Variability and extremes in water resources in the Nile river basin

Climate variability represents a significant challenge for water resources management. Further changes in rainfall and river flows, caused by human-induced climate change, undermine traditional methods of water resource management. They increase the severity and frequency of floods and droughts, and increase water scarcity. This is causing major problems for people in the Nile river basin, from farmers in the Ethiopian highlands, the main source area, to those in Egypt who are almost wholly dependent upon water that originates from these highlands.

Water supplies from the Ethiopian highlands have been reliable for thousands of years. Complete dependence on natural rainfall and low-input farming methods are typical features of Ethiopian agriculture. The amount and temporal distribution of rainfall is the most important factor in national crop production levels, and changes caused by climate change represent a huge threat.

Rainfall in central Ethiopia provides over 50 per cent of the main Nile flows to Egypt. During the 1970s and 1980s, rainfall across much of the Ethiopian highlands declined. This contributed to the major famine of 1984-5 in Ethiopia. Low rainfall also meant that Egypt suffered a succession of low Nile flows. By 1988, Egypt was very close to a major water shortage. The government initiated a set of responses and anticipatory planning to cope with future drought conditions. This included:

• reduction in the annual releases from the Lake Nasser reservoir through more efficient regulation
• extension of the irrigation system’s winter closure period
• a reduction in the area under rice
• improving the Nile’s navigable channels to maintain levels and supply irrigation outtakes.

By the mid-1990s, however, rainfall levels had recovered. Within ten years, the short-term management challenge was completely reversed from a deficit to a surplus. Measures to deal with prolonged high flows and excess storage had to be considered. This has contributed to a major expansion programme of irrigated agriculture into the Western Desert and Sinai Peninsula. However, an increasing demand for water will reduce this flexibility in water management. Future changes in water supply, caused by climate change and non-climate factors, are likely to create further shortages.

Rainwater harvesting has recently been suggested as one response to protect against rainfall variability and climate change. This involves capturing and storing rainwater to provide households in drought-prone areas with water for agricultural and domestic uses during times of low rainfall (or intra-seasonal dry spells). In many parts of Ethiopia, it is often the variability of rainfall, rather than the total seasonal amount, that affects crop production. Rainwater harvesting and buffering during times of scarcity is a good option to protect against the crop losses or even complete crop failure. However, it is important that such approaches are related carefully to local situations before attempts are made to introduce large scale rainwater harvesting programmes.

Water supply responses in Egypt are limited by the size and accessibility of reserves. For instance, water saving schemes in Sudan, which can benefit Egypt, often involve wetland drainage. This is controversial on social, political and environmental grounds and not realistic in the current political situation. Responses that manage water demand have more potential in terms of improved use and sectoral allocation. These are likely to be promoted in Egypt and more widely in all areas facing water scarcity.

The uncertainty surrounding future impacts of climate change, and the changing nature of these impacts, makes adaptation difficult, particularly across country borders. The example of the Nile river basin demonstrates the importance of a flexible approach to adaptation measures.

Declan Conway and Woldeamlak Bewket
School of Development Studies
University of East Anglia
Norwich
NR4 7TJ
UK
Email: D.Conway@uea.ac.uk

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