Determining the effect of land use change on streamflow using soil water assessment tool (SWAT) Model

Citation:
Obiero JPO, Hassan. MA. Determining the effect of land use change on streamflow using soil water assessment tool (SWAT) Model. Pula/Sardinia/Italy: CRS4 Research Centre, Italy; 2015.

Abstract

Changes in land use influence catchment water resource availability. The purpose of this study was to assess the effect of land use change on streamflow for Naro Moru river catchment, Kenya. Satellite images was obtained for the years 1984 and 2010 and processed to derive land use classes. Land use data was obtained directly for the year 2000 from Kenya Soil Survey, Nairobi, Kenya. The Soil Water Assessment Tool (SWAT) model was used to predict streamflow during the period 1992 to 2000 under different land use practices based on the years 1984, 2000 and 2010. Other input model parameters were kept constant while varying the land use during flow simulation. Between the years 1984 and 2000, the area under natural forest cover increased by 14% while that under agriculture reduced by 21%. The area under grassland during this period was negligible at less than 1%. The simulated average daily streamflow in month decreased by 40% in the period 1984 to 2000. This decrease was attributed to increase in forest cover. During the period 2000 to 2010, there was a further decrease in simulated average daily streamflow in month by 14% attributed to further increase in forest cover which may have increased soil infiltration thereby reducing surface flow. There was an increase in land area under agriculture during this period, however relatively less compared to that under forest cover. Changes in other land use practices including bushland, bare soil and rock was negligible. Assessment of changes in catchment hydrologic response under changing land use is important in watershed water resources management.

Key words:Land use change, Streamflow simulation, Model calibration and validation.

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