Modelling of Nonpoint Source Pollution in Akagera Transboundary River in Rwanda

In this paper, we to assess the level of pollution in the Akagera Transboundary River. The followings parameters namely NH4-N, NO3-N, PO4-P, Total Dissolved Solids (TDS), conductivity, pH, Temperature, and Turbidity were identified and quantified. Sampling was conducted a monthly basis from March 2008 to February 2009 at eleven sampling points on the Akagera River system. The landuse and land form characteristics were studied using satellite imagery and ground truthing. From this pollution reduction factors in terms of kg/ha.yr of pollution load were developed for each landuse type and used for developing the model. Rainfall and river flow data were obtained from gauging stations in and around the river. Water quality parameters particularly values of NH3-N changed from 0 to 2.36 mg/l, NO3-N from 1.8 mg/l to 314.4 mg/l and PO4-P from 0.02 mg/l to 19.3 mg/l. Field observations supported with computed export coefficient values showed that bare soils are the most influencing negative factor on water quality in the Akagera River.