Climatic impacts on water resources in a tropical catchment in Uganda and adaptation measures proposed by resident stakeholders

Abstract

The Ruhezamyenda catchment in Uganda includes a unique lake, Lake Bunyonyi, and is threatened by increasing social and environmental pressures. The COSERO hydrological model was used to assess the impact of climate change on future surface runoff and evapotranspiration in the Lake Bunyonyi catchment (381 km2). The model was forced with an ensemble of CMIP5 global climate model (GCM) simulations for the mid-term future (2041–2070) and for the far future (2071–2100), each with RCP4.5 and RCP8.5. In the Ruhezamyenda catchment, compared to 1971–2000, the median of all GCMs (for both RCPs) showed the mean monthly air temperature to increase by approximately 1.5 to 3.0 °C in the mid-term future and by roughly 2.0 to 4.5 °C in the far future. The mean annual precipitation is generally projected to increase, with future changes between − 25 and + 75% (RCP8.5). AET in the Lake Bunyonyi catchment was simulated to increase for the future by approximately + 8 mm/month in the median of all GCMs for RCP8.5 for the far future. The runoff for future periods showed much uncertainty, but with an overall increasing trend. A combination of no-regrets adaptation options in the five categories of: governance; communication and capacity development; water, soil, land management and livelihoods improvement; data management; and research, was identified and validated with stakeholders, who also identified additional adaptation actions based on the model results. This study contributes to improving scientific knowledge on the impacts of climate change on water resources in Uganda with the purpose to support adaptation.

The Effect of Papyrus Wetlands on Flow Regulation in a Tropical River Catchment

“…Although mean low flow magnitude may not significantly change with warming, extreme warming (i.e., at GWL4) is predicted to significantly reduce low flows and increase their variability. These findings on the broader impact of climate change are similar to other studies in Uganda, with indications of increased future flood magnitude [104][105][106][107][108] and occurrence of drought flows [104]. Thus, there is a need for the development of sustainable catchment flood and low flow management plans.…”

Observed and Future Precipitation and Evapotranspiration in Water Management Zones of Uganda: CMIP6 Projections

“…This is highly important since temperature, as a key determinant of potential evapotranspiration (PET) rate, is expected to sharply increase as a result of intensified global warming in the future [24]. In a study in Ruhezamyenda catchment in Uganda, Mehdi et al [25] quantified future water availability by projecting surface runoff derived from the COSERO hydrological model forced with CMIP5 simulations. The study projected an increase in actual runoff by about 8 mm/month towards the end of the century under RCP8.5.…”

On the application of rainfall projections from a convection-permitting climate model to lumped catchment models

“…The area has an equatorial climate with a bimodal rainfall pattern ("long rains" from March to May, and "short rains" from October to December). Numerous studies have evaluated impacts of climate change on river flows using lumped and semidistributed models in the LVB (Dessu and Melesse, 2013;Gabiri et al, 2020;Githui et al, 2009;Kingston and Taylor, 2010;Mehdi et al, 2021;Taye et al, 2011) and the wider East African region (Meresa and Gatachew, 2018;Siam and Eltahir, 2017;van Griensven et al, 2012). However, previous studies used downscaled GCM outputs which parameterize convection.…”