IPCC Fourth Assessment Report: Climate Change 2007
Climate Change 2007: Working Group II: Impacts, Adaptation and Vulnerability

10.5.2 Hydrology and water resources

In some parts of Asia, conversion of cropland to forest (grassland), restoration and re-establishment of vegetation, improvement of the tree and herb varieties, and selection and cultivation of new drought-resistant varieties are effective measures to prevent water scarcity due to climate change. Water saving schemes for irrigation should be enforced to avert water scarcity in regions already under water stress (Wang, 2003). In North Asia, recycling and reuse of municipal wastewater (Frolov et al., 2004), increasing efficiency of water used for irrigation and other purposes (Alcamo et al., 2004), reduction of hydropower production (Kirpichnikov et al., 2004) and improved use of rivers for navigation (Golitsyn and Yu, 2002) will likely help avert water scarcity.

There are many adaptation measures that could be applied in various parts of Asia to minimise the impacts of climate change on water resources and use: several of which address the existing inefficiency in the use of water. Modernisation of existing irrigation schemes and demand management aimed at optimising physical and economic efficiency in the use of water resources and recycled water in water stressed countries of Asia could be useful in many agricultural areas in Asia, particularly in arid and semi-arid countries. Public investment policies which are aimed at improving access to available water resources, integrated water management, respect for the environment and promotion of better practices for wise use of water in agriculture, including recycled waste water could potentially enhance adaptive capacity. As an adaptation measure, apart from meeting non-potable water demands, recycled water can be used for recharging groundwater aquifers and augmenting surface water reservoirs. Recycled water can also be used to create or enhance wetlands and riparian habitats. While water recycling is a sustainable approach towards adaptation to climate change and can be cost-effective in the long term, the treatment of wastewater for reuse, such as that being practiced now in Singapore, and the installation of distribution systems, can be initially expensive compared to such water supply alternatives as imported water or groundwater, but are potentially important adaptive options in many countries of Asia. Reduction of water wastage and leakages, which in some cities like Damascus can be substantial, could be practiced to cushion the decrease in water supply due to decline in precipitation and increase in temperature. The use of market-oriented approaches to reduce wasteful water uses could also be effective in reducing effects of climate change on water resources (Ragab and Prudhomme, 2002). In rivers like the Mekong where wet season riverflows are estimated to increase and the dry season flows projected to decrease, planned water management interventions could marginally decrease wet season flows and substantially increase dry season flows (World Bank, 2004).