SYNTHESIS OF DATA FROM STUDIES BY THE NATIONAL IRRIGATION WATER‐QUALITY PROGRAM¹

Abstract

From 1986 to 1993, the National Irrigation Water‐Quality Program (NIWQP) of the U.S. Department of the Interior studied whether contamination was induced by irrigation drainage in 26 areas of the Western United States. In 1992, a study to evaluate and synthesize data collected during these 26 investigations began. Selenium, boron, and molybdenum are the trace elements and DDT the pesticide most commonly found in surface water at concentrations exceeding chronic criteria for the protection of aquatic life. In six of the areas, the median selenium concentration exceeded the criterion. Aquatic‐life criteria have not been developed for uranium, but the median uranium concentration exceeded the proposed Maximum Contaminant Level for drinking water in seven areas. A principal components analysis indicates that severity of selenium contamination is not related to the severity of contamination by boron, molybdenum, and arsenic. Arsenic, boron, molybdenum, and selenium concentrations are nearly the same in both filtered and unfiltered samples, which indicates that contaminant concentrations in filtered samples can be directly compared with biological‐effects data developed using unfiltered samples. At a given site, selenium concentrations in surface water can change by an order of magnitude during the course of a year and from one year to another.

Irrigation Water Quality—A Contemporary Perspective

“…NIWQP data from the 26 areas under study suggested that degradation of groundwater quality due to irrigation is a common occurrence [11,36]. The study indicated that selenium was the most common contaminant, followed by arsenic, uranium and molybdenum [11,37]. This study also suggested regular co-occurrence of these contaminants.…”

Trace-element enrichment in streambed sediment and crayfish, Carson and Truckee rivers, Nevada and California, September 1992

“…2). Potential sources of these trace elements include lead and chromium from urban runoff (Driver and others, 1985) in the Fallen area, arsenic and selenium from irrigation drainage (Hoffman and others, 1990;Seller, 1996), and silver and mercury from the erosion of Comstock era mill tailings before Lahontan Reservoir was created in 1916 (Gustin and others, 1994;Hoffman, 1994).…”

Concentrations, loads, and yields of potentially toxic constituents in irrigation-drain systems, Newlands Project area, Carson Desert, Nevada, November 1994-October 1995

“…All samples collected from the TJ Drain system exceeded the proposed criterion. High concentrations of uranium have been shown to exist in many irrigated agricultural areas in the western United States (Seiler, 1996).…”