||Hydrology of Two Interdunal Valleys in the Nebraska Sand Hills.
Drda, S. ;
||Nebraska Univ.-Lincoln. Inst. of Agriculture and Natural Resources.;Corvallis Environmental Research Lab., OR.
Water levels ;
Water table ;
Groundwater movement ;
Base flow ;
Groundwater recharge ;
Surface drainage ;
Surface-groundwater relationships ;
Hydraulic gradient ;
Spatial distribution ;
Seasonal variations ;
Sand Hills Region ;
Interdunal valleys ;
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||Two neighborhood interdunal valleys are compared within a study area of about 15 square miles in the Nebraska Sand Hills. The goal of this study is to identify the factors responsible for the hydrologic regime present in each valley, and to discern the reasons for the differences between the two valleys. Water levels in 39 piezometers positioned at different locations across both valleys, and at different depths were monitored for two-and-a-half years to determine groundwater flow paths, gradients, and seasonal variability. Surface waters in and near the site include the South Branch of the Middle Loup River, a drainage ditch, and Phipps lake--all believed to be in hydraulic connection with groundwater. Seasonal variations in surface- and ground-water levels exist, but are of different magnitude in different parts of the system. The region receives about 20 inches of precipitation annually, but recharge to groundwater is signficant due to rapid infiltration through the sandy material. Local variations in the configuration of the water table are complex, particularly in the vicinity of the ditch, and appear to be influenced by topography. The drainage ditch affects the shallow flow system in the wet valley. This ditch may be responsible for a reversal in flow direction on one side of the valley as well as a steep upward gradient under the valley floor. Evapotranspiration controls the spatial distribution of groundwater recharge and discharge.
||Sponsored by Corvallis Environmental Research Lab., OR.
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||PC A07/MF A02