Land use dynamics are known to cause considerable modifications to the environment with broad and sometimes severe impacts on water quality and aquatic natural resources. In this study, the impacts of land use practices on water quality were estimated during the dry and wet seasons in Ruiru and Ndarugu Rivers, Kenya using remote sensing, geographic information systems and statistical techniques. A total of 12 sampling sites associated with three different land use types (forest, agriculture and urban) were selected. All water quality parameters were measured in situ in two dry seasons and two wet seasons and subjected to Kruskal Wallis statistical analyses. Significant variations were seen in water quality parameters between land use types. Higher temperatures were associated with urban dominated sub-basins, while dissolved oxygen was highest in forest sites. Turbidity was highest in agricultural sites and lowest in forested sites, but pH did not differ significantly across all sites. Seasonal impacts were recorded for most water quality parameters tested in all land use types, with agriculture and urban land use showing stronger impacts on water quality in the wet season than in the dry season. This study indicates that both agricultural and urban land use are key factors that affect water quality change. Land-use specific water conservation measures should be enhanced to limit both point and non-point sources of pollution in the study area.
Key words: Land use, water quality, seasons, Ruiru and Ndarugu Rivers, water conservation measures.
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