Effects of Land-Use and Climate Change on Hydrological Processes in the River Gucha Catchment, Kenya

Abstract

The hydrological response of catchment areas to rainfall depends on the interplay between climatic, geological and land use variables. Understanding how land use activities and climatic factors influence stream flow will enable planners to formulate policies toward minimizing undesirable effects of future land-use changes on stream flow patterns. The objective of this study was to determine the relationship between rainfall amounts, temperature patterns, land use and land cover changes on stream flow regime in River Gucha Catchment. Land use and land cover, rainfall, temperature and stream flow annual data of the study area for the year 1976, 1993 and 2010 were computed. Regression scatter diagrams were computed and coefficient of determination R2 determined using data on total annual rainfall, average annual temperatures, and area percentages of land use and land cover types against total annual stream flow from 1976-2010. Total stream flow versus land use and land cover showed a strong relationship with R2 of 0.8440. Correlation between rainfall and temperature with stream flow showed moderate (R2) of 0.4595 and 0.5564 respectively. The higher correlation of land use and land cover with total stream flow could be either due to expansion of agriculture and reduction of forem cover hence reducing evapotranspiration which cause soils to be wetter and therefore more responsive to rainfall, or lack of good land husbandry which reduces infiltrability of the soil surface. If all other variables like rainfall and temperature were held constant, a significant increase in stream flow was expected as a consequence of expansion of agriculture and reduction of forest cover. This could lead to increased soil erosion and flooding in the lower parts of the catchment. Control measures against increased runoff need to be applied, where agricultural land has to be given priority with emphasis on proper farming practices and planting trees suited to the area.