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Morton County Geology

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Ground Water, continued

Discharge of Subsurface Water

The discharge of subsurface water has been divided by Meinzer (1923a, pp. 48-56) into vadose-water discharge (discharge of soil water not derived from the zone of saturation) and ground-water discharge (discharge of water from the zone of saturation).

Vadose-water Discharge

The discharge of soil water not derived from the zone of saturation is called vadose-water discharge and includes the discharge of water directly from the soil by evaporation and through growing plants and crops by transpiration. In semiarid regions the consumption of soil water by crops may be large and is of vital importance to agriculture. This consumption of soil water generally reduces the recharge somewhat, for the deficiency of soil moisture must first be replenished before recharge can take place.

Ground-water Discharge

Ground-water discharge is the discharge of water directly from the zone of saturation or from the capillary fringe, and may take place through evaporation and transpiration or as hydraulic discharge through springs, seeps, wells, or infiltration galleries.

Transpiration and evaporation--Water may be taken into the roots of plants directly from the zone of saturation or from the capillary fringe, and discharged from the plants by the process known as transpiration. The depths from which plants will lift the ground water varies with different plant species and different types of soil. The limit of lift by ordinary grasses and field crops is not more than a few feet; however, alfalfa and certain types of desert plants have been known to send their roots to depths of 60 or more feet to reach the water table (Meinzer, 1923, p. 82).

In Morton County, any significant discharge of water by evaporation and transpiration is limited to the areas in which the water table lies within 30 feet of the surface, although some discharge may take place through transpiration in some of the areas where the water table lies within 50 feet. As shown in plate 2, the shallow-water areas comprise a narrow belt along Cimarron River and small areas in the northeastern part of the county. Throughout the rest of the county the water table lies 50 to 250 feet below the surface so that little or no water is discharged in this way.

Considerable ground water probably is discharged by evaporation and transpiration along the Cimarron River valley, although the discharge must have been much greater in the past when the valley was grass covered. When the stream is dry the water table lies only a few inches beneath the sandy river channel, allowing direct evaporation to take place.

Springs and seeps--Ground water is discharged from the ground-water reservoir through springs and seeps along Cimarron River. The valley of Cimarron River cuts into the ground-water body, causing water to seep out along the stream's course. Several of these seeps may be found in the bluffs along the north side of the Cimarron valley and are especially prominent near Spring creek on the east side of Point Rock. The water comes out near the contact of the Ogallala formation and the Triassic (?) redbeds. At one time there were several springs along Cimarron River in Morton and Stevens counties. It is probably that the discharge of ground water through seeps and springs into Cimarron River, together with the consumption of water along this valley by transpiration and evaporation, account for most of the natural ground-water discharge in Morton County.

Wells--The above discussion treats of the natural discharge of ground water along the Cimarron valley, which seems to account for most of the discharge in the county. The rest of the ground water discharged within the county comes from wells, principally by pumping, but in small part by natural flow, and the recovery of ground water from wells is discussed below. Together the natural and artificial ground-water discharge seems to be small as compared with the total quantity of ground water stored in the county. Most of the ground water moves slowly out of the county (pl. 1) toward points of discharge farther east.

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Kansas Geological Survey, Morton County Geohydrology
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Web version Sept. 2004. Original publication date March 1942.