Effective Procedure for Determination of Aquifer Parameters from Late Time-Drawdown Data

Abstract

In this study an effective procedure is developed to evaluate the aquifer parameters from the late time-drawdown data observed both at pumping and observation wells in confined aquifers. For this aim, the time-drawdown data graph is considered by means of the MS Excel spreadsheets and later, its regression line and equation for the late time-drawdown data are obtained. The data after the minimum pumping duration criterion valid for both pumping and observation wells, in the case of flow toward a large-diameter well, by M. Çimen in 2006 and after the some early drawdown for observation wells, in the absence of the pumping well data, are considered in the calculations. It is observed that this late time-drawdown data yield the straight line in the logarithmic function. The transmissivity of the confined aquifer is then obtained from the slope value of the regression equation derived for late time data. The storage coefficient is also calculated with the Cooper–Jacob equation. In the Cooper–Jacob equation, the time intercepting zero drawdown is easily found from this regression equation. Finally, the application of the methodology has been tested for some data sets of the pumping and observation wells and the well storage effect has been taken, in some applications, into account.