Climate change implications
It is estimated that by the year 2050, except Godavari, Brahamani-Baitarani, Mahanadi and Narmada all river basins would be facing water scarcity. Eight river basins would be critically water scarce according to standard definition of water scarcity. These estimates do not account for possible impacts due to climate change. The IPCC report on climate change (e.g., IPCC, 2001) suggests that changes in climate could aggravate periodic and chronic shortfalls of water, particularly in arid and semi-arid areas of the world. Most part of India being arid or semi-arid, the country may be particularly vulnerable, especially with water resources mainly derived from single-point systems such as bore wells or isolated reservoirs. Given the limited technical, financial and management resources, adjusting to shortages and/or implementing adaptation measures may impose a heavy burden on the national economy. It is also suggested that flooding is likely to become a larger problem in many temperate and humid regions, requiring adaptations not only to droughts and chronic water shortages but also to floods and associated damages. Since, in the projected climate change scenario, extreme high flows are likely to be higher, and extreme low flows are likely to be lower, the flood and drought prone regions of the country will need a special attention. The IPCC (IPCC, 2001) has suggested that increased precipitation intensity, particularly during the summer monsoon, could increase the flood prone areas in temperate and tropical Asia. It is also suggested that countries whose water use is more than 20% of the total potential water resources available are expected to experience severe water stress during the drought periods, and that the surface runoff is expected to decrease drastically in arid and semi-arid Asia under projected climate change scenarios. India typically falls in this category.