GEOLOGICAL AND STRUCTURAL INFLUENCE ON GROUNDWATER FLOW AND DISTRIBUTION IN KARINGA AREA, KENYA
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ABSTRACT

Groundwater has become one of the most reliable resources in the growth of Kenya’s economy. Water being also a basic need to man’s daily life, its demand increases every day of the year. The demand for water has increased in Nairobi County mainly due to population growth caused by rural-urban migration, industrialization as well as agricultural activities. Karinga/Kirenga Area is located in the North West of Nairobi water catchment, and is surrounded by a number of industries mainly tea factories that could also bring about the issues of groundwater pollution.

The aim of the study is to identify the effects of the faults and other geological factors in groundwater transmissivity and distribution in this area, whereby different methods were applied which include G.I.S that was used to come up with a geology and structural map as well as piezometric and transmissivity maps that were used to correlate the results and hence the effects. Data from the pre-existing borehole data was used in developing a hydrogeological understanding of the site. Software that was used includes ArcGIS (Arc map).

The geology of the area is mainly comprised of Tertiary volcanic layers of basalts, trachyte, phonolites and tuffs that are overlain by thick layers of clay soils. These soils retain water during the rainy seasons and hence recharging the aquifers. The area is also characterized by faulting and fractures that play a role in the influence of groundwater flow and distribution, where they may act as drainage channels, aquifers when filled with weathered material and also as barrier to flow of groundwater if filled with impermeable material that include clay, alluvial.

The outputs are analyzed in this report accordingly and interpreted for the benefit of exploitation and future planning of borehole drill site.