Browsing by Author "Turyahabwe, Catherine"

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Assessment of impacts of land use changes on water resources of river Mpanga catchment
(Kyambogo University, 2019-11) Turyahabwe, Catherine
Mpanga Catchment has in recent decades been exposed to changes in land use/cover (LULC). This could have been due to intensive agricultural activities to sustain the needs of the increasing population. Transition in land use/cover tends to impact on the hydrology of a given catchment. This study assessed the impacts of land use changes on water resources of Mpanga catchment. The study was three-fold. Firstly, land use changes were identified and analysed. In the second step, the question of whether land use changes impacted on water resources was answered through hydrological modelling using Soil and Water Assessment Tool (SWAT). SWAT was automatically calibrated and validated using daily data from 2003 to 2013. Thirdly, the model was applied to conduct scenario analysis. Major land use/covers included cropland, forest, pasture, wetland, water body and settlement. Cultivated area increased by 31.79% while grassland and forests decreased by 31.79% and 11.38%, respectively. Hydrological model performance evaluation yielded Nash-Sutcliffe model efficiency (NSE) 0.86 and 0.77 during calibration and validation periods, respectively. Changes in the land uses between 2000 and 2014 increased stream flow ratios from 0.49 to 0.54, surface runoff from 0.26 to 0.33 and evapotranspiration ratios reduced from 0.49 to 0.44. Scenario analysis showed that the catchment was more influenced by the land use changes with respect to dry than wet conditions. Thus, control measures like agroforestry, deep tillage and banding should be adopted to minimize run off and facilitate infiltration and ground water recharge. Key words: Catchment, land use/cover, water resources, scenarios, hydrological modelling
Impacts of climate variability and changing land use/land cover on River Mpanga flows in Uganda, East Africa
(Environmental Challenges : Elsevier, 2021-12-09) Onyutha, Charles; Turyahabwe, Catherine; Kaweesa, Paul
We analyzed River Mpanga Catchment (RMC) land use/land cover (LULC) types based on Landsat images for 2000, 2008 and 2014. Soil and Water Assessment Tool (SWAT) was driven by daily meteorological data from 2000 to 2011 to investigate impacts of LULC changes on river flow variation. In 2000, 2008, and 2014, cropland covered 33.0%, 69.1%, and 72.2% of RMC area, respectively. However, the fractions of the RMC area covered by grassland in 2000, 2008, and 2014 were 39.4%, 12.5%, and 10.4%, respectively. The portion of RMC area covered by human settlement increased from 0.2% in 2000 to 0.5% by 2014. RMC was characterized by increasing trends in annual rainfall and river flows. SWAT calibration and validation at daily scale over the periods 2000–2005 and 2006–2011 yielded Nash Sutcliffe Efficiency of 0.77 and 0.75, respectively. Contribution from transitions in LULC types to river flow changes over the period 2000–2008 was 7.65%. Generally, 70.46% of the total river flow variation was contributed by climate variability in terms of changes in climatic conditions. However, 21.89% of the total river flow variance remained unexplained and this could be attributed to other factors not considered in this study including extra impacts of human activities such water abstractions for agricultural, industrial and domestic needs. These findings are important for planning predictive land and water resources management amidst impacts of climate variability and human activities on water resources.