Investigating Groundwater Variations Using Water Table Fluctuation Method: Case Study of Kawempe Division Kampala Uganda.

Abstract

Evaluating groundwater levels is part of sustainably managing the water supply and predicting the possibility of water shortages. Unreliable groundwater supply has far reaching consequences on the economy and the social fabric of the country. Therefore, monitoring fluctuations in groundwater levels and modelling different abstraction scenarios is very vital in development of groundwater resources. Investigation of the variations in groundwater levels of Kawempe division in Kampala city using the Water Table Fluctuation (WTF) method was the main objective of this research. The specific objectives were; characterisation the hydrogeological system of the study area, estimation of ground water recharge in Kawempe division, modelling the variations in ground water levels using the WTF method and assessment of the quality of groundwater for domestic use. The study was conducted under the framework of the T-GroUp research project, “Experimenting with practical transition groundwater management strategies for the urban poor in sub Saharan Africa”. Water quality analysis was done for all the existing monitoring wells under the T-GroUp project and a total of 39 samples were tested for the physical, chemical and biological parameters of water quality. Modelling the groundwater level fluctuations was specific to BH1 (50m), BH10 (48m) and BH5 (40m). Water level data was downloaded from the pressure transducers installed by T-GroUp in the different monitoring wells and manual water level measurements were done in order to calibrate the automatic measurements. The calibrated data was modelled using the Water Table Fluctuation method. The recharge to the aquifer was estimated using the linear regression relationship between the precipitation and the groundwater levels of the area.

From the linear regression analysis of the water level data from BH1 and the rainfall data, the average recharge to the aquifer was 2.2mm/month. The WTF method was able to model the water levels for boreholes 1, 5 and 10 relatively well. The correlation coefficients for the observed and modelled data were +0.98, +0.81, and +0.5 respectively. Findings of the water quality analysis carried out on 39 groundwater samples indicate that the water quality is not compliant with the Uganda Standards criteria for microbiological quality of water for drinking without treatment. 100% of the samples were compliant with the criteria for physical and chemical quality of potable water.