Abstract
This study employed Soil and Water Assessment Tool (SWAT) to analyze the impacts of climate variability and human activities on River Rwizi flows. Changes in land use and land cover (LULC) types from 1997 to 2019 were characterized using remotely sensed images retrieved from Landsat ETM/TM satellites. SWAT was calibrated and validated over the periods 2002–2008 and 2009–2013, respectively. Correlation between rainfall and river flow was analyzed. By keeping the optimal values of model parameters fixed while varying the LULC maps, differences in the modeled flows were taken to reflect the impacts of LULC changes on rainfall–runoff generation. Impacts due to human activities included contributions from changes in LULC types and the rates of water abstracted from the river as a percentage of the observed flow. Climate variability was considered in terms of changes in climatic variables such as rainfall and evapotranspiration, among others. Variability of rainfall was analyzed with respect to changes in large-scale ocean-atmosphere conditions. From 2000 to 2014, the portion of River Rwizi catchment area covered by cropland increased from 23.0% to 51.6%, grassland reduced from 63.3% to 37.8%, and wetland decreased from 8.1% to 4.7%. Nash–Sutcliffe Efficiency values for calibration and validation were 0.60 and 0.71, respectively. Contributions of human activities to monthly river flow changes varied from 2.3% to 23.5%. Impacts of human activities on the river flow were on average found to be larger during the dry (14.7%) than wet (5.8%) season. Using rainfall, 20.9% of the total river flow variance was explained. However, climate variability contributed 73% of the river flow changes. Rainfall was positively and negatively correlated with Indian Ocean Dipole (IOD) and Niño 3, respectively. The largest percentages of the total rainfall variance explained by IOD and Niño 3 were 12.7% and 9.8%, respectively. The magnitude of the correlation between rainfall and IOD decreased with increasing lag in time. These findings are relevant for developing River Rwizi catchment management plans.
Highlights
The hydrological cycle of a river basin comprises complex processes which may be impacted upon by climate variability and human activities [1,2,3,4]
Analysis of the influence of climate variability and human activities on river flow temporal variation is relevant for adaptive planning of water resources management
After land use and land cover (LULC) reclassification based on Soil and Water Assessment Tool (SWAT) database, six classes were obtained, namely, FRST—Forest, AGRL—Cropland, WATR—Water, URBN—Settlement, WETL— Wetland, and PAST—Pasture and Grasslands
Summary
The hydrological cycle of a river basin comprises complex processes which may be impacted upon by climate variability and human activities [1,2,3,4]. Analysis of the influence of climate variability and human activities on river flow temporal variation is relevant for adaptive planning of water resources management. The River Rwizi (which drains over 8000 km area and is used by communities in at least 12 districts of Uganda, East Africa) has been reported to be undergoing decline in its volume and subsequent drying of wetlands within the catchment [6,7,8]. Concern on the declining River Rwizi can be found reported on several occasions, for instance:
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
