مارچ 31, 2014
Around 1.2 billion people around the world live in areas of physical water scarcity, while another 1.6 billion face what can be called economic water shortage. It is estimated that by 2025, 1.8 billion people will live in countries or regions with absolute water scarcity, with almost half of the world living in conditions of water stress, says the Worldwatch Institute.
As people around the globe observe World Water Day on March 22, the Vital Signs Online service of Worldwatch Institute said the situation is expected to worsen because population growth, climate change, investment and management shortfalls and inefficient use of existing resources restrict the amount of water available to people.
Water scarcity happens at several levels. Physical scarcity occurs when there is not enough water to meet demand; its symptoms include severe environmental degradation, declining groundwater, and unequal water distribution. Economic water scarcity occurs when there is a lack of investment and proper management to meet the demand of people who do not have the financial means to use existing water sources; the symptoms in this case normally include poor infrastructure.
A region is said to face water scarcity when supplies fall below 1,000 cubic metres per person per year, and absolute water scarcity is when supplies drop below 500 cubic metres.
Global population is predicted to grow from over seven billion today to 9.1 billion by 2050, putting a strain on water resources to meet increased food, energy, and industrial demands. But there are many other pressures, including increased urbanization and overconsumption, lack of proper management and climate change. According to the United Nations Food and Agriculture Organization and UN Water, global water use has been growing at more than twice the rate of population increase in the last century.
At the global level, 70% of water withdrawals are for the agricultural sector, 11% are to meet municipal demands, and 19% are for industrial needs. These numbers, however, are distorted by the few countries that have very high water withdrawals, such as China, India, and the United States, says the report.
Agricultural water withdrawal accounts for 44% of total water withdrawal among members of the Organisation for Economic Co-operation and Development (OECD), but this rises to more than 60 per cent within the eight OECD countries that rely heavily on irrigated agriculture. In the four transitional economies of Brazil, Russia, India, and China, agriculture accounts for 74% of water withdrawals, but this ranges from 20% in Russia to 87% in India, according to the report. Officials in India’s Ministry of Water Resources say they do not have an accurate estimate of this percentage, though they think it ranges between 80 and 85%.
Urging policymakers to introduce a variety of measures to address global water scarcity, Worldwatch says one important initiative is to support smallholder farmers. Much of the public investment in agricultural water management has focused on large-scale irrigation systems. Farmers can also use water more efficiently by taking a number of steps, including growing a diverse array of crops suited to local conditions and adopting irrigation systems like “drip” lines that deliver water directly to plants’ roots, or sprinklers that use up to 30% less water.
Climate change will affect global water resources at varying levels. In Asia, the large areas of irrigated land that rely on snowmelt and high mountain glaciers for water will be affected by changes in runoff patterns, while highly populated deltas are at risk from a combination of reduced inflows, increased salinity, and rising sea levels. Rising temperatures will translate into increased crop water demand.
According to Worldwatch, to combat the effects of climate change, efforts must be made to follow an integrated water resource management approach on a global scale. “This involves water management that recognizes the holistic nature of the water cycle and the importance of managing trade-offs within it, that emphasizes the importance of effective institutions, and that is inherently adaptive.”