Modeling the fluxes of nitrogen, phosphate and sediments in Linthipe catchment, Southern Lake Malawi Basin: Implications for catchment management

This study was carried out to investigate the fluxes of nutrients and sediments in Linthipe River catchment of Lake Malawi basin and the manner in which it is affected by anthropogenic activities and natural processes. Data on climate, nutrients, land use, soil and hydrology were collected to model fluxes of nutrients and sediments using the generalized watershed loading function (GWLF) model. The correlation coefficient (r2) derived from comparing the observed and simulated river discharge was 0.92. For sediments, total nitrogen and total phosphorus, comparison of predicted values with observed data were not statistically significant. The data was also used to model hypothetical management scenarios. A hypothetical 10% deforestation of the catchment may lead to an increase in annual sediment, nitrogen and phosphorus loads by 27.1, 15.7 and 2.9%, respectively. The GWLF approach overall appears to provide reasonably good estimates of mean annual sediment and nutrient loads. Results from this study suggest that anthropogenic activities (agriculture and deforestation) may be by far the largest source of sediment and nutrient loading especially during the rainy season.