The sand thickness contour map was prepared by contouring points of equal sand thickness obtained from logs of wells and test holes and does not include silt and clay beds that were present at the well site. 3) and drawing contours through points of equal saturated thickness. The saturated thickness map was prepared by superimposing the water-table contour map (Pl. These properties of the sediments in the Arkansas Valley are shown by means of contours on Figures 21 to 23. Maximum well yields will be obtained generally where the saturated thickness, sand and gravel thickness, and transmissibility of the sediments are greatest. The yield of individual wells designed and developed for maximum yield is dependent on several geologic and hydrologic factors. In favorable areas, well yields of 2,500 gpm should be possible without excessive draw down. The yields of wells in the Arkansas Valley range from a few gallons per minute for small domestic and livestock wells to about 1,500 gpm for large municipal and industrial wells. Maximum utilization of the ground-water supply by this method, while feasible, might cause some water quality problems owing to movement of poor quality water from the Arkansas River and social and economic problems in regard to established water rights and agricultural practices. Much of the natural discharge of ground water in the Arkansas Valley could be salvaged by pumping strategically spaced wells to lower the water table below the level where evapotranspiration is effective and to intercept ground water that is now discharged to streams. No studies of this phenomenon have been made in the area, but random observations of soil moisture conditions and crop growth strongly suggest that the capillary fringe above the water table may contribute significantly to ground-water discharge. In much of the remaining area of the valley the water table is deeper but is in clayey silt or other fine-grained sediments underlying the surface, and the capillary rise of water in these sediments may bring a large volume of water close enough to the surface for evapotranspiration to become an effective means of discharge. 1) and discharge by evapotranspiration in this area is thought to exceed all other forms of natural discharge. In much of the Arkansas Valley adjacent to the principal streams the depth to water below the land surface is less than 10 feet (Pl. However, this figure does not take into account the concurrent natural discharge by seepage into streams and evapotranspiration, and if these losses from the ground-water reservoir could be salvaged for use, the effective recharge rate would be much greater. Experience has shown this recharge rate to be approximately correct for the Wichita well-field area of Harvey County (Stramel, 1956). 129) estimated the net average recharge in the Arkansas Valley to be about 20 percent of the annual precipitation or about 320 acre-feet per square mile per year in years of normal precipitation. Ultimately, the perennial field will depend on the average annual recharge. This volume of water does not represent the amount that could ultimately be withdrawn from the area, but rather a reserve that could be regulated to provide a perennial yield without progressive depletion of storage if other hydrologic factors affecting the aquifer are known. The quantity of ground water in storage within the sediments of the valley is about 6.1 million acre-feet if an assumed specific yield of 20 percent for the sediments is correct. The Arkansas River valley contains most of the usable ground water in the County, and most of the large ground-water supplies are obtained from this area. 2)., the sand and gravel beds containing most of the ground water are interconnected, and the complete sequence of silt, clay, sand, and gravel beds responds to long-term withdrawals of water as a singe aquifer. Although the deposits are stratified and lenticular (Pl. The area is underlain by alluvial sediments of Pliocene to Recent age that are the most productive water-bearing rocks in the County. The Arkansas Valley is characterized by its extreme flatness and the poorly developed surface drainage of the land flanking the Arkansas River. Where ground-water conditions are not uniform within an area, it has been divided into subareas.įigure 20-Map of Sedgwick County, Kansas, showing generalized ground-water areas and subareas.
There are four major ground-water areas: the Arkansas Valley, the Ninnescah Valley, the Wellington Upland, and the Ninnescah-Wellington Upland. Generalized ground-water areas and subareas within the County are shown on Figure 20 and are explained in the section of the report that follows. Ground Water, continued Ground-water Areas
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