Groundwater Recharge and DischargeThe addition of water to the underground reservoir is called recharge. The most important source of recharge in Johnson County is local precipitation; for shallow upland wells, local precipitation is the only source of recharge. Lesser amounts are contributed elsewhere by influent seepage from streams and ponds and by subsurface inflow from adjacent areas.
Recharge is seasonal in Johnson County. Generally, water levels in wells are lowered by natural drainage into streams or valley areas during the winter when the soil is frozen and precipitation is slight. During the spring months frost leaves the ground, precipitation is more abundant, temperatures are moderately cool, and transpiration and evaporation demands are low, resulting in considerable recharge. Seasonal effects are most noticeable in shallow water-table aquifers and least apparent in deeper artesian aquifers. Recharge occurs, however, anytime that the infiltration of precipitation exceeds soil-moisture requirements.
Groundwater moves downward through permeable rocks under the influence of gravity. The direction and rate of movement of the water may be affected by the character and structure of the rocks. Groundwater may discharge directly to a stream or to a spring or seep, or it may evaporate or be transpired by plants. Part of the ground water is discharged from wells, but except for the municipal, industrial, and irrigation pumpage in the Kansas River valley, the amount discharged by wells is small compared with that discharged by other means. Over a long period of time, approximate equilibrium generally exists between the amount of water that is added annually to groundwater storage and the amount that is discharged.
Kansas Geological Survey, Johnson County Geohydrology|
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Web version April 2002. Original publication date Dec. 1971.