USGS to Develp Indicators to Better Measure Nation's H2O Supply: Greenwire

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in the region, the absence of large river basins has resulted in increasing and often controversial interbasin transfers to meet water - supply needs. Across the region, public supply withdrawals are split almost equally between surface and ground water. There are, however, large differences among States in the region. Florida, for example, withdraws about 90 percent of its public water supply from the ground -water system, whereas Georgia, North Carolina, and South Carolina all utilize surface water for about 80 percent of their public water supplies. About 20 percent of the population in the region relies on private ground -water systems for water supply. Heavy ground -water pumping in many areas of the region, particularly in the Coastal Plain, has resulted in the loss of wetlands, disappearance of lakes, land subsidence, and saltwater intrusion into coastal aquifers. The presence of karst formations throughout much of the region and intensive agricultural operations in other areas means that shallow ground -water systems are highly susceptible to contamination. Aquifer storage and recovery is increasingly seen as a method for storing water supplies in the Coastal Plain where topography prevents the construction of large reservoirs, and several large cities are considering desalinization. 4 Great Lakes Region - -The Great Lakes Region includes parts of eight States and two Canadian Provinces and contains a reservoir of fresh surface water that is 18 percent of the world's supply and 95 percent of North America's supply. Even though the resource is vast, uncertainties in the estimates of the water inflows, outflows, and water use in the Great Lakes Basin threatens the ability of the States to provide defensible decision making under Annex 2001 to the Great Lakes Charter. In particular, improvements are needed in the computations of tributary and connecting channel streamflow, ground- water contributions, and consumptive uses. Some water withdrawals may be negligible compared to the total amount of water in the Great Lakes, but they may be large relative to the tributary stream or ground -water reservoir from which they are withdrawn. 5 Ohio Region - -The Ohio Region includes most of Indiana, Kentucky, Ohio, West Virginia, and small portions of seven other States. The region on average is water rich, accounting for one third of the annual outflow of the Mississippi River. Although the resource especially along the major river systems is large, surface- and ground -water availability in many areas can be limited by lower natural storage and flow characteristics or by a lack of supply development and infrastucture. Surface -water systems are a much more common source of public -water supply than are ground -water systems, especially in the bedrock dominated portions of the region. Exceptions, however, include the alluvial and glacial outwash aquifers bordering the major rivers where large quantities of ground water are pumped from the sand and gravel deposits and used for public and industrial water supplies. A rapidly growing portion of the population is expanding into suburban and rural areas. These areas tend to be more dependent upon the use of local surface- and ground -water systems that often are less reliable during drought conditions and prone to contamination. One distinguishing characteristic of the region is the large proportion of karst (mostly limestone) terrain whose hydrologic complexity has not yet been quantitatively well defined. 17