By Marios Sophocleous
Originally released in 1980 as Kansas Geological Survey Open-file Report 80-6. This is, in general, the original text as published. The information has not been updated.
The use of groundwater increased rapidly in the Pawnee Valley during the last two decades, causing groundwater levels to decline and streamflow to diminish. Because of the severity of groundwater declines, Groundwater Management District No. 5 declared a moratorium on new drilling in that area, pending public hearings on the matter. For this reason, the Kansas Geological Survey was asked to undertake a short-term investigation of the alluvial aquifer in the Pawnee Valley and to evaluate the impact of present and future groundwater withdrawals in the region.
The topics covered in this report include the availability of groundwater in the Pawnee Valley; documentation of the depleting water resource of the area; calculation of a preliminary hydrologic budget for the area with emphasis on the groundwater component of the budget; and the adaptation, calibration, and application of a mathematical model that adequately simulates the operation of the hydrogeologic system for the purpose of evaluating several schemes for managing the groundwater resource. Two different estimates of regional groundwater recharge in the area based on interpretation of streamflow records at the discharge end of the flow system and on the use of a modulated soil-moisture budget based on hydrometeorological and soil data, indicated that the average natural recharge is approximately 0.5 inches per year. On the other hand, it was found that the amount of appropriated groundwater in the area exceeded the natural recharge figure more than 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 groundwater withdrawals n the Pawnee Valley are of such magnitude. One option put forth for consideration is to prolong the life of the groundwater resource through the application of all the following recommendations: concerted efforts to reduce water wasting and to increase efficiency of water use; implementation of a 40% 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 1n an artificial-recharge program.
Kansas Geological Survey, Hydrogeology
Placed on web Aug. 1, 2012; originally published April 1980.
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