Science to Sustain At-Risk Terminal Lakes Walker River Basin Project

Science to Sustain At-Risk Terminal Lakes

Walker River Basin Project

In Cooperation with the Bureau of Reclamation

Legislative Committee on Public Lands

March 24, 2006

Presentation Overview

•Problem•Objectives•Status of activities•Plans for upcoming year

Location of Walker

River Basin

West Walker R. West Walker R. near Hudsonnear Hudson

Walker R. near Walker R. near WabuskaWabuska

East Walker R. East Walker R. above above Strosnider Strosnider Ditch near Ditch near MasonMason

Walker R. at Walker R. at Lateral 2-A Lateral 2-A near Schurznear Schurz

Walker Lake Salinity

Walker River Streamflow

Objectives

• Quantify streamflow in the Walker Basin

• Estimate evapotranspiration from the lake and vegetation

• Develop an improved water budget for Walker Lake

• Develop the capability to predict how changes in upstream irrigation practices would affect flows to Walker Lake

Activities

• Surface-Water (SW) network• Ground-Water (GW) network• Evapotranspiration (ET) network• Mapping vegetation, elevation,

bathymetry• Preliminary streamflow analysis• Web Site

SW Network –new and upgraded

gages

New Stream Gages

Green Ck near Bridgeport Virginia Ck near Bridgeport

Real-Time Data on Walker Lake Gage

GW Network

• GW sites

Ground-Water/Surface-Water Sites

• Willows ET (above Weber)• Cow Camp Gage• Lateral 2-A Gage• Powerline Road• Walker River

at Mouth

GW/SW Site Locations

WillowsWillows

Above WeberAbove Weber

Lateral 2-ALateral 2-A

Powerline RoadPowerline Road

Walker River MouthWalker River Mouth

ET Networ

k

Results – ET from Walker Lake

Measured ET on Walker Lake

Water year 2005

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

ET

(m

m)

0

2

4

6

8

10

12

14

Net

Rad

iati

on

(W

/m^

2)

-50

0

50

100

150

200

250

300

ET Net Radiation

Provisional-—Subject to revision

ET compared with RAWS Radiation

Water year 2005

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

ET

(m

m)

0

2

4

6

8

10

12

14

So

lar

Rad

iati

on

(kW

-hr/

m2)

0

2

4

6

8

10

12

ET RAWS Solar Radiation

Provisional-—Subject to revision

ET vs RAWS radiation

y = 0.0548x2 + 0.5356x

R2 = 0.6533

0

2

4

6

8

10

12

14

0 2 4 6 8 10 12

Daily Solar Radiation (KW-hr/m^2)

Dai

ly E

T (

mm

)Provisional—Subject to revision

Total ET for 2005 Water Year

Water year 2005

Oct Nov Dec Jan Feb Mar Apr May Jun Jul Aug Sep Oct

ET

(m

m)

0

2

4

6

8

10

12

14

ET Estimated ET

Total 2005 Water Year ET = 1814 mm or 6.0 ft*

Provisional—Subject to revision

Results – ET from Walker Lake

• ET for WY2005 was 6.0 ft*, up from previous estimates of 4.1 ft.

• Area of Walker Lake in June 2005 was 32,000 acres.

• Volume evaporated from Walker Lake in 2005 was 192,000 acre-ft*.

• ~ 50% increase over previous estimates.• If relation between Lake ET and RAWS

solar radiation holds, may be able to estimate annual ET from 1999-2004.

* Provisional—Subject to revision

Salt Cedar site• Site underwent substantial defoliation due to

introduction of a biologic control agent: Salt Cedar Leaf Beetle (Diorhabda elongata)

• Changed characteristics and ET rate for large stand of Salt Cedar

Reduction of ET using Salt Grass

Date 2005

Mar May Jul Sep Nov

ET

(m

m)

0.0

0.5

1.0

1.5

2.0

2.5

3.0

3.5

Leaf

Cov

er (

%)

0

20

40

60

80

100

Salt CedarNormalized Salt GrassSalt Cedar Leaf Cover

203 mm*

57 mm*

This is a 22% reduction in ET*

Provisional—Subject to revision

Results – ET Summary

ET Station

Wal

ker

Lake

Will

ow

Alfa

lfa B

11

Alfa

lfa B

01

Sal

t Gra

ss

Sal

t Ced

ar

Rab

bit B

rush

Gre

asew

ood

ET

(in

ches

)

0

20

40

60

806.0 ft

3.5 ft 3.3 ft2.8 ft

0.7 ft 0.7 ft0.4 ft 0.4 ft

Provisional—Subject to revision

Mapping:

• Satellite imagery

• New imagery• Lidar• Bathymetry• Side-scan

sonar

Bathymetry

Imagery (infrared)

Scaling up of ET

• Create map of ET units

• Extrapolate ET data to ET units to estimate total ET in basin

Bathymetry

Provisional—Subject to revision

Maximum depth Maximum depth Spring 2005 was Spring 2005 was 82.8 ft82.8 ft

Tufa Mounds in

Walker Lake?

• Side-scan sonar• More GW

inflow?

Effect of ET on Streamflow

Streamflow—Wabuska vs Schurz

Web Site

http://nevada.usgs.gov/walker/

Click on Data link for interactive map page

Plans for This Year

• Continue to collect data – Data network is essentially in full operation

• Report on bathymetry of Walker Lake• Classify and map vegetation• Geophysics near Double Springs, river

mouth, and south end of lake• Install additional observation wells to

refine hydrologic understanding of GW system