The addition of water to the underground reservoir is called recharge and may be accomplished in several ways. Local precipitation is the principal source of recharge. Lesser amounts are contributed by influent seepage from streams and ponds and by subsurface inflow from adjacent areas.
Recharge and Disposition of Precipitation
The normal annual precipitation in Lyon County is approximately 34 inches or nearly 600 million gallons of water per square mile. Only a very small part of this reaches the zone of saturation. Of this precipitation, a part runs off directly, a part is discharged by evaporation and transpiration, and a part is added as recharge to the ground-water reservoir, later being discharged into streams or by transpiration and evaporation, or pumped from wells.
Runoff, including both direct runoff and ground-water discharge into streams, accounts for only a small part of the precipitation except after prolonged or intense rains. According to records of the Division of Water Resources of the Kansas State Board of Agriculture, the annual net runoff in the drainage area of Neosho River, at Iola, Kansas, the nearest gaging station below Lyon County, during the 17 years 1928 to 1945 inclusive averaged 5.66 inches. The runoff ranged from 0.74 inch in 1939 to 15.79 inches in 1941. If related to precipitation records at Emporia, which has a total precipitation approximating an average for the drainage area above Iola, for the same period of time, a runoff of approximately 15 percent of the precipitation is indicated. The percent of runoff for the Lyon County area only, probably averages between 10 and 20 percent.
The amount of water discharged by transpiration and evaporation depends on the temperature, humidity, vegetative covering, wind velocity, depth to the water table below land surface, and the length of time the processes of evaporation have access to the moisture. In Lyon County most of the water that does not run off into streams, averaging about 28 or 29 inches, is discharged by transpiration and evaporation.
Seepage from Streams and Ponds
Stream beds generally are cut below the soil zone; therefore, the seepage rate depends on the character and structure of the rock between the stream bed and the water table. In upland areas intermittent streams contribute to the recharge of the ground-water reservoir chiefly through open joints and fractures, or granular beds such as sandstone. In lowlands, streams contribute influent seepage to the unconsolidated alluvial sediments during times when stream levels are above the level of the adjacent water table. Ponds and lakes in the upland areas contribute small amounts of recharge to the unconsolidated surface deposits below the lake or pond but to some extent to the stratified rocks also.
Percolation from Outside the Area
The amount of ground-water recharge by subsurface percolation from adjacent areas is probably small and is approximately equal to the amount leaving the county in the same manner.
Kansas Geological Survey, Lyon County Geohydrology
Web version Sept. 2001. Original publication date March 1953.
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