Simulated Water-Management Alternatives 

Using the Modular Modeling System for the 

Methow River Basin, Washington

By Christopher P. Konrad

Prepared in cooperation with the

U.S. Bureau of Reclamation

Open-File Report 2004-1051

U.S. Department of the Interior

U.S. Geological Survey
U.S. Geological Survey, Reston, Virginia: 2004

For sale by U.S. Geological Survey, Information Services

Box 25286, Denver Federal Center

Denver, CO 80225-0286

U.S. Department of the Interior

Gale A. Norton, Secretary

U.S. Geological Survey

Charles G. Groat, Director

For more information about the USGS and its products:

Telephone: 1-888-ASK-USGS

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

endorsement by the U.S. Government.

Although this report is in the public domain, permission must be secured from the individual copyright owners to 

reproduce any copyrighted materials contained within this report.

Suggested citation:

Konrad, C.P., 2004, Simulated water-management alternatives using the Modular Modeling System for the Methow 

River Basin, Washington: U.S. Geological Survey Open-File Report 2004–1051, 12 p.
iii

Contents

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

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

Description of Water-Management Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Alternative 1. Baseline. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Alternative 2. Lined Irrigation Canals . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .3

Alternative 3. Increased Aquifer Recharge by Irrigation-Canal Seepage . . . . . . . . . . . . . . 3

Alternative 4. Conversion of Irrigation-Water Supply from Surface-Water to 

Ground-Water Resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 3

Alternative 5. Forest-Cover Reduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Alternative 6. Natural Flow . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Simulations of Water-Management Alternatives . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5

Effects of Water-Management Alternatives on Annual Streamflow . . . . . . . . . . . . . . . . . . . 5

Effects of Water-Management Alternatives on Low-Flow Conditions . . . . . . . . . . . . . . . . . . 10

Summary and Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11

References Cited . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 12
iv

Figures

Figure 1. Map showing location of the Methow River Basin and streamflowgaging stations used in the study of water-management alternatives . . . . . . . . . . . 2

Figure 2. Graphs showing 90-percent exceedence values for simulated daily 

streamflow at selected gaging stations for water years 1960–2001 

for six water-management alternatives in the Methow River Basin . . . . . . . . . . . . . 9
v

Tables

Table 1. Modular Modeling System parameters modified to represent 

changes in forest cover. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 4

Table 2. 90-, 50-, and 10-percent exceedence values for simulated annual 

mean streamflow for water years 1960 to 2001 under six water-management 

alternatives, and percent difference from baseline alternative . . . . . . . . . . . . . . . . . 6

Table 3. 90- and 50-percent exceedence values for simulated annual mean 

streamflow for September water years 1960 to 2001 under six watermanagement alternatives, and percent difference from baseline alternative. . . . . 7

Table 4. 90- and 50-percent exceedence values for simulated monthly 

mean streamflow for January for water years 1960 to 2001 

under six water-management alternatives, and percent 

difference from baseline alternative . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Simulated Water-Management Alternatives Using the 

Modular Modeling System for the Methow River Basin, 

Washington

By Christopher P. Konrad

Abstract

A precipitation-runoff model for the Methow River Basin 

was used to simulate six alternatives: (1) baseline of current 

flow, (2) line irrigation canals to limit seepage losses, (3) 

increase surface-water diversions through unlined canals for 

aquifer recharge, (4) convert from surface-water to groundwater resources to supply water for irrigation, and (5) reduce 

tree density in forested headwater catchments, and (6) natural 

flow. Daily streamflow from October 1, 1959, to September 30, 

2001 (water years 1960–2001) was simulated. Lining irrigation 

canals (alternative 2) increased flows in the Chewuch, Twisp, 

and the Methow (upstream and at Twisp) Rivers during 

September because of lower diversion rates, but not in the 

Methow River near Pateros. Increasing diversions for aquifer 

recharge (alternative 3) increased streamflow from September 

into January, but reduced streamflow earlier in the summer. 

Conversion of surface-water diversions to ground-water wells 

(alternative 4) resulted in the largest increase in September 

streamflow of any alternative, but also marginally lower 

January flows (at most -8 percent in the 90-percent exceedence 

value). Forest-cover reduction (alternative 5) produced large 

increases in streamflow during high-flow periods in May and 

June and earlier onset of high flows and small increases in 

January streamflows. September streamflows were largely 

unaffected by alternative 5. Natural streamflow (alternative 6) 

was higher in September and lower in January than the baseline 

alternative.

Introduction

At the request of the U.S. Bureau of Reclamation, the U.S. 

Geological Survey (USGS) used a recently developed 

precipitation-runoff model for the Methow River Basin (Ely, 

2003) to assess the effects of different water-management 

alternatives on streamflow throughout the Methow River Basin 

(fig. 1). The water-management alternatives represented a 

range of alternatives that are being considered by the Methow 

Basin Planning Unit in the development of a watershed plan. 

The alternatives include possible actions such as lining 

irrigation canals to limit seepage losses, increasing surfacewater diversions through unlined canals for aquifer recharge, 

converting from surface-water to ground-water resources to 

supply water for irrigation, and reducing tree density in 

forested headwater catchments. Streamflow under these 

alternatives was compared with a simulated baseline 

representing current conditions and a “natural” flow alternative 

representing streamflow patterns without surface-water 

diversions or ground-water pumping, but with the same 

vegetation as the baseline alternative.

A precipitation-runoff model for the Methow River Basin 

(fig. 1) was constructed using the USGS Modular Modeling 

System (MMS) (Leavesley and others, 1996). The model 

calculates evapotranspiration (ET), subsurface flow, and 

surface-water runoff from hillslope areas, or hydrologic 

response units (HRU), on the basis of daily records of 

precipitation and air temperature, with values distributed across 

the basin as described by Ely (2003). MMS routes the runoff 

through a channel network represented by a series of nodes. 

The Methow River Basin was divided into 620 HRUs. 

Vegetation and soil parameters were assigned using automated 

algorithms in the GIS Weasel (Viger and others, 1998). The 

model represented 16 surface-water diversions to irrigation 

canals, canal seepage, application of water to agricultural 

fields, and ET and infiltration of applied water. Surface-water 

diversions were subtracted from streamflow at the node (a point 

along a river) specified for each diversion. Where the specified 

diversion rate is greater than streamflow at the node of 

diversion, the model limits the diversions to the streamflow 

available at the node. Seepage from irrigation canals was 

allocated to ground-water reservoirs, which represent the 

shallow aquifer under a specific area of the valley.
Black Canyon Creek

McFa rland Creek

G o dl Creek S. Fk

Libby Creek

Twisp River

Eagle Creek

War Creek

Twisp River

Earl y W ni ters Creek

Robinson Creek

Eightmile Creek

Lake Creek

Andrews Creek

Chewuch River

Cub Creek

Goat Creek

Bou ld er Creek

Beaver Creek

Wolf Creek

Methow River Lost River

Bear Creek

Twenty Mile Creek

Cathe dral Creek

Buttermilk Creek

Harts Pass

Poorman Creek

Newby Creek

Little Bridge Creek

Benson Creek

Little Boulder Creek

Columbia R iver

Squaw Creek

Alder Creek

Foggy Dew Creek

Gold Creek N. Fk

Carlton

Pateros

Winthrop

Mazama

Methow

Twisp

Study area

WASHINGTON

EXPLANATION

0

0

10 MILES

10 KILOMETERS

Base from U.S. Geological Survey Digital Data, 1:100,000, 1985 Universal Transverse Mercator projection,

Zone 10, Datum NAD 83

WENATCHEE-OKANOGAN NATIONAL FOREST

METHOW STUDY AND BOUNDARY

STREAMFLOWGAGING STATION

AND NO.

R18E R20E R22E R24E

T

N

T

N

T

N

T

N

T

N

T

N

40

38

36

34

32

30

120°30'W 120°0'W

49°

48°30'

48°

12447390

12447382

12447370

12447370

12447383

12447387

12447600

12448500

12448620

12448996

12448998

12449500

12449710

12449600

12449950

12448992

12448990

12448000

O

K

A

N

O

G

A

N

H I G

H L A

N

D

S

C

A

S

C

A

D

E

R

A

N

G

E

2 Simulated Water-Management Alternatives Using the Modular Modeling System for the Methow River Basin, Washington

Figure 1. Location of the Methow River Basin and streamflow-gaging stations used in the study of water-management alternatives.
Description of Water-Management Alternatives 3

Description of Water-Management 

Alternatives

Alternative 1. Baseline

This alternative represents current conditions as simulated 

by Ely (2003). Surface water was diverted from nodes to the 16 

canals from May through October at rates that varied during the 

season (see table 3 in Ely, 2003), but were constant year-toyear. There were no seepage losses from two canals (Wolf 

Creek and Skyline) for the baseline alternative because they 

have been replaced by pipes. Seepage losses in the other 14 

canals were assumed to be 50 percent of the amount of water 

diverted to each canal. Requirements for shutting down the 

Early Winters (T. 36 N., R. 19 E., sec. 26), Willis (T. 36 N., 

R. 21 E., sec. 27), Skyline (T. 36 N., R. 21 E., sec. 25), and 

Wolf Creek (T. 34 N., R. 20 E., sec. 2) canals to maintain 

minimum instream flows (National Marine Fisheries Service, 

2000a; 2000b; and 2000c) are not included in the baseline or 

other alternatives.

Alternative 2. Lined Irrigation Canals

The baseline alternative was modified by eliminating 

seepage from all canals and reducing the surface-water 

diversions by 50 percent in the 14 canals that had seepage 

losses under the baseline alternative. The diversion rates for the 

Skyline and Wolf Creek canals were the same as those under 

the baseline alternative because seepage losses are assumed to 

have been eliminated when large portions of these canals were 

replaced with pipes.

Alternative 3. Increased Aquifer Recharge by 

Irrigation-Canal Seepage

The baseline alternative was modified by increasing 

surface-water diversions by 25 percent, except for Wolf Creek 

and Skyline, for which diversions were increased 50 percent, 

and by increasing seepage to 60 percent of diversions for all 16 

canals. Diversions during September were not increased above 

the rates used for the baseline alternative. The additional 

surface water diverted from rivers and streams under this 

alternative was allocated to canal seepage. The net effect of the 

increased rate of diversion and seepage was to increase 

recharge from irrigation-canal seepage by approximately 50 

percent.

Alternative 4. Conversion of Irrigation-Water Supply 

from Surface-Water to Ground-Water Resources

The baseline alternative was modified by eliminating 

surface-water diversions and, instead, supplying water to each 

irrigation system from a ground-water reservoir. Ground-water 

pumping rates were equal to half of the surface-water diversion 

rates to account for the elimination of seepage losses in all 

systems except Wolf Creek and Skyline, for which seepage 

losses are assumed to have been eliminated when these canals 

were replaced with pipes. The pumped water was subtracted in 

MMS from ground-water storage in ground-water reservoirs 

associated with the HRUs for each irrigation system. At the 

node where an irrigation system previously (under the baseline 

alternative) diverted surface water, streamflow was still 

required to be available before water could be pumped from a 

ground-water reservoir by an irrigation system. The 

requirement kept pumping equivalent to diversion during lowflow periods, so that any difference in streamflow between 

alternatives was a result of the different sources of water and 

not in the rate of use. The requirement also is consistent with 

the conversion of an appropriative right from a surface-water 

source to a ground-water source, which could limit use of 

ground water to periods when surface water is available at the 

prior source.

MMS modules provide a simplified representation of 

ground-water flow hydraulics and ground-water discharge to 

rivers, and therefore do not represent the hydraulics of groundwater flow over short distances or aquifer recharge by rivers. 

As a result, this alternative does not address the local effects of 

ground-water pumping, including streamflow losses resulting 

from pumping close to a river or stream. Instead, ground-water 

pumping is represented as the uniform drawdown of the ground 

water over the area covered by each ground-water reservoir, 

which is equal to the area of the corresponding HRU. 

Two existing MMS modules (listed in italics), originally 

developed by Mastin and Vacarro (2002), were modified for 

this alternative. Variables and hillslope parameters that are 

referenced are listed in [CAPITALS]. First, the module 

divrt_apply_prms was modified so that surface-water 

diversions were not subtracted from streamflow at a node.
4 Simulated Water-Management Alternatives Using the Modular Modeling System for the Methow River Basin, Washington

Second, the module gwflow_loss_min_darcy was modified so 

that “seepage” [GW_IN_LOSS] was subtracted from inflow to 

a ground-water reservoir [GWRES_IN(i)] rather than added to 

it, as was the case for irrigation-canal seepage in the module 

developed by Mastin and Vacarro. By subtracting 

GW_IN_LOSS from ground-water storage, GW_IN_LOSS 

represents the amount of water pumped from the aquifer. The 

parameter [LOSS_DIV] was set at 100 percent, so the total 

pumping rate specified in the data file, *.dat.div, for a given 

canal was subtracted from the ground-water reservoirs that 

previously had been recharged by that canal. Pumping rates 

may be higher than surface-water diversions under the baseline 

because the model dynamically adjusts diversion (or pumping 

rate, in this case) to the streamflow available at the node of 

diversion, but pumping does not directly reduce streamflow at 

a node.

Alternative 5. Forest-Cover Reduction

The baseline alternative was modified to represent the 

removal of forest canopy and soil removal or compaction that 

might occur in response to an intense forest fire or timber 

harvest. Data from the Methow River Basin were not available 

to calibrate the model for the effects of significant forest-cover 

reduction. However, five parameters would likely be affected 

by such changes: the density of forest cover in the summer 

[COVDEN_SUM] and winter [COVDEN_WIN], the 

shortwave-radiation transmission coefficient [RAD_TRNCF], 

the storage capacity of the upper part of the soil column 

[SOIL_RECHR_MAX], and the total storage capacity of the 

soil column [SOIL_MOIST_MAX]. Because there is a 

physical basis for each of these parameters, plausible changes 

in their values were selected to simulate changes in forest 

cover (table 1).

The values of the five hillslope parameters (table 1) were 

modified in 36 HRUs representing the drainage basins for 

Andrews, Lake, Little Bridge, and Buttermilk Creeks. The 

Andrews Creek and Lake Creek Basins constitute 12 percent 

(62 of 525 square miles) of the Chewuch River Basin, and 

Little Bridge and Buttermilk Creek Basins constitute 24 

percent (59 of 245 square miles) of the Twisp River Basin. 

Combined, the four catchments constitute about 7 percent of 

the drainage area of the Methow River near Pateros (121 of 

1,777 square miles).

Alternative 6. Natural Flow

The baseline alternative was modified by eliminating 

surface-water diversions. Otherwise, the model parameters 

and data from the baseline alternative were used for 

alternative 6.

Table 1. Modular Modeling System parameters modified to represent changes in forest cover

Parameter Description Old values New values

COVDEN_SUM Fraction of HRU area covered by 

dominant vegetation in summer

0.482 to 1.0 0.1

COVDEN_WIN Fraction of HRU area covered by 

dominant vegetation in winter

0.349 to 1.0 .1

RAD_TRNCF Fraction of shortwave radiation 

transmitted through canopy

0.063 to 0.448 .75

SOIL_RECHR_MAX Upper soil storage capacity, in 

inches, over HRU area

1.69 to 1.75 .5

SOIL_MOIST_MAX Total soil storage capacity, in 

inches, over HRU area

2.99 to 3.46 1.5
Simulations of Water-Management Alternatives 5

Simulations of Water-Management 

Alternatives

Daily streamflow for the period from October 1, 1959, to 

September 30, 2001, (water years 1960-2001) was simulated. 

The results are summarized in terms of simulated annual 

streamflow at 12 nodes where there are USGS streamflowgaging stations in the Methow River Basin (table 2). The 

effects of water-management alternatives on low flows were 

evaluated in terms of percent difference from the baseline 

alternative using simulated monthly mean streamflow that was 

exceeded in 50 and 90 percent of the months of September and 

January in the simulation period. These months typically have 

the lowest streamflows of the year and bracket the period when 

water-management activities are most likely to affect 

streamflow. In September, streamflow is still used for irrigation 

but is also critical for incubation of upper Columbia River 

spring chinook salmon. Maintaining streamflow in January 

may be critical for salmonid rearing because of ice formation in 

the rivers during periods of extremely low temperatures. The 

monthly statistics are provided for all 12 stations (table 3 and 

table 4). Water management alternatives are not expected to 

affect high-flow conditions, with the exception of alternative 5, 

and, consequently, were not analyzed.

Although Ely (2003) showed that simulated streamflow 

for current conditions was generally unbiased and was accurate 

to about 10 percent compared with observed monthly mean 

streamflow in the summer and autumn at most gages during the 

calibration period (water years 1992 to 2001), simulated daily 

streamflow is not sufficiently accurate to distinguish between 

the results of different alternatives. In general, the baseline 

alternative is biased toward under-predicting flows during lowflow periods in dry years. Because of the error and potential 

bias in the simulated streamflow, the results from each of the 

water-management alternatives were evaluated relative to the 

baseline alternative rather than to observed streamflow. The 

10-, 50-, and 90-percent exceedence values for daily 

streamflow were calculated for the simulation period. The daily 

results for the Chewuch River at Winthrop, Twisp River near 

Twisp, and Methow River near Pateros are presented here 

(fig. 2). The patterns observed at these gages are similar and are 

generally representative of streamflow patterns at points 

downstream of surface-water diversions.

Effects of Water-Management Alternatives on Annual 

Streamflow

Conversion from surface-water to ground-water resources 

(alternative 4) and forest-cover reduction (alternative 5) 

produced the largest increase in annual streamflow from the 

baseline (alternative 1) of any of water-management 

alternatives (table 2). The effect on streamflow of conversion to 

ground-water resources was greatest at stations where a 

relatively large proportion of streamflow currently is diverted 

for irrigation and the water is conveyed and applied to fields 

that are downstream or outside of the drainage area of the 

station. For example, Wolf Creek below the diversion and the 

Chewuch River at Winthrop had the largest increases in median 

annual streamflow (50 percent exceedence), 10 and 7 percent 

respectively, under alternative 4. Streamflow increased under 

alternative 4 at both these stations because, under the baseline 

alternative, surface water was diverted and conveyed 

downstream of these stations. Conversion to ground-water 

resources had the greatest relative effect on streamflow during 

low flow years: the 90-percent exceedence value for annual 

streamflow increased 17 percent in Wolf Creek below the 

diversion and 14 percent in the Chewuch River at Winthrop. 

Conversion to ground-water resources also increased annual 

streamflow in the Methow River near Pateros. The increase 

was a result of using ground-water storage, although the 

increase was at most only 6 percent for annual streamflow 

exceeded 90 percent of the time.

The increase in streamflow from forest-cover reduction 

(alternative 5) was even greater at stations downstream of areas 

where forest cover was reduced than under alternative 4, with a 

50-percent increase in median annual streamflow in Andrews 

Creek and a 13-percent increase in median annual streamflow 

in the Twisp River near Twisp. The increase in streamflow is a 

result of a decrease in interception and sublimation of snow 

from trees. As with alternative 4, the largest increase in 

response to forest-cover reduction was during low-flow years. 

The 90-percent exceedence value for annual streamflow 

increased 91 percent in Andrews Creek and 17 percent in the 

Twisp River near Twisp. Annual streamflow also increased in 

wet years: the 10-percent exceedence value for annual 

streamflow increased by 36 percent in Andrews Creek and 14 

percent in the Twisp River near Twisp. Peak runoff is likely to 

be higher and earlier if forest cover is removed than under 

current conditions (fig. 2). Streamflow for the Twisp River 

above Newby Creek had the same increases as the Twisp River 

near Twisp. Streamflow in the Chewuch River above Cub 

Creek and at Winthrop had increases like Andrews Creek but 

of smaller percentages of streamflow. 

There was no more than a 4-percent difference between 

alternatives 2 or 3 and the baseline alternative in the 10th, 50th, 

and 90th percentiles of annual streamflow at the 12 streamgaging stations. Annual streamflow under alternative 6 was 

higher at stations downstream of surface-water diversion than 

streamflow under the baseline alternative.
Table 2. 90-, 50-, and 10-percent exceedence values for simulated annual mean streamflow for water years 1960 to 2001 under six water-management 

alternatives, and percent difference from baseline alternative

[ft3/s, cubic feet per second; –, difference from baseline alternative is less than 1 percent]

Streamflow-gaging station and No.

Baseline

(alternative 1) Alternative 2 Alternative 3 Alternative 4 Alternative 5 Unregulated (alternative 6)

ft3/s ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

90-percent exceedence

Lost River near Mazama (12447370) 139 139 – 139 – 139 – 139 – 139 –

Twisp River above Newby Creek (12448990) 165 165 – 165 – 165 – 192 17 165 –

Twisp River near Twisp (12448998) 160 163 2 159 – 170 6 187 17 170 6

Methow River above Goat Creek (12447383) 369 369 – 370 – 372 1 369 – 370 --

Methow River at Winthrop (12448500) 582 591 2 583 0 617 6 621 7 609 5

Methow River at Twisp (12449500) 753 765 1 755 0 809 7 831 10 755 0

Early Winters Creek near Mazama 

(12447382)

101 104 3 100 -1 107 6 101 – 104 3

Methow River near Pateros (12449950) 832 832 – 839 1 879 6 909 9 826 -1

Wolf Creek below diversion near Winthrop 

(12447387)

18 18 – 17 – 21 17 18 – 21 17

Andrews Creek (12447390) 15 15 – 15 – 15 – 29 91 15 –

Chewuch River above Cub Creek (12447600) 132 133 – 130 -2 138 5 174 31 139 5

Chewuch River at Winthrop (12448000) 146 153 4 147 1 167 14 188 28 162 11

50-percent exceedence

Lost River near Mazama (12447370) 255 255 – 255 – 255 – 255 – 255 –

Twisp River above Newby Creek (12448990) 283 283 – 283 – 283 – 319 13 283 –

Twisp River near Twisp (12448998) 284 286 1 283 – 294 3 320 13 294 4

Methow River above Goat Creek (12447383) 657 657 – 657 – 660 0 657 – 658 0

Methow River at Winthrop (12448500) 1,143 1,153 1 1,145 0 1,181 3 1,177 3 1,174 3

Methow River at Twisp (12449500) 1,457 1,468 1 1,459 0 1,515 4 1,529 5 1,476 1

Early Winters Creek near Mazama 

(12447382)

166 169 2 165 -1 172 4 166 – 168 1

Methow River near Pateros (12449950) 1,609 1,609 – 1,616 0 1,659 3 1,681 4 1,620 1

Wolf Creek below diversion near Winthrop 

(12447387)

35 35 – 34 -4 38 10 35 – 38 10

Andrews Creek (12447390) 29 29 – 29 – 29 – 44 50 29 –

Chewuch River above Cub Creek (12447600) 333 333 – 329 -1 342 3 367 10 342 3

Chewuch River at Winthrop (12448000) 366 372 2 366 – 390 7 405 11 384 5

10-percent exceedence

Lost River near Mazama (12447370) 335 335 – 335 – 335 – 335 – 335 –

Twisp River above Newby Creek (12448990) 389 389 – 389 – 389 – 434 12 389 –

Twisp River near Twisp (12448998) 397 399 1 396 – 406 2 451 14 407 3

Methow River above Goat Creek (12447383) 879 879 – 879 – 879 – 879 – 878 0

Methow River at Winthrop (12448500) 1,596 1,606 1 1,598 0 1,637 3 1,635 2 1,630 2

Methow River at Twisp (12449500) 2,041 2,052 1 2,043 0 2,102 3 2,126 4 2,069 1

Early Winters Creek near Mazama 

(12447382)

237 240 1 235 -1 243 3 237 – 238 1

Methow River near Pateros (12449950) 2,315 2,315 – 2,321 0 2,367 2 2,421 5 2,335 1

Wolf Creek below diversion near Winthrop 

(12447387)

48 48 – 47 -3 52 7 48 – 52 7

Andrews Creek (12447390) 47 47 – 47 – 47 – 63 36 47 –

Chewuch River above Cub Creek (12447600) 562 562 – 558 -1 570 1 605 8 571 2

Chewuch River at Winthrop (12448000) 613 619 1 613 – 636 4 654 7 631 3

6 Simulated Water-Management Alternatives Using the Modular Modeling System for the Methow River Basin, Washington
Table 3. 90- and 50-percent exceedence values for simulated annual mean streamflow for September water years 1960 to 2001 under six water-management 

alternatives, and percent difference from baseline alternative

[ft3/s, cubic feet per second; –, difference from baseline alternative is less than 1 percent; NA, not applicable]

Streamflow-gaging station and No.

Baseline

(alternative 1) Alternative 2 Alternative 3 Alternative 4 Alternative 5 Unregulated (alternative 6)

ft3/s ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

90-percent exceedence

Lost River near Mazama (12447370) 28 28 – 28 – 28 – 28 – 28 –

Twisp River above Newby Creek (12448990) 36 36 – 36 – 36 – 36 – 36 –

Twisp River near Twisp (12448998) 15 20 40 19 30 37 152 14 – 37 152

Methow River above Goat Creek (12447383) 89 89 – 90 2 96 8 89 – 94 6

Methow River at Winthrop (12448500) 107 125 17 133 25 180 69 107 – 173 62

Methow River at Twisp (12449500) 100 126 26 129 29 220 119 101 – 181 80

Early Winters Creek near Mazama 

(12447382)

9 16 77 9 – 22 144 9 – 18 97

Methow River near Pateros (12449950) 141 143 1 177 26 244 73 141 – 200 42

Wolf Creek below diversion near Winthrop 

(12447387)

0 0 – 0 – 6.3 NA 0 – 6.3 NA

Andrews Creek (12447390) 3.8 3.8 – 3.8 – 3.8 – 4.0 5 3.8 –

Chewuch River above Cub Creek (12447600) 36 38 6 33 -7 53 47 45 25 53 49

Chewuch River at Winthrop (12448000) 18 29 60 33 82 60 228 21 13 55 197

50-percent exceedence

Lost River near Mazama (12447370) 41 41 – 41 – 41 – 41 – 41 –

Twisp River above Newby Creek (12448990) 54 54 – 54 – 54 – 53 -3 54 –

Twisp River near Twisp (12448998) 34 40 17 38 13 50 48 34 – 56 64

Methow River above Goat Creek (12447383) 136 136 – 138 1 143 5 136 – 140 3

Methow River at Winthrop (12448500) 200 221 10 220 10 265 33 197 -1 275 38

Methow River at Twisp (12449500) 217 243 12 250 15 319 47 212 -2 307 42

Early Winters Creek near Mazama 

(12447382)

28 35 23 28 – 35 23 28 – 35 25

Methow River near Pateros (12449950) 281 283 1 323 15 389 38 276 -2 352 25

Wolf Creek below diversion near Winthrop 

(12447387)

2.9 2.9 – 1.3 -55 2.9 – 2.9 – 10.5 260

Andrews Creek (12447390) 5.4 5.4 – 5.4 – 5.4 – 5.2 -4 5.4 –

Chewuch River above Cub Creek (12447600) 78 80 3 76 -3 81 4 76 -2 96 23

Chewuch River at Winthrop (12448000) 56 71 27 70 24 95 69 54 -3 99 77

Simulations of Water-Management Alternatives 7
Table 4. 90- and 50-percent exceedence values for simulated monthly mean streamflow for January for water years 1960 to 2001 under six watermanagement alternatives, and percent difference from baseline alternative

[ft3/s, cubic feet per second; –, difference from baseline alternative is less than 1 percent]

Streamflow-gaging station and No.

Baseline

(alternative 1) Alternative 2 Alternative 3 Alternative 4 Alternative 5 Unregulated (alternative 6)

ft3/s ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

ft3/s

Percent 

difference

90-percent exceedence

Lost River near Mazama (12447370) 24 24 – 24 – 24 – 24 – 24 –

Twisp River above Newby Creek (12448990) 20 20 – 20 – 20 – 25 27 20 –

Twisp River near Twisp (12448998) 22 21 -5 22 – 21 -5 26 21 21 -5

Methow River above Goat Creek (12447383) 61 61 – 61 – 61 – 61 – 58 -6

Methow River at Winthrop (12448500) 121 119 -2 126 4 118 -3 123 2 109 -10

Methow River at Twisp (12449500) 150 143 -5 156 4 142 -5 153 2 95 -36

Early Winters Creek near Mazama 

(12447382)

8 8 – 8 – 8 – 8 – 3 -59

Methow River near Pateros (12449950) 175 166 -5 182 4 165 -6 177 1 129 -26

Wolf Creek below diversion near Winthrop 

(12447387)

3.3 3.3 – 3.3 – 3.3 – 3.3 – 3.3 –

Andrews Creek (12447390) 2.9 2.9 – 2.9 – 2.9 – 3.6 24 2.9 –

Chewuch River above Cub Creek (12447600) 38 37 -3 39 – 36 -6 41 7 37 -3

Chewuch River at Winthrop (12448000) 44 41 -6 47 9 40 -8 46 6 34 -21

50-percent exceedence

Lost River near Mazama (12447370) 35 35 – 35 – 35 – 35 – 35 –

Twisp River above Newby Creek (12448990) 47 47 – 47 – 47 – 53 13 47 –

Twisp River near Twisp (12448998) 57 56 – 57 – 56 – 64 13 56 –

Methow River above Goat Creek (12447383) 91 91 – 91 – 91 – 91 – 88 -3

Methow River at Winthrop (12448500) 231 229 -1 235 1 228 -1 235 2 223 -4

Methow River at Twisp (12449500) 328 322 -2 334 2 321 -2 336 2 275 -16

Early Winters Creek near Mazama 

(12447382)

18 18 – 18 – 18 – 18 – 14 -24

Methow River near Pateros (12449950) 404 395 -2 412 2 394 -3 414 2 369 -9

Wolf Creek below diversion near Winthrop 

(12447387)

5.2 5.2 – 5.2 – 5.2 – 5.2 – 5.2 –

Andrews Creek (12447390) 3.6 3.6 – 3.6 – 3.6 – 5.6 58 3.6 –

Chewuch River above Cub Creek (12447600) 58 57 -2 59 – 56 -3 62 7 57 -2

Chewuch River at Winthrop (12448000) 88 85 -3 91 4 84 -4 92 5 78 -11

8 Simulated Water-Management Alternatives Using the Modular Modeling System for the Methow River Basin, Washington
A. Twisp River near Twisp (USGS station 12448998)

1

10

100

1,000

Oct 1 Dec 1 Feb 1 Apr 1 Jun 1 Aug 1 Oct 1 Dec 1

DAILY MEAN DISCHARGE, IN CUBIC FEET PER SECOND

Baseline

ALTERNATIVE

2

3

4

5

6

DAILY MEAN DISCHARGE, IN CUBIC FEET PER SECOND

B. Chewuch River at Winthrop (USGS Station 1244800)

Oct 1 Dec 1 Feb 1 Apr 1 Jun 1 Aug 1 Oct 1 Dec 1

1

10

100

1,000

Baseline

ALTERNATIVE

2

3

4

5

6

Simulations of Water-Management Alternatives 9

Figure 2. 90-percent exceedence values for simulated daily streamflow at selected gaging stations for water years 

1960–2001 for six water-management alternatives in the Methow River Basin. 
10 Simulated Water-Management Alternatives Using the Modular Modeling System for the Methow River Basin, Washington

Effects of Water-Management Alternatives on

Low-Flow Conditions 

Baseline

ALTERNATIVE

2

3

4

5

6

C. Methow River near Pateros (USGS station 12449950)

Oct 1 Dec 1 Feb 1 Apr 1 Jun 1 Aug 1 Oct 1 Dec 1

DAILY MEAN DISCHARGE, IN CUBIC FEET PER SECOND

10,000

100

1,000

The results of water-management alternatives for lowflow conditions were summarized in terms of monthly mean 

flows for September (table 3) and January (table 4) for all 12 

stations and of daily streamflow that was exceeded in 90 percent 

of years in the Chewuch River near Winthrop, the Twisp River 

near Twisp, and the Methow River near Pateros (fig. 2). Lining 

irrigation canals (alternative 2) increased median September 

streamflow at most of the stations downstream of surface-water 

diversions (table 3, fig. 2). The increase in flows was a 

consequence of lower diversion rates, however it is not certain 

that surface-water diversions would be lower during September 

than under current conditions because seepage rates are already 

relatively low during September (Konrad and others, 2003). 

The largest increases in median September streamflow under 

alternative 2 were in the Chewuch River at Winthrop (27 

percent), Early Winters Creek (23 percent), and the Twisp River 

near Twisp (17 percent).

Lining canals, however, had little effect on September 

flows in the Methow River near Pateros because of the small 

effect of lower diversions relative to flow near the mouth of the 

river, combined with the lack of ground-water discharge from 

irrigation-canal seepage. Lining canals had the greatest relative 

effect on September streamflow during dry years. The 

90-percent exceedence value for September streamflow 

increased 77 percent in Early Winters Creek, 60 percent in the 

Chewuch River at Winthrop, and 40 percent in the Twisp River 

near Twisp.

Increasing diversions for additional aquifer recharge 

(alternative 3) increased median September streamflow at most 

of the stations downstream of surface-water diversions. The 

additional aquifer recharge increased ground-water discharge to 

rivers and streams. The increase in median September 

streamflow under alternative 3 was slightly more than the 

increase under alternative 2 (where there is no simulated 

seepage from irrigation canals) in the Methow River at Twisp 

and the Methow River near Pateros. With regard to dry years, 

the 90-percent exceedence value for September streamflow 

increased under alternative 3 at all stations downstream of 

Figure 2.—Continued.
Summary and Conclusions 11

surface-water diversions except Early Winter Creek, Chewuch 

River above Cub Creek, and Wolf Creek. Lost River, Andrews 

Creek, and Twisp River above Newby Creek are above all 

diversions, so streamflow was unaffected under alternative 3 at 

these stations. The increase ranged from 2 percent in the 

Methow River at Goat Creek to 82 percent for the Chewuch 

River at Winthrop. The increase in the 90-percent exceedence 

value for September streamflow was greater under alternative 

3 than alternative 2 for Methow River stations and the 

Chewuch River at Winthrop because recharge increased with 

diversions during early and mid-summer under alternative 3, 

but diversions in September were maintained at baseline 

levels.

Conversion to ground-water resources (alternative 4) 

generally increased September streamflow more than the other 

alternatives including natural streamflow (alternative 6) 

because some water applied to irrigate fields returned via 

ground-water flow to the rivers and streams. Median 

September streamflow increased by more than 23 to 69 percent 

at all stations below surface-water diversions except the 

Methow River above Goat Creek, where the increase was 5 

percent. The increase was greater during low-flow years than 

during high-flow years, with all stations downstream of 

surface-water diversions showing at least a 47-percent increase 

in the 90-percent exceedence value for September streamflow, 

except the Methow River above Goat Creek, where the 

increase was 8 percent.

Forest-cover reduction (alternative 5) decreased median 

September streamflow by 4 percent in Andrews Creek, which 

was likely a result of earlier snowmelt and runoff in the year. 

Forest-cover changes in the Chewuch River Basin increased 

low flows during dry years: the 90-percent exceedence value 

for September streamflow increased by 25 percent at the 

Chewuch River above Cub Creek. A similar effect was not 

simulated for the Twisp River. Because the increase in annual 

flows was larger than the increase in low flows, much of the 

increase in annual runoff production due to forest-cover 

reduction would occur as a result of increased high flows 

during late spring and early summer in both the Chewuch and 

Twisp Rivers.

Natural streamflow (alternative 6) in September was 

higher than the baseline alternative at the stations downstream 

of surface-water diversions. Thus, under the baseline 

alternative, irrigation-canal seepage was less than the amount 

of water diverted from rivers in September.

The effects of all of the water-management alternatives 

on January flows are small, with the exception of changes in 

forest cover (alternative 5) and natural streamflow (alternative 

6). Forest-cover conversion had the greatest effect at the 

stations located immediately downstream of the catchments 

with conversion (Twisp River above Newby and Andrews 

Creek), though it also affected streamflow at stations farther 

downstream. For example, the 90-percent exceedence value 

for January streamflow increased by 21 percent in the Twisp 

River near Twisp, 24 percent in Andrews Creek,7 percent in 

the Chewuch River above Cub Creek, and 6 percent in the 

Chewuch River at Winthrop. Natural streamflow (alternative 

6) was lower in January than the baseline alternative at stations 

downstream of irrigated lands because of the elimination of 

irrigation-canal seepage.

Summary and Conclusions

The MMS precipitation-runoff model constructed for the 

Methow River Basin was used to simulate streamflow for the 

period from water years 1960 through 2001 under six 

alternatives representing current conditions, various watermanagement options, and natural flows. Lining irrigation 

canals (alternative 2) increased flows in the Chewuch, Twisp, 

and the Methow (upstream and at Twisp) Rivers during 

September because of lower diversion rates, but not in the 

Methow River near Pateros. Increasing diversions for aquifer 

recharge (alternative 3) increased streamflow from September 

into January, but reduced streamflow earlier in the summer at 

stations downstream of diversions. Conversion of surfacewater diversions to ground-water wells (alternative 4) resulted 

in the largest increase in September streamflow of any 

alternative, but also marginally lower January flows (at most -

8 percent in the 90-percent exceedence value). Forest-cover 

reduction (alternative 5) produced large increases in 

streamflow during high-flow periods and earlier onset of high 

flows and small increases in January streamflows. September 

streamflows were largely unaffected by alternative 5. Natural 

streamflow (alternative 6) was higher in September and lower 

in January than the baseline alternative.

The alternatives indicate that these types of watermanagement actions could cause substantial changes in the 

seasonal distribution of streamflow in the Methow River 

Basin. Late-summer streamflow could be increased in many 

reaches by (listed in descending order of effect): conversion of 

surface-water diversions to ground-water wells; lining 

irrigation canals; or artificial recharge through increased 

diversions earlier in the year. Winter flows could be increased 

by forest-cover reduction and, during dry years, artificial 

recharge through increased diversions.
12 Simulated Water-Management Alternatives Using the Modular Modeling System for the Methow River Basin, Washington

References Cited

Ely, D.M., 2003, Precipitation-runoff simulations of current 

and natural streamflow conditions in the Methow River 

Basin, Washington: U.S. Geological Survey WaterResources Investigations Report 03-4246, 35 p.

Konrad, C.P., Drost, B.W., and Wagner, R.J., 2003, 

Hydrogeology of the unconsolidated sediments, water 

quality, and ground-water/surface-water exchanges in the 

Methow River Basin, Okanogan County, Washington: U.S. 

Geological Survey Water-Resources Investigations Report 

03-4244, 137 p.

Leavesley, G.H., Restrepo, P.J., Markstrom, S.L., Dixon, M., 

and Stannard, L.G., 1996, The modular modeling system 

(MMS): User’s manual: U.S. Geological Survey Open-File 

Report 96-1511, 200 p.

Mastin, M.C., and Vaccaro, J.J., 2002, Documentation of 

Precipitation–Runoff Modeling System modules for the 

Modular Modeling System modified for the Watershed and 

River Systems Management Program: U.S. Geological 

Survey Open-File Report 02-362, 5 p.

National Marine Fisheries Service, 2000a, Endangered Species 

Act—Section 7: Biological opinion for the Wolf Creek 

irrigation ditch, Okanogan National Forest: 

WSB-98-050, 43 p.

National Marine Fisheries Service, 2000b, Endangered Species 

Act—Section 7: Biological opinion for the Early Winters 

and Willis irrigation ditches, Okanogan National Forest: 

WSB-98-058, 40 p.

National Marine Fisheries Service, 2000c, Endangered Species 

Act—Section 7: Biological Opinion for the Skyline 

Irrigation Ditch, Okanogan National Forest, 

WSB-98-061, 51 p.

Viger, R.J., Markstrom, S.L., and Leavesly, G.H., 1998. The 

GIS Weasel – An interface for the treatment of spatial 

information used in watershed modeling and water resources 

management, in Proceedings of First Federal Interagency 

Hydrologic Modeling Conference, April 19-23, 1998: Las 

Vegas, Nevada, v. II, chapter 7, p. 73-80.
Manuscript approved for publication, February 12, 2004

Prepared by the Publishing Group, U.S. Geological Survey, 

Washington Water Science Center, Tacoma, Washington

USGS Publishing staff

Judith A. Wayenberg

Bill Gibbs

Linda S. Rogers

For more information concerning the research in this report, contact the 

Washington Water Science Center Director, 

U.S. Geological Survey, 1201 Pacific Avenue – Suite 600 

Tacoma, Washington 98402

http://wa.water.usgs.gov
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