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International Institute for Aerospace Survey, Netherlands (2001)

Geophysical study of the groundwater system south of Lake Naivasha Kenya

Pastor Michael, S

Titre : Geophysical study of the groundwater system south of Lake Naivasha Kenya

Auteur :  : Pastor Michael, S

Etablissement de soutenance : International Institute for Aerospace Survey, Netherlands

Grade : Master of Science (MSc) 2001

Lake Naivasha has been considered as a highly significant national fresh water resource in Kenya by several authors. Its water is not only being utilized for domestic water supply and recreation but also sustains important economic activities such as flower and vegetable growing, geothermal power generation, tourism and fishing. Different geophysical data sets, which include DC Schlumberger and TEM soundings, gravity and magnetics, were used in this study to establish the presence and extent of the groundwater system south of the lake in perspective of domestic and agricultural water supply. Other available information such as aerial photos, TM images and existing reports were also used in determining the geology and structures of the study area. The author used the available DC Schlumberger and TEM sounding and gravity data of KENGEN and magnetic data of ITC. These geophysical data were re-processed, re-interpreted and integrated with other existing information, resulting in a number of iso-resistivity maps, resistivity cross sections and a 3D presentation of the groundwater occurrence south of Lake Naivasha. The results indicate the presence of two aquifers on the basis of low resistivity value of 15-30 m at shallow and deeper levels. The shallow aquifer exists close to the lake stretching from Sulmac Farm towards Obsidian Ridge. It occurs generally at lake levels of 1880 m.a.s.l. with thickness ranging from 70-175 meters. Existing shallow boreholes correlate well with the geophysical results. A possible second deeper aquifer occurs southeast of the lake towards Mt. Longonot at around 1400 m.a.s.l. The real nature of this second aquifer must be established by drilling. It is recommended to refine the coverage of particularly the area east of the Sulmac Farm with additional TEM soundings to improve the detailing of both aquifers. Additional boreholes logging should be drilled to check the interpretation of both depth and extension of the aquifers. The boreholes should be placed in such a position that they can be used to establish general flow conditions between Lake Naivasha and the deeper geothermal zones around Olkaria

Sujets : Lake Naivasha, Kenya ; Olkaria, Kenya ; Mount Longonot, Kenya ; Aquifers ; Groundwater ;

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Page publiée le 29 décembre 2016, mise à jour le 18 octobre 2018