Water is essential for all life is and occurs in various natural stores of the Earth’s hydrological cycle, including lakes, wetlands, rivers and aquifers. However, natural spatial and temporal variability in climate means that water of sufficient quantity and adequate quality is not always available for human needs (drinking, growing crops, generating power, supporting industry or maintaining ecosystem services, such as fisheries). Almost 900 million people lack safe and reliable water supplies. To meet the Millennium Development Goals we need to improve water availability. Future anticipated climate change and population increases will exacerbate this problem. Economic performance of countries is linked to their ability to cope with floods and droughts. Many countries, particularly in Africa have exploited little of their water storage potential restricting the development of hydropower production and irrigated agriculture. The World Commission on Dams (2000) concluded that large dams had made an important and significant contribution to human development by providing stable water resources and flood alleviation, but the social and environmental costs had, in too many cases, been unacceptable and often unnecessary. Large dams may be high risk under unstable political regimes and changing climates. In certain circumstances reservoir may release greenhouse gases. DFID supported the Dams and Development Project that provided guidance on how to implement the Commission’s recommendation, which included assessment of alternative options and improved stakeholder participation and environmental safeguards where dams are considered the best solution. Other organisations, such as the International Hydropower Association, the World Bank and IUCN also produced guidelines to make dams more sustainable, such as releasing sufficient water to maintain downstream ecosystems and their dependent livelihoods. Other water storage options include exploiting and enhancing natural storage, such as groundwater, managing catchments to maximise water yield, using virtual water, demand management, desalinsation and waste water reuse. Where dams provide the only option, networks of small dams may provide greater flexibility than single large dams. Based on a review focused on hydrological issues, we suggest 10 principles in developing storage that could contribute to a DFID policy. These are summarised as: 1. Undertake a full water resources assessment and implications for economic growth and poverty alleviation using best science and appropriate long-term data sets. 2. Undertake a full options assessment before selecting the most appropriate development solution. 3. Undertake a full life cycle analysis of the options including design, construction, operation, long term viability and decommissioning. 4. Assess flexibility and vulnerability to climatic variability and change including water availability and sedimentation using best science and appropriate data. 5. For schemes having trans-boundary nature implications, assess the political security and vulnerability issues and use benefits sharing 6. Calculate a full carbon balance for water storage options, especially hydropower, including a baseline survey of current conditions 7. Ensure that full safeguards are implemented including appropriate environmental flow releases and effective management to reduce health risks 8. Ensure that dams are multi-purpose, where possible combining irrigation, fisheries, public supply, power generation and flood management 9. Evaluate the relative merits of large single dams against a distributed networks of smaller dams to assess overall costs, flexibility in water management, exposure to climate change 10. Ensure that all proposed developments are part of an integrated catchment approach including developing appropriate laws and institutional capacity.
Acreman, MC, Harding, R, Sullivan, CA, Stratford, C, Farquharson, F, Rees, G, Houghton-Carr, H, Gale, I, Calow, R, MacDonald, A & Chilton, J 2009, Review of hydrological issues on water storage in international development, report to Centre for Ecology and Hydrology & British Geological Survey, Wallingford, UK.