Statistical evaluation of the effects of irrigation on chemical quality of ground water and base flow in three river valleys in north-central Kansas

The chemical quality of groundwater and base flow in three alluvial valleys in Kansas has been changed as a result of 10 or more years of irrigation. Sulfate concentrations in groundwater in the Prairie Dog Creek valley statistically larger during 1981-82 than before irrigation began. Concentrations of calcium, bicarbonate, sulfate, and dissolved solids in groundwater in the Republican River valley and calcium, sodium plus potassium, sulfate, chloride, and dissolved solids in groundwater in the Smoky Hill River valley were significantly larger during 1981-82 than before irrigation began. No significant long-term changes in nitrate concentrations in groundwater were detected in any of the three valleys. Irrigation generally has not caused contamination of groundwater in the alluvium with organic pesticides for which National Primary drinking-water standards have been established. The pesticide 2, 4-D was detected, however, at concentrations of less than 2 micrograms per liter in water from several wells and surface-water sampling sites. (USGS)