# Presentation: 367778

## Evaporation (E) from Walker Lake, Nevada

- U.S. Geological Survey
- Walker River Basin Project
- Kip K. Allander:      Project Hydrologist
- Thomas J. Lopes:            Project Chief

- An Update for the Walker Mediation Group - April 11, 2006

## Overview

- Walker River Basin Study
- Objectives
- E on Walker Lake
- Measurement
- Updated value
- Historic value
- Other open water
- Water budget
- Summary

**Notes:**
The Walker River Basin study is a project by the USGS and is funded in cooperation from the BOR. The projects overall goal is to get a watershed-based understanding of the quantity and hydrology of water resources in the Walker River Basin. Funding for this project comes from the 2002 Farm bill.

## Walker River Basin Project

- In cooperation with Bureau of Reclamation
- Watershed-based understanding of quantity of water and hydrology of basin
- Funding from 2002 Farm Bill
- The project began during the winter of 2004

**Notes:**
The Walker River Basin study is a project by the USGS and is funded in cooperation from the BOR. The projects overall goal is to get a watershed-based understanding of the quantity and hydrology of water resources in the Walker River Basin. Funding for this project comes from the 2002 Farm bill.

## Objectives

- Quantify the volume of natural streamflow in the Basin; determine percentage of streamflow by hydrographic area
- Determine evapotranspiration (ET) losses from natural and agricultural vegetation and E from open water
- Develop an improved water budget for Walker Lake
- Develop capability to predict how changes in upstream water distribution practices will affect streamflow deliveries to Walker Lake

**Notes:**
The primary objective of the ET component of the Walker River Basin project is to estimate ET losses from natural and agricultural vegetation and from direct evaporation from open water surfaces. 

## Measurement of E on Walker Lake

- Installation of floating platform (November 2004)
- Installation of micrometeorologic equipment
- Use of Bowen-ratio energy budget method

## Bowen-ratio energy budget method

**=**

## Results – E from Walker Lake in water year (WY) 2005

- Results – E from Walker Lake in water year (WY) 2005

**Notes:**
Total of 8 ET stations: (1) lake
Natural vegetation: (2) salt cedar (3) willow (4) rabbitbrush (5) greasewood (6) salt grass
Ag vegetation: (7,8) alfalfa

## Measured E on Walker Lake

- Provisional data has not received final approval and is subject to change with further review

## E compared with Net Radiation

- Provisional data has not received final approval and is subject to change with further review

## Remote Automated Weather Station (RAWS) – Dead Camel Site

- Photo obtained from _[http://www.wrcc.dri.edu/wraws/pictures/ndea/200509/ndea.ST3.jpg ](http://www.wrcc.dri.edu/wraws/pictures/ndea/200509/ndea.ST3.jpg)_

## E compared with RAWS Radiation

- Provisional data has not received final approval and is subject to change with further review

## Relation between E and RAWS solar radiation

- Provisional data has not received final approval and is subject to change with further review

## Total E for WY 2005

**Total E, WY 2005 = 1,814 mm or 6.0 ft***

- *  Provisional data has not received final approval and is subject to change with further review

## Does this value represent long-term average?

- Provisional data has not received final approval and is subject to change with further review

## Does this value represent long-term average?

**Mean annual E from WY 1999 through WY 2005 is 1,720 mm or 5.6 ft***

- *  Provisional data has not received final approval and is subject to change with further review

## E from Walker Lake

- Preliminary estimate of E for WY 2005 was 6.0 ft*, up from previous estimates of 4.1 ft.
- Average surface area of Walker Lake in WY2005 was 31,840 acres.
- Estimated water volume evaporated from Walker Lake in WY2005 was 191,000 acre-ft*.
- ~ 50% increase over previous estimate.
- If relation between lake E and RAWS solar radiation data holds, may be able to estimate annual E back to 1999 (provisionally is about 5.6 ft/yr*).

- *  Provisional data has not received final approval and is subject to change with further review

## Why is new estimate of E so much greater than old estimate?

- Where does 4.1 ft/yr come from and how was it developed?

## Where is 4.1 ft/yr from?

- S. T. Harding (1965)

## Where is 4.1 ft/yr from?

## Where is 4.1 ft/yr from?

## How does Walker Lake E compare with E on other open water in NV?

- Ruby Lake in NE NV, WY 2000: 5.3 ft (Berger, D.L., Johnson, M.J., and Tumbusch, M.L., 2001, Estimates of ET from Ruby Lake NWR Area: USGS WRIR 01-4234, p. 16.).
- Peterson Reservoir in S Central NV, WY 1996 & 1997: 8.6 ft(Laczniak, R.J. and others, 1999, Estimates of GW discharge determined from measurements of ET, Ash Meadows Area: USGS WRIR 99-4079, p. 31.).

## What are implications to Walker Lake water budget?

- Precip + SW + GW – E = Δ Storage
- Large increase in estimate of E indicates that a greater amount of water is going into Walker Lake than previously estimated.

## Water Budget – 2005 WY

|  | Component | Lake area (acres) | (ft) | (acre-ft) |
| --- | --- | --- | --- | --- |
| Outflow | Evaporation | 31,840 | 6.0 | 191,000* |
| Inflow | Walker River |  |  | 95,000* |
|  | Precip | 31,840 | 0.46 | 15,000 |
|  | Ground water |  |  | 17,000 |
|  | Runoff |  |  | 3,000 |
|  | Total |  |  | 130,000* |
|  | Inflow-Outflow |  |  | -61,000* |
| Storage Change |  |  |  | -21,000* |
| Unaccounted Inflow |  |  |  | -40,000* |

- *  Provisional data has not received final approval and is subject to change with further review

## Water Budget

- Δ Storage:
- Recent work by Lopes and Smith (in progress) shows that storage values computed by Rush (1970) are very good.
- SW:
- SW from Walker River is gaged.
- SW from Wassuk streams are not gaged and have a variety of estimates.

## Water Budget

- Precip:
- Is small and is measured on Walker Lake and in Hawthorne. Agreement between the sites are good and therefore estimates of precip are good.
- GW:
-  GW = GW(north) + GW(south) + GW(Wassuk) + GW(Gillis).
- A very complicated component that isn’t well understood.

## Water Budget

- Least known components are SW from the Wassuk and GW inflow.

## Summary

- E is being measured on Walker Lake since November 2004.
- E in WY 2005 was 6.0 ft*.
- Annual E may be less and around 5.6 ft*.
- Previous estimate of E (4.1 ft/yr) did not include local runoff or GW in computation and therefore underestimated annual E.
- New estimate of E compares well with other NV lakes with modern measurements.

- *  Provisional data has not received final approval and is subject to change with further review

## Summary (continued)

- Walker Lake is receiving more water than previously recognized.
- Water budget components of Walker River inflow, direct precipitation, and storage components are good.
- Water budget components of SW inflow from Wassuk and overall GW inflows to Walker Lake are not well understood.

## Questions/Discussion

- _[http://](http://nevada.usgs.gov/walker/index.htm)__[nevada.usgs.gov](http://nevada.usgs.gov/walker/index.htm)__[/walker/](http://nevada.usgs.gov/walker/index.htm)_