The compensated drawdown was then used to determine the transmissivity and storativity of the aquifer and the degree of leakage of water from the confining layers. The drawdown was corrected by compensating for the effects of well interference, atmospheric pressure changes, and continuing recovery of the water level from a previous period of pumping. The test was performed by pumping a high-yield irrigation well at a constant rate and observing drawdown in a nearby observation well. The purpose of this report is to describe a pumping test in a sandstone of the Dakota aquifer in north-central Kansas (Figure 1) in August 1990. Therefore, little is known about the hydraulic properties of the aquifer in this part of the state. Although aquifer properties have been determined in a few areas of southwestern Kansas by means of pumping tests, there is no published record of any pumping test using observation wells in north-central Kansas. The Dakota aquifer is the second most geographically extensive aquifer system in Kansas. They can also be used to estimate the leakage from less permeable sediments which confine the aquifer. Pumping tests using observation wells provide invaluable information concerning the transmissivity and storage of an aquifer. Later drawdown was greater than expected probably due to decreasing aquifer transmissivity, caused by thinning of the sandstone away from the test site rather than an abrupt no-flow boundary. The average hydraulic conductivity and storativity of the sandstone and the leakance from the upper confining layer were calculated from this period of drawdown to be 570 gpd/sq.ft., 1.28x10 -4, and 3.8x10 -8 min -1, respectively.
The first 27 hours of the compensated drawdown-time curve was fitted to the Hantush-Jacob leaky artesian well function by a computer program using non-linear regression.
From water level fluctuations due to atmospheric pressure changes it was found that the barometric efficiency of the aquifer at this location is 95%, which implies its structure is very rigid. It was then adjusted to compensate for (1) atmospheric pressure fluctuations, (2) recovery of the water level from a previous period of pumping and (3) interference from another pumping well. The test was performed near Clifton in August 1990 using a high-yield irrigation well and an observation well drilled by the Kansas Geological Survey.ĭrawdown in the observation well was recorded during pumping of the irrigation well. Prior to this test little was known about the hydraulic properties of the Dakota aquifer in this area although it is an important source of water. The objective of this pumping test was to estimate the hydraulic conductivity and storativity of a sandstone and the leakance of its overlying mudstone confining layer in the Dakota aquifer at a site in Washington County, Kansas. Kansas Geological Survey, Open-file Report 91-1cĭetermination of aquifer properties of the Dakota aquifer in Washington County, Kansas from a pumping test by A. KGS-OFR 91-1c-Determination of aquifer properties of the Dakota aquifer in Washington County, Kansas from a pumping test
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