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Titre : GEOPHYSICAL AND GEOLOGICAL STUDY OF THE MANGA GROUNDWATER FORMATION SYSTEM – NYAMIRA COUNTY, KENYA

Auteur : WEKESA, MAKONJO ALICE

Université de soutenance : Kisii University

Grade : MASTER OF SCIENCE IN PHYSICS 2021

Résumé partiel
Groundwater is the water present beneath earth’s surface in soil spaces and in the fractures of the rock formation. Groundwater has a wide range of uses across the world. For Manga region found in Nyamira County in Kenya, groundwater is the key source of both domestic and agricultural use for the growing population in this region. The groundwater flow in the Manga region was found out to be controlled not only by one or two factors but also by the combined relationship of various factors that control the balance between recharge and discharge of groundwater that exist in the region. These factors include the rainfall and relief controls, geological controls and the geomorphological controls. The study was undertaken to understand the groundwater formation system and its groundwater quality. Around the world, the use of geophysical methods that include seismic, gravitational, electrical and electromagnetic has revealed that the nature of groundwater formation system can be identified when some of these methods are employed. The study involved the use of electrical resistivity method using SSR-MP-ATS terrameter. Vertical electrical soundings with schlumberger array was performed. The geo-electric models which are associated with groundwater modeling which is a way to represent a system in another form to investigate the response of the system under certain conditions, or to predict the behavior of the system in the future were obtained. These geo-electric models revealed the existence of an average of five subsurface layers with aquifers found in varied layers of the subsurface across the region. These sub- surface layers characterized by KHKQ, KH, KHK and AKHK type of curves. The aquifer protection capacity is “moderate protection” at Kiangoso, Kerora and Manga while being “poor” in Kerongo. The overburden protection capacity is “weak”. The groundwater quality and quantity data from three springs was obtained and used. The quality entailed the use of physical, chemical and biological parameters.

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