Waters
of Life: Enough for All Earth Day Sunday 2003 |
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Fresh
Water: Our Earth Community's Survival Global Abundance, Local Scarcity Fresh water is one of the earths most precious resources. While there is plenty of water to meet human need, it is often distributed unevenly. Fresh water comprises about 2.5 percent of the worlds total volume of water. Most of that amount is in the form of ice or snow and lies deep in underground aquifers or is in remote locations. Less than one percent of the worlds freshwater is readily available for human use. i Freshwater stores are continually being replenished through the hydrologic cycle, a continuous cycling of water from the earths oceans to land through evaporation, condensation, precipitation as rain, sleet or snow, and back to the ocean again through runoff. Most of the water that does not runoff quickly seeps into the ground to recharge aquifers. Good water management plays a vital role in realizing the abundance of the earths freshwater supply. For instance, two countries that experience the highest levels of water scarcity, Israel and Jordan, also have water supplies adequate to meet their peoples need due, in part, to an efficient irrigation system. ii Global
Supplies: A Management Issue Agriculture and industry claim the highest rates of use of freshwater resources. Globally, about 70 percent of freshwater consumption is used for agriculture. The highest rates of agricultural use occur in Asia and Africa. North America and Europe use more water for industry than for agriculture. Overall, if trends continue, water use is expected to increase by 40 percent over the next 25 years, with 17 percent more going for agricultural use and another 20 percent for industry. Groundwater resources are used by about one-third of the worlds people. Excess withdrawals, withdrawals of ground water at a rate greater than can be naturally recharged, are occurring in parts of the Arabian Peninsula, China, India, Mexico, the former Soviet Union and the United States. In parts of the world, overuse of groundwater resources threaten water supply systems that have been used for thousands of years. Excess withdrawal of groundwater also increases the risk of land subsidence and saltwater intrusion. Californias San Joaquin Valley has sunk by eight meters since the 1920s, a clear example of the secondary effects of excess water withdrawals. iv In addition to overuse, urbanization threatens groundwater recharge rates. By estimating the increase in impervious surfaces in 20 of the fastest growing metropolitan areas in the US between 1982 and 1997, the Natural Resources Defense Council (NRDC) has concluded that Atlanta, GA, may have lost between 56.9 billion to 132.8 billion gallons of water to excess runoff, an amount that could have supplied the household needs of 1.5 million to 3.6 million people. v Human-induced climate change also presents a concern for water managers, as erratic weather increases the likelihood that both floods and droughts will contribute to the problem of water scarcity. Worldwide, one-in-five persons lack access to safe drinking water and one-half lacks adequate sanitation. Sewage, the worlds largest pollution problem, affects both surfacewater and groundwater supplies. Annually, water pollution affects the health of about 1.2 billion people and contributes to the deaths of 15 million children under age five. vi As industrial and agricultural use increases, so will the risk of pollution. Industrial pollutant emissions are expected to increase fourfold over the next 25 years. Agricultural uses of pesticides and fertilizers have a deleterious effect on the earths water stores. Nitrates from fertilizer are one of the most serious water pollution problems, affecting both human and ecosystem health. Excess nitrates in water systems lead to brain damage and even death in some infants. In the United States more than 40 million people take their drinking water from systems that exceed health-based standards. In Africa, nitrates in some groundwater supplies are six to eight times higher than World Health Organization standards. In the natural world, excess nitrates stimulate excess algae growth, leading to the death of waterways, like the dead zone that develops in the Gulf of Mexico. vii For more resources on fresh water from the United Nations visit http://www.unesco.org/water/iyfw. Footnotes |
Earth
Day Sunday
"Freshwater
consumption increased sixfold between 1990 and 1995
at more than twice the rate of population growth" |