS, U.S. Forest Ser
INVENTORY AND MEASUREMENT METHODS 23

Site No. 43 - Upper Truckee River at S. Upper Truckee Rd07-03-96 1440 73 23 -- 23.0 12.0 -- 0.004 0.002 0.04 0.022 07-19-96 1520 30 31 7.6 22.5 12.0 8.6 .006 .003 .06 .043 07-31-96 1200 13 37 -- 24.0 13.0 -- -- -- -- -- 08-16-96 1305 12 41 -- 26.0 13.0 -- .015 .007 .08 .030 09-06-96 1410 3.7 49 7.8 23.0 10.0 9.5 .021 <.001 .06 .056 09-23-96 0930 3.1 51 -- 10.0 6.0 -- -- -- -- -- 10-02-96 1710 3.0 52 -- 14.0 9.5 -- .036 .013 .42 .032 11-05-96 1430 2.7 49 -- 4.5 1.5 -- .002 .001 .17 .021 11-18-96 1700 102 18 -- 3.5 2.0 -- .012 .002 .22 .032 11-19-96 1705 67 24 -- 4.0 3.0 -- .008 <.001 .09 .026 12-05-96 1550 103 18 -- .5 1.0 -- .003 <.001 .23 .021 12-12-96 1600 109 17 -- 1.0 1.0 -- .003 .002 .28 .016 

Trout Creek watershed

Site No. 49 - Trout Creek at South Lake Tahoe

07-02-96 1040 87 33 -- 20.5 10.0 -- .006 .002 .17 .038 07-19-96 1235 66 35 7.3 18.0 10.0 -- .007 .001 .25 .062 08-16-96 0950 34 44 -- 19.0 12.0 -- .010 <.001 .12 .030 09-06-96 1030 25 46 7.6 13.0 7.0 9.8 .003 <.001 .26 .030 09-26-96 1010 23 50 -- 14.0 7.0 -- -- -- -- -- 10-02-96 1840 20 50 -- 14.0 10.5 -- .004 .002 .24 .023 11-05-96 1200 22 52 -- 5.0 3.0 -- .007 .002 .22 .019 11-18-96 1410 70 41 -- 8.0 4.5 -- .017 .003 .37 .133 12-05-96 1120 150 40 -- 3.0 0.5 -- .014 <.001 .24 .241 12-09-96 1340 40 50 -- 2.5 2.0 -- .006 .002 .17 .027 12-12-96 1210 40 46 -- 4.5 2.5 -- .011 .002 .31 .109 12-31-96 1415 100 48 -- 6.5 2.0 -- .010 <.001 .28 .067 

Table 6. Water-quality data for selected streamflow sites in Upper Truckee River and Trout Creek watersheds, California, July - Decembe

Date Time

Discharge,

 instantaneous

 (ft3/s)

Specific

 conductance

 (μs/cm)

pH

 field

(standard

 units)

Air

temperature

 (°C)

Water

temperature

 (°C)

Oxygen,

dissolved

 (mg/L)

Nitrogen,

NO2+NO3

dissolved

(mg/L as N)

Nitrogen,ammonia

dissolved

 (mg/L as N)

Nitrogen,

ammonia +

organic, 

total

(mg/L as N)

Phosphorus

 total

 (mg/L as P
24 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe Site No. 57 - Trout Creek at Pioneer Trail 07-02-96 1205 41 34 -- 23.0 10.5 -- 0.004 0.002 0.10 0.032 

07-19-96 1555 20 40 6.6 21.5 13.0 8.3 .004 .001 .15 .040 07-29-96 0935 24 54 -- 19.0 11.0 -- -- -- -- -- 08-16-96 1500 18 49 -- 23.0 14.5 -- .005 <.001 .12 .028 09-06-96 1615 14 51 7.7 20.0 11.5 8.7 .005 .001 .40 .026 09-26-96 1547 11 54 -- 14.5 10.5 -- -- -- -- -- 10-02-96 1420 11 55 -- 20.0 10.0 -- .004 .003 .31 .020 11-05-96 1510 12 53 -- 3.0 2.0 -- .004 .001 .19 .016 11-18-96 1640 36 43 -- 5.5 4.0 -- .015 .002 .25 .074 12-05-96 1520 72 38 -- 1.0 1.0 -- .010 .001 .18 .087 12-12-96 1530 79 41 -- 2.0 2.5 -- .009 .001 .32 .071 Site No. 68 - Trout Creek at USFS Rd 12N01 07-02-96 1300 22 31 -- 25.0 10.0 -- .003 .001 .16 .025 07-19-96 1440 14 37 7.1 18.5 10.0 8.7 .004 .001 .06 .039 07-29-96 1300 12 46 -- 23.0 11.0 -- -- -- -- -- 08-16-96 1430 10 47 -- 23.0 10.5 -- .003 .001 .07 .021 09-06-96 1530 8.4 49 7.7 18.5 7.5 9.3 .006 <.001 .35 .027 09-26-96 1014 6.1 53 -- 9.5 5.0 -- -- -- -- -- 10-02-96 1455 5.5 52 -- 16.5 7.0 -- .004 .003 .25 .018 11-04-96 1145 7.2 50 -- 4.5 2.0 -- .002 .002 .13 .016 11-21-96 1455 10 46 -- 6.5 4.5 -- .003 <.001 .27 .018 12-13-96 1040 8.0 46 -- 3.0 2.5 -- .003 .001 .07 .022 

Table 6. Water-quality data for selected streamflow sites in Upper Truckee River and Trout Creek watersheds, California, July - Decembe

Date Time Discharge, instantaneous (ft3/s) Specific conductance (μs/cm) pH field (standard units) Air temper- ature (°C) Water temper- ature (°C) Oxygen, dissolved (mg/L) Nitrogen, NO2+NO3 dissolved (mg/L as N) Nitrogen, ammonia dissolved (mg/L as N) Nitrogen, ammonia + organic, total (mg/L as N) Phosphorus total (mg/L as P
INVENTORY AND MEASUREMENT METHODS 25 Figure 5. Water-quality field measurements for surface- and ground-water sites, Upper Truckee River and Trout Creek watersheds, Califo

(48) (14)

0

350

50

100150200250300

SPECIFIC CONDUCTANCE, IN MICROSIEMENSPER CENTIMETER AT 25 DEGREES CELSIUS

(12) (14)

5.09.5

5.56.06.57.07.58.08.59.0

PH, IN STANDARD UNITS

(48) (14)

0

18

2468

10121416

WATER TEMPERATURE, IN DEGREES CELSIUS

SPECIFIC

CONDUCTANCE

pH WATER

TEMPERATURE
26 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake TahoeFigure 6. Nutrient concentrations for surface- and ground-water sites, Upper Truckee River and Trout Creek watersheds, California, Ju

(48) (14) (48) (14) (48) (14) (48) (14) (48) (14) 0.000110 0.0002 0.0003 0.0004 0.0005 0.0007 0.001 0.002 0.003 0.004 0.005 0.007 0.01 0.02 0.03 0.04 0.05 0.07 0.1 0.2 0.3 0.4 0.5 0.7

123457

CONCENTRATION, IN MILLIGRAMS PER LITER AS NITROGEN OR PHOSPHOROUS

(48) (14)

0.110,0000.2

0.30.40.50.71234571020304050701002003004005007001,0002,0003,0004,0005,0007,000

IRON CONCENTRATION, IN MICROGRAMS PER LITER

Filtered

Nitrite plus

Nitrate

Filtered

Ammonia

Phosphorous Filtered

Orthophoshorous

Ammonia

plus Organic

Nitrogen

Bioreactive

Iron

For PhNitrogwater water valid wconstiin the 
INVENTORY AND MEASUREMENT METHODS 27

Table 7. Water-quality data for ground-water monitoring sites in Upper Truckee River and Trout Creek watersheds, California, July-Dec[Abbreviations: ft3/s, cubic feet per second; mg/L, milligrams per liter; μs/cm, microsiemens per centimeter at 25 degrees Celsius; °C, degrees Celsius. 

Site 

no.

 (pl. 1)

Date Time

Specific

conductance

(μs/cm)

pH

field

 (standard

 units)

Air

temperature 

(°C)

Water

temperature

 (°C)

Nitrogen

NO2+NO3

dissolved

 (mg/L as N)

Nitrogen,ammonia

dissolved

 (mg/L as N)

Nitrogen,

ammonia+

organic 

dissolved

 (mg/L as N)

Phosphorus

dissolved

 (mg/L as P)

P

 

Upper Truckee River watershed

71 07-15-96 1145 154 6.5 22.5 9.5 0.059 0.523 1.2 0.074 71 11-21-96 1255 155 5.5 10.0 8.0 .073 .429 1.7 .047 72 07-15-96 1420 106 8.2 24.5 10.0 .454 .001 .10 .051 72 11-22-96 1325 105 7.5 5.5 10.0 .393 .003 <.01 .031 77 07-16-96 0755 131 7.8 14.0 8.5 .531 .018 .05 .059 77 12-13-96 0750 160 7.9 3.5 8.0 .999 .002 .04 .034 80 07-16-96 0955 110 9.0 18.5 10.5 .010 .009 .10 .101 80 12-13-96 0830 110 8.9 4.0 10.0 .012 .008 .05 .056 97 07-16-96 0940 161 8.6 20.0 14.5 .095 .001 .07 .051 97 12-13-96 0900 156 8.6 4.0 14.0 .135 .010 .22 .038 

Trout Creek watershed

135 07-15-96 1320 305 6.4 25.0 12.0 2.02 .006 .12 .055 135 11-21-96 1130 173 6.4 12.0 8.5 3.24 .001 .03 .018 137 07-18-96 1350 94 6.4 22.5 10.0 .002 .409 .36 .069 137 11-26-96 1255 94 6.6 4.0 8.5 .002 .375 .04 .034 143 11-26-96 1400 542 6.3 5.0 11.0 1.89 .002 .13 .039 

Adjacent to study area

164 07-15-96 0950 101 6.5 19.5 9.0 .449 .001 .01 .055 164 11-22-96 1240 98 7.0 5.0 8.0 .430 .001 .01 .020 
28 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

water temperature, water level, and pH were measured 

in the field during sampling. Specific conductance and 

pH measurements were made from water taken with 

field meters that were calibrated before each sample.

Ground-water-quality data are presented in 

table 7. The ground-water data are reported also in 

the 1996 annual data report for Nevada (Bostic and 

others, 1997, p. 532-536). 

Summary statistics were computed for the combined samples of the seven ground-water-quality sites 

within the Upper Truckee and Trout Creek watersheds 

that were sampled in July 1996 and in NovemberDecember 1996 (figs. 5 and 6). Well 143 was not used 

in the analysis because only one sample was collected 

during the study period. Also, this well is suspected of 

being affected by the landfill near Meyers, which is 

directly upgradient, and therefore probably is not a 

good representation of the overall ground-water quality 

in that area.

SURFACE- AND GROUND-WATER 

CONDITIONS

Streamflow and Seepage Estimates

The measured streamflows in the Upper Truckee 

River watershed ranged from zero to 11.6 ft3

/s (table 

3). Streamflow measured along the main stem of the 

Upper Truckee River increased from 2.6 ft3

/s at site 45 

to 11.6 ft3

/s at site 3 in a downstream direction (fig. 3, 

pl. 1). At site 1, flow was not measured because the 

river was too deep to wade and velocities too slow for 

an accurate measurement due to backwater effects 

caused by the high level of Lake Tahoe on September 

23, 1996. Three of the 13 remaining main-stem sites 

had no streamflow because these sites were on dry, 

divergent branches of the main stem. Of the 31 streamflow measurement sites that are tributary to the Upper 

Truckee River or are along the tributaries, 13 had no 

measurable streamflow. Major tributary inflows to the 

Upper Truckee River on September 23, 1996, included 

2.0 ft3/s at sites 27 and 28 (sum of divergent flows in 

tributary), 0.9 ft3/s at site 37, and 0.8 ft3/s at site 12.

The measured streamflows in the Trout Creek 

watershed ranged from 0 to 23.0 ft3

/s. Streamflow 

measured along the main stem of Trout Creek 

increased from 4.7 ft3

/s at site 70 to 23.0 ft3/s for 

combined sites 46-48 (fig. 3, pl. 1). All the main stem 

sites had streamflow. Of the 14 streamflow measurement sites that are tributary to Trout Creek or are along 

the tributaries, only 1 (site 55) had no measurable 

streamflow. Major tributary inflows to Trout Creek on 

September 26, 1996, included 11.2 ft3

/s at site 53, 2.4 

ft3/s at site 61, 1.4 ft3/s at site 67, and 0.8 ft3/s at site 66.

The streamflows measured in September 1996, 

for both watersheds, were representative of base-flow 

conditions from August through December. The smallest daily streamflow for the 1996 water year at the most 

downstream gage on the Upper Truckee River (site 6) 

was 7.7 ft3

/s in late October 1995 (Bostic and others, 

1997, p. 268). The lowest monthly mean streamflow, 

10.2 ft3

/s, occurred during November 1995. The lowest 

daily streamflow for the 1996 water year at the most 

downstream gage on Trout Creek (site 52) was 14.0 

ft3/s in late December 1995. The lowest monthly mean 

streamflow occurred during November 1995, and was 

22.0 ft3/s (Bostic and others, 1997, p. 333). Hydrographs for these two streamgages are shown in figure 7, 

along with the daily precipitation record for a nearby 

NRCS SNOTEL site.

All streamflow data were entered into the USGS 

National Water Information System (NWIS) databases. Streamflow measurement data for September 

1996 also appear in the annual data report for Nevada 

(Bostic and others, 1997).

Results of the streamflow measurements, seepage 

estimates, seepage rates per unit length, and unit runoffs are listed in table 4. In addition, the location of 

gaining, losing, and steady reaches are shown on plate 

1 and figure 3.

Seepage estimates for reaches along the Upper 

Truckee River indicate that, of the 11.6 ft3

/s streamflow near the mouth at site 3, 4.4 ft3/s (38 percent) was 

gained from ground-water seepage to the main stem, 

4.5 ft3/s (39 percent) was gained from tributary 

inflows, and 2.6 ft3

/s (23 percent) was the beginning 

streamflow at site 45. The average rate of gain per unit 

length along the main stem over the distance from site 

45 to site 3 (13.3 mi) was 0.33 ft3

/s per mile. Of the 10 

reach segments along the main stem of the Upper Truckee River, 5 were gaining from ground-water seepage, 

1 was losing due to ground-water seepage, 3 had no 

measurable influence due to ground water, and 1 was 

undetermined because a streamflow measurement was 

not possible (fig. 8). 

Seepage estimates for reaches along Trout Creek 

indicate that, of the 23.0 ft3

/s streamflow near the 

mouth at sites 46-48, 0.7 ft3/s (3 percent) was gained 

from ground-water seepage to the main stem, 17.4 ft3

/s 

(76 percent) was gained from tributary inflows, and 4.7 

ft3

/s (21 percent) is the beginning streamflow at site 70. 
SURFACE- AND GROUND-WATER CONDITIONS 29

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

Oct Nov Dec Jan Feb Mar Apr May June July Aug Sept

1995 1996

0

1,600

200

400

600

800

1,000

1,200

1,400

STREAMFLOW, IN CUBIC FEET PER SECOND

1995 1996

0

300

50

100

150

200

250

STREAMFLOW, IN CUBIC FEET PER SECOND

1995 1996

0

4

1

2

3

PRECIPITATION, IN INCHES

Site 6. Upper Truckee River at Highway 50

 at South Lake Tahoe, California

Site 52. Trout Creek at Martin Ave.

 near Tahoe Valley, California

Fallen Leaf Lake SNOTEL site

Figure 7. Streamflow for the Upper Truckee River at South Lake Tahoe, California, and for Trout Creek near Tahoe Valley, 

California, and daily precipitation below Fallen Leaf Lake, California, 1996 water year. (Precipitation data courtesy of 

National Resource Conservation Service.)
30 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

The average rate of gain per unit length along the main 

stem over the distance from site 70 (8.9 mi) to sites 46-

48 was about 0.08 ft3

/s per mile. Of the six reach segments along the main stem of Trout Creek, three were 

gaining from ground-water seepage, two were losing, 

and one had no measurable loss or gain (fig. 8). 

The Upper Truckee River and Trout Creek have 

similar characteristics in the location of ground-water 

seepage contributions to their streamflows. Both 

streams are gaining in their upper reaches, both are 

steady or losing through their middle reaches, and both 

gain streamflow over a mile reach starting at about 2.5 

mi upstream from Lake Tahoe (fig. 8).

The value obtained when discharge is divided by 

contributing drainage area, termed unit runoff, is often 

useful in comparing the magnitude of flow between 

two basins or the discharge at two or more locations in 

one basin. Unit runoff along the main stem of the Upper 

Truckee River ranged only slightly from 0.21 to 0.23 

ft3

/s/mi2 while its tributaries had greater variation, 

from zero at many of the tributaries to 0.31 ft3

/s/mi2

at site 28 (table 3). Unit runoff along the main stem 

of Trout Creek ranged from 0.56 ft3

/s/mi2 in the 

lower reaches to 0.84 ft3/s/mi2

 in the upper reaches 

while its tributaries ranged from 0.07 ft3

/s/mi2 at site 

50 to 1.00 ft3

/s/mi2 at site 67. The unit runoff in Trout 

Creek is larger than that of the Upper Truckee River. 

This is because most of the streamflow into Trout 

Creek is from the Cold Creek tributary whose unit 

runoff is 0.88 ft3/s/mi2. The high unit runoff of the 

Cold Creek tributary is assumed to be from delayed 

snowpack melt because the drainage has a significant 

percentage of north-facing aspect (Peltz and others, 

1994) or because the capacity of ground-water storage 

within the Cold Creek watershed is large.

Ground-Water Levels and Direction of Flow

The distribution of inventoried wells, their water 

use, and geology (consolidated rock or unconsolidated 

basin fill) of the study area are shown in figure 4. 

Because of the lack of drillers’ reports for many wells, 

the distribution of wells completed in unconsolidated 

basin-fill deposits or consolidated rock is unknown. 

For wells with drillers’ reports, most are completed in 

basin-fill deposits (unconsolidated) with a few wells 

completed in fractured granite (consolidated).

The median depth to water on the basis of measurements from 60 non-pumping wells was 12.7 ft 

below land surface and ranged from 1.33 ft below land 

0 2 4 6 8 10 12 14 16

DISTANCE FROM LAKE TAHOE, IN RIVER MILE

-5

5

-4

-3

-2

-1

0

1

2

3

4

STREAMFLOW GAINS AND LOSSES, IN CUBIC FEET PER SECOND

Upper Truckee River 2 3

4

5

6

7

8

9 10

Trout Creek

11 12

13

14 15

16

Reach number

Figure 8. Cumulative streamflow gains and losses for Upper Truckee River and Trout Creek, California, 

September 1996.
SURFACE- AND GROUND-WATER CONDITIONS 31

surface at well 94 to 69.85 ft below land surface at well 

137. Depths to water were generally shallow in observation wells in meadows and particularly along the 

meadow near the mouth of Angora Creek where it is 

tributary to the Upper Truckee River. Depths to water 

were the greatest in observation wells in the old landfill 

near Meyers.

Well locations, results of seepage estimates, 

water-level contours, generalized directions of groundwater flow, and consolidated and unconsolidated geology are shown on plate 1. Water-level contours derived 

from measured water levels and results of seepage estimates are represented on plate 1 by solid lines; contours determined by using a median depth to water of 

about 13 ft are represented on plate 1 by dashed lines. 

The interpretation of the water-level contours in areas 

with wells that have land-surface altitudes determined 

from topographic maps has an inherent uncertainty due 

to uncertainties associated with the water-level altitudes. In steeply sloping terrain, the horizontal uncertainty of the water-level contours is small. In the more 

gently sloping terrain, where the topographic-contour 

interval is 40 ft, this horizontal uncertainty can be 

greater. Where the topographic-contour interval is 20 ft 

or less, the horizontal uncertainty is less. Water-level 

contours exist only in the unconsolidated sediments of 

the study area and do not cross consolidated rock. The 

water-level contour interval on plate 1 is variable and 

in general increases to the south, from about 10 ft in 

South Lake Tahoe to 200 ft along Highway 89 near 

Luther Pass.

Ground-water altitudes (pl. 1) in the Upper 

Truckee River watershed range from about 6,220 ft at 

well 76 in the northern part of the study area near Lake 

Tahoe to 7,250 ft at well 130 in the southern part of the 

study area. Ground-water altitudes in the Trout Creek 

watershed range from 6,190 ft at well 137 in the northern part of the study area to 6,380 ft at well 148 in 

the old Meyers landfill. Ground-water altitudes in the 

study area generally mimic the topography, with higher 

altitudes in the upland areas and lower altitudes near 

Lake Tahoe.

Ground-water levels in two wells in the study 

area (wells 73 and 131) have been monitored by 

California Department of Water Resources since June 

1962. These two wells have responded to climatic 

variations such as drought and wet years (fig. 9).

In general, ground water in the study area is flowing northward toward Lake Tahoe (pl. 1) and parallels 

surface-water flow. Ground water generally discharges 

to the Upper Truckee River and Trout Creek along the 

upper reaches, whereas in the middle reaches ground 

water is flowing parallel to both streams. In the middle 

reach, the Upper Truckee River is losing streamflow 

for about 1.9 mi and Trout Creek has a net loss over 

its middle reaches. Ground water discharges to both 

streams between river miles 1.5 and 2.8 as both streams 

have a net gain in streamflow that is not accounted for 

by tributary flows. Both streams show little gain in 

flow further downstream suggesting that little ground 

water discharges to the two streams close to Lake 

Tahoe (table 4, pl. 1). 

From July to November 1996, altitude of ground 

water in wells in the area between Lake Tahoe and 

Highway 50 (about river mile 1.5 on both stems) was 

nearly the same as the lake-surface altitude (table 5, 

pl. 1). This suggests that the ground-water flow 

beneath the Upper Truckee River and Trout Creek 

drainages between Highway 50 and Lake Tahoe was 

minimal during the study. Much of the ground-water 

discharge in these drainages was to the channels of the 

Upper Truckee River and Trout Creek upstream from 

Highway 50 (pl. 1).

Hydraulic gradients in the study area upstream 

from Highway 50 ranged from 10 to 1,400 ft/mi. 

Hydraulic gradients in the Upper Truckee River watershed are greatest in the upland areas. For example, 

the gradient near Luther Pass is 700 to 1,400 ft/mi. 

Hydraulic gradients tend to decrease rapidly in the 

lower areas, such as Christmas Valley, where gradients 

ranged from 30 to 60 ft/mi. In the Tahoe Paradise area, 

the hydraulic gradients ranged from about 20 to 40 

ft/mi. In the northern part of the study area, the hydraulic gradients ranged from 10 ft/mi along the Upper 

Truckee River near the airport to as much as 50 ft/mi 

in the South Lake Tahoe area near the intersection of 

Highway 50 and Highway 89 in the Upper Truckee 

River watershed. The hydraulic gradients in the Trout 

Creek watershed ranged from about 420 ft/mi for areas 

along Saxon Creek to about 20 ft/mi along the lower 

reaches of Trout Creek upstream from the confluence 

of Heavenly Valley Creek. In the South Lake Tahoe 

area of the Trout Creek watershed, just south of Highway 50, the hydraulic gradient is about 30 ft/mi except 

in the area of well 137, where a cone of depression is 

caused by municipal pumping (Woodling, 1987, p. 21) 

and the hydraulic gradient is as high as 300 ft/mi. 

Hydraulic gradients vary on either side of the large 

lateral glacial moraine that divides the Trout Creek 

watershed from the Upper Truckee River watershed. 
32 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

Figure 9. Water-level changes in wells 73 and 131 in Upper Truckee River and Trout Creek watersheds, California. 

(Data courtesy of California Department of Water Resources.) Location of wells is shown on plate 1. 

1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996

6,222

6,242

6,224

6,226

6,228

6,230

6,232

6,234

6,236

6,238

6,240

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

1958 1960 1962 1964 1966 1968 1970 1972 1974 1976 1978 1980 1982 1984 1986 1988 1990 1992 1994 1996

DATE

6,214

6,228

6,216

6,218

6,220

6,222

6,224

6,226

WATER-LEVEL ALTITUDE, IN FEET ABOVE SEA LEVEL

Well 73, Upper Truckee River watershed, south of Tahoe Keys and north of Highway 89.

Well 131, Trout Creek watershed, near confluence of Trout Creek with Lake Tahoe.
SURFACE- AND GROUND-WATER CONDITIONS 33

Hydraulic gradients ranged from 170 to 1,300 ft/mi on 

the west side of the moraine and from 60 to 730 ft/mi 

on the east side.

Water Quality

Specific conductance of surface-water samples 

from sites in the Upper Truckee River watershed on 

September 23, 1996, ranged from 31 μS/cm at site 16 

to 148 μS/cm at site 19 (table 3). Specific conductance 

in the main channel of the Upper Truckee River 

increased in a downstream direction from 50 μS/cm at 

site 45 to 99 μS/cm at site 15 and then remained relatively constant from site 15 to site 1 with a range of 

only 96 to 99 μS/cm (fig. 10). The relatively large 

increase in specific conductance with downstream 

direction for the upper half of the Upper Truckee River 

was probably caused by the relatively large component 

of higher conductance ground water contributing to the 

rivers streamflow for this segment (fig. 3, tables 3 and 

4). The lower half of the Upper Truckee River has 

relatively constant specific conductance probably 

because streamflow has almost no gain from groundwater seepage for this segment (fig. 3, tables 3 and 4). 

The specific conductance values found along the main 

stem of the Upper Truckee River during base-flow conditions are similar to the highest values found during 

the 1996 water year. For the 1996 water year, specific 

conductance ranged from 22 to 96 μS/cm at site 6 near 

the mouth to 14 to 51 μS/cm at site 43 (Bostic and others, 1997, p. 263-269). Specific conductances are usually greatest during the low streamflow of late summer 

through fall and immediately following some storms 

prior to snowmelt. Specific conductances are lowest 

during snowmelt runoff, which generally peaks in late 

spring through early summer. 

Specific conductance of surface-water samples 

from sites in the Trout Creek watershed on September 

26, 1996, ranged from 43 μS/cm at site 53 to 92 μS/cm 

at site 58 (table 3). The specific conductance measured 

in the main channel of Trout Creek ranged from 49 to 

54 μS/cm (fig. 10). The lack of increase in specific 

conductance with downstream direction in Trout Creek 

as compared with the Upper Truckee River might be 

due to the minimal contribution of ground-water seepage to streamflow. The specific conductance values 

found along the main stem of Trout Creek during baseflow conditions are similar to the highest values found 

during the 1996 water year. For the 1996 water year, 

specific conductance ranged from 25 to 54 μS/cm at 

site 49 near the mouth and from 19 to 53 μS/cm at site 

68 (Bostic and others, 1997, p. 329 and 334). Specific 

conductances also are the greatest during the low-flow 

periods of late summer through fall and the smallest 

during snow melt runoff in late spring to early summer.

Specific conductance of surface-water samples 

for the three Upper Truckee River water-quality sites 

from early July through mid-December 1996, ranged 

from 17 μS/cm at site 43 to 101 μS/cm at site 17 (table 

6). Specific conductances for the three Trout Creek 

water-quality network sites for the same period ranged 

from 31 μS/cm at site 68 to 55 μS/cm at site 57.

Specific conductance of ground-water samples 

for wells in the Upper Truckee River and Trout Creek 

watersheds from mid-July through mid-December 

1996, ranged from 94 μS/cm at well 137 to 542 μS/cm 

at well 143 (table 7). As stated earlier, the water-quality 

results from well 143 may not represent the overall 

ground-water conditions due to the proximity of the 

old Meyers landfill. The next highest value of specific 

conductance is 305 μS/cm at well 135. Specific conductances varied in only two wells between summer 

and fall samples (fig. 11). Specific conductance did not 

appear to have any trend with respect to distance from 

Lake Tahoe (fig. 11).

Water temperatures measured at streamflow sites 

in the Upper Truckee River watershed on September 

23, 1996, ranged from 4.5°C at site 14 to 13.5°C in 

the lower reaches of the main channel at site 6 (table 3). 

The main channel water temperatures generally 

increased in a downstream direction. Water temperatures ranged from 6.0 to 9.5°C at the upper sites and 

ranged from 11.5 to 13.5°C at the lower sites. Water 

temperatures can be affected by air temperatures, 

which ranged from 3.5°C in the morning to 25.0°C in 

the afternoon. Water temperature measured at streamflow sites in the Trout Creek watershed on September 

26, 1996, ranged from 5.0°C at site 68 to 11.5°C near 

the mouth at sites 46 and 48. Water temperatures also 

increased in a downstream direction with a range of 5.0 

to 6.5°C in the upper reaches to 7.0 to 11.5°C in the 

lower reaches. The air temperatures ranged from 9.5°C 

in the morning to 30.0°C in the afternoon. Weather was 

clear and warm on both days of the seepage run.

Water temperatures for the six surface-waterquality sites in the Upper Truckee River and Trout 

Creek watersheds ranged from 0.5°C at site 49 in early 

December to 16.0°C at site 6 in mid-July. Water temperatures of ground water for the seven wells in both 

watersheds ranged from 8.0°C at wells 71 and 77 in late 
34 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

November and mid-December to 14.5°C at well 97 in 

mid-July. Ground-water temperatures varied seasonally by more than a half degree Celsius at only three 

wells (fig. 10). 

Values of pH in surface water for the six sites 

for the Upper Truckee River and Trout Creek had a 

narrow range from 6.6 at site 57 to 7.8 at sites 6, 17, 

and 43 (table 6). Values of pH in ground water for the 

seven wells in both watersheds had a greater range 

from 5.5 at well 71 to 9.0 at well 80 (table 7). About 

53 percent of ground-water quality sites had pH values 

from 6 to 8. Determination of the cause of this variability is beyond the scope of this study. The variation of 

values between summer and fall samples were small 

except for well 71, which varied by 1 pH unit (fig. 11). 

Values of pH did not appear to have any trends with 

respect to distance from Lake Tahoe (fig. 11).

Nutrient data collected from the six surfacewater-quality sites for July through December 1996 

are listed in table 6. Nitrite plus nitrate (NO2+NO3) 

concentrations ranged from 0.002 to 0.036 mg/L. The 

NO2+NO3 concentrations are well below the USEPA 

drinking water standard of 10 mg/L (U.S. Environmental Protection Agency, 1996). Ammonia nitrogen 

(NH4) concentrations ranged from less than the detection limit of 0.001 to 0.013 mg/L. Kjeldahl (NH4 plus 

organic nitrogen) concentrations ranged from 0.04 to 

0.51 mg/L. Phosphorous (P) concentrations ranged 

from 0.014 to 0.241 mg/L. Orthophosphorus concentrations ranged from 0.003 to 0.032 mg/L. Bioreactive 

iron (Fe) concentrations ranged from 45 to 2,650 ug/L. 

Some of these extreme values were from samples collected during storms and are not representative of normal flow conditions. Samples collected during storms 

were not used in the summary statistic comparisons 

between surface- and ground-water quality in figure 6 

because they were not randomly collected.

Nutrient data collected from nine ground-waterquality sites in July through December 1996 are 

listed in table 7. NO2+NO3 concentrations ranged 

0 2 4 6 8 10 12 14 16

DISTANCE FROM LAKE TAHOE, IN RIVER MILES

0

160

20

40

60

80

100

120

140

SPECIFIC CONDUCTANCE, IN MICROSIEMENS PER CENTIMETER AT 25 DEGREES CELSIUS

Upper Truckee River water-quality monitoring site

Trout Creek water-quality monitoring site

1 3

52

1

6 7 9 15

17

20

25

43 45

46-47

48

49 52 57 65 68

70

Figure 10. Relation between distance from Lake Tahoe and specific conductance for surface-water-quality 

monitoring sites on Upper Truckee River and Trout Creek, California, September 1996, as listed in table 4.
SURFACE- AND GROUND-WATER CONDITIONS 35

5

10

6

7

8

9

Summer 1996

Late Fall 1996

71 72 135 77 137 80 143 97

WELL NUMBER

7

15

8

9

10

11

12

13

14

0

600

100

200

300

400

500

pH, IN STANDARD UNITS WATER TEMPERATURE, IN DEGREES CELSIUS SPECIFIC CONDUCTANCE IN MICROSIEMENS PER CENTIMETER

AT 25 DEGREES CELSIUS

Figure 11. Field ground-water-quality measurements, Upper Truckee River and Trout 

Creek watersheds, California, July-December 1996. Sites are listed with increasing 

distance from Lake Tahoe from left to right.
36 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

from 0.002 to 3.24 mg/L. Three samples, all from the 

Trout Creek watershed, were greater than 1.8 mg/L, 

whereas, 75 percent of concentrations were below 0.76 

mg/L. These NO2+NO3 concentrations are below the 

USEPA drinking water standard of 10 mg/L (U.S. 

Environmental Protection Agency, 1996). Ammonia 

(NH4) concentrations ranged from 0.001 to 0.523 

mg/L, with 75 percent below 0.2 mg/L. Kjeldahl 

(ammonia plus organic nitrogen) concentrations 

ranged from less than 0.01 to 1.7 mg/L, with two 

samples greater than 1.2 mg/L and 75 percent below 

0.18 mg/L. Phosphorus (P) concentrations ranged from 

0.018 to 0.101 mg/L, with 75 percent below 0.06 mg/L. 

Phosphorus concentrations were lower in samples collected in the fall than in the summer at all wells. Orthophosphorus concentrations ranged from 0.010 to 0.067 

mg/L, with 75 percent below 0.032 mg/L. Bioreactive 

iron (Fe) concentrations ranged from 4.3 to 8,800 ug/L, 

with 75 percent of samples having concentrations 

below 32 μg/L. The highest values of the ammonia 

species of nitrogen nutrients occurred in one shallow 

observation well near the Truckee Marsh (well 71). 

Ground water from this well also had high concentrations of ammonia in the 1995 and 1996 water years 

(Bauer and others, 1996; Bostic and others, 1997). 

These high values probably are due to decomposition 

of organic material from the wetland.

SUMMARY AND CONCLUSIONS

Lake Tahoe is an outstanding natural resource 

and known for its deep, clear waters. Increased nutrient 

concentrations within Lake Tahoe are considered the 

leading cause of algal growth and loss of clarity in the 

lake. Surface- and ground-water discharge throughout 

the Lake Tahoe Basin are assumed to be significant 

mechanisms for nutrient transport to Lake Tahoe. 

The Tahoe Regional Planning Agency has primary 

responsibility for the environmental protection of Lake 

Tahoe with an emphasis on reducing the loss of lake 

clarity in Lake Tahoe.

The Upper Truckee River and Trout Creek watersheds are the two largest watersheds and have the greatest areas of urban land use within the Lake Tahoe 

Basin. In 1996, the USGS, in cooperation with TRPA, 

began a study to improve the understanding of the surface-water and ground-water systems and their interactions within the Upper Truckee River and Trout Creek 

watersheds.

The contribution of ground water to surface-water 

streamflow, the unit runoff, the general direction of 

ground-water flow, and the comparisons of water quality from the surface-water system to the ground-water 

system during a period of minimal snowmelt runoff for 

the Upper Truckee River and Trout Creek watersheds 

were evaluated. Streamflow and water-quality data 

were collected at existing and supplemental surfacewater streamflow and water-quality sites and waterlevel and water-quality data were collected at existing 

and supplemental ground-water sites.

Seepage estimates were determined for the Upper 

Truckee River and Trout Creek by measuring streamflow at designated sites used to define reach segments. 

Seepage gains and losses were determined for the 

selected reaches by subtracting the sum of the flow 

at the upstream end of the reach plus any tributary 

inflows from the flow at the downstream end of the 

reach. Unit-runoff values were determined by normalizing streamflow to contributing drainage-area size. 

Specific conductance and water temperature were 

determined at the time of streamflow measurements 

to provide synoptic field water-quality conditions for 

both watersheds.

Water levels were determined for wells within 

the study area and were used to produce a water-level 

altitude map, to determine directions of ground-water 

flow, and to determine hydraulic gradients.

Samples from six surface-water-quality and eight 

ground-water-quality sites were collected for nutrient 

species and iron as well as the basic field measurements of specific conductance, pH, and water temperature. Summary statistics for the chemical and field data 

were computed for surface- and ground-water-quality 

sites.

Streamflows measured during the seepage run 

were during a base flow period for both the Upper 

Truckee River and Trout Creek. All but 3 of the 13 

streamflow measurement sites on the main stem of 

the Upper Truckee River had measurable streamflow. 

The three dry sites were divergent branches of the main 

stem. Forty-eight percent of the streamflow measurement sites that are tributary to the Upper Truckee River 

or along the tributaries were dry. All the streamflow 

measurement sites on the main stem of Trout Creek 

had measurable flow. Only one of the streamflow sites 

measured in the Trout Creek watershed was dry. This 

indicates that streamflows in the Trout Creek watershed are more perennial than those in the Upper 

Truckee River.
SUMMARY AND CONCLUSIONS 37

The largest tributary inflow into the Upper 

Truckee River was from Grass Lake Creek, which 

accounted for 17 percent of the total flow near the 

mouth of the Upper Truckee River. The largest tributary inflow into Trout Creek was Cold Creek, which 

accounted for 49 percent of the total flow near the 

mouth of Trout Creek.

The Upper Truckee River has greater groundwater seepage contributing to its overall streamflow 

than Trout Creek, while Trout Creek has greater 

tributary inflows contributing to its overall streamflow. 

Both streams had a similar proportion of streamflow 

at their uppermost main stem sites (when computed as 

a percentage of the most downstream sites). The total 

streamflow of the Upper Truckee River near its mouth 

was 38 percent ground-water seepage to the main stem, 

39 percent tributary inflows, and 23 percent was the 

streamflow at the uppermost main stem site. The total 

streamflow of Trout Creek near its mouth was 4 percent ground-water seepage to the main stem, 76 percent 

tributary inflows, and 20 percent streamflow from the 

upper most main stem site.

Both the Upper Truckee River and Trout Creek 

had streamflow that was gaining from ground-water 

seepage in their upper reaches, both were steady or 

losing to ground-water seepage in their middle reaches, 

and both were again gaining flow from ground-water 

seepage in their lower reaches. 

Unit runoff values for the Upper Truckee River 

watershed were less than those of the Trout Creek 

watershed. This was mainly due to the large contribution of flow from the Cold Creek tributary to Trout 

Creek. The large unit runoff of the Cold Creek tributary 

is assumed to be due to protracted snowmelt resulting 

from the high percentage of north-facing aspect or due 

to the delayed release of ground water from storage.

The median depth to water in the study area 

during this period was 12.7 ft below land surface with 

a range of 1.33 to 69.85 ft below land surface. Depths 

to water were generally least in meadows and greatest 

in the old Meyers landfill. Ground-water altitudes in 

the study area ranged from 6,190 to 7,250 ft and 

generally mimicked the land-surface topography. 

Ground-water in the study area generally flows 

parallel to surface water. In the upper reaches of both 

watersheds, ground water flows towards the stream 

channels and in the middle reaches it flows parallel to 

the main channels. In the lower reaches near Lake 

Tahoe, ground-water levels and the water level at 

Lake Tahoe are nearly equal resulting in a very small 

hydraulic gradient. This suggests that ground-water 

discharge directly to Lake Tahoe is minimal.

Hydraulic gradients in the study area varied 

greatly, ranging from nearly zero to 1,400 ft/mi 

upstream from Highway 50. Hydraulic gradients were 

the greatest in upland areas and least near Lake Tahoe 

and along the middle reaches of the main stems of both 

streams.

The specific conductance of surface water measured during the seepage study had a greater range in 

the Upper Truckee River watershed than in the Trout 

Creek watershed and was generally greater in value 

also. In the Upper Truckee River watershed, specific 

conductance ranged from 31 to 148 μS/cm and in the 

Trout Creek watershed it ranged from 43 to 92 μS/cm. 

The specific conductance of water in the upper half of 

the main stem of the Upper Truckee River increased in 

the downstream direction and was consistent for the 

lower half. The specific conductance for Trout Creek 

was consistent throughout the length of its main stem. 

This is likely attributed to the larger ground-water 

seepage component of total streamflow in the upper 

half of the Upper Truckee River than in Trout Creek.

Specific conductance for surface water was much 

less than that of ground water and had a much smaller 

range. Specific conductance for the six surface-waterquality sites for the period of study ranged from 17 to 

101 μS/cm. Specific conductance for the groundwater-quality sites for the same period ranged from 94 

to 305 μS/cm for wells that were considered representative of general ground-water conditions.

Temperature of surface water measured during 

the seepage study was generally lowest at upstream 

sites and highest at downstream sites in both the Upper 

Truckee River and Trout Creek. The overall range was 

4.5 to 13.5°C. Air temperatures ranged from 3.5 to 

30.0°C during the seepage study.

Median values of water temperature for both 

surface water and ground water were similar. Surfacewater temperatures (0.5 to 16.0°C) had a significantly 

greater range than those measured in ground water (8.0 

to 14.5°C).

Median values of pH for surface and ground 

water were similar; however, pH ranges for ground 

water (5.5 to 9.0) were significantly greater than 

those measured for surface water (6.6 to 7.8). 

Concentrations of nitrite plus nitrate, ammonia, 

and orthophosphorus were greater for the ground-water 

samples than for the surface-water samples collected. 
38 Surface- and Ground-Water Characteristics in the Upper Truckee River and Trout Creek Watersheds, South Lake Tahoe

Concentrations of bioreactive iron were generally 

greater for ground-water samples than for surfacewater samples. Both surface- and ground-water samples had similar concentrations of phosphorous and 

kjeldahl (ammonia plus organic nitrogen). Ground 

water typically had greater variation in nitrite plus 

nitrate, ammonia, kjeldahl, and bioreactive iron concentrations than surface water. Surface- and groundwater samples had similar variations in phosphorous 

and orthophosphorus.

The most important results of this study are that, 

even though the Upper Truckee River and Trout Creek 

share many similarities in geology, vegetation, land 

use, and location, they had significantly different characteristics with respect to their interactions with the 

ground-water system. In particular, 38 percent of the 

streamflow of the Upper Truckee River near its mouth 

originated from ground-water seepage to its main channel while that of Trout Creek was only 4 percent. 

Ground-water contribution to streamflow also can be 

seen in the field measurement of specific conductance 

because ground water generally has greater conductivity. At the upper sites of both streams, specific conductance values are similar. However, the specific 

conductance increased in the downstream direction 

along the upper half of the Upper Truckee River but 

remained relatively constant along the lower half of the 

main stem. Specific conductance remained fairly constant for the entire length of Trout Creek. 

Another important result is that during July to 

November 1996, the altitude of ground-water between 

Lake Tahoe and Highway 50 was nearly the same as 

the lake-surface altitude. This suggests ground-water 

discharge beneath the Upper Truckee River and Trout 

Creek drainages directly to Lake Tahoe was minimal 

and that much of the ground-water discharge was to the 

channels of the Upper Truckee River and Trout Creek 

upstream from Highway 50.

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