Christian Siderius (United Kingdom) 1; Japhet Kashaigili (Tanzania) 2; Seshagiri Kolusu (United Kingdom) 3; Martin Todd (United Kingdom) 3; Joanna Pardoe (United Kingdom) 1; Declan Conway (United Kingdom) 4
1 - London School of Economics; 2 - Sokoine University of Agriculture; 3 - Sussex University; 4 - London School of Ecconomics
Planned major investments in irrigated agriculture and hydropower alongside climate change, could lead to potentially conflicting claims on water resources in Tanzania’s Rufiji basin. Close to the basin’s delta, the construction of one of the largest hydropower dams in Africa – the Rufiji Hydropower Project, or ‘Stiegler’s Gorge’ – has recently been approved. Promoted for its potential to supply a considerable part of Tanzania’s future electricity demand, but controversial because of its size and possible impact on the surrounding ecosystem, the influence of changing climate on the damÕs performance have yet to be assessed. Tanzania is situated in a climatic transition zone between east and southern Africa where both the magnitude and direction of future climate change are uncertain, complicating such assessments.
We test a novel, process-based method of constraining the latest climate projection ensemble for Africa, to explore the extent to which investment decisions in the Rufiji basin are impacted by climate change. Detailed impact assessments in developing countries are often hampered by lack of data and suitable analysis tools. We first evaluated the performance of a regionalized global crop-hydrology model (GHM) for assessing impacts at the scale of the Rufiji basin. Constrained climate change projections were then translated into relevant indicators of environmental flows, agricultural production and hydropower generation, framing the dam’s impact in a nexus context. Conclusions are embedded in a wider policy analysis.
With the regionalized GHM we show that under historic land use and climate conditions, both average and firm energy of future hydropower dams would be met. But ongoing rapid socio-economic development, leading to considerable changes in land use and resulting sharp increases in water demand from agriculture over the past 10 years, is already aggravating low-flow conditions in years of below rainfall. A better understanding of the role of elevation in the regional circulation pattern has helped constrain the number of plausible models, but not the overall uncertainty in projections. Initial findings suggest that low-flow years might increase further in intensity, likely to affect firm energy production rather than total.
A better understanding of the impact of changing patterns and magnitudes of weather variability on the dam’s performance will provide advice on a better future management, reducing the risk of failure. Although climate change is mentioned in the policies that guide agriculture and energy planning, concrete approaches to integrate climate change into actual developments, such as the Rufiji Hydropower Project, are still lacking in practice.