Derivation of Equations for Ground Level, Water Surface Depth and Well Depth and Determination of Flow Directions of Shallow Aquifers

Abstract

Water is essential to maintain and sustain human life, animal and water therefore is important in that it is essential for growing food, for household water uses, as a critical input into industry, for tourism and cultural purposes, and for its role in sustaining the earth's ecosystem. The study is to determine the direction of ground water flow and also establish the parametric relationship of the measured topographical and derived data for the management of exploration and exploitation of groundwater in shallow aquifers of the study area. The methods involve the selection of ten wells within the University campus. The wells were used to obtain information on ground water topographical information. Data was acquired using a Global Positioning System (GPS) Garmin 76csx which is a satellite based equipment for position determination. The data acquired were wells coordinates and the elevation of the well location above mean seal level (amsl), while the water level values of wells as measured with the aid of an Electronic Water Level Indicator was used to measure the water surface depth from the ground surface.The relative positions of the wells were plotted using AutoCAD 2012 version and it was superimposed on the base map of the area. Suffer for window (version 8, topographical analysis software) was used to produce the contour of the Ground Level, Water surface Level and the Well Level water flow direction. Simple regression analysis was applied to the computed values according to their functional relationships, ground level-water surface level, ground level-well level and depth of well-depth of water surface. The derived equations from the measured and derived parameters were of the linear, power, exponential, logarithmic and 2^nd degree polynomial types. The coefficient of determination (R²) obtained from the various analysis ranges from 0.8485 to 0.9834. The coefficient of determination (R²) of 0.98 is close to unity which is the highest theoretically possible thus indicating that whenever the values of the independent variables or assigned variables are known exactly, the corresponding values of the dependent or derived variables can be evaluated with a high degree of accuracy. In all the relationships the 2^nd degree polynomial is consistent with higher values of the coefficient of determination. The results of the equations derived from this study indicate that there was an explanatory independent variable for ground level in predicting water surface level with a coefficient of determination r²=98% and also the results of well level prediction of r² of 94% - 95% and depth of well prediction of 85% - 97% for all the five different equations considered in the study. The equations established can be a useful and essential tool in the development of sound groundwater management plans, formulation of policies for exploration and exploitation of shallow aquifers.

Keywords: Coefficient of determination, Shallow Aquifer, 2^nd degree polynomial, Power equation, Exponential equation