Analysis of the Effects of Land Use / Land Cover on River Flow Regime. A Case Study of Mkurumudzi River Sub - Catchment

Abstract

The population in Mkurumudzi catchment rely on river water for their livelihood. There are limited studies that focused on the effects of land use / land cover on river flows for sustainable water management. Land Use and Land Cover affect river flows in different ways. Physiographic characteristics of a watershed affect the hydrology. SWAT model is a reliable model used for estimating total runoff. SWAT modelling of watersheds is important in development and management of water resources. This study involved analysis of river flow discharges based on land use practices in the catchment resulting from human activities. The task included use of land use, soil properties and meteorological conditions in the area to obtain simulated flows. Landsat images for 1987, 1997 and 2017 were classified into four categories that is forest, shrubs, grassland and agricultural land and used in simulation of stream flows. Land use prediction for 2030 was made by assuming that there would be an increase in forest cover by 10 % and increase agricultural land thrice the area of 2016. SWAT calibration for the period 1982 – 1995 with three years warm up period and validated from 1996 – 2005. SWAT – CUP model was used for calibration and validation. Three indices were used for model validation and uncertainty used in this study with their respective performance factors were as follows; coefficient of determination (R2) (0.25 – 0.31); (b) Nash–Sutcliffe efficiency (NS) (0.74 – 0.89); and Percent Bias (PBIAS) (4.51 – 8.82). The results obtained indicated that there were effect of land use change that affected the flows for the periods that were examined. Future prediction showed that there would be changes of stream flow as compared with the current flows. Therefore, it is important that the area of forest cover be increased to maintain and land degradation interventions be adopted inorder to maintain environmental flows.