Decreasing irrigation could affect shallow aquifer near Fallon

A report prepared by the U.S. Geological Survey shows that decreasing irrigation in Fallon could result in as much as a 10-foot drop in the water table.

Fallon farmers' water rights are being purchased to transfer into the Stillwater National Wildlife Refuge or Pyramid Lake.

Since 1902 water has been diverted from the Truckee River to irrigate the Newlands Project, which was designed to green the desert.

According to the report, construction of canals in the Fallon area to help irrigate farmland caused the water table to increase.

Before the irrigation, the water table varied between 5 and 25 feet below the surface. By 1992, with the installation of drains, ground-water levels ranged from 5 to 10 feet below the surface.

Purchase of the water rights from Fallon farmers will reduce irrigation in the area and with it the water table.

The shallow aquifer is used by many residents for domestic supply in areas outside Fallon's service area. Recent efforts to purchase agricultural water rights for use in wetland areas have caused concern by local residents on how decreasing irrigation could affect the water supply in the shallow aquifer.

Infiltration of water beneath irrigated fields accounts for about 60 percent of the salt added to the shallow aquifer. Decreasing irrigation while maintaining canals would likely improve the general water quality near Fallon, but not near Stillwater because the area is naturally saline.

The study also reports that removing canals from service could adversely affect the water quality of some wells whose source of water is seepage from canals.

The 70-page report, titled "Conceptual Evaluation of Ground-Water Flow and Simulated Effects of Changing Irrigation Practice on the Shallow Aquifer in the Fallon and Stillwater Areas, Churchill County, Nevada," by Nora B. Herrera, Ralph L. Seiler, and David E. Prudic, is U.S. Geological Survey Water Resources Investigations Report 99-4191. It is available for inspection at the U.S. Geological Survey offices in Carson City at 333 W. Nye Lane, Room 103.

The report may be purchased at cost from the U.S. Geological Survey, Branch of Information Services, Box 25286, Denver, CO 80225-0286. The prices are $4 per paper copy plus $5 per order for shipping and handling. Requests must specify report number WRIR 99-4191 and should include a check or money order payable to Department of the Interior - USGS.