Groundwater Availability in the Lower Arkansas River Basin

Background

Large parts of the lower Arkansas and Walnut River basins in Kansas--an area which includes Wichita, the largest city in Kansas--are experiencing rapid population growth and consequently placing increased demands on surface and groundwater resources. The quantity and quality of water available in the lower Arkansas and Walnut River basins will become crucial if population and water use continue to increase as projected. The population and water use in the area are estimated to have increased by about 19 and 8 percent, respectively, between 1985 and 1995 (population was about 414,000 in 1985 and about 491,000 in 1995; water use was about 26.5 million gallons per year (Mgal/yr) in 1985 and about 28.7 Mgal/yr in 1995 (Joan Kenny, oral commun., November 15, 1999) and are projected to increase by another 13 and 21 percent, respectively, between 1995 and 2010 (Institute for Public Policy and Business Research, accessed October 20, 1999, Kansas Water Office, accessed October 20, 1999, and U.S. Census Bureau, accessed October 20, 1999). Much of the increase in population and water use has and is projected to occur in and near Wichita. This area accounted for, and is projected to continue to account for, about 60-65 percent of the population and about 65-70 percent of the water use in the basin. The Kansas Department of Agriculture, Division of Water Resources (DWR), which is charged with the beneficial allocation of the water resources in Kansas, is concerned about these increased and projected demands because of the limited water resources available in the lower Arkansas and Walnut River basins.

The concerns about water quantity and quality issues in the area that includes the lower Arkansas and Walnut River basins are not new. Important ongoing concerns include (Kansas Water Resources Board, 1960a and 1960b):

•   The Ninnescah and Arkansas Rivers are the only streams in the area likely to continue flowing during a severe drought (as occurred in 1952-56), and the streamflows are likely to be insufficient for all the usersó needs.

• Outside of the river valleys, there are no widespread, large-yielding sources of fresh groundwater in the area. Groundwater resources, while not adequate in most areas for large users such as public water suppliers, typically have been adequate during most climate conditions for the demands of domestic-supply wells. However, during a severe drought the groundwater resources will likely be inadequate in some parts of the area even for these small demands--as occurred during the 1952-56 drought. Shortages may also occur if water demands increase due to increases in population or in other sources of demand.

• Poor water quality limits the use of surface water in most streams in the area, especially during periods of low flow. Groundwater use is limited locally by the poor quality of the water. Sources of the poor-quality water (generally large chloride or sulfate content) include natural discharge of water from dissolution of salt or gypsum deposits in the underlying bedrock, surface-water transport from areas upstream and within the lower Arkansas and Walnut River basins, and past oilfield brine disposal practices.

• Interaction of the ground and surface water can strongly influence the quantity and quality of the water available for use. For example, increases in groundwater pumping may reduce the amount of surface water available for use or may induce poorer quality water to flow into an aquifer from either an overlying surface-water source or underlying rocks. Groundwater pits and other man-made areas where the water table has been exposed may act as both areas of recharge and of discharge, depending on the hydrologic and climatic conditions.

DWR has recognized that the currently available hydrologic information for this area is not sufficient for it to effectively apply existing water management and regulatory measures to protect and allocate the limited water resources of the lower Arkansas and Walnut River basins, especially during periods of drought. Information DWR needs includes better delineation of the aquifers in the area, improved estimates of groundwater recharge, a better understanding of the groundwater flow conditions in the area, the interaction of the ground and surface waters, and the effect of these hydrologic conditions on the availability and quality of the surface and groundwaters. Acquisition of this information will also enable DWR to meet the second of the 16 long-range objectives of the Kansas Water Plan endorsed by the Kansas Water Authority (July 8, 1999). The second Kansas Water Plan objective is ôBy 2010, over 95 percent of public water suppliers dependent upon surface water supplies and alluvial aquifers shall have a source of supply sufficient to meet their needs during a drought having a two percent chance of occurrence.Ý