Large parts of the lower Arkansas, Ninnescah, and Walnut River Basins in south-central Kansasan area that includes Wichita, the largest city in Kansasare experiencing rapid population growth and, consequently, increasing demands on surface- and ground-water resources in addition to agricultural irrigation in the area. The quantity and quality of water available in the lower Arkansas, Ninnescah, and Walnut River Basins in Butler, Cowley, Sedgwick, and Sumner Counties are crucial as population and water use continue to increase in the region. A steady-state model was constructed to simulate flow in the Arkansas River alluvial aquifer between Wichita and Arkansas City. Calibration was achieved using March 2001 measured water levels and streamflow gain using long-term (19402001) streamflow records. Average recharge about 5 inches per year; average aquifer hydraulic conductivity was about 500 feet per day; well pumpage (average of reported 19982001 use) was 56 cubic feet per second; and net flow from the alluvial aquifer to streams in the modeled area was computed by hydrograph separation to be 157 cubic feet per second. Nine hypothetical simulations were conducted with ground-water pumpage varying from zero to double authorized pumpage (206 cubic feet per second). Net remaining aquifer thickness declined for the largest simulated pumpage increases in comparison to 19982001 average pumping, as did flow from the aquifer to the Arkansas River. Simulated aquifer thickness decreases were more pronounced in areas where pumpage is currently (2004) greatest.