Determination of aquifer properties in northern Qatar for application to artificial recharge

The aquifer system in Qatar has been heavily exploited for agricultural purposes for over 20 years, leading to a decline in groundwater quality. In 1992 the Ministry of Municipal Affairs and Agriculture appointed Entec to carry out a two-year study into the feasibility of using artificial recharge to restore the aquifer system. This study involved field testing and modelling of the Pus and Umm Er Radhuma (UER) aquifers at four sites. Step, constant rate and tracer injection/reabstraction tests were carried out on each aquifer at each site. The step tests on boreholes in the UER indicated that non-Darcian behaviour occurred in the aquifer and extended a significant distance from the pumping boreholes. This was not observed during the step tests on boreholes in the Pus. A variety of techniques were used to analyse data from the constant rate tests and these provided a range of values for standard aquifer parameters as well as allowing a conceptual model of flow processes in the aquifer to be developed. This understanding was used in developing finite difference solute transport models to replicate the results from the tracer tests. Values of dispersivity of 0.5-5 m were derived for the Pus aquifer whilst values in the range 10-150 m were derived for the UER. Effective porosities were high at around 0.2 for both aquifers.