Browsing by Author "Johnston, R.H."
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Item Digital Model Of The Unconfined Aquifer In Central And Southeastern Delaware(Newark, DE: Delaware Geological Survey, University of Delaware, 1977-05) Johnston, R.H.The unconfined aquifer in central and southeastern Delaware occurs as a southward-thickening blanket of fine to coarse sand, and is recharged almost totally by precipitation and discharge is principally by seepage to streams, bays, and the ocean.Item Hydrology Of The Columbia (Pleistocene) Deposits Of Delaware: An Appraisal Of A Regional Water-Table Aquifer(Newark, DE: Delaware Geological Survey, University of Delaware, 1973-06) Johnston, R.H.The Columbia (Pleistocene) deposits of Delaware form a regional water-table aquifer, which supplies about half the ground water pumped in the State. The aquifer is composed principally of sands which occur as channel fillings in northern Delaware and as a broad sheet across central and southern Delaware. The saturated thickness of the aquifer ranges from a few feet in many parts of northern Delaware to more than 180 feet in southern Delaware. Throughout 1,500 square miles of central and southern Delaware (75 percent of the State's area), the saturated thickness ranges from 25 to 180 feet and the Columbia deposits compose all or nearly all of the water-table aquifer.Item Relation Of Ground Water To Surface Water In Four Small Basins Of The Delaware Coastal Plain(Newark, DE: Delaware Geological Survey, University of Delaware, 1976-02) Johnston, R.H.Beaverdam Branch, the Nanticoke River, Sowbridge Branch, and Stockley Branch drain small basins in the Delaware Coastal Plain that are characterized by similar climate, topography, geology, and land use. Withdrawals of ground water and surface water are very small, there is little urbanization, and other man-made effects, which include minor regulation on Sowbridge Branch and construction of drainage ditches in the Nanticoke basin, probably have had minimal effect on the natural hydrologic regimen. These are virtually natural-flow streams, which, because of similar basin characteristics, have nearly identical rates of evapotranspiration and runoff. During the 10-year period, 1959-68, precipitation averaged 40-42 inches annually, runoff averaged 16-17 inches annually, and evapotranspiration averaged 23-25 inches annually.