Contributions of Human Activities and Climatic Variability to Changes in River Rwizi Flows in Uganda, East Africa
| Autor: | Resty Nyesigire, Anne Nakagiri, Charles Onyutha |
|---|---|
| Jazyk: | angličtina |
| Rok vydání: | 2021 |
| Předmět: |
Hydrology
climate variability geography geography.geographical_feature_category rainfall–runoff Soil and Water Assessment Tool Science Drainage basin land-use or land cover (LULC) changes Wetland Land cover Oceanography Grassland hydrological modeling Evapotranspiration Streamflow River Rwizi catchment Environmental science Uganda SWAT Indian Ocean Dipole Waste Management and Disposal Earth-Surface Processes Water Science and Technology |
| Zdroj: | Hydrology, Vol 8, Iss 145, p 145 (2021) Hydrology Volume 8 Issue 4 |
| ISSN: | 2306-5338 |
| Popis: | 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. |
| Databáze: | OpenAIRE |
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