Abstract
This study assesses the impacts of climate change on water resources over Mbarali River sub-catchment using high resolution climate simulations from the Coordinated Regional Climate Downscaling Experiment Regional Climate Models (CORDEX_RCMs). Daily rainfall, minimum and maximum temperatures for historical climate (1971-2000) and for the future climate projection (2011-2100) under two Representative Concentration Pathways RCP 8.5 and RCP 4.5 were used as input into the Soil and Water Assessment Tool (SWAT) hydrological model to simulate stream flows and water balance components for the Mbarali River sub-catchment. The impacts of climate change on hydrological conditions over Mbarali river catchment were assessed by comparing the mean values of stream flows and water balance components during the present (2011-2040), mid (2041-2070) and end (2071-2100) centuries with their respective mean values in the baseline (1971-2000) climate condition. The results of the study indicate that, in the future, under both RCP 4.5 and RCP 8.5 emission scenarios, the four main components that determine change in catchment water balance (rainfall, ground water recharge, evaporation and surface runoff) over Mbarali river catchment are projected to increase. While the stream flows are projected to decline in the future by 13.33% under RCP 4.5 and 13.67% under RCP 8.5 emission scenarios, it is important to note that simulated surface runoff under RCP8.5 emission scenario is higher than that which is obtained under the RCP4.5 emission scenario.
Highlights
According to the Intergovernmental Panel on Climate Change (IPCC) assessment reports, climate change is projected to substantially reduce water availability in the watershed (IPCC, 2007, 2013 and 2014)
HIRHAM5 forced by ICHEC and RACMO22T forced by ICHEC simulate rainfall amount of 269.41 mm in January and 222.9 mm in December respectively. These results indicate that, there are high uncertainties in simulating rainfall over Mbarali river sub catchment from individual model
The sources of uncertainties can be analysed and quantified when the same regional climate models (RCMs) are forced by different General Circulation Models (GCMs) and different RCMs are forced by the same GCM simulate rainfall over Mbarali river sub catchment differently
Summary
According to the Intergovernmental Panel on Climate Change (IPCC) assessment reports, climate change is projected to substantially reduce water availability in the watershed (IPCC, 2007, 2013 and 2014). Tanzania inclusive, by the year 2020, between 75 to 250 million of people are predicted to be exposed to increased water stress due to climate change (IPCC, 2007). The only strategy to reduce impacts of climate change on water resources is to invest in the development of adaptation strategies. The development of water resources adaptation strategies to overcome impacts of climate change on hydrological systems is challenging (Muerth et al, 2014; Piani et al, 2010). The challenges on one hand are attributed by a lack of scientific evidence which shows the projection of how the future climate change will impact the hydrological systems. There are high uncertainties associated with the projections
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