Effects of Land Use, Land Cover Changes, and Sedimentation of Lake Nakuru Catchment on Lake Water Level Fluctuations

Abstract

Lake Nakuru and its catchment are important resources for Kenya. Since 2010, the lake has experienced a drastic increase in its water level. Identifying the fluctuation behaviour of the lake water level is important. Through a combination of remote sensing and GIS techniques, this study evaluated the water level fluctuations of the lake between 1990 to 2020.  Landsat 5, Landsat 7 and Landsat 8 images obtained from the USGS were used to generate land cover maps consisting of five land cover classes: forests, cropland, bare land, water and built-up area. A SWAT-2012 model was used to estimate sediment output from the lake’s catchment. The results show that the lake extent increased from 35.270 Km2 in 1990 to 51.140Km2 in 2020, with a projection of 52.62Km² in 2030. Forest cover reduced from 312.06Km² to 229.70Km², the built-up area increased from 49.60Km² to 214.51Km², cropland reduced from 1015.32Km² to 884.86Km² while bare land increased from 152.45Km² to 184.49Km² over the same period. The sediment yield rose from a maximum of 0.245Kg/Ha in 1990, dropped to 0.108Kg/Ha in 2000, rose again in 2010 to 0.220Kg/Ha and to 1.975Kg/Ha in 2020, with a prediction of 1.741Kg/Ha in 2030. The sediment yield had a positive relationship with the surface area of the lake, with a coefficient of determination of 0.9202. There was also a positive relationship between rainfall and the lake surface area, with a coefficient of determination of 0.2892. The results also showed a negative relationship between the lake surface area and forest cover, with a coefficient of determination of 0.280, and a positive relationship between the lake surface area and bare land, with a coefficient of determination of 0.650. The results underscore the need for comprehensive monitoring and management strategies to address the challenges posed by rising water levels, LULC changes and sedimentation within the lake catchment.