U.S. Department of the Interior

U.S. Geological Survey

Scientific Investigations Report 2015–5087

Prepared in cooperation with the Bureau of Reclamation and the U.S. Fish and Wildlife Service

Effects of Groundwater Pumping on Agricultural Drains in the 

Tule Lake Subbasin, Oregon and California
Cover:

Top left: Sheepy Ridge and the Tule Lake subbasin as seen looking north from Lava Beds 

National Monument, California. (Photograph by Marshall Gannett, U.S. Geological Survey.)

Top right: Pump A motors, with Drain 46 in background, Tulelake Irrigation District, Oregon 

and California. (Photograph taken by Brian Wagner, U.S. Geological Survey.)

Bottom left: Tulelake Irrigation District irrigation well 1 pumping into a canal, California. 

(Photograph by Marshall Gannett, U.S. Geological Survey.)

Bottom right: Pumping Plant D, looking west toward Sheepy Ridge, Tulelake Irrigation 

District, Oregon and California. (Photograph by Marshall Gannett, U.S. Geological Survey.)
Effects of Groundwater Pumping on 

Agricultural Drains in the Tule Lake 

Subbasin, Oregon and California

By Esther M. Pischel and Marshall W. Gannett

Prepared in cooperation with the Bureau of Reclamation and the

U.S. Fish and Wildlife Service

Scientific Investigations Report 2015–5087

U.S. Department of the Interior

U.S. Geological Survey
U.S. Department of the Interior

SALLY JEWELL, Secretary

U.S. Geological Survey

Suzette M. Kimball, Acting Director

U.S. Geological Survey, Reston, Virginia: 2015

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Suggested citation:

Pischel, E.M., and Gannett, M.W., 2015, Effects of groundwater pumping on agricultural drains in the Tule Lake 

subbasin, Oregon and California: U.S. Geological Survey Scientific Investigations Report 2015–5087, 44 p., 

http://dx.doi.org/10.3133/sir20155087.

ISSN 2328-0328 (online)
iii

Contents

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

Introduction ....................................................................................................................................................1

Purpose and Scope ..............................................................................................................................3

Background.....................................................................................................................................................3

Study Area..............................................................................................................................................3

Increases in Groundwater Pumping..................................................................................................4

Changes in Discharge to Drains.........................................................................................................5

Sources of Water to Wells ..................................................................................................................5

Changes in Hydraulic Head and Flow ...............................................................................................6

Upper Klamath Basin Regional Model ..............................................................................................7

Study Objectives ............................................................................................................................................7

Methods...........................................................................................................................................................7

Drain Flow Analysis..............................................................................................................................7

Drain Subareas.............................................................................................................................7

North Tulelake and Klamath Irrigation Districts ............................................................8

Copic Bay .............................................................................................................................8

Lease Lands.........................................................................................................................8

Operational Spills.........................................................................................................................8

Other Possible Causes of Decreased Drain Flow ................................................................10

Groundwater Model ...........................................................................................................................10

Discretization..............................................................................................................................10

Hydrogeologic Zonation ...........................................................................................................10

Boundary Conditions.................................................................................................................15

Specified Flow Boundaries .............................................................................................15

Recharge...................................................................................................................15

Groundwater Pumping............................................................................................15

Head-Dependent Flow Boundaries ...............................................................................16

Lost River...................................................................................................................16

Tule Lake Sumps ......................................................................................................16

Drains .......................................................................................................................16

Interbasin Groundwater Flow................................................................................16

Model Calibration ......................................................................................................................17

Agricultural Drain Flow Analysis ..............................................................................................................19

Groundwater Model Results......................................................................................................................21

Calibration ...........................................................................................................................................21

Parameter Sensitivity................................................................................................................22

Model Fit......................................................................................................................................22

Comparison of Measured and Simulated Hydraulic Heads ...............................................23

Simulated Hydrologic Budget and Sources of Water to Wells...................................................30

Potential Implications..................................................................................................................................34
iv

Contents—Continued

Study Limitations and Uncertainty............................................................................................................34

Uncertainty in the Drain-Flow Analysis ..........................................................................................34

Uncertainty in the Groundwater Model ..........................................................................................34

Summary .......................................................................................................................................................35

Acknowledgments.......................................................................................................................................35

References Cited..........................................................................................................................................36

Appendix A. Model Observation Wells ....................................................................................................37

Figures

1. Map showing Tule Lake study area of the upper Klamath Basin, Oregon and 

California ........................................................................................................................................2

2. Photograph showing example of an agricultural drain in the Tule Lake

subbasin, California......................................................................................................................4

3. Graph showing total diversions, D Plant pumpage, and ratio of D Plant

pumpage to total diversions, Tule Lake subbasin, Oregon and California, 1961–2011......5

4. Hydrographs showing four observation wells in the Tule Lake subbasin, California .......6

5. Photograph showing example of a drain pump in the Tulelake Irrigation District

system, California .........................................................................................................................8

6. Map showing subareas and drain pumps used in analysis of drain flow, Tule

Lake subbasin, Oregon and California ......................................................................................9

7. Map showing groundwater-model grid and boundary conditions, Tule Lake

subbasin, Oregon and California..............................................................................................11

8. Maps showing hydrogeologic zonation of the Tule Lake groundwater model,

Tule Lake subbasin, Oregon and California............................................................................12

9. Cross sections of Tule Lake groundwater model, Tule Lake subbasin, Oregon

and California ..............................................................................................................................14

10. Map showing locations of observation wells for the Tule Lake subbasin model,

Oregon and California ................................................................................................................18

11. Graph showing yearly volume of water from pumps integrating the North

Tulelake and Klamath Irrigation District (TID/KID) subarea, Oregon and California.......20

12. Graph showing yearly volume of water from pumps integrating the Copic Bay

subarea, Tule Lake subbasin, California .................................................................................20

13. Graph showing yearly volume of water from pumps integrating the Lease

Lands subarea, Tule Lake subbasin, California .....................................................................20
v

Figures—Continued

14. Graph showing composite scaled sensitivities of parameters in the Tule Lake

groundwater model ....................................................................................................................22

15. Graph showing weighted residuals and weighted simulated hydraulic head

values, Tule Lake subbasin, Oregon and California .............................................................23

16. Graphs showing observed and simulated hydraulic heads for selected

observation wells, Tule Lake subbasin, Oregon and California .........................................24

17. Graphs showing water levels in U.S. Geological Survey observation wells

430837121473201 (28.00S/08.00E-17DBC01), about 80 miles north-northwest of the

Tule Lake subbasin, and 414043121155501 (44.00N/06.00E-03P01M), about 10

miles southeast of the Tule Lake subbasin, Oregon and California ...................................28

18. Graph showing observed and simulated decrease in flow to drains relative to

drain flow in 2000, Tule Lake subbasin, Oregon and California ..........................................29

19. Graph showing simulated water budget components of the Tule Lake subbasin,

Oregon and California ................................................................................................................30

20. Graph showing simulated cumulative change in volume of selected budget

components of the Tule Lake subbasin, Oregon and California .........................................31

21. Map showing spatial distribution of simulated reduction in discharge to drains,

calculated as the discharge to drains in 2006 subtracted from the discharge to

drains in 2000, Tule Lake subbasin, Oregon and California .................................................33

Tables

1. Layer thicknesses for the Tule Lake groundwater model....................................................10

2. MODFLOW-2000 packages and files used in the Tule Lake subbasin model ...................17

3. Model observation wells...........................................................................................................19

4. Calibrated values of parameters for the Tule Lake subbasin groundwater flow

model, Oregon and California ...................................................................................................21

5. Simulated cumulative change in volumetric budget, Tule Lake subbasin, Oregon

and California ..............................................................................................................................32
vi

Conversion Factors

Inch/Pound to International System of Units

Multiply By To obtain

Length

foot (ft) 0.3048 meter (m)

mile (mi) 1.609 kilometer (km)

Area

acre 0.4047 hectare (ha)

acre 0.004047 square kilometer (km2

)

square foot (ft2

) 929.0 square centimeter (cm2)

square foot (ft2

) 0.09290 square meter (m2)

Volume

acre-foot (acre-ft) 1,233 cubic meter (m3

)

Flow rate

acre-foot per year (acre-ft/yr) 1,233 cubic meter per year (m3

/yr)

acre-foot per year (acre-ft/yr) 0.001233 cubic hectometer per year (hm3

/yr)

foot per second (ft/s) 0.3048 meter per second (m/s)

foot per year (ft/yr) 0.3048 meter per year (m/yr)

cubic foot per second (ft3

/s) 0.02832 cubic meter per second (m3/s)

Datums

Vertical coordinate information is referenced to the National Geodetic Vertical Datum of 1929 

(NGVD 29).

Horizontal coordinate information is referenced to the North American Datum of 1927 (NAD 27).

Elevation, as used in this report, refers to distance above the vertical datum. 
Effects of Groundwater Pumping on Agricultural 

Drains in the Tule Lake Subbasin, Oregon and California

By Esther M. Pischel and Marshall W. Gannett

Abstract

Since 2001, irrigators in the upper Klamath Basin 

have increasingly turned to groundwater to compensate for 

reductions in surface-water allocation caused by shifts from 

irrigation use to instream flows for Endangered Species Act 

listed fishes. The largest increase in groundwater pumping 

has been in and around the Bureau of Reclamation’s Klamath 

Irrigation Project, which includes the Tule Lake subbasin in 

the southern part of the upper Klamath Basin. Agricultural 

drains on the Klamath Project are an important source of water 

for downstream irrigators and for the Tule Lake and Lower 

Klamath Lake National Wildlife Refuges. U.S. Geological 

Survey regional groundwater-flow model simulations and 

records of irrigation-return flow pumped from the Tule Lake 

subbasin into the adjacent Lower Klamath Lake subbasin 

have indicated that water-level declines from pumping 

may be causing decreased flow of shallow groundwater to 

agricultural drains. 

To better define the effect of increased pumping on 

drain flow and on the water balance of the groundwater 

system, the annual water volume pumped from drains in 

three subareas of the Tule Lake subbasin was estimated 

and a fine-grid, local groundwater model of the Tule Lake 

subbasin was constructed. Results of the agricultural-drain 

flow analysis indicate that groundwater discharge to drains 

has decreased such that flows in 2012 were approximately 

32,400 acre-ft less than the 1997–2000 average flow. This 

decrease was concentrated in the northern and southeastern 

parts of the subbasin, which corresponds with the areas of 

greatest groundwater pumping. Model simulation results 

of the Tule Lake subbasin groundwater model indicate that 

increased supplemental pumping is the dominant stress to the 

groundwater system in the subbasin. Simulated supplemental 

pumping and decreased recharge from irrigation between 

2000 and 2010 totaled 323,573 acre-ft, 234,800 acre-ft 

(73 percent) of which was from supplemental pumping. The 

response of the groundwater system to this change in stress 

included about 180,500 acre-ft (56 percent) of decreased 

groundwater discharge to drains and a 126,000 acre-ft 

(39 percent) reduction in aquifer storage. The remaining 

5 percent came from reduced groundwater flow to other model 

boundaries, including the Lost River, the Tule Lake sumps, 

and interbasin flow. 

Introduction 

The allocation of water between agriculture and aquatic 

wildlife has been challenging for resource managers in 

the upper Klamath Basin of southern Oregon and northern 

California (fig. 1). In 2001, drought conditions resulted in 

nearly all of the available water in the Upper Klamath Basin 

being reallocated to maintain water levels in Upper Klamath 

Lake to protect the endangered Lost River and shortnose 

suckers, and to maintain flows in the Klamath River to protect 

the threatened coho salmon (National Research Council, 

2004). In response to this reallocation of water, irrigators have 

increasingly turned to groundwater to offset the shortages in 

surface water availability. The largest increase has been in 

and around the Bureau of Reclamation’s Klamath Irrigation 

Project (Project), which includes the Tule Lake subbasin in 

the southern part of the upper Klamath Basin (Gannett and 

others, 2007).

Groundwater pumping has resulted in water-level 

declines in wells near the centers of pumping, which 

affects directions and rates of groundwater flow. Results 

of U.S. Geological Survey (USGS) groundwater modeling 

efforts (Gannett and others, 2012), analysis of monitoring well 

data, and hydrologic budget information from the Bureau of 

Reclamation and irrigation districts that operate in the Tule 

Lake subbasin indicate that pumping-related hydraulic head 

changes may be resulting in decreased flow to agricultural 

drains. The lowering of hydraulic heads in aquifers may be 

inducing downward flow of shallow groundwater, decreasing 

lateral flow toward drains. Decreased shallow groundwater 

discharge to agricultural drains has potential implications for 

Project operations and for water supplies to the Tule Lake and 

Lower Klamath National Wildlife Refuges.
2 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig01

OREGON

CALIFORNIA

Upper

Klamath

Basin

Tule Lake

subbasin

Horton

Algoma

Shady

Pine Hildebrand

Wocus

Pelican City

Dairy

Altamont

Hager

Olene

Henley Lorella

Midland Stukel

Worden

Malin

Langell

Valley

Klamath

Falls Bonanza

Keno

Merrill

Dorris

Tulelake

OREGON

CALIFORNIA

UPPER 

KLAMATH 

 LAKE

LOWER

KLAMATH 

LAKE

Tule Lake 

Sump 1A

Sump 1B

CLEAR

LAKE

RESERVOIR

Clear

Lake

subbasin

Sheepy Ridge

Pit River Basin

Klamath River

Poe Valley Lost River

Lower Klamath 

Lake subbasin

Tule Lake subbasin

122°00' 45' 30' 15' 121°00'

42°

15'

42°

00'

45'

41°

30'

Universal Transverse Mercator projection, Zone 10N 

North American Datum of 1927

0 5 10 MILES

0 5 10 KILOMETERS

EXPLANATION

Active model boundary

Tule Lake National Wildlife 

Refuge boundary

Lower Klamath National 

Wildlife Refuge boundary

Agricultural drain

Figure 1. Tule Lake study area of the upper Klamath Basin, Oregon and California.
Background 3

Purpose and Scope

This report presents the results of a cooperative study 

with the Bureau of Reclamation and U.S. Fish and Wildlife 

Service to develop a quantitative understanding of the 

connection between volcanic and overlying sedimentary 

aquifers in the Tule Lake subbasin of the upper Klamath 

Basin to assess the effect of pumping on agricultural drains. 

As part of that goal, data on diversions, operational spills, 

and drain flows from irrigation districts that serve the Tule 

Lake subbasin were analyzed to evaluate changes in the water 

balance of the subbasin. Additionally, a groundwater-flow 

model of the Tule Lake subbasin was developed to integrate 

knowledge about the groundwater hydrology of the subbasin 

and to explore the degree to which increased groundwater 

pumping may be affecting flow in drains.

Background

Study Area

The Tule Lake subbasin is in the southeastern part of 

the upper Klamath Basin and straddles the Oregon-California 

border (fig. 1). Prior to development, the Tule Lake subbasin 

contained a large lake with an area exceeding 96,000 acres 

fringed by extensive wetlands. In 1912, a canal and dam 

were constructed to divert the flow of the Lost River to the 

Klamath River, cutting off inflow to Tule Lake (LaRue, 1922). 

Much of the lake was drained and is now under cultivation. 

The Tule Lake subbasin is a structural basin created by 

faulting of middle to late Tertiary volcanic rocks. The basin 

has been filled with predominantly fine-grained sediment to 

depths locally exceeding 1,800 ft. The basin-filling sediment 

is saturated, and wells that produce from it have modest 

yields because of low to moderate permeability. Beneath the 

sediment, the basin is underlain by a thick sequence of highly 

permeable basaltic lava flows that are also saturated. Wells 

in the underlying lava generally produce large volumes of 

water suitable for irrigation. At the southern edge of the Tule 

Lake subbasin, permeable Quaternary lava flows and vent 

deposits overlie and are interbedded with the upper parts of 

the basin‐filling sediment (Gannett and others, 2007). Aquifers

within these Quaternary volcanic deposits are also used 

for irrigation.

In this report, the low-permeability basin-fill sediment 

will be referred to as the “sedimentary aquifer,” and the 

high-permeability basalt lava flows underlying the basinfill sediment will be referred to as the “deep volcanic 

aquifer.” The Quaternary volcanics at the southern edge of 

the Tule Lake subbasin will be referred to as the “shallow 

volcanic aquifer.”

Much of the Tule Lake subbasin is within boundaries 

of the Project, which is irrigated with water primarily from 

Upper Klamath Lake. Water diverted from Upper Klamath 

Lake is transferred through a series of canals and applied to 

crops in large areas of the lower Lost River Basin and Tule 

Lake subbasin. The Tule Lake subbasin includes the Klamath 

Irrigation District (KID) and Tulelake Irrigation District (TID). 

A certain amount of the diverted water is lost through canal 

leakage during transmission and through deep percolation in 

fields, recharging the shallow parts of the groundwater system. 

Generally, the land gently slopes toward the Tule Lake sumps, 

which are the ultimate collectors of irrigation tailwater in 

the subbasin. 

In addition to supply canals, the Project area is 

crisscrossed by agricultural drains. Agricultural drains 

accumulate excess water that has percolated to the shallow 

subsurface. If this water were not collected in the drains 

and pumped out, soils in the basin would become saturated 

and unsuitable for farming. Drains in the Project area are 

generally large open ditches extending roughly 10 ft below 

land surface and commonly extending laterally many hundreds 

or thousands of feet (fig. 2). In contrast, canals are generally at 

elevations above land surface to allow gravity flow to fields.

Water enters the drain system as groundwater discharge 

from shallow flow within the soil (interflow) or as overland 

surface flow. Shallow groundwater discharging to drains 

begins either as precipitation, as applied irrigation water, or 

as water that seeped from the canal system. Water applied 

to crops generally either returns to the atmosphere through 

evapotranspiration (ET) or percolates beneath the root zone 

and recharges the shallow parts of the groundwater system.

Once in the shallow parts of the Tule Lake subbasin 

groundwater system, water flows either laterally and 

discharges to the network of agricultural drains, or vertically 

through the shallow sedimentary aquifer to the underlying 

volcanic aquifer. Comparison of water levels in shallow and 

deep wells indicates that there are no upward gradients in the 

groundwater system. (Eaves and others, California Department 

of Water Resources, unpub. data, 2002; Gannett and others, 

2007). Lateral flow in deeper volcanic deposits is toward the 

southern boundary of the basin (Gannett and others, 2007). 

A local connection between the shallow and deep aquifers is 

evidenced by the response of water levels in the deep volcanic 

aquifer to the onset of canal operation each spring (Palmer 

and others, 2006; Gannett and others, 2007). Isotopic analysis 

of groundwater in aquifers supplying deep irrigation wells in 

the subbasin also suggests a hydraulic connection between the 

shallow and deep aquifer (Palmer and others, 2006).

Another source of water to agricultural drains is 

operational spill, which occurs in the transition between 

the KID (which irrigates the northern part of the Tule Lake 

subbasin in Oregon) and the TID (which irrigates within the 

rest of the subbasin). Operational spill is excess water that 

must be discharged at the end of a conveyance system when 

the flow in the system exceeds demand. Operational spills 

occur because districts may keep more water in supply canals 

than needed at a given time to provide a buffer for the variable 

demands of water users. Operational spill from the KID is 

discharged to the TID drain system at the boundary between 

two districts, roughly at the State line. 
4 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

Figure 2. Example of an agricultural drain in the Tule Lake subbasin, California. Photograph taken by Ben 

Perkins, Portland State University, March 29, 2012. Used with permission. 

Water in the drain system either gets pumped back into 

the distribution canal system or flows to the Tule Lake sump 

system, the remnant of Tule Lake. The Tule Lake sumps 

consist of two interconnected lakes that are located in the 

southern and western parts of the basin, called Sump 1A 

and Sump 1B (fig. 1). Since 1942, water from the sumps has 

been pumped by Pumping Plant D (D Plant) through a tunnel 

in Sheepy Ridge, westward into the Lower Klamath Lake 

subbasin (fig. 1). Large parts of the TID rely on drain flows 

for their irrigation supply. Additionally, water that drains to 

the Tule Lake sumps is a critical part of the water supply for 

the Tule Lake and Lower Klamath Lake National Wildlife 

Refuges (fig. 1), comprising 75 and 67 percent of each 

refuge’s total inflow, respectively (Risley and Gannett, 2006). 

A change in shallow groundwater discharge to agricultural 

drains, therefore, has consequences for the irrigation project 

and for water management of the refuge system. Part of 

the water pumped to the Lower Klamath Lake Refuge is 

eventually returned to the Klamath River. 

Increases in Groundwater Pumping

Since 2001, groundwater pumping has increased in the 

Upper Klamath Basin in response to changes in surfacewater management and to a series of drier-than-average 

years. Much of this increase was related to programs 

to supplement pumping for the Project. In 2000, total 

pumping in the upper Klamath Basin was estimated to be 

150,000 acre-ft (not including supplemental pumping in 

Oregon). Additional pumping for the Project began in 2001 

and reached 75,800 acre-ft by 2004. Of this additional 

pumping, 61,000 acre-ft took place in the Lower Klamath 

Lake subbasin and lower Lost River drainage, which 

includes the Tule Lake subbasin (Gannett and others, 2007). 

Supplemental groundwater pumping continued through 2007. 

No reported Project-sponsored supplemental groundwater 

pumping occurred in 2008 and 2009, but drought conditions 

in 2010 resulted in supplemental pumping of more than 

100,000 acre-ft.
Background 5

Changes in Discharge to Drains

Monthly TID records of total flows for diversions, pump 

stations, and canals for the Project are of particular importance 

to the analysis of the change in drain flows. Chief among the 

pumping stations is the D Plant, which lifts water from the 

Tule Lake sumps through Sheepy Ridge to the Lower Klamath 

Lake subbasin. Because the sumps are the ultimate collector 

of drain water from the Project, flow through the D Plant is 

a reasonable proxy for net discharge to drains in the Tule 

Lake subbasin. 

Records of water volumes moved through the D Plant 

indicate decreased flow to agricultural drains on the Project 

since 2001 (fig. 3). Flow through the D Plant over the past 

decade has decreased by 61,000 acre-ft (from 81,000 acre-ft 

in 2000 to 20,000 acre-ft in 2011). There was, however, no 

corresponding decrease in diversions (fig. 3), so the difference 

was largely due to decreased flow to drains.

Sources of Water to Wells

Surface water features such as wetlands, streams, 

springs, and drains are potential sources of water to wells 

(Barlow and Leake, 2012). As a well is pumped, most of the 

water initially supplied to the well is from aquifer storage. If 

pumping continues, a cone of depression forms in the aquifer 

around the well, which over time can capture groundwater that 

would otherwise flow to surface water features (Theis, 1940). 

Captured water consists of either a reduction in the natural 

discharge of groundwater from the aquifer to the surface 

features or an increase in the natural or artificial recharge 

rate to the aquifer (Theis, 1940; Reilly and others, 2008; 

Barlow and Leake, 2012). The manifestation of these effects 

to surface water features depends on pumping rate, duration, 

and the geometry and hydraulic characteristics of the aquifer 

being pumped.

0.00 

0.10 

0.20 

0.30 

0.40 

0.50 

0.60 

0.70 

0.80 

0.90 

1.00 

0 

50 

100 

150 

200 

250 

300 

350 

400 

Volume of diverted water and drain pumpage,

in thousand acre-feet 

Ratio of D plant pumpage to total diversions

Total diversions

D Plant pumpage

Ratio of D Plant pumpage to 

total diversions 

EXPLANATION

1961 1971 1981 1991 2001 2011

Figure 3. Total diversions (defined as the sum of March through October A Canal diversions and Lost River 

Diversion Channel deliveries), D Plant pumpage, and ratio of D Plant pumpage to total diversions, Tule Lake 

subbasin, Oregon and California, 1961–2011. Data points for 2001 and 2010 have been removed because 

Klamath Irrigation Project operations were severely curtailed during those years.
6 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

Changes in Hydraulic Head and Flow

Groundwater pumping in the Project area from 

2001–10 has removed groundwater from storage, resulting in 

water-level declines in the area’s aquifers. Between 2001 and 

2004, total declines of more than 10 ft were documented in 

the deep volcanic aquifer over large areas of the Project, with 

declines exceeding 15 ft over the northern part of the Tule 

Lake subbasin (Gannett and others, 2007). Recent analysis 

by the Oregon Water Resources Department documents 

water-level declines since 2001 of 10–20 ft in areas of the 

Klamath Valley and northern part of the Tule Lake subbasin, 

with declines of 20–30 ft locally (Gall, 2011). Water-level 

measurements show that declines occur in all geologic units 

at all depths, but are largest in the deep volcanic aquifer 

underlying the area (fig. 4).

3,985 

3,995 

4,005 

4,015 

4,025 

4,035 

Well 21 (65 ft depth)

Well 26 (1,575 ft depth) 

3,985 

3,995 

4,005 

4,015 

4,025 

4,035 

Well 36 (220 ft depth)

Well 37 (2,676 ft depth) 

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011

Water-level elevation, in feet above the National Geodetic Vertical Datum of 1929

A

B

EXPLANATION

EXPLANATION

Figure 4. Four observation wells in the Tule Lake subbasin, California. Hydraulic heads declined more rapidly in deep zones than 

in shallow zones during the period of record (2001–11), which increased the downward vertical hydraulic gradient. Well numbers 

correspond to identification numbers used in the Tule Lake groundwater model. Well locations are shown in figure 10 and table 3.
Methods 7

Groundwater moves from regions of high hydraulic head 

to low hydraulic head (Freeze and Cherry, 1979). In the Tule 

Lake subbasin, hydraulic heads have historically been lower 

in the deep volcanic aquifer than in the shallow sedimentary 

aquifer, indicating a component of downward vertical flow. 

Hydraulic heads at depth have declined faster than those in 

shallower wells over the past decade (fig. 4), increasing the 

downward hydraulic head gradient. Thus, the proportion of 

shallow groundwater flowing vertically to the deep aquifer 

rather than laterally discharging to drains has increased.

Upper Klamath Basin Regional Model

The USGS developed a groundwater-flow model for the 

upper Klamath Basin to simulate regional groundwater flow 

to help assess the resource and test management scenarios 

within the basin (Gannett and others, 2012). Simulations of 

pumping in the Tule Lake subbasin indicate that a substantial 

portion of the water pumped from the deep volcanic aquifer is 

ultimately captured from diminished discharge to drains. The 

model simulation results are consistent with everything known 

about the groundwater system, and with independent data on 

changes in water levels and drain discharge (as indicated by 

records from the D Plant).

Owing to the coarseness of the model grid, however, this 

USGS regional-scale flow model cannot simulate the details 

of the observed changes in vertical hydraulic head gradients. 

For example, the model cannot accurately simulate the vertical 

hydraulic head gradients observed within the sedimentary 

aquifer because the sediment is represented as a single layer 

in the model. Consequently, information from dozens of 

observation wells in the Tule Lake subbasin was not fully used 

for model calibration or to evaluate model accuracy. 

Study Objectives

Simulations from the regional model and the marked 

drop in volumes of water pumped through the D Plant 

suggest that agricultural drains are affected by groundwater 

pumping. Other factors, however, could affect the D Plant 

volumes. Increased electrical power costs since 2000 have 

made it desirable to keep as much water as possible on the 

Tule Lake side of Sheepy Ridge. However, the ability to 

store, evaporate, or consumptively use this water is limited. 

Additionally, changes in diversion volumes, irrigation 

efficiency, or cropping patterns could affect drain flows (and 

D Plant volumes). 

The goal of this investigation was to determine the 

magnitude of changes to drain flow in the Tule Lake subbasin 

and the degree to which increased groundwater pumping could 

be responsible for these changes. To understand the effect of 

increased groundwater pumping on drains, this goal has been 

divided into two objectives:

1. Construct a quantitative hydrologic budget of the drains 

to estimate changes in groundwater discharge to drains 

as groundwater pumping increased.

2. Develop a fine-grid groundwater model of the Tule Lake 

subbasin to explore the connection between groundwater 

and surface water in the subbasin.

Methods

Drain Flow Analysis

To evaluate the effect of increased groundwater pumping 

on drain flow, the change in volume pumped by the TID 

from drains (which reflects the change in flow to the drains 

from groundwater discharge and other sources) over time 

was analyzed. The TID manages the irrigation infrastructure, 

including drains, in the Oregon and California areas of the 

Tule Lake subbasin. TID infrastructure includes 24 pumps 

(fig. 5) that lift water from agricultural drains back into the 

water delivery system (canals and laterals) for reuse or to the 

Tule Lake sumps for storage and removal to Lower Klamath 

National Wildlife Refuge (through the D Plant). The TID 

maintains monthly records of the volumes pumped from these 

drain pumps, which are located throughout the TID system. 

To analyze these data, monthly time series for 1997–2012 

were summed to create yearly volumes for pumps that remove 

water from specific areas.

Drain Subareas

When evaluating drain pump data to estimate net 

groundwater discharge, care must be taken to avoid double 

accounting of water. Drain water to be reused is pumped into 

a canal or lateral where it is either transported to another part 

of the Project or applied to land adjacent to the drain. If the 

water is reused in an area close to the drain, some of the water 

might become drain flow again. If volume from all of the drain 

pumps is summed for the entire irrigation district, the water 

that is recycled and enters the drain system again is being 

counted more than once. To avoid such double accounting, 

the irrigation districts were split into three subareas for 

which “terminal” pumps that discharge water outside the 

subarea could be identified. Yearly volumes were calculated 

for these terminal drain pumps and then summed to provide 

an estimate of total pumped volume per year for the entire 

irrigation district. 
8 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

Figure 5. Example of a drain pump (pump A) in the Tulelake Irrigation District system, California. Photograph 

taken by Esther Pischel, U.S. Geological Survey, July 31, 2013.

North Tulelake and Klamath Irrigation Districts

North TID/KID is the largest of the subareas (fig. 6). It 

extends from the northern part of the Tule Lake subbasin south 

to the Copic Bay subarea and east to the Lease Lands subarea. 

Pumping from wells occurs in this subarea primarily to the 

north and east. The drain pumps that integrate this area are 

3, 4, 5, 6, 12, 27, and A. These pumps move drain water into 

major canals that supply water to other subareas; little or none 

of this water is reused in the North TID subarea.

Copic Bay

Copic Bay is in the southeastern corner of the study area 

(fig. 6). Groundwater pumping takes place throughout this 

subarea. Pump B is located at the end of the Copic Bay system 

and integrates most of the drain flow. Pump B discharges 

into Sump 1B, and the water is not recycled in the Copic 

Bay subarea. 

Lease Lands

Tule Lake National Wildlife Refuge contains 

17,000 acres of Federal land that is leased to farmers. These 

lands are referred to as the “Lease Lands” (fig. 6). The Lease 

Lands are located directly south and east of Sump 1A and 

north of Sump 1B, and include the lowest elevation areas in 

the subbasin. The pumps that integrate this region are pumps 

9, 10, 10A, 11, and C, which pump directly into Sumps 1A 

and 1B. The water pumped from the drains into the sumps is 

not reused in the subarea, reducing the chance that drain water 

will be double accounted. Unlike the North TID/KID and 

Copic Bay subareas, little to no groundwater pumping takes 

place in the Lease Lands.

Operational Spills

To evaluate the changes that have taken place in drain 

flow because of changes in the groundwater system, the 

component of the drain flow that is from operational spill by 

the KID must be subtracted because changes in surface-water 

deliveries to drains could mask changes occurring in the 

groundwater component of flow. Although the operational spill 

volumes recorded by the KID are not precise, they are the best 

information available to understand the magnitude of spills to 

TID drains. Backspill from canals to maintain water levels in 

drains for pumps to work effectively is another quantifiable 

source of additional water to drains. This occurs at pump A, 

one drain pump used in this analysis. Annual volumes of water 

spilled to the drain near pump A were subtracted from the total 

drain pumpage. Operational spill from KID and TID backspills 

are two sources of drain inflow that can be reasonably 

estimated. Some potential sources of surface water to drains, 

such as direct runoff from fields (overland flow), cannot be as 

easily quantified and are assumed to have remained constant 

during the period analyzed.
Methods 9

tac15-0995_fig06

121°35' 30' 25' 121°20'

42°

00'

55'

41°

50'

0 1 2 3 4 MILES

0 2 3 4 1 KILOMETERS

Universal Transverse Mercator projection, Zone 10N 

North American Datum of 1927

Lost River

Pump 9

Pump B

Pump A

Pump C

Pump 10, 10A

Pump 11

Pump 5

Pump 6

Pump 12

Pump 3

Pump 27

Pump 4 Pump D

Tule Lake

Sump 1A

Tule Lake

Sump 1B

OREGON

CALIFORNIA

EXPLANATION

Tulelake Irrigation District pump

Agricultural Drain

North TID/KID subarea

Copic Bay subarea

Lease Lands subarea

Pump B

Figure 6. Subareas and drain pumps used in analysis of drain flow, Tule Lake subbasin, Oregon and California. Although not 

included in the analysis of drain flow, the D Plant is included here for reference.
10 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

Other Possible Causes of Decreased Drain Flow

Factors other than groundwater pumping could 

contribute to decreases in drain flow, including reductions in 

surface‐water diversions, increased irrigation efficiency, or

reductions in acreage farmed in the subbasin. Total annual 

diversion volumes (defined as the sum of March–October 

A-Canal diversions and Lost River Diversion Channel 

deliveries), although variable, did not change systematically 

between 2000 and 2010, whereas D Plant pumpage decreased 

(fig. 3). Moreover, the ratio of D Plant volumes to total annual 

diversions decreased in a manner similar to the D Plant 

volumes, indicating that increasingly smaller proportions of 

diverted water end up at the D Plant (fig. 3).

Irrigation efficiency has not increased significantly from 

at least 2001 through 2012 in the Tule Lake subbasin. In 

the TID, which covers most of the Tule Lake subbasin, the 

main types of irrigation are solid-set sprinkler and wheel-line 

irrigation. About 18 percent of the acreage in the TID is flood 

irrigated. These irrigation methods have, for the most part, 

remained constant (Brad Kirby, Tulelake Irrigation District, 

oral commun., 2014). 

Likewise, the acreage farmed has not changed 

significantly from 2001 through 2012 (Brad Kirby, Tulelake 

Irrigation District, oral commun., 2014). Cropping patterns 

have remained steady since 2002. Major crops grown in the 

Tule Lake subbasin are alfalfa, grains such as barley and 

wheat, potatoes, onions, and mint. 

Groundwater Model

A smaller-scale, fine-grid groundwater model based 

on the larger-scale regional groundwater model (Gannett 

and others, 2012) was constructed, integrating hydrologic 

and geologic data for the subbasin. To be consistent with 

the regional model and to take advantage of its parameter 

estimation capabilities (Hill and others, 2000), the Tule 

Lake groundwater model uses the USGS MODFLOW 2000 

modeling code (Harbaugh and others, 2000). Subbasin 

geometry and starting values for certain model parameters 

were used from the regional model. The model was calibrated 

to water level time series from 24 wells in the study area 

using trial-and-error and inverse methods. The calibration 

was also constrained by observed changes in drain flows and 

independent estimates of recharge.

Discretization

To address the limitations of the regional model and 

more accurately simulate pumping and water levels, the Tule 

Lake subbasin was discretized at a finer scale in the horizontal 

and vertical dimensions. Finer discretization allows for finer 

resolution of drains, vertical hydraulic head gradients, and 

hydrogeologic zonation to better determine effects on drain 

flows from increased groundwater pumping.

Model cells in the Tule Lake groundwater model have a 

lateral dimension of 1,250 by 1,250 ft (one-fourth the area of cells 

in the regional model), which captures the resolution of important 

features such as drains while limiting the number of model cells 

for computational efficiency. The model domain is 84 rows north 

to south, 67 columns east to west (fig. 7), and 12 layers, for a total 

of 67,536 model cells. All layers are modeled as confined, and 

layer thicknesses range from 25 to 700 ft (table 1). For transient 

models, time is discretized using stress periods and time steps. The 

Tule Lake groundwater model has been constructed to simulate 

quarterly stress periods for water years 2000–10, preceded by a 

single steady-state stress period (a water year begins on October 1 

and ends on September 30; for example, the 2000 water year 

started October 1, 1999 and ended September 30, 2000.) The 

steady state stress period simulates initial conditions for the 

transient simulation. 

Hydrogeologic Zonation

The zonation of the model (fig. 8) is based on the 

hydrogeology of the upper Klamath Basin presented in Gannett 

and others (2007) and is specified in the model using the 

Layer Property Flow package (figs. 8 and 9). The youngest 

hydrogeologic units in the subbasin represented in the model 

are Quaternary sediments (Qs) and Quaternary volcanics (Qv). 

The Quaternary sediments are the topmost part of the basin‐fill

sediment and are modeled in layer 1. Quaternary volcanics are 

present in the southernmost part of the model and were determined 

to be about 150 ft thick, based on drillers’ logs; they extend from 

layer 1 to layer 4. Tertiary sediments of younger basins (Tsy) 

compose the remainder of the basin-fill sediment and are in 

layers 2–11. Underlying the basin-fill sediment and cropping out 

on the fringes of the subbasin are Tertiary sediments and volcanic 

rocks (Tsv). Tsv is present in all 12 layers. Faulting occurs in the 

subbasin, related predominantly to Basin and Range extension. 

These faults are on the west and east boundaries of the subbasin. 

Table 1. Layer thicknesses for the Tule Lake groundwater model.

[Hydrogeologic units represented: Qs, Quaternary sediments; Qv, 

Quaternary volcanics; Tsv, Tertiary sediments and volcanics; Tsy, Tertiary 

sediments of younger basins]

Layer Thickness

(feet)

Hydrogeologic units 

represented

1 25 Qs, Qv, Tsv

2 25 Qv, Tsv, Tsy

3 50 Qv, Tsv, Tsy

4 50 Qv, Tsv, Tsy

5 50 Tsv, Tsy

6 100 Tsv, Tsy

7 200 Tsv, Tsy

8 200 Tsv, Tsy

9 300 Tsv, Tsy

10 400 Tsv, Tsy

11 500 Tsv, Tsy

12 700 Tsv
Methods 11

tac15-0995_fig07

Row 60

Column 30

121°40' 35' 30' 25' 121°20'

42°

00'

55'

41°

50'

Universal Transverse Mercator projection, Zone 10N 

North American Datum of 1927

0 21 3 4 MILES

0 3 421 KILOMETERS

EXPLANATION

Pumping wells

Drain cells

Reservoir cells

River cells

General head boundary cells

Inactive cells

Active model cells

Figure 7. Groundwater-model grid and boundary conditions, Tule Lake subbasin, Oregon and California. Highlighted column 30 

and row 60 correspond to sections shown in figure 9.
12 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig08a

Malin

Merrill

Tule lake

Tule Lake

Sump 1A

Tule Lake

Sump 1B

Universal Transverse Mercator projection, Zone 10N 

North American Datum of 1927

121°33' 26' 121°19'

42°

04'

57'

41°

50'

42°

04'

57'

41°

50'

121°33' 26' 121°19' 121°33' 26' 121°19' 121°33' 26' 121°19'

42°

04'

57'

41°

50'

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

Layer 1, 0–25 feet Layer 2, 25–50 feet Layer 3, 50–100 feet

Layer 4, 100–150 feet Layer 5, 150–200 feet Layer 6, 200–300 feet

EXPLANATION

Inactive cells

Quaternary sediments

Quaternary volcanics

Tertiary sediments of younger basins

Tertiary sediments and volcanics

Tule Lake Sump 1A and 1B

Figure 8. Hydrogeologic zonation of the Tule Lake groundwater model, Tule Lake subbasin, Oregon and California. The Tule 

Lake sumps, shown in the index map, are shown in the first layer as a spatial reference. Depth interval follows each layer 

number.
Methods 13

tac15-0995_fig08b

42°

04'

57'

41°

50'

121°33' 26' 121°19' 121°33' 26' 121°19' 121°33' 26' 121°19'

42°

04'

57'

41°

50'

Universal Transverse Mercator projection, Zone 10N 

North American Datum of 1927

0 5 10 15 20 MILES

0 5 10 15 20 KILOMETERS

EXPLANATION

Inactive cells

Tertiary sediments of younger basins

Tertiary sediments and volcanics

Layer 7, 300–500 feet Layer 8, 500–700 feet Layer 9, 700–1,000 feet

Layer 10, 1,000–1,400 feet Layer 11, 1,400–1,900 feet Layer 12, 1,900–2,600 feet

Figure 8.—Continued
14 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig09ab

Cross section along row 60

Model columns

20 40 60

1,000

2,000

3,000

4,000

5,000

6,000

Feet

Sea levelSea level Elevation, in feet above the National Geodetic Vertical Datum of 1929

West East

Cross section along column 30

20 40 60

1,000

2,000

3,000

4,000

5,000

Model rows

Feet

Sea levelSea level Elevation, in feet above the National Geodetic Vertical Datum of 1929

North South

EXPLANATION

Quaternary sediments

Quaternary volcanics

Tertiary sediments of younger basins 

Tertiary sediments and volcanics

A

B

Figure 9. Tule Lake groundwater model, Tule Lake subbasin, Oregon and California. (A) Section west to east 

along model row 60, and (B) section north to south along model column 30. Row and column locations are 

shown in figure 7.
Methods 15

Boundary Conditions

Boundary conditions determine the way in which water 

is allowed to move into or out of the groundwater model. 

Boundary conditions for the Tule Lake groundwater model are 

shown in figure 7.

Specified Flow Boundaries

Specified flow boundaries are those across which 

groundwater flows into or out of the model at specified rates. 

These specified rates can vary in time and space. Specified 

flow boundaries in this model are areally distributed recharge 

and pumping wells.

Recharge

Recharge is water that infiltrates to the water table and 

becomes groundwater (Anderson and Woessner, 1992). 

The primary source of recharge in the Tule Lake subbasin 

is infiltration of applied irrigation water and canal leakage. 

Precipitation is also a source of recharge but is comparatively 

small. The volume of recharge from precipitation was 

estimated using the Precipitation-Runoff Modeling System 

and was taken directly from the upper Klamath Basin regional 

model (Gannett and others, 2012). Recharge rates from water 

year 1980 (which are close to the long-term average [Gannett 

and others, 2012]) were varied on a seasonal basis and 

repeated during the simulation to simplify model analysis.

Recharge from infiltration of irrigation water and canal 

leakage was estimated for the regional model by Gannett and 

others (2012) using a water balance calculated for the Project 

by the Irrigation Training and Research Center (Burt and 

Freeman, Irrigation Training and Research Center, unpub. 

data, 2003). A value of 1 ft/yr was applied to the Project 

area. Gannett and others (2012) detail the calculation of 

recharge volumes for the regional model. Because simulated 

net recharge accounts for ET, it is not explicitly simulated in 

the model. Throughout this report, net recharge is referred to 

simply as recharge.

Given that irrigation canal leakage is a predominant 

source of recharge in the Tule Lake subbasin, refinements 

to recharge were made in the Tule Lake subbasin model 

based on two factors relating to irrigation: (1) relatively low 

density of canals in the northern part of the study area and (2) 

curtailed Project diversions in the dry years 2001 and 2010. 

The low density of canals in the northern part of the study 

area means that less recharge can be expected due to canal 

leakage. Adjusting recharge to reflect the lower density of 

canals resulted in more accurate simulation of water-levels in 

that area. The final value of recharge in the northern part of 

the study area, assuming constant ET and irrigation efficiency, 

was approximately 0.25 ft/yr. 

The other refinement of recharge in the Tule Lake model 

was related to curtailed irrigation diversions in 2001 and 2010. 

In all years except 2001 and 2010, a 1.0 ft/yr recharge rate was 

used. The Project received considerably less surface water for 

irrigation during the dry years of 2001 and 2010, and artificial 

recharge from deep percolation of applied irrigation water and 

canal leakage was likely reduced in the same proportion as 

the reduced diversions. To account for decreased diversions, 

recharge was scaled back throughout the model domain 

to 32 percent in 2001 and 55 percent in 2010 to match the 

scaling-back of irrigation diversions those years. 

Groundwater Pumping

Groundwater pumped from wells also is represented as a 

specified-flow boundary. Groundwater pumping is commonly 

divided into two categories: primary and supplemental. 

Primary pumping is water pumped to irrigate land where 

groundwater is the sole source of water. Supplemental 

pumping is water pumped to irrigate land normally irrigated 

by surface water during times when surface water is not 

available, such as drought. Most of the supplemental 

pumping in the Tule Lake subbasin over the past decade 

has been part of government-sponsored efforts. A smaller 

(but generally less well quantified) amount of supplemental 

pumping occurs privately. For this study, primary 

pumping and private supplemental pumping is referred to 

as “background pumping,” and the term “supplemental 

pumping” is reserved hereafter for pumping done under 

government-sponsored programs.

Background pumping rates are based on surveys of crop 

type and irrigation methods, analysis of satellite imagery, 

water rights information, and flowmeter readings, and are 

derived from the work of Gall (2011) and Gannett and others 

(2007). In the Tule Lake subbasin, background pumping 

(which includes primary and private-supplemental pumping) 

averages about 7,970 acre-ft/yr. 

Supplemental pumping rates are based on information 

from the Bureau of Reclamation, Oregon Water Resources 

Department (OWRD), and the Klamath Water and Power 

Authority (KWAPA). Supplemental pumping in the model 

averages 23,500 acre-ft/yr. The pumping data were provided 

in differing formats depending on the year and the agency. 

For 2001–04, the pumping data were provided as an annual 

total for individual wells or groups of wells. For 2005–07, the 

data were provided as the aggregate total of pumping for all 

supplemental wells. The quarterly pumping volume used in the 

model for each well in 2005–07 was calculated in proportion 

to the relative pumping volumes in 2004 (2004 data were 

provided for single wells or well groups). No supplemental 

pumping was reported for 2008 and 2009, and for 2010, data 

were provided well by well by OWRD and KWAPA.
16 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

Some values for supplemental pumping were modified 

from reported values to adjust for possible under- or overestimation of pumping rates. For example, although there 

was no stated Project-sponsored pumping in 2008 and 2009, 

hydrograph data during those years show some effects 

greater than what would be expected solely from estimated 

background pumping. To account for this in the model, 

supplemental pumping rates in 2008 and 2009 were adjusted 

until simulated pumping resulted in observed drawdowns. 

Additionally, supplemental pumping rates in 2001–04 were 

adjusted to reflect new information on actual pumping 

capacities of wells and to better match observed drawdowns in 

hydrograph data.

The average rate of pumping is defined for each stress 

period in cells that contain a pumping well. Pumping data 

were most commonly provided as annual totals, so the exact 

timing of pumping is poorly known. Moreover, some data 

were provided as total pumped-water volumes for groups of 

wells, or all wells for a particular year. This uncertainty in 

the exact location and timing of pumping limited the ability 

to precisely match observed water table fluctuations. Wells 

are assigned to single layers based on the open interval of the 

wells and water-bearing zones described by drillers.

Head-Dependent Flow Boundaries

Head-dependent flow boundaries in the model include 

the Lost River, Tule Lake sumps, drains, and interbasin 

groundwater flow. The rate of groundwater flow to or from 

these features is controlled by the difference between the 

hydraulic head in the cell and the hydraulic head of the feature 

(such as the stage of the river, sump, or drain). 

Lost River

The Lost River is the only river in the study area, 

and is modeled using MODFLOW’s river (RIV) package 

(McDonald and Harbaugh, 1988). The RIV package was 

used instead of a more sophisticated package such as the 

streamflow routing (SFR) package because it met the needs 

of the study. The spatial extent of the river within the model 

domain was determined using digital geographic information 

system (GIS) data, and river width and stage were determined 

using 1:24,000 USGS topographic maps. Water from a RIV 

boundary can move to or from the groundwater system, 

depending on the hydraulic head difference between the 

river and the cell in which it is simulated. The rate of flow 

is proportional to the riverbed conductance. The initial 

riverbed conductance was calculated based on estimates of 

aquifer properties from the regional model and then adjusted 

during calibration. 

Tule Lake Sumps

The Tule Lake sumps are simulated as reservoirs in 

the model because they are artificially controlled. As such, 

MODFLOW’s reservoir (RES) package was used. The spatial 

extent of each sump was determined using a USGS 1:24,000 

topographic map. Stage measurements of the Tule Lake 

sumps were not available during the simulation period, so the 

water level in each sump was fixed at a long-term average 

value of 4,033 ft (Gannett and others, 2007). Water moves 

to or from the sumps in proportion to the hydraulic head 

difference between the sumps and the cells in which they are 

modeled and the conductance of the reservoir bottom. The 

initial RES conductance was calculated based on estimates of 

aquifer properties from the regional model and then adjusted 

during calibration.

Drains

Agricultural drains are modeled using MODFLOW’s 

drain (DRN) package. The spatial distribution of drains in 

the study area was delineated using GIS data provided by the 

Bureau of Reclamation. The drain elevation in MODFLOW 

was set to 10 ft below land surface based on field observations 

and the regional model calibration, and the drain width 

was set to a constant 10 ft. Like other head-dependent flow 

boundaries, the flow of water to the drain is dependent on the 

hydraulic head difference between the drain and the cell in 

which it is modeled and the conductance of the drain bottom. 

Unlike other head-dependent flow boundaries, flow in drain 

cells is unidirectional; that is, flow can occur only from the 

groundwater system to the drain (as opposed to a river cell, 

for example, in which flow can move from the groundwater 

system to the river or from the river to the groundwater 

system). This is because drains are designed to provide an 

outlet for shallow groundwater to be carried away and do 

not function as a source of groundwater to the aquifer like a 

river. The initial drain conductance was calculated based on 

estimates of aquifer properties from the regional model and 

then adjusted during calibration.

Interbasin Groundwater Flow

Interbasin groundwater flow represents horizontal flow 

across the model domain boundaries. Interbasin groundwater 

flow from the Tule Lake subbasin southward toward the 

Pit River Basin (fig. 1) is discussed in Gannett and others 

(2007). Additionally, interbasin flow is expected across other 

model boundaries because the permeable Tertiary volcanics 

and basin-filling sediment in the subbasin extend beneath 

the fault‐block ridges that separate the Tule Lake subbasin

from the Poe Valley to the north, the Clear Lake subbasin 
Methods 17

to the east, and the Lower Klamath Lake subbasin to the 

west, allowing groundwater to flow between these areas 

(fig. 1). Flow to and from adjacent areas was simulated 

using MODFLOW’s general head boundary (GHB) package. 

GHB cells, therefore, are located around the edge of the 

model domain. 

General head boundaries are similar to river or reservoir 

boundaries in that flow to or from the model is controlled 

by hydraulic head relations between the model cells and an 

external source or sink. Head values adjacent to the model 

were derived from hydraulic head contours from Gannett and 

others (2007). The initial GHB conductance was calculated by 

using estimates of aquifer properties from the regional model 

then adjusted during model calibration. A list of MODFLOW 

packages used in this model is shown in table 2. 

Model Calibration

Calibration is a process in which model structure and 

parameters are adjusted to achieve the best fit between 

simulated and observed values of hydraulic heads and flows. 

The observed, or measured, values used to calibrate the Tule 

Lake model included spring (March, or sometimes March 

and April) water-level measurements from 24 observation 

wells located throughout the subbasin (fig. 10, table 3). Spring 

water levels were used to minimize error due to drawdown 

during pumping. Although there are 42 observation wells 

in the modeled area, 18 were not used because the water 

levels contained anomalous values caused by stresses not 

simulated in the model, such as localized canal influence and 

nearby groundwater pumping. The changes in summed drain 

pumpage from the three Tule Lake subareas (fig. 6) used in 

the drain flow analysis were also used to constrain calibration. 

The model was calibrated using both trial-and-error and 

parameter estimation methods. The trial-and-error method 

involves iteratively adjusting model structure and model 

parameters (such as hydraulic conductivity) to achieve an 

acceptable match between simulated and observed hydraulic 

head values. Parameter estimation is an automated process in 

which non-linear regression is used to determine parameter 

values that provide the best overall fit between observations 

and simulated values. In total, there are 21 parameters. 

Sixteen of these parameters were estimated using parameter 

estimation. The remaining parameters were determined using 

trial-and-error calibration. Parameters in the model include 

hydraulic conductivity (HK), vertical anisotropy (VANI), 

and specific storage (SS) for the four geology types present 

in the model; the recharge multiplier, which can be used 

to scale recharge up and down; and the conductance of the 

general head boundaries, drain bed, and river bed. The model 

simulates the hydrogeologic system as entirely confined, so 

specific yields are not part of the parameter set; rather, specific 

storage is included for each geology type in the model. 

Table 2. MODFLOW-2000 packages and files used in the Tule 

Lake subbasin model.

MODFLOW-2000 processes, packages, and files

Basic (BAS) Package

Output Control (OC) Option file

Discretization (DIS) file

Layer Property Flow (LPF) Package

Multiplier (MULT) file

Zone (ZONE) file

Preconditioned Conjugate-Gradient (PCG) Solver Package

Observation (OBS) Process

Sensitivity (SEN) Process

Parameter-Estimation (PES) Process

Head-Observation (HOB) Package

Drain (DRN) Package

River (RIV) Package

Reservoir (RES) Package

General Head Boundary (GHB) Package

Recharge (RCH) Package

Well (WEL) Package

The specific storage of the Tsy and Tsv are each split into two 

parameters, one for the upper section (layers 2–4 for Tsy and 

layers 1–4 for Tsv) and one for the lower section (layers 5–11 

for Tsy and layers 5–12 for Tsv). This allowed flexibility in 

estimating the specific storage for geology types that span 

multiple model layers.

The parameter estimation process of MODFLOW 2000 

uses a weighted least-squares objective function, S(b), to 

quantitatively compare observed and simulated values:

( ) ( ) 2

1

N

ii i

i

Sb y y b

=

=ω −  ′  ∑   (1)

where

b is a vector containing values of each of the 

parameters being estimated,

N is the number of observations,

yi is the ith observation being matched by the 

regression,

y b i

′( ) is the simulated value which corresponds to 

the ith observation (a function of b), and

	 ωi is the weight for the ith observation (Hill, 

1998). 

Only hydraulic heads were used for parameter estimation. 

Weights for hydraulic-head measurements were based on 

measurement error. Because most well elevations were 

surveyed and all observations are springtime measurements, 

weights were based on an assumed standard deviation of 1 ft. 

The regression process calculates the set of parameter values 

that minimize the objective function, providing the best fit 

given a particular model (Hill, 1998).
18 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig10

Tule Lake

Sump 1A

Tule Lake

Sump 1A

Lower

Klamath

Lake

Tule

Lake Sump 1B

Tule

Lake Sump 1B

Lost River

1

2

6

8

14

15

16

17

18 19

21

22

23

24

26

28

30

32

33

35

34

36

37

42

CALIFORNIA

OREGON

0 1 2 3 4 MILES

0 2 3 4 1 KILOMETERS

121°35' 30' 121°25' 121°20'

42°

05'

42°

00'

41°

55'

41°

50'

Universal Transverse Mercator projection, Zone 10N 

North American Datum of 1927

EXPLANATION

Observation well and No.

used in the model

Model grid

Inactive cells

Active model cells

16

Figure 10. Locations of observation wells for the Tule Lake subbasin model, Oregon and California.
Agricultural Drain Flow Analysis 19

Table 3. Model observation wells.

[CASGEM, California Statewide Groundwater Elevation Monitoring; NWIS, National Water Information System; –, not applicable]

Model 

well No. State Location NWIS site identifier

State 

well No.

CASGEM

station 

identifier

CASGEM

well No.

1 Oregon 41.00S/12.00E-15CBB01 420049121211101 KLAM 15096 – –

2 Oregon 41.00S/12.00E-10CCC01 420116121241801 KLAM 11254 – –

6 Oregon 41.00S/12.00E-09BAD01 420154121250301 KLAM 51611 – –

8 Oregon 41.00S/12.00E-04CBC01 420220121253701 KLAM 10462 – –

14 California 46.00N/05.00E-03M01M – 46N05E03M001M 36889 418570N1213980W001

15 California 46.00N/05.00E-03P01M – 46N05E03P001M 36890 418512N1213927W001

16 California 46.00N/05.00E-09J02M – 46N05E09J002M – 418393N1214003W001

17 California 46.00N/05.00E-23G02M – 46N05E23G002M 36891 418133N1213697W001

18 California 46.00N/06.00E-07K02M – 46N06E07K002M 24092 418385N1213278W001

19 California 46.00N/06.00E-08E01M – 46N06E08E001M 24093 418410N1213207W001

21 California 47.00N/05.00E-01N01M – 47N05E01N001M 37478 419361N1213534W001

22 California 47.00N/05.00E-04M01M – 47N05E04M001M 23452 419406N1214179W001

23 California 47.00N/05.00E-26F01M – 47N05E26F001M 23453 418852N1213706W001

24 California 47.00N/05.00E-33F01M – 47N05E33F001M 23454 418745N1214096W001

26 California 47.00N/06.00E-06N02M – 47N06E06N002M 37481 419362N1213389W001

28 California 47.00N/06.00E-30H01M – 47N06E30H001M 23459 418863N1213240W001

30 California 48.00N/04.00E-16L02M – 48N04E16L002M 23471 419980N1215138W001

32 California 48.00N/04.00E-28D01M – 48N04E28D001M 23472 419756N1215209W001

33 California 48.00N/04.00E-30F01M – 48N04E30F001M 23473 419726N1215574W001

34 California 48.00N/04.00E-31M01M – 48N04E31M001M 37484 419542N1215655W001

35 California 48.00N/04.00E-31N02M – 48N04E31N002M 23474 419534N1215666W001

36 California 48.00N/04.00E-35G01M – 48N04E35G001M 37485 419608N1214731W001

37 California 48.00N/04.00E-35L02M – 48N04E35L002M 48704 419568N1214809W001

42 California 48.00N/05.00E-36A02M – 48N05E36A002M 36329 419614N1213411W001

Agricultural Drain Flow Analysis 

To estimate changes in groundwater discharge to drains, 

an analysis was performed on spill and drain pumping data 

provided by the KID and TID, respectively. Changes in drain 

flow since 2000 are calculated as the difference between 

the 2012 drain pumpage and the 1997–2000 average drain 

pumpage, after accounting for operational and back spills. 

The 1997–2000 average drain pumpage is the best available 

data for estimating the volume of water pumped from the 

drains prior to 2001, when groundwater pumping increased 

significantly in response to shortages of surface water. 

Because the drain pumping data are used as a proxy for drain 

flow, the following paragraphs will reference drain flow rather 

than pumpage.

In the North TID/KID area, drain flow decreased by 

22,300 acre-ft from the average 1997–2000 flow to 2012 

flow (fig. 11).

The area with the next greatest change in drain flow 

is the Copic Bay area, where 2012 drain flows were about 

7,300 acre-ft less than the 1997–2000 average after following 

an approximate linear decrease (fig. 12). 

In the Lease Lands area, drain flow decreased by 

2,800 acre-ft between 2000 and 2012 (fig. 13). Unlike the 

North TID/KID and Copic Bay areas, no clear long-term trend 

in drain flow is apparent in this area. On a long-term average 

basis, the change in Lease Lands drain flow has been minor. 

The drain analysis shows that drain flow has decreased 

from 2000 to 2012. In total, the drain flows from the 

three areas in 2012 is about 32,400 acre-ft less than the 

1997–2000 average. 
20 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig11

40,000 

50,000 

60,000 

70,000 

80,000 

90,000 

1996 1998 2000 2002 2004 2006 2008 2010 2012

North TID/KID yearly volume pumped, in acre-feet

Figure 11. Yearly volume of water from pumps integrating the North Tulelake and Klamath 

Irrigation District (TID/KID) subarea, Oregon and California. Reference line shows average 

1997–2000 pumping. Data for 2001 and 2010 were omitted because of the effects of severely 

curtailed surface-water deliveries during those years.

5,000

7,000

9,000

11,000

13,000 

15,000 

17,000 

Copic Bay yearly volume pumped, in acre-feet

1996 1998 2000 2002 2004 2006 2008 2010 2012

Figure 12. Yearly volume of water from pumps integrating the Copic Bay subarea, Tule 

Lake subbasin, California. Reference line shows average 1997–2000 pumping. Note the scale 

change between this and graphs for the other subareas. Data for 2001 and 2010 were omitted 

because of the effects of severely curtailed surface-water deliveries during those years.

40,000 

50,000 

60,000 

70,000 

80,000 

90,000 

Lease lands yearly volume pumped, in acre-feet

1996 1998 2000 2002 2004 2006 2008 2010 2012

Figure 13. Yearly volume of water from pumps integrating the Lease Lands subarea, Tule Lake 

subbasin, California. Reference line shows average 1997–2000 pumping. Data for 2001 and 2010 

were omitted because they were drier-than-average years and do not reflect typical conditions.
Groundwater Model Results 21

Groundwater Model Results

Calibration 

The purpose of model calibration is to determine the 

model structure and parameter values that provide the best fit 

between measured and simulated values. The final parameter 

values (table 4) are within ranges estimated in previous studies 

(for example, Gannett and others, 2012). HK, VANI, and 

SS parameters for each geology type have the same name 

in both the upper Klamath regional and Tule Lake models, 

except SS for Tsy and Tsv. These have each been split into 

two parameters for the upper and lower aquifers, as discussed 

previously in section, “Model Calibration.” 

Some parameter values differ between the Tule Lake 

model and the upper Klamath Basin regional groundwater 

model of Gannett and others (2012). The SS parameter 

values for the Tsv unit are smaller than values for the same 

geology type in the upper Klamath Basin regional model. 

Values of storativity (the product of specific storage and 

aquifer thickness) are, however, within reasonable ranges. The 

SS parameter of the Tsv unit is split between the upper part 

(SS_TSVU; layers 1–4) and the lower part (SS_TSVL; layers 

5–12) of the model. Storativity values for the upper layers 

range from 1 × 10-6 to 2 × 10-6. These are slightly less than 

the typical range of values for confined aquifers (10-5 to 10-3). 

However, because there are no observation wells to inform 

the model about water level changes in the upper part of the 

Tsv unit, the model is not sensitive to this parameter (fig. 14), 

meaning it has little effect on calibration results. Storativity 

values for the lower layers range from 2 × 10-6 to 3 × 10-5. The 

arithmetic mean of Tsv storativity values for the lower eight 

layers of the model is 1.3 × 10-5, a typical value for storativity 

in a confined volcanic aquifer (Freeze and Cherry, 1979) and 

comparable to the regional model. High SS_QS and SS_QV 

parameters reflect unconfined conditions near land surface.

The vertical anisotropy parameter (which controls the 

ratio of horizontal to vertical hydraulic conductivity) for the 

Qs unit is two orders of magnitude different between the 

regional and Tule Lake models (17.6 and 5,290, respectively). 

Both values, however, are within reasonable ranges for 

sedimentary deposits. The high value of vertical anisotropy 

in the Tule Lake model is reasonable given the nature of the 

Quaternary deposits in the basin. Lake sediments are typically 

stratified with alternating coarse-and fine-grained deposits, 

which means that water is more likely to flow horizontally 

through the coarse-grained deposits than vertically through the 

lower permeability fine-grained deposits. Due to the relatively 

coarse vertical discretization, the regional model could not 

simulate the shallow vertical head gradients and was relatively 

insensitive to the vertical anisotropy of Quaternary sediments 

(see Gannett and others, 2012, fig. 11). Because of the finer 

vertical discretization, the Tule Lake model is better able to 

simulate vertical head gradients. The high vertical anisotropy 

in the Quaternary sediments (which are in only the upper 

25 ft of the model) resulted in more accurate simulation of the 

observed downward vertical head gradients.

Table 4. Calibrated values of parameters for the Tule Lake subbasin groundwater flow model, Oregon and California.

[Abbreviations: ft/s, foot per second; ft-1, 1/foot]

Parameter type Zone or boundary Label Value Unit

Hydraulic conductivity Quaternary sedimentary rocks HK_QS 1.59E-3 ft/s

Vertical anisotropy Quaternary sedimentary rocks VANI_QS 5.29E+3 Dimensionless

Specific storage Quaternary sedimentary rocks SS_QS 5.37E-3 ft-1

Hydraulic conductivity Quaternary volcanic rocks HK_QV 9.90E-5 ft/s

Vertical anisotropy Quaternary volcanic rocks VANI_QV 1.14E+1 Dimensionless

Specific storage Quaternary volcanic rocks SS_QV 9.92E-4 ft-1

Hydraulic conductivity Tertiary basin-filling sediment HK_TSY 2.67E-5 ft/s

Vertical anisotropy Tertiary basin-filling sediment VANI_TSY 6.21E+1 Dimensionless

Specific storage Tertiary basin-filling sediment—Layers 2–4 SS_TSYU 7.46E-5 ft-1

Specific storage Tertiary basin-filling sediment—Layers 5–11 SS_TSYL 6.76E-5 ft-1

Hydraulic conductivity Tertiary sediments and volcanics HK_TSV 3.25E-5 ft/s

Vertical anisotropy Tertiary sediments and volcanics VANI_TSV 1.14E+1 Dimensionless

Specific storage Tertiary sediments and volcanics—Layers 1–4 SS_TSVU 3.92E-8 ft-1

Specific storage Tertiary sediments and volcanics—Layers 5–12 SS_TSVL 4.20E-8 ft-1

Muliplier General head boundary conductance—Tertiary sediments and 

volcanics

GHB_TSV 1.22E-2 Dimensionless

Muliplier General head boundary conductance—Tertiary sediments of 

younger basins

GHB_TSY 4.10E-3 Dimensionless

Muliplier Drain conductance DRN_COND 2.94E+1 Dimensionless

Muliplier Recharge RECHARGE 1.00E+0 Dimensionless

Muliplier Riverbed conductance RIV_COND 1.00E-2 Dimensionless
22 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig14

0.0001 

0.001 

0.01 

0.1 

1 

10 

HK_QS HK_QV 

HK_TSY 

HK_TSV 

VANI_QS 

VANI_QV 

VANI_TSY 

VANI_TSV 

SS_QS 

SS_QV 

SS_TSYU 

SS_TSYL 

SS_TSVU 

SS_TSVL 

GHB_TSV 

GHB_TSY 

GHB_QS 

GHB_QV 

DRN_COND 

RECHARGE 

RIV_COND 

Composite scaled sensitivity, dimensionless

Parameter name

Figure 14. Composite scaled sensitivities of parameters in the Tule Lake groundwater model. Parameter names are 

defined in table 4.

The values for the hydraulic conductivity and vertical 

anisotropy of the Tertiary sediments of younger basins (basin 

fill: HK_TSY, VANI_TSY) for the regional and Tule Lake 

models are different by one order of magnitude (2.9 × 10-

4

 and 2.7 × 10-5, respectively for HK_TSY, and 250 and 

62, respectively for VANI_TSY). Although the values are 

different, the ratio of HK:VANI, which is equivalent to the 

vertical hydraulic conductivity, is nearly the same. Although 

the hydraulic conductivity values for the basin fill are different 

by an order of magnitude, both are within the typical range for 

sedimentary aquifers (Freeze and Cherry, 1979).

Other values of hydraulic conductivity in the model are 

within the typical range for their respective geology types 

(Freeze and Cherry, 1979), and SS values other than those 

for Tsv are reasonably close to values in the regional model 

(Gannett and others, 2012). Other parameters include the 

conductance of the drains, the bed of the Lost River, and the 

general head boundaries. These parameters, like the HK, 

VANI, and SS parameters, were optimized during parameter 

estimation to find the best match between observed and 

simulated hydraulic head values. Recharge parameter values 

were not changed during calibration.

Parameter Sensitivity

MODFLOW calculates the scaled sensitivity of each 

observation to each parameter and a composite scaled 

sensitivity for each parameter (see Hill, 1998, eqs. 8–10, 

p. 14–15, for the calculation of scaled sensitivities and 

composite scaled sensitivities). The composite scaled 

sensitivity is a measure of the total information provided by 

the observations for the estimation of a particular parameter 

(Hill, 1998). Parameters that have sensitivities that are 

significantly lower (more than two orders of magnitude) than 

other parameters are considered to be relatively insensitive; 

that is, the parameter value can change significantly without 

substantially changing model fit. The composite scaled 

sensitivities of parameters in the Tule Lake model are 

shown in figure 14. Most parameters are within two orders 

of magnitude, except SS_TSVU, the specific storage of the 

lower part of the aquifer composed of Tertiary sediments and 

volcanics. The insensitivity of this parameter is due in part to 

the few observations available to constrain it. The model was 

most sensitive to Recharge, GHB_QS, and HK_TSY.

Model Fit

The fit between simulated and observed values can be 

evaluated using graphical analysis of residuals, diagnostic 

statistics, and graphical inspection of observed and simulated 

hydraulic head plots (Hill, 1998). To identify possible 

error and bias in the model, it is also useful to evaluate 

the patterns of model residuals (observed minus simulated 

hydraulic heads). 

Residuals from the Tule Lake model plotted with 

weighted simulated hydraulic-head values (fig. 15) show 

a slight trend—hydraulic heads are overestimated with 

increasing simulated hydraulic-head value. Overall, there is a 

slight negative bias, indicating that simulated hydraulic-head 

values tend to be too high. This bias may be an artifact of 
Groundwater Model Results 23

tac15-0995_fig15

-25 

-20 

-15 

-10 

-5 

0 

5 

10 

15 

20 

25 

3,995 4,000 4,005 4,010 4,015 4,020 4,025 4,030 4,035 4,040

Weighted residuals

Weighted simulated hydraulic head values, in feet above the National Geodetic Vertical Datum of 1929

Figure 15. Weighted residuals (measured hydraulic head minus simulated hydraulic head) and weighted 

simulated hydraulic head values, Tule Lake subbasin, Oregon and California.

model discretization or because the generally drier climatic 

trend during the 2000s, which lowered observed hydraulic 

heads late in the simulation period, is not represented in the 

model. 

Other statistical measures of model fit are the calculated 

error variance, standard error, and fitted standard error of 

the regression. These statistics provide means of assessing 

the average magnitude of model residuals (Hill, 1998). The 

calculated error variance, s2, is calculated as:

( )

( )

2 S b

s

N NP = − (2)

where

S b( ) is the objective function value (equation 1),

N is the number of observations, and

NP is the number of estimated parameters (Hill, 

1998).

The standard error of the regression, s, is the square root 

of the calculated error variance. The smaller these values are, 

the closer the fit is to observed data. For the Tule Lake model, 

the calculated error variance, s2, is 71.4. The standard error of 

the regression, s, is 8.5. 

The fitted standard error of the regression is a more 

intuitive means of understanding the average magnitude 

of residuals (Hill, 1998). The fitted standard error of the 

regression is the product of the standard error of the regression 

and the statistic used to determine the weights. In the Tule 

Lake model, the statistic used to calculate weights was 

the standard deviation of the measurement error, 1 ft. The 

resulting fitted standard error of the regression is 8.5 ft. 

This means that over the entire active model domain, most 

simulated hydraulic head values are within about 8.5 ft of the 

measured value.

Comparison of Measured and Simulated 

Hydraulic Heads

One goal of model calibration is to find an acceptable 

fit between simulated hydraulic-head values and field 

observations. During model calibration, focus was placed 

on matching springtime values of observed hydraulic head 

in order to match long-term trends in the data. Many shortterm fluctuations in the observed hydraulic heads reflect 

stresses that could not be accurately simulated in the model 

because of incomplete information on the geographic location 

and timing of pumping stresses. The long-term decreasing 

trend in hydraulic head is captured by the model in nearly 

all of the observation wells (figs. 16A–H). Simulated water 

level trends in some wells show recovery after 2007 (for 

example, figs. 16C–E). The simulated recovery may partly 

result from underestimates of pumping in 2008 and 2009. 

Although no supplemental groundwater was purchased by the 

Bureau of Reclamation or KWAPA during those years, the 

observed hydraulic head data show that there is a pumping 

signal, indicating that groundwater pumping continued 

(figs. 16D, E, and H). There is also a probable climate signal 

not accounted for in the model. To simplify the model, 

average recharge was assumed. There was, however, a drying 

trend in the upper Klamath Basin during the period of the 

simulation. The drying trend can be seen in wells outside the 

area affected by irrigation pumping (figs. 17A and B, about 

80 mi north‐northwest and 10 mi southeast of the Tule Lake

subbasin, respectively). The omission of this drying trend 

in the model may be partly responsible for the simulated 

water-level rise in some wells late in the simulation period.
24 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig16ab

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Simulated 

Observed 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

A. Observation well 1

EXPLANATION

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Simulated 

Observed 

B. Observation well 6

EXPLANATION

Water year

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Figure 16. Observed and simulated hydraulic heads for selected observation wells, Tule Lake subbasin, Oregon and 

California.
Groundwater Model Results 25

tac15-0995_fig16cd

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

C. Observation well 8

D. Observation well 17

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure 16.—Continued
26 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig16ef

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

E. Observation well 19

F. Observation well 28

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure 16.—Continued
Groundwater Model Results 27

tac15-0995_fig16gh

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

G. Observation well 42

H. Observation well 36

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure 16.—Continued
28 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_fig17

4,520 

4,525 

4,530 

4,535 

4,540 

4,545 

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 2012 2013

Water level, in feet above the National Geodetic Vertical Datum of 1929

A

B

4,510 

4,512 

4,514 

4,516 

4,518 

4,520 

Water year

Figure 17. Water levels in U.S. Geological Survey observation wells (A) 430837121473201 

(28.00S/08.00E-17DBC01), about 80 miles north-northwest of the Tule Lake subbasin, and (B) 

414043121155501 (44.00N/06.00E-03P01M), about 10 miles southeast of the Tule Lake subbasin, 

Oregon and California.
Groundwater Model Results 29

The match between simulated and observed water levels 

varies from year to year in some wells, primarily because 

of uncertainty in the pumping data. The pumping rates for 

wells were provided, in some cases, as either an annual total 

for all wells or as totals for individual wells or groups of 

wells. The seasonal distribution of pumping is generally not 

known. Consequently, there is uncertainty as to the timing and 

spatial distribution of pumping. Simulated water levels reflect 

this uncertainty. Another potential cause of the difference 

between observed and simulated water levels is localized 

canal recharge. Recharge from irrigation in the model is 

distributed evenly over the irrigation district. In reality, some 

irrigation canals provide localized recharge to the groundwater 

system. Shallow wells near leaky canals show a signal from 

this recharge in their hydrographs. The spatial and temporal 

variability of canal leakage is not included in the model.

Like the simulated and observed hydraulic heads, the 

simulated and observed reduction in drain flow also can be 

compared (fig. 18). The observed decrease in drain flow is 

calculated from the summed decreased drain flow for the 

North KID/TID, Lease Lands, and Copic Bay subareas of the 

Tule Lake subbasin. To calculate drain flow decreases, the 

observed drain flow in 2000 was considered to be the base, 

pre-pumping condition, and the drain flow for each subsequent 

year (until 2010) was subtracted from the 2000 value. 

Changes in simulated drain flows were calculated in a similar 

manner. Simulated decreases in drain flow in 2001 and 2010 

were less than observed, likely because factors in addition 

to groundwater pumping, such as diminished interflow and 

surface runoff due to curtailed Project operations influenced 

drains as well. In years when supplemental groundwater 

pumping was the largest post-2000 stress on the system and 

effects due to drought and curtailed Project diversions played 

a relatively minor role, simulated and observed changes in 

drain flows are similar (fig. 18).

-20,000 

0 

20,000 

40,000 

60,000 

80,000 

100,000 

120,000 

140,000 

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 

Post-2000 change in drain flow, in acre-feet

Observed

Simulated 

EXPLANATION

Water year

Figure 18. Observed and simulated decrease in flow to drains relative to drain flow in 2000, Tule Lake subbasin, 

Oregon and California. Observed decrease in flow to drains represents drain flow decreases from all three areas 

of the Tule Lake subbasin.
30 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

Simulated Hydrologic Budget and Sources of 

Water to Wells

The groundwater model can be used to quantify the 

changes in groundwater flow to and from model boundaries 

such as drains, rivers, lakes, and adjacent basins, and to and 

from groundwater storage in response to pumping (fig. 19). 

Recharge and pumping are specified in the model. Other 

flows, such as those to or from adjacent subbasins, drains, the 

Lost River, the Tule Lake sumps, and groundwater storage 

vary in response to these external stressors. Recharge is the 

largest budget component and, except for 2001 and 2010, 

is the same each year in simulations, varying seasonally. 

Recharge was decreased in 2001 and 2010 to reflect 

diminished canal leakage and infiltration of applied irrigation 

water resulting from curtailed Project operations. Recharge 

was scaled back to 32 percent in 2001 and 55 percent in 2010 

to reflect the diminished irrigation application those years. 

Recharge is positive in figure 19 because it represents a 

source of water. Pumping varies from year to year in response 

to demand for supplemental irrigation water and is shown 

as a negative value in figure 19 because it represents a sink 

for water.

The next largest flux of groundwater in the model is 

discharge to agricultural drains. Drains are the primary avenue 

by which groundwater leaves the model. Like pumping, the 

drain flux is negative because it represents a sink for water.

-250 

-200 

-150 

-100 

-50 

0 

50 

100 

150 

200 

250 

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Groundwater out Groundwater in

Tule Lake sumps

Recharge

Lost River

Aquifer storage 

Interbasin boundaries

Drains

Pumping 

EXPLANATION

Flux, in cubic feet per second

Figure 19. Simulated water budget components of the Tule Lake subbasin, Oregon and California.
Groundwater Model Results 31

The remaining major flux is net change in aquifer storage, 

which represents the change in water stored in the aquifer 

over time. Storage is the only flux that can be either positive 

or negative. A positive value indicates that storage is a source 

of water (commonly to wells) and is reflected as a water-level 

decline. A negative value indicates that water (commonly 

from recharge) is going into storage, which results in a rising 

water level. Other components such as interbasin flow, and net 

flow to other surface water bodies (Lost River and Tule Lake 

sumps), are small in comparison.

The major budget components of the model changed 

during the simulation period in response to changes in 

recharge and pumping. During the first years of the simulation 

(2001–05) the storage term was mostly positive, indicating 

that water was coming from storage in response to increased 

pumping and decreased recharge in 2001. Groundwater levels 

declined during this period. From 2006 to 2010 changes in 

storage fluctuate closely around zero, indicating that pumped 

groundwater was coming mostly from diminished drain flows. 

2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

EXPLANATION

0 

50,000 

100,000 

150,000 

200,000 

250,000 

300,000 

350,000 

Cumulative volume, in acre-feet

Supplemental pumping plus recharge deficit

Supplemental pumping only

Captured drain flow

Water from aquifer storage 

Captured flow from basin boundaries

Captured Lost River flow

Captured Tule Lake sump flow 

Figure 20. Simulated cumulative change in volume of selected budget components of the Tule Lake subbasin, 

Oregon and California.
32 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

Groundwater levels were mostly stable during this period. 

Aquifer storage spiked positively again in 2010 in response to 

diminished recharge resulting from curtailed Project operation 

due to drought and to a large increase in pumping. Water 

levels declined sharply as a result.

Another representation of each budget component 

can be seen in figure 20. Whereas figure 19 shows the 

instantaneous rates of flow associated with each budget 

component at the end of each model stress period, figure 20

shows the cumulative volumes of these budget components. 

The line representing cumulative supplemental pumping 

plus the recharge deficit represents the total stress on the 

groundwater system. The recharge deficit is the stress on the 

groundwater system resulting from decreases in recharge. 

As the total stress is imposed on the groundwater system, the 

other model boundaries (agricultural drains, aquifer storage, 

interbasin boundaries, the Lost River, and the Tule Lake 

sumps) vary in response. Other lines in figure 20 show the 

cumulative change in storage and the cumulative volume 

captured from each model boundary due to supplemental 

pumping and decreased recharge in 2001 and 2010.

Annual water levels (groundwater storage), drain flows, 

and other boundary fluxes were relatively stable prior to 2001 

because pumping was relatively constant. When pumping 

sharply increased and recharge diminished in 2001, aquifer 

storage and discharge to drains began to decrease as a result. 

This is shown in figure 20 as an increase in the volume 

captured from both drains and storage in 2001. Although 

simulated recharge returned to normal conditions after 

2001, pumping remained above 2000 levels. The cumulative 

volumes of decreased, or captured, drain flow and storage 

tracked closely with cumulative supplemental pumping and 

decreased recharge, until about 2005 (fig. 20, table 5). From 

2005 to 2009, cumulative storage remains approximately 

constant (with the slope becoming slightly negative) indicating 

that storage was no longer a major source of water. At this 

point, most pumped water was from diminished groundwater 

discharge to drains. Another drought year (2010) led to a sharp 

increase in pumping and diminished recharge. This forced the 

system further out of equilibrium, resulting in sharp increases 

in captured drain flow and aquifer storage. 

The sources of water most affected by groundwater 

pumping are agricultural drains and storage. The cumulative 

volume of supplemental pumping and reduced recharge (the 

Table 5. Simulated cumulative change in volumetric budget, Tule 

Lake subbasin, Oregon and California. 

[Negative values represent losses to the groundwater system. Positive values 

represent sources of water]

Budget element

Cumulative

change

(acre-feet)

Totals

(acre-feet)

Supplemental pumping -234,758 -323,573

Recharge deficit -88,815

Aquifer storage 126,089 323,180

Drains 180,596

Lost River 9,471

Interbasin boundaries 6,795

Tule Lake sumps 229

Difference -393

total stress on the groundwater system) between 2000 and 

2010 (which includes annual supplemental irrigation and 

diminished recharge in 2001 and 2010) totaled 323,573 acre-ft. 

Supplemental pumping is the primary stress on the system; 

of the 323,573 acre-ft of cumulative pumping and decreased 

recharge, 234,800 acre-ft (73 percent) resulted from increased 

pumping above 2000 levels (table 5). The response of the 

groundwater system to this change in stress included about 

180,500 acre-ft of decreased groundwater discharge to drains 

(about 56 percent of the total stress) and a 126,000 acre-ft 

reduction in aquifer storage (which amounts to about 

39 percent of the total stress and is reflected by groundwater 

level declines). The remaining 5 percent of the stress (about 

16,500 acre-ft) is reflected as decreased groundwater flow 

to other boundaries, including the Lost River, the Tule Lake 

sumps, and interbasin flow.

The greatest decrease in discharge to drains occurs in 

the northern and southeastern parts of the study area (fig. 21) 

where pumping wells are concentrated. In areas where 

pumping does not occur, drain effects are much less. This is 

consistent with the results of the Klamath/Tulelake Irrigation 

District drain analysis, in which most of the effect to drains 

was observed in the northern and southeastern subareas.
Groundwater Model Results 33

tac15-0995_fig21

Tule Lake

Sump 1A

Tule Lake 

Sump 1B

CALIFORNIA

OREGON

0 1 2 3 4 MILES

0 2 3 4 1 KILOMETERS

121°35' 30' 121°25' 121°20'

42°

05'

42°

00'

41°

55'

41°

50'

Universal Transverse Mercator projection, Zone 10N 

North American Datum of 1927

EXPLANATION

Pumping wells

Change in drain discharge, 

in cubic feet per second

-0.04 - 0.02

0.03 - 0.06

0.07 - 0.14

0.15 - 0.24

0.25 - 0.44

Figure 21. Spatial distribution of simulated reduction in discharge to drains, calculated as the discharge to drains in 2006 (year 

of maximum drain effect) subtracted from the discharge to drains in 2000, Tule Lake subbasin, Oregon and California.
34 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

Potential Implications

Decreases in drain flow could affect water availability for 

the Lower Klamath and Tule Lake National Wildlife refuges. 

Irrigation return flows delivered by agricultural drains are 

the main source of water for both refuges. For water years 

2003–05, the percentage of total inflow to the Lower Klamath 

and Tule Lake refuges from irrigation return flow was 67 and 

75 percent, respectively. Because most of the water to both 

refuges is composed of return flow in drains, a decrease in this 

flow will affect both refuges. 

Diminished drain flows could also affect downstream 

irrigators, including the TID. To date, growers who irrigate 

primarily with Project return flow from the drain system 

have not been affected by decreases in drain flow. With 

continued pumping and a drying climate, further reductions 

in drain flow are expected, which may require the TID to alter 

operations to meet the water demand of its member farmers. 

Recent management modeling by Wagner and Gannett (2014) 

suggests that practical and regulatory limits on drawdown 

in the aquifer would likely limit pumping before drain flows 

diminish to the point that there would be insufficient water to 

irrigate lands in the southern part of the Project. 

The results of this study also have implications for the 

Project in a broader sense. In 2010, stakeholders in the basin 

developed an agreement that would balance the benefits 

of water for both aquatic wildlife and agriculture. The 

Klamath Basin Restoration Agreement (KBRA) (Klamath 

Basin Restoration Agreement, 2010) defines the limits on 

the “adverse impacts” of Project groundwater pumping on 

flow in certain streams and springs in the upper Klamath 

Basin to 6 percent of baseline flow (defined by pre-2001 

pumping conditions). Drain data, along with the results of the 

groundwater model, show that the effects of Project pumping 

are largely limited to agricultural drains and changes in 

groundwater storage within the Project area, and that effects 

to KBRA listed streams, which are outside the Project area, 

are small or unlikely. This is consistent with the findings of 

Wagner and Gannett (2014), who showed that effects from 

probable future on-Project pumping to listed streams are well 

below the 6 percent limit.

Study Limitations and Uncertainty

Uncertainty in the Drain-Flow Analysis

The time series of volumes pumped from agricultural 

drains used in the drain-flow analysis were collected according 

to the operational needs of the Project or the irrigation 

districts. Estimates of volumes pumped from drains were 

determined using the pump rating and time of operation of 

each pump. Volumes of operational spills were determined 

using weirs and spill points. Water depths at weirs were 

sometimes estimated visually (Mark Stuntebeck, Klamath 

Irrigation District, oral commun., 2013). As such, there is 

uncertainty associated with these measurements. 

The method by which changes in groundwater discharge 

to drains were estimated from pump data also introduced 

uncertainty. Water was pumped from the drains and reused 

in parts of the subbasin, so the drain flow analysis focused 

on three subareas with drain pumps that best integrate flow 

for each subarea to avoid double accounting of drain flow. 

However, some drain flow still may be accounted for more 

than once. Finally, the only quantifiable source of surface 

water available for this analysis was operational spill to drains 

from the KID. There may be other sources of surface water 

to drains, such as overland flow from precipitation or direct 

runoff from fields. Changes in unaccounted surface-water 

sources in this analysis could potentially affect estimates of the 

changes in the groundwater component of drain flow. Given 

that total diversions have not changed markedly, these other 

surface-water sources likely did not change during 2000–10. 

Uncertainty in the Groundwater Model

Groundwater models are representations of complex 

natural systems. As such, simplifications must be made in 

order to create a practical groundwater model. Because the 

subsurface geology of the Tule Lake subbasin is complex 

and poorly known where well data are not available, it must 

be simplified and its structure inferred. For example, the 

boundary flow of groundwater into the Tule Lake subbasin 

from adjacent subbasins has not been directly measured. 

The final structure of the interbasin flow boundaries was 

determined by experimentation during model calibration. 

There was also uncertainty in the recharge and pumping 

data used in the model. Recharge in the model is based on 

a water balance by Burt and Freeman (2003), which itself 

used uncertain data. However, it is the best data available on 

recharge in the upper Klamath Basin. The pumping data used 

in the model is imprecise because the spatial distribution and 

seasonality of the pumping are poorly known. Additionally, 

unmeasured pumping took place during the study years, 

as evidenced by supplemental pumping signals in well 

hydrographs during 2008 and 2009, years when there was 

no supplemental pumping accounted for under government 

programs. In addition to data uncertainty, some processes 

could not be simulated with the model. The stresses that 

were not simulated were the decadal climate signal present in 

the upper Klamath Basin and localized recharge from leaky 

irrigation canals. Future work may include incorporating a 

climate signal within the modeled recharge and integrating 

localized recharge using the MODFLOW One-Water 

Hydrologic Flow Model (MODFLOW-OWHM), which 

simulates a wide range of processes relating to conjunctive use 

(Hanson and others, 2014).
Acknowledgments 35

Summary 

The allocation of water in the Tule Lake subbasin 

is challenging for resource managers and water users. 

Groundwater is used increasingly in the subbasin to make 

up for shortages due to reallocation of surface water for 

in-stream uses. U.S. Geological Survey regional groundwater 

flow model simulations and records of irrigation return flow 

pumped from the Tule Lake subbasin into the adjacent Lower 

Klamath Lake subbasin indicate that increased groundwater 

pumping has decreased the volume of shallow groundwater 

that discharges to agricultural drains. These drains, designed 

to convey excess irrigation water that percolates to the shallow 

subsurface, are an important source of water to downstream 

irrigators and are the primary source of water to the Lower 

Klamath and Tule Lake National Wildlife refuges. Changes 

in the volume of water discharging to drains and the causes 

of that change are of interest to water managers. The U.S. 

Geological Survey entered into a cooperative study with the 

Bureau of Reclamation and U.S. Fish and Wildlife Service to 

develop a quantitative evaluation of the connection between 

volcanic and overlying sedimentary aquifers in the Tule Lake 

subbasin of the Upper Klamath Basin to assess the effect of 

pumping on agricultural drains.

In the study, data from the Klamath Irrigation District 

(KID) and Tulelake Irrigation District (TID) were analyzed 

to quantify drain flow changes over time. Additionally, a 

groundwater model of the Tule Lake subbasin was constructed 

to integrate data regarding pumping, geology, structure of the 

subbasin, and proximity of stresses to other boundaries such 

as drains, the Lost River, the Tule Lake sumps, and interbasin 

flow margins to quantify how the interplay of these variables 

manifest as changes to drain flow.

Results of the drain flow analysis indicate that flow to 

agricultural drains had decreased since 2000. In all three 

subareas evaluated (North KID/TID, Copic Bay, and the 

Lease Lands), drain flows decreased to varying degrees. The 

greatest change occurred in the North KID/TID and Copic 

Bay subareas, where the differences between the 2012 drain 

flows and pre-2001 flows were 22,300 and 7,300 acre-ft, 

respectively. The Lease Lands showed a comparatively 

small overall change of 2,800 acre-ft. In total, combined 

drain flow for all three subareas in 2012 was approximately 

32,400 acre-ft less than the pre-2001volumes. 

In addition to increases in pumping, diminished recharge 

likely results in decreases in drain flows. Changes in recharge 

were probably a major influence on reduced drain flows in 

2001 and 2010, dry years in which irrigation diversions were 

curtailed. This is evident in an analysis of the calculated and 

simulated yearly loss of groundwater flow to drains.

The groundwater model indicates that drain flows 

are being decreased primarily by groundwater pumping. 

Analysis of the model budget shows that in the early 2000s, 

pumped water is sourced from both groundwater storage and 

diminished groundwater discharge to drains, and with time 

the source shifts from aquifer-storage depletion to capture of 

agricultural drain flows. The Lost River, interbasin flow, and 

Tule Lake sumps all provide a comparably small amount of 

water to pumping wells.

Simulations and data show that the effect of supplemental 

pumping on drains remained relatively constant after 2001, 

and the contribution from groundwater storage began to 

decrease. The system was approaching a new equilibrium 

until 2010, when a large increase in pumping and decreased 

recharge resulted in increased reductions in drain flow and 

groundwater storage. These findings are consistent with what 

is known about the behavior of groundwater systems that 

undergo pumping stress. 

Acknowledgments

The authors thank the following individuals for their 

help and their knowledge, both of which were keys to this 

study. Brad Kirby of the Tulelake Irrigation District and Mark 

Stuntebeck of the Klamath Irrigation District provided critical 

data on pump and drain flows, operational spills, and cropping 

patterns, and patiently explained the complex plumbing of 

their districts. The Bureau of Reclamation Klamath Basin 

Area Office provided information on Project operations and 

diversions, as well as funding for this effort. Tim Mayer of the 

U.S. Fish and Wildlife Service provided useful discussions 

on refuge water operations, and was instrumental in securing 

funding for the first year of the project. 
36 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

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groundwater modeling—Simulation of flow and advective 

transport: San Diego, Academic Press, 381 p.

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by wells—Understanding and managing the effects of 

groundwater pumping on streamflow: U.S. Geological 

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Englewood Cliff, N.J., Prentice-Hall, 604 p.

Gall, I.K., 2011, Technical assistance for the U.S. Bureau of 

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for the U.S. Bureau of Reclamation under agreement 

R10AC20099, 17 p., plus tables and appendices.

Gannett, M.W., Lite, K.E., Jr., La Marche, J.L., Fisher, B.J, 

and Polette, D.J., 2007, Ground-water hydrology of 

the Upper Klamath Basin, Oregon and California 

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Investigations Report 2007-5050, 84 p. 

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Groundwater simulation and management models 

for the upper Klamath Basin, Oregon and California: 

U.S. Geological Survey Scientific Investigations Report 

2012-5062, 92 p.

Hanson, R.T., Boyce, S.E., Schmid, W., Hughes, J.D., 

Mehl, S.M., Leake, S.A., Maddock, Thomas, III, and 

Niswonger, R.G., 2014, One-Water Hydrologic Flow Model 

(MODFLOW-OWHM): U.S. Geological Survey Techniques 

and Methods 6-A51, 120 p.

Harbaugh, A.W., Banta, E.R., Hill, M.C., and McDonald, 

M.G., 2000, MODFLOW-2000, the U.S. Geological 

Survey modular ground-water model—User guide to 

modularization concepts and the Ground-Water Flow 

Process: U.S. Geological Survey Open-File Report 00-92, 

121 p.

Hill, M.C., 1998, Methods and guidelines for effective model 

calibration: U.S. Geological Survey Water-Resources 

Investigations Report 98-4005, 90 p.

Hill, M.C., Banta, E.R., Harbaugh, A.W., and Anderman, 

E.R., 2000, MODFLOW-2000, The U.S. Geological 

Survey modular ground-water model—User guide to the 

observation, sensitivity, and parameter-estimation processes 

and three post-processing programs: U.S. Geological 

Survey Open-File Report 00-184, 209 p.

Klamath Basin Restoration Agreement (KBRA), 2010, 

Klamath Basin restoration agreement for the sustainability 

of public and trust resources and affected communities—

February 18, 2010: Klamath Basin Restoration 

Agreement, 378 p., accessed January 17, 2012, at http://

klamathrestoration.gov/.

La Rue, E.C., 1922, Klamath River and its utilization: Salem, 

Oregon, Report to the Office of the State Engineer, 204 p. 

McDonald, M.G., and Harbaugh, A.W., 1988, A modular 

three-dimensional finite-difference ground-water flow 

model: U.S. Geological Survey Techniques of WaterResources Investigations, book 6, chap. A1, 586 p.

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fishes in the Klamath River Basin: National Research 

Council, 384 p.

Palmer, P.C., Gannett, M.W., and Hinkle, S.R., 2006, Isotopic 

characterization of three groundwater recharge sources and 

inferences for selected aquifers in the upper Klamath Basin 

of Oregon and California, USA: Journal of Hydrology, 

v. 336, 13 p.

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W.L., 2008, Ground-water availability in the United States: 

U.S. Geological Survey Circular 1323, 70 p.

Risley, J.C., and Gannett, M.W., 2006, An evaluation and 

review of water-use estimates and flow data for the 

Lower Klamath and Tule Lake National Wildlife Refuges, 

Oregon and California: U.S. Geological Survey Scientific 

Investigations Report 2006-5036, 18 p.

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Essential factors controlling the response of an aquifer to 

development: Civil Engineering, v. 10, no. 5, p. 277–280.

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alternative groundwater-management strategies for 

the upper Klamath Basin, Oregon and California: 

U.S. Geological Survey Scientific Investigations 

Report 2014-5054, 48 p. 
Appendix A 37

Appendix A. Model Observation Wells

Water-level measurements from 24 wells located throughout the Tule Lake subbasin were used to calibrate the Tule Lake 

subbasin groundwater model. Spring (March, or sometimes March and April) water levels were used to minimize error due 

to drawdown during pumping. A selection of these wells with observed and simulated water levels is shown in figure 16. The 

remaining wells are shown in figure A1, which can be accessed as a PDF at http://pubs.er.usgs.gov/publication/sir20155087. 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

A. Observation well 2

B. Observation well 14

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

Water year

Figure A1. Simulated and measured hydraulic head data for the Tule Lake groundwater model, Tule Lake subbasin, 

Oregon and California, water years 2001–10.
38 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_figA1-cd

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

C. Observation well 15

D. Observation well 16

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure A1.—Continued
Appendix A 39

tac15-0995_figA1-ef

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

E. Observation well 18

F. Observation well 21 

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure A1.—Continued
40 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_figA1-gh

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

G. Observation well 22

H. Observation well 23

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure A1.—Continued
Appendix A 41

tac15-0995_figA1-ij

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

I. Observation well 24

J. Observation well 26

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure A1.—Continued
42 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_figA1-kl

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

K. Observation well 30

L. Observation well 32

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure A1.—Continued
Appendix A 43

tac15-0995_figA1-mn

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

M. Observation well 33

N. Observation well 34

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure A1.—Continued
44 Effects of Groundwater Pumping on Agricultural Drains, Tule Lake Subbasin, Oregon and California

tac15-0995_figA1-op

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

3,990 

4,000 

4,010 

4,020 

4,030 

4,040 

Hydraulic head, in feet above the National Geodetic Vertical Datum of 1929

O. Observation well 35

P. Observation well 37

Simulated 

Observed 

Simulated 

Observed 

EXPLANATION

EXPLANATION

1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 2009 2010 2011 

Water year

Figure A1.—Continued
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For more information concerning the research in this report, contact the

Director, Oregon Water Science Center

U.S. Geological Survey

2130 SW 5th Avenue

Portland, Oregon 97201

http://or.water.usgs.gov
Pischel and Gannett—Effects of Groundwater Pumping on Agricultural Drains in the Tule Lake Subbasin, Oregon and California—Scientific Investigations Report 2015–5087

ISSN 2328-0328 (online)

http://dx.doi.org/10.3133/sir20155087