PATTERN OF GROUNDWATER LEVEL DECLINE IN THE HIGH-PLAINS AQUIFER NEBRASKA

Ground-water level decline patterns in parts of Nebraska conform to th e circular island concept of Bredehoeft et al. (1982), which indicates how water is derived by wells developed in a circular island. If elon gated, the center of the island corresponds to a regional ground-water divide while the shoreline corresponds to a regional river. In both v ersions, ground-watertable elevation is a function of recharge and tra nsmissivity. A dynamic equilibrium exists such that the gradient of th e water table will convey all recharge to discharge areas. Withdrawals of ground water result initially in mining, with a new equilibrium at tained when pumping equals capture. During early development, capture is an important source of water in discharge areas, while mining is mo re significant in recharge areas. The pattern observed in many areas s hows the greatest ground-water level decline in the vicinity of ground -water divides and the steepest gradient near regional rivers. A simil ar pattern has been observed adjacent to the Arkansas River in south-c entral Kansas. Similar decline patterns can be modeled for a hypotheti cal ground-water basin. This is of major importance to water-resource managers because it dictates that management programs be applied to th e entire hydrologic system.