Sediment loading on inland lakes/wetlands: A case study of lake Nakuru, Kenya.

Abstract

Total suspended sediments and discharge were studied on the river mouths and sewage drain that. empty into Lake Nakuru, Kenya. Total suspended sediment loading into Lake Nakuru is a function of the concentration of total suspended solids and discharge at each mouth. The study was conducted at the mouths of rivers Njoro, Makalia, Nderit, Baharini springbrook and Sewage drain. In situ measurements of discharge were done, at each mouth, and 500ml water samples were taken and determination of total suspended solids done in the laboratory. Historical data was also used to provide typical discharge and total suspended solids values for each month. Loading was then calculated for each river mouth and the sewage drain. Although River Nderit had the highest concentration of total suspended solids, than rivers Njoro and Makalia, it delivered a lower amount of total suspended solids due to its lower discharge volume. River Njoro was found to deliver the most loads of total suspended solids (70%) despite having a lower concentration of total suspended solids followed by Makalia (21%), Nderit (4%), Sewage drain (4%) and Baharini (1%)in that order. Baharini is fed by a number of clean water springs emanating from the Lake Nakuru National Park which is a protected area. All the other rivers, especially Njoro and Makalia drain rural and urban watersheds with intensively cultivated easily eroded landscapes. This study shows that rivers emanating from outside protected areas under agriculture and urbanization contribute the highest to lake sediment loading and management of sedimentation of Lake Nakuru should focus mainly on soil management in the landscape.