Description

Abstract: Rapid land cover and land use changes occurring in Kenya’s Rift Valley are altering the hydrologic response in the River Njoro watershed. This watershed is a critical contributor of runoff to Lake Nakuru National Park, an internationally recognized wetlands area. Three remote sensing images were classified to determine the land cover transitions that occurred over a 17-year period from the mid-1980’s through the mid-1990’s. The results served as the primary land cover data set for surface runoff simulation using a GIS-based hydrologic modeling system called the Automated Geospatial Watershed Assessment (AGWA) tool. AGWA was used to generate parameter input files for the Soil and Water Assessment Tool (SWAT). SWAT is a hydrologic model suitable for assessing land cover change impacts on hydrologic response. Results show that changes have resulted in corresponding increases in surface runoff and changes to the timing and intensity of runoff. Increases in surface runoff and changes to water yield show a high degree of spatial and temporal heterogeneity that are linked to land cover and land use changes. Modeling serves an important role in land management since the time, cost, and expertise required to install, monitor, and identify problems in the field using hydrological instrumentation can be prohibitive, while lessons learned in a modeling environment can be transferred to other similar environments.