Separation of Regional and Residual Components by Finite Element Analysis – A New Approach for Analysis of Water Level Data

Abstract

Trend surfaces are generally used in the study of water level data to understanding the causes and effects of various trend surfaces. In the present paper the separation of regional and residual components of water level data is attempted using a method based on the Finite Element Analysis techniques. The residual is obtained by calculating the difference between the computed value of the trend surface at a point and the value of observed actual surface at that point. If the trend surface is thought to be regional or large scale component representing the total aquifer then the residual value can be considered the local ore small scale component representing the local variations in the aquifer. Removal of the regional trend has the effect of isolating and emphasizing local components represented by the residual values. Various techniques have been proposed and are widely in use for the separation of regional and the residual components, specially for separating the geophysical data. But the main drawback of all these techniques is that the regional component, so computed, has always the remnance of the residual components. Hence, the regional and residual components do not give a clear picture of the variations. In the present paper a new technique is suggested, in which the regional and residual components are computed using finite element analysis technique. This technique requires the water level data at only eight or twelve points representing the aquifer boundaries for the computation of regional component. A case history is presented wherein the data from the literature is analyzed using the technique proposed. The paper gives the details of the method and its advantages over the other methods which are supported by its application on the field data.