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University of Birmingham (1981)

The evaluation of groundwater resources in the crystalline basement of northern Nigeria

Acworth, R. Ian

Titre : The evaluation of groundwater resources in the crystalline basement of northern Nigeria

Auteur : Acworth, R. Ian

Université de soutenance : University of Birmingham.

Grade : Doctor of Philosophy (PhD) 1981

Résumé
A methodology of assessment is presented of the groundwater resources available in fracture zones, within the weathered mantle of gneiss, migmatite and granite. A model of weathering is developed, and values of porosity, hydraulic conductivity and electrical resistivity assigned to the different grades of weathering. A geophysical technique is developed, based upon a combination of electrical resistivity profiling and sounding, which allows a volume estimate of the various weathering grades to be made. A finite difference algorithm is used for this estimate which enables the apparent resistivity response of an inhomogeneous resistivity distribution to be calculated. An iterative approach is then adopted, adjusting the resistivity model until the calculated response agrees with the field data.
An analysis of recharge in a savanna climate is developed based upon the Monteith equation for predicting evapotranspiration, and upon a model of unsaturated zone soil moisture movement. The recharge function developed is included in a one dimensional catchment water balance model. The results from this model are compared with observed runoff and groundwater hydrographs.
The estimate of recharge is combined with the estimate of aquifer storage to produce an assessment of available groundwater. Optimal methods for the development of the resource are discussed. While developed in Northern Nigeria, the methodology of assessment is applicable to any similar geological and climatological environment.

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Page publiée le 6 octobre 2012, mise à jour le 19 octobre 2018