Effects of pumping municipal wells at Junction City, Kansas, on streamflow in the Republican River, Northeast Kansas, 1992-94

A digital ground-water flow model was developed to simulate steady-state and transient effects of municipal well pumping from an alluvial aquifer on streamflow in the Republican River near Junction City, Kansas. Seepage survey results indicated that streamflow loss in the vicinity of the municipal well field ranged from 1 to 5 ft3/s (cubic feet per second). Simulations of May 1993 conditions indicate that well pumping decreased simulated streamflow by an average of 3.03 ft3/s for the month, of which 2.45 ft3/s was induced infiltration from the stream and 0.58 ft3/s was intercepted baseflow. Of the total well pumpage for May 1993 (265 acre-feet), about 57 percent was from induced infiltration from the river, about 13 percent was from intercepted base flow, and about 30 percent was from decreased aquifer storage, outflow from the aquifer, evapotranspiration, and increased recharge and inflow to the aquifer. Simulations of November 1994 conditions indicate that well pumping decreased simulated streamflow by an average of 3.15 ft3/s for the month, of which 1.0 ft3/s was contributed from the stream and 2.15 ft3/s was contributed from intercepted base flow. Of the total well pumpage for November 1994 (264 acre-feet), about 22 percent was from induced infiltration from the river, about 48 percent was from intercepted base flow, and about 30 percent was from decreased aquifer storage, outflow from the aquifer, evapotranspiration, and increased recharge and inflow to the aquifer. Steady-state simulations of hypothetical conditions were conducted to develop graphs that show the relations among ground-water levels in the well field, pumping rate, and streamflow.