![]() The Theis recovery formula is expressed as: ![]() 522) utilizes measurements of the water level in the pumped well during the recovery period. The recovery method of determining the coefficient of transmissibility (Theis, 1935, p. Values for transmissibility were computed from the test data by the formulas developed by Theis, Thiem, and Cooper and Jacob. The coefficients of transmissibility and permeability of the alluvium and terrace deposits in the Republican River valley in Cloud County were determined by aquifer tests using three wells. The field coefficient of permeability multiplied by the thickness of the saturated water-bearing materials in feet, is equal to the coefficient of transmissibility.ĭeterminations of Transmissibility and Permeability The field coefficient (Pf) may be measured in terms of the number of gallons of water a day, at the prevailing temperature, conducted laterally through each mile of aquifer under investigation (measured at right angles to the direction of flow) for each foot of thickness of the aquifer, and for each foot per mile of hydraulic gradient. The coefficient of permeability (P) of an aquifer is the discharge per unit of area per unit of hydraulic gradient. Under water-table conditions the coefficient of storage (S) is virtually the same as the specific yield of the aquifer. The coefficient of storage (S) of an aquifer is the change in its stored volume of water per unit change in head per unit surface area of the aquifer. The coefficient of transmissibility (T) may be defined as the number of gallons of water, at the prevailing temperature, that will move in 1 day through a vertical strip of the aquifer 1 foot wide, having a height equal to the full saturated thickness of the aquifer, under a hydraulic gradient of 100 per cent or 1 foot per foot. Controlled aquifer tests in the field provide the data required to compute these coefficients. These factors are used in making estimates of the quantity of water available in an aquifer and for predicting water-level decline resulting from continued pumping. The two hydrologic properties of greatest significance are the coefficients of transmissibility (T) and storage (S). The quantity of water that a water-bearing formation will yield to wells depends upon the hydrologic properties of the material penetrated by the wells. Hydrologic Properties of Water-bearing Materials
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