The Declining Ground‐Water Resources of Alluvial Valleys: A Case Study

The use of ground water increased rapidly in the Pawnee Valley, Kansas, during the last two decades, causing ground-water levels to decline and streamflow to diminish. Therefore, this study was undertaken to evaluate the impact of present and future ground-water withdrawals in the region. This report documents the depleting water resource of the area and calculates a preliminary hydrologic budget for the region. It also adapts, automatically calibrates, and applies a mathematical model that adequately simulates the operation of the hydrogeologic system for the purpose of evaluating several schemes for managing the ground-water resource. Two different estimates of regional ground-water recharge in the area indicated that the average natural recharge is approximately 0.5 inch per year. On the other hand, it was found that the amount of appropriated ground water in the area exceeded the natural recharge figure by about 11 times. Digital simulations of the aquifer system indicated that, even without any additional development or with very wet periods, water-level declines will continue indefinitely, since ground-water withdrawals in the Pawnee Valley are of such magnitude. One option put forth for consideration is to prolong the life of the ground-water resource through the application of all the following recommendations: concerted efforts to reduce water wasting and to increase efficiency of water use; implementation of not more than a 40 percent saturated-thickness depletion allowance for the next several years; imposition of a freeze on the number of irrigation wells to the present levels; and engagement in an artifical-recharge program.