Water is critical to the society’s welfare: it is vital for agriculture and industry, the healthy functioning of natural ecosystems on which humans depend, the production of energy, transportation, recreation and the disposal of wastes. Availability of fresh water to meet the demands of the growing population while sustaining a healthy environment has emerged as one of the primary issues around the world.

In India though there is enough water to sustain the population of the country, there are a number of difficulties in actually accessing the available sources of water. Nearly two third of the total water available, is confined to the north of the Tropic of Cancer. Almost half of the water of the coastal minor and medium rivers cannot be harnessed and is inevitably wasted. In fact, the area under cultivation south of the Tropic of Cancer amounts to 50 per cent of the total cultivable area. It is clear that the rest of the country has inadequate water resources and conflicts are bound to occur over control and optimal administration of water resources.

Besides the problems of growing demand for freshwater and the deteriorating quality of water available, water managers today are keeping their fingers crossed in view of a long term climate change and its impacts on water resources. Scientific researches have shown that climate change will have major impacts on precipitation, evapo-transpiration and runoff - and ultimately on the world’s water supply.

An increase in temperature would lead to a more vigorous hydrological cycle. A higher temperature will result into greater evaporation. This is most likely to increase the precipitation and run-off, but the state of affairs is not so straight forward. There are significant regional and seasonal differences. Increased temperature would also start melting the polar ice much ahead of the normal timings, leading to increased soil moisture and greater run-off in ice-fed rivers in winters. Several climate models suggest that the mid-continent, mid-latitude areas would be drier, especially in summers.

Attempts to evaluate the regional hydrological implications of climatic change, in a number of watersheds in United States and Europe, have shown that relatively small changes in precipitation and evaporation patterns might result in significant changes in the regional water availability. Another effect will be the change in the spatial distribution of precipitation and evapo-transpiration. The latter effect is more important if one is interested in future freshwater availability.

The changes in climate would affect the surface and ground water resources of a region also, with associated socio-economic problems. Earlier, snow-melt and greater run-off in spring season and increase in evaporation rates lead to a shortage of water in summers. Ground water resources in the coastal regions are also made unfit for human consumption due to the increased salt-water intrusion.

An intense hydrological cycle and modifications in the water resources will influence everyone to some extent but the worst sufferers will be the poor with little options available for adapting quickly to the altered climate.

The demand for water for various human uses will also change. In a warmer world, the demand for electricity for coolers and air-conditioners may go up and more and more of water may be required for electricity generation. In view of the decreasing soil-moisture, demand for irrigation water will also go up. The demand for water for various other purposes may also shoot up.

Increasing demand for water and its decreasing availability will widen the gap between the two. Reduced water availability would place an additional stress on people, agriculture and the environment, more so in developing countries. Climate change will exacerbate the stress caused by the pollution and by growing population and economies.

Water management has always attracted a great deal of public attention. However, because of the important role of water in the functioning of societies and ecosystems, it has increasingly become a field of expertise. In most countries, the management of water resources has become a separate domain of public policy.

The importance of water for a wide range of societal needs makes it imperative to develop methods for assessing the impacts of future climatic changes on regional water resources. Studies have provided the first tentative evidence that relatively small changes in regional precipitation and evapo-transpiration patterns might result in large scale changes in regional water availability. For realistic estimates of actual changes in regional water availability, a number of improvements need to be made over the earlier studies. For the studies to be valuable to water resource planners, regional hydrological assessments should focus on short time-scales such as months and seasons, rather than on annual averages.

Unless new approaches to water management are developed that take into account these new uncertainties, future of the water resource availability will be very poor. Besides the intensive research in this particular field, existing supplies should be used more efficiently and new supplies must be developed. Long term management strategies may also include regulations and technologies for directly controlling land and water use and improvements in water management operations and institutions.

While water management systems are often flexible, adaptation to new hydrological conditions may incur a substantial economic cost. It is, therefore, important to re-examine engineering design assumptions, operating rules, system optimization and contingency planning for existing and planned water management systems under a wider range of climatic conditions than traditionally used.

Governments at all levels should re-evaluate legal, technical and economic approaches for managing water resources in the light of possible climate changes. The timely flow of information from the scientific global community to the public and to water managers and planners is the need of the hour.