Impact of climate change and development scenarios on flow patterns in the Okavango River

This paper lays the foundation for the use of scenario modelling as a tool for integrated water resource management in the Okavango River basin. The Pitman hydrological model is used to assess the impact of various development and climate change scenarios on downstream river flow. The simulated impact on modelled river discharge of increased water use for domestic use, livestock, and informal irrigation (proportional to expected population increase) is very limited. Implementation of all likely potential formal irrigation schemes mentioned in available reports is expected to decrease the annual flow by 2% and the minimum monthly flow by 5%. The maximum possible impact of irrigation on annual average flow is estimated as 8%, with a reduction of minimum monthly flow by 17%. Deforestation of all areas within a 1 km buffer around the rivers is estimated to increase the flow by 6%. However, construction of all potential hydropower reservoirs in the basin may change the monthly mean flow distribution dramatically, although under the assumed operational rules, the impact of the dams is only substantial during wet years. The simulated impacts of climate change are considerable larger that those of the development scenarios (with exception of the high development scenario of hydropower schemes) although the results are sensitive to the choice of GCM and the IPCC SRES greenhouse gas (GHG) emission scenarios. The annual mean water flow predictions for the period 2020-2050 averaged over scenarios from all the four GCMs used in this study are close to the present situation for both the A2 and B2 GHG scenarios. For the 2050-2080 and 2070-2099 periods the all-GCM mean shows a flow decrease of 20% (14%) and 26% (17%) respectively for the A2 (B2) GHG scenarios. However, the uncertainty in the magnitude of simulated future changes remains high. The simulated effect of climate change on minimum monthly flow is proportionally higher

Transboundary Water Management and the Climate Change Debate

Climate change has an impact on the ability of transboundary water management institutions to deliver on their respective mandates. The starting point for this book is that actors within transboundary water management institutions develop responses to the climate change debate, as distinct from the physical phenomenon of climate change. Actors respond to this debate broadly in three distinct ways – adapt, resist (as in avoiding the issue) and subvert (as in using the debate to fulfil their own agenda). The book charts approaches which have been taken over the past two decades to promote more effective water management institutions, covering issues of conflict, cooperation, power and law. A new framework for a better understanding of the interaction between transboundary water management institutional resilience and global change is developed through analysis of the way these institutions respond to the climate change debate. This framework is applied to six river case studies from Africa, Asia and the Middle East (Ganges-Brahmaputra, Jordan, Mekong, Niger, Nile, Orange-Senqu) from which learning conclusions and policy recommendations are developed