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Impact of climate change on the terrestrial hydrology of a humid, equatorial catchment in Uganda

Mileham, L.J.; (2008) Impact of climate change on the terrestrial hydrology of a humid, equatorial catchment in Uganda. Doctoral thesis , UCL (University College London).

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Predicted future warming in equatorial Africa, accompanied by greater evaporation and frequent heavy precipitation events, is expected to have substantial but uncertain impacts on terrestrial hydrology. Current low-resolution (~250km) General Circulation Models (GCM) are of limited use to regional and local-scale decision support systems for climate change impacts. Quantitative analyses of the impact of climate change at the local scale requires the improved representation of land-surface characteristics that is afforded by dynamical downscaling of GCM output (HadCM3) using a higher resolution (<50 km) Regional Climate Model (RCM). In this study, precipitation simulated by the RCM, PRECIS (Providing Regional Climates for Impact Studies), is validated at regional (236 000 Km^2) and catchment scales (2 100km^2) and used to quantify the impacts of climate change on runoff and groundwater recharge in the River Mitano catchment of south-western Uganda using a semi-distributed soil moisture balance model (SMBM). PRECIS represents well the spatial and temporal distribution of precipitation but substantially overestimates its magnitude at regional and catchment scales. SMBMs explicitly account for changes in soil moisture and enable assessments of climate change on groundwater by partitioning effective precipitation into groundwater recharge and runoff. The semi-distributed SMBM, calibrated with daily station data a 15-year period (1965-1980), estimates a mean annual recharge of 104 mm•a^{-1} and mean annual surface runoff of 144 mm•a^{-1}. PRECIS predicts a 17% increase in catchment precipitation accompanied by increased precipitation intensity and a 53% increase in potential evapotranspiration by 2070-2100, based on A2 SRS emission scenarios. Under these future conditions, a 62% increase in mean annual recharge to 159 mm•a^{-1} is predicted. This doctoral thesis presents one of the first catchment-scale, hydrological models driven by a RCM in east Africa and one of the first quantitative assessment of the catchment-scale impacts of climate change on groundwater in the humid tropics.

Type: Thesis (Doctoral)
Title: Impact of climate change on the terrestrial hydrology of a humid, equatorial catchment in Uganda
Language: English
Additional information: Authorisation for digitisation not received. Abstract contains LATEX text. Please see thesis for rendered formulae and equations
UCL classification: UCL > Provost and Vice Provost Offices > UCL SLASH > Faculty of S&HS > Dept of Geography
URI: https://discovery.ucl.ac.uk/id/eprint/17227
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