Effects of pumping municipal wells at Manhattan, Kansas, on streamflow in the Big Blue and Kansas Rivers, Northeast Kansas, 1992-94

A ground-water flow model was developed to simulate the effects of municipal well pumping on streamflow in the Big Blue and Kansas Rivers near Manhattan, Kansas, from 1992 through 1994.Model simulations of the effects of municipal well pumping on streamflow in the Big Blue and Kansas Rivers indicate that well pumping decreases streamflow. Simulations of May 1993 conditions indicate that well pumping decreased simulated streamflow in the Big Blue and Kansas Rivers by 5.28 ft3/s (cubic feet per second) for the month, of which 3.22 ft3/s were contributed from the streams (induced infiltration) and 2.06 ft3/s werecontributed from ground water that would have seeped to the streams if the wells had not been pumping (intercepted base flow). Of the total 414acre-feet pumped by municipal wells during May 1993, about 48 percent was from induced infiltration, and about 31 percent was from intercepted base flow. Simulations of October 16 through November 14, 1994, conditions indicate that well pumping decreased simulated streamflow in the Big Blue and Kansas Rivers by 6.67 ft3/s for the period, of which 6.51 ft3/s was from induced infiltration and 0.61 ft3/s was from intercepted base flow. Of the 506 acre-feet pumped by municipal wells during October 16 through November 14, 1994, about 76 percent was induced from infiltration, and about 2 percent was from intercepted base flow. Steady-state simulations of hypothetical conditions were conducted to develop relations among average and minimum ground- water altitudes in the Manhattan municipal well field and precipitation, pumping, and streamflow rates.