Examining the impact of climate and land use/cover changes on the water resources of River Rwizi catchment.

Abstract

River Rwizi catchment is vulnerable to changing climate and land use type/land cover changes because it relies heavily on rainfall. The main objective of the study was to examine the relationship between climate and land use/cover changes on river Rwizi streamflow. The data used in this study included monthly rainfall from the Tropical Rainfall Measurement Mission (TRMM) obtained from (https://mirador.gsfc.nasa.gov, accessed on 22nd February 2020), daily stream flow data for river Rwizi obtained from Uganda Ministry of Water and Environment and Land use and land cover data obtained from the Uganda National Forestry Authority (NFA). Spatial results of rainfall distribution indicated that the major rainfall patterns are generally oriented to the east and south east, with general maxima and strong rainfall gradients located along with the eastern and southern parts of the catchment. Mann Kendall trend test for the temporal variations indicate negative slopes in the normalized rainfall time series over the river Rwizi catchment though not significant. Spatio-temporal variations of land use/cover change revealed built-up area as the dominant land use activity in 2014 compared to the year 1996, bushland and wetland dominated most parts in 1996, whereas in 2014 most of the catchment parts were dominated by woodland and tropical high forests. Woodland, built-up areas and coniferous plantation areas increased significantly over the years while bush land, open water, and wet land areas decreased significantly. Regression results indicate a moderate positive statistically significant linear correlation between observed streamflow and rainfall for the period from 1996 to 2014. However, for the land use/ cover types, regression results showed a highly positive statistically significant linear relationship between open water and streamflow. A perfectly negative significant relationship was observed between built-up and stream flow.