USGS Washington Water Science Center
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WA315 - Ground-Water Study for Benton and Franklin Counties - Completed FY1987
Problem - The area surrounding the Tri-Cities of Kennewick, Pasco, and Richland, Washington has been progressively changing from rangeland and dryland farming to one of the major irrigated agriculture areas of the Northwest. With the introduction of new canal systems the dependence upon ground water for irrigation has decreased. There is new concern about ground water, but the question is no longer is there enough but rather, is there too much. There are rising water table and seepage and ponding problems throughout the region; the source of this water has been difficult to ascertain. Water quality is also a major problem--various agencies have documented the increase in nitrate and other contaminants in local ground waters but it is evident that the source and patterns of contaminant movement/migration can only be identified after the hydrology of the area is determined.
Approach - We will construct three-dimensional ground-water models of the four major problem areas in the basin. This will require mapping of the lithologic units that compromise the unconsolidated deposits and mass water-level measurements just prior to, during, and after irrigation. The models will simulate the movement of ground water in the unconsolidated deposits and the basalts and simulate the response of the system to man-induced stresses. Concurrent to this effort, a water-quality program will be initiated to allow the nature and magnitude of water-quality problems to be identified as well as the source(s) of these problems. Solute transport analysis for one or more chemical constituents could be utilized with the ground-water model should this prove to be a desirable tool.