ASSESSMENT OF EFFECTS OF LAND USE PRACTICES ON RIVER CATCHMENTS A CASE STUDY OF NYONGORES RIVER CATCHMENT

Abstract

Nyongores River is one of the major tributaries of Mara River and is located at the upper catchment of Mara River Basin. Over the years, rising population pressure and intensification of agriculture in the catchment has led to; reduced vegetation cover, poor land use management practices and increased soil erosion. The river is currently one of the major contributors of sediment and agrochemicals in the Mara River and Lake Victoria. The goal of the study was to assess the effects of land use and management practices on sediment concentrations in rivers. The specific objectives were: to map land use types, determine sediment delivery rates from land use types, determine sediment load from the main tributaries and assess the existing land use management practices for soil conservation. GIS mapping, water sampling and interviews of farmers from the catchment were carried out in the month of December 2009, January, February and March 2010. The study revealed that 43.2% of the catchment land use was under maize, 33.6% grasslands, 16.1% tea cover, 4.9% forest cover and 2.2% bare land. Land use under maize cultivation contributed the highest sediment concentration of 0.26g/l, forest (0.024g/l) and tea cultivation contributed the least concentration of 0.0351g/l. Among the tributaries of Nyongores River, Chepkositonik River delivered the highest sediment of 0.493 g/l followed by Kagawet with 0.324 g/l, then Ainopng'etunyek with 0.255 g/l while Kiprurugit was the least with 0.198g/l. The study estimated sediment flow into Nyongores River from the four tributaries at about 0.559Kg/s. The study established that the land use management practices for soil conservation within the catchment were; contour ploughing (24%), terraces (20%), agroforestry (17%), planting of trees (17%), intercropping (12%), mulching (6%), gabions (3%) and sand bags (1%). The study has demonstrated that there exists relationship between land use and sediment delivery rates in the tributaries. The study also shows that various land use management practices influences the rates of sediment concentrations in the rivers. Hence, recommends the adoption of integrated river catchment management for sustainable environment and agriculture.