LEAST SQUARES ANALYSIS OF TEST PUMPING DATA OF UNCONFINED AQUIFERS

Abstract

A model has been develoved for the estimation of aquifer parameters of unconfined aquifer b #' Boulton's theory. The model is based upon minimisation of the sum of the squares of differences between the observed and computed drawdowns by non-linear optimisation techniques. The computation of draw-downs is carried out by numerical solution of infinite integral incorporated in Boulton's theory. The proposed model, apart from being more rigorous and objective than the conventional graphical, procedure, eliminates the rather restrictive assump-tion of S ,/ tending to infinity. Y; ~C The applicability of the proposed model to real life data has been demonstrated by analysisng the data of a test pumping carried out at BHANERA TANDA of district Saharanpur by GWTG(U.P. ). The parameters so estimated give a much better reproduction of drawdowns as compared to the graphical estimates. The same data set were also subsequently analysed by Neuman's theory which can account for the effects of partial penetration of well and vertical anisotropy. The analysis, carried out by a model developed earlier at the School of Hydrology yielded regular aquifer parameters (S Sy and T) and the estimates of vertical anisotropy and saturated thickness of aquifer. The parameters vary significantly from the earlier estimates by Boulton's theory - emphasising the desirability of accounting. for the effects of partial penetration of well and vertical anisotropy in the analysis of test pumvving data.