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

Home Browse Search

6 Tennessee River Region —The Tennessee River drains portions of 7 States and is one of the most highly regulated rivers in the Nation. The Tennessee Valley Authority has statutory authority to manage the entire Tennessee River basin for flood control, power production, and navigation, which effectively gives TVA a large measure of control over surface -water withdrawals. Some of the highest annual rainfall amounts in the continental U.S, occur in the southeastern corner of the basin, and surface -water is abundant, in large part, because of the more than 22 billion m3 of storage in TVA reservoirs. Despite the presence of 17 TVA reservoirs in the eastern half of the basin, ground water supplies about 42 percent of the population in this area, but the presence of thin soil layers, caves, and sinkholes make ground water susceptible to contamination. In the western part of the basin, surface water accounts for about two - thirds of the public supply withdrawals. The region is experiencing rapid population growth, and since 1998, there have been ongoing discussions of interbasin transfers of water from the Tennessee River basin to the Atlanta metropolitan region. Moreover, as much as 1 percent of the mean annual flow of the Tennessee River could be diverted to the Tombigbee Waterway, if traffic on the waterway reaches design capacity. 7 Upper Mississippi Region - -The Upper Mississippi Region includes the Mississippi River watershed upstream of the confluence of the Ohio River. Adequate water supplies generally can be obtained from the Mississippi River and its tributaries under normal flow conditions and with adequate treatment water suitable for drinking can be obtained. Floods and droughts are common and these extreme events affect the reliability of these rivers as sources of water supply. A system of dams was constructed to aid river navigation and can mitigate extreme flow conditions on the Mississippi River main stem. Ground water is primarily available from four principal bedrock aquifer systems and from glacial and alluvial deposits. Water may be difficult to obtain where the aquifers are thin or missing, or have low permeability. Where the aquifer systems are in good hydraulic connection to surface -water bodies, reduction in stream base flow and spring flow, and the drying of wetlands can be a concern if there are high - pumping rates, such as those of irrigation or municipal wells. In urban or rapidly developing areas, declining water levels may exist due to well interference caused by too many wells pumping at high rates and spaced too closely. Water supplies that use shallow sand - and - gravel deposits along lakes, streams, or rivers may induce flow from surface water, which can be of undesirable quality. The quality of water available is affected by the heavy agriculture land -use activities in the region. 8 Lower Mississippi Region —The Lower Mississippi Region includes the Mississippi River watershed downstream from the confluence of the Ohio River. A series of layered freshwater aquifers that are part of the depositional zone known as the Mississippi Embayment coincides with much of the Lower Mississippi River Basin. Although for decades the region has been considered "water rich," many and varied competing demands have caused the sustainability of the resources to become a significant concern. Declining water levels in the Mississippi River Valley Alluvial aquifer, a major aquifer in 18