Irrigation Effects in Six Western States

Abstract

Results of field and laboratory studies performed over the past 20 years in Idaho, Montana, Nevada, Oregon, Utah, and Washington are reviewed. The studies varied in number, intensity, and breadth from state to state, but none was able to demonstrate conclusively the effects that agricultural irrigation had or was having on the quality of underlying groundwater, the effects that were sought both by these reviewers and by the original investigators. It is concluded that sampling projects to determine these effects must follow rigorous salt balance investigation schemata, that such projects are and will be expensive and time‐consuming, and that the state‐of‐the‐art techniques for gleaning true knowledge about waters within the earth are still emerging. Nonetheless, the review also leads to the inescapable conclusion that western U.S. groundwater quality has deteriorated in many places, and agricultural irrigation practices are strongly implicated as contributing sources of that decline.