Land use / cover change and pollution loading along River Namatala in Eastern Uganda

Abstract

River Namatala is a very important river for communities in Eastern Uganda as it harbors one of the biggest slums in Uganda (the Namatala slum). It is also a source of water for hundreds of people living in Bududa, Sironko, Mbale and the downstream areas of Eastern Uganda. The effects of land use/ cover changes on pollution loading along the river had not been assessed yet this is very important for water source protection. The objectives of this study were to: (i) to determine the land use/cover change of River Namatala micro catchment, (ii) to assess the quality of water at different locations along the river and (iii) to determine pollution loads from different land use/ cover and economic activities. In this regard, water samples were collected and analyzed from 8 sampling points during the wet and dry season. Physio-chemical parameters investigated included temperature, pH, Dissolved Oxygen, electrical conductivity (EC), Total Phosphorus (TP), Total Nitrogen (TN), Total Suspended Solids (TSS). Non-point source pollution contributions were determined using the Export Coefficients Model (ECM). Physio chemical parameters of water in River Namatala indicated that only COD values of the downstream (111.71-103.92 mg/L) were above the maximum permissible limits of NEMA, UNBS and WHO indicating that the river is polluted. The water quality parameters for point sources mid and downstream of the River Namatala for TP, TN, TSS and COD also were above the maximum permissible limits of NEMA and WHO. The study also revealed that cropland systems are contributing greatly to pollution loads in the River Namatala over the years. As the cropland use systems increased (through extensification) in the micro catchment, their contribution to pollution loading also increased. These results clearly indicate that croplands are the major contributing factor to the pollution loading in the river. Ecofriendly management practices such as conservation agriculture, mixed farming and agroforestry should be emphasized in the micro catchment to reduce run off and pollution of the river.