Browsing by Author "Arineitwe, Wenseslas"

Now showing 1 - 2 of 2

Investigating the sensitivity of tropical catchments to changes in precipitation and evapotranspiration under different climatic conditions
(Kyambogo University (Unpublished work), 2024-06) Arineitwe, Wenseslas
Globally, effective management of water resources is needed to provide sustainable water sources for human and ecosystem consumption. For the sustainability of water resources, careful planning is required for the management of catchments. One way to yield relevant information to support actionable policy is scenario analysis using hydrological modeling as a tool. This study investigated the sensitivity of Tropical catchments to changes in precipitation and evapotranspiration under different climatic conditions. The idea was to determine the extent to which flows would change given some incremental changes in rainfall and Potential evapotranspiration (PET). Six sub-catchments were considered and data from 1999-2016 (Malaba), 1980-2018 (Mpanga), 1990-2019 (Kabalega), 1980-2000 (Blue Nile), and 1980-2002 (El-diem & Ribb) were utilized. The AWBM and Hydrological Model focusing on Sub-Flow Variation (HMSV) were applied to data from each selected sub-catchment. Performance of AWBM in terms of Nash-Sutcliffe Efficiency (NSE) considering the full data period was 0.838 (Malaba), 0.686 (Kabalega), 0.676 (Mpanga), 0.812 (Blue Nile), 0.745 (El-Diem) and 0.56 (Ribb). Corresponding values for HMSV were 0.806 (Malaba), 0.748 (Kabalega), 0.620 (Mpanga), 0.806 (Blue Nile), 0.800 (El-Diem) and 0.520 (Ribb). Mean annual flows exhibited increasing trends in all sub-catchments except Kabalega. A positive trend ranged from 0.005-2.294m3/s/year in magnitude. A negative trend in the flow of Kabalega was at a rate of -0.015m3/s/year. All trends in flows were not significant since p-values were all above 0.05. The sensitivity of sub-catchments to increasing rainfall under constant PET ranged from 0.968m3/s/year (Malaba) to 2.700m3/s/year (Blue Nile) for every percentage increase in rainfall. The sensitivity of sub-catchments to increasing PET under constant rainfall ranged from -0.3603 m3/s/year (Kabalega) to -1.288 m3/s/year (Blue Nile) for every percentage increase in PET. Under simultaneous changes in rainfall totals and PET, the sensitivity of sub-catchments varied, ranging from 0.00821 m3/s/year (Malaba) to 1.2218 m3/s/year (Blue Nile) for every percentage increase in rainfall. Climate variability is characterized by both increases and decreases in flows depending on underlying factors. These results underscore the importance of careful planning of watershed management given factors like changes in climatic conditions that influence spatial and temporal variation in rainfall and PET.
Sensitivity of streamflow to changing rainfall and evapotranspiration in catchments across the Nile Basin
(MDPI, 2024-11-25) Onyutha, Charles; Ayugi, Brian Odhiambo; Sian, Kenny Thiam Choy Lim Kam; Babaousmail, Hassen; Arineitwe, Wenseslas; Akobo, Josephine Taata; Chelangat, Cyrus; Mubialiwo, Ambrose
This research focuses on the complex dynamics governing the sensitivity of streamflow to variations in rainfall and potential evapotranspiration (PET) within the Nile basin. By employing a hydrological model, our study examines the interrelationships between meteorological variables and hydrological responses across six catchments (Blue Nile, El Diem, Kabalega, Malaba, Mpanga, and Ribb) and explores the intricate balance between rainfall, PET, and streamflow. Nash Sutcliffe Efficiency (NSE) for calibration of the hydrological model ranged from 0.636 (Ribb) to 0.831 (El Diem). For validation, NSE ranged from 0.608 (Ribb) to 0.811 (Blue Nile). With rainfall kept constant while PET was increased by 5%, the streamflows of the Blue Nile, El Diem, Kabalega, Malaba, Mpanga, and Ribb decreased by 7.00, 5.08, 2.49, 4.10, 1.84, and 7.67%, respectively. With the original PET data unchanged, increasing rainfall of the Blue Nile, El Diem, Kabalega, Malaba, Mpanga, and Ribb by 5% led to an increase in streamflow by 9.02, 9.87, 5.38, 4.34, 6.58, and 8.32%, respectively. The research reveals that the rate at which a catchment losing water to the atmosphere (determined by PET) substantially influences its drying rate. Utilizing linear models, we demonstrate that the surplus rainfall available for increasing streamflow (represented by model intercepts) amplifies with higher rainfall intensities. This highlights the pivotal role of rainfall in shaping catchment water balance dynamics. Moreover, our study stresses the varied sensitivities of catchments within the basin to changes in PET and rainfall. Catchments with lower PET exhibit heightened responsiveness to increasing rainfall, accentuating the influence of evaporative demand on streamflow patterns. Conversely, regions with higher PET rates necessitate refined management strategies due to their increased sensitivity to changes in evaporative demand. Understanding the intricate interplay between rainfall, PET, and streamflow is paramount for developing adaptive strategies amidst climate variability. By examining these relationships, our research contributes essential knowledge for sustainable water resource management practices at both the catchment and regional scales, especially in regions susceptible to varying sensitivities of catchments to climatic conditions.