Ground Water: A Critical Component of the Nation’s Water Resources Ground water is a critical component of the nation’s water resources. Globally, ground water resources dwarf surface Ground water water supplies. Approximately 25 percent of the earth’s total resources dwarf fresh water supply is stored as ground water, while less than surface water 1% is stored in surface water resources, such as rivers, lakes, supplies. and soil moisture. The rest of the freshwater supply is locked away in polar ice and glaciers (Alley 1999a). Because ground water is hidden, the resource is often forgotten or misunderstood. In fact, until 1984, courts in Ohio held ground water movement “secret” and “occult” (Cline 1984). Ground water is, in fact, vital to public health, the environment, and the economy. Approximately 75% of community water systems rely on ground water (U.S. Environmental Protection Agency 2002a). Nearly all of rural America, as well as large metropolitan areas, use ground water supplied water systems. In many parts of the country, surface water supplies are inadequate or unavailable, and ground water is the only practical source of water supply. Ground water feeds streams and rivers, especially during periods of drought or low flow. The agricultural industry uses ground water for irrigation. The percentage of total irrigation withdrawals from ground water increased from 23 percent in 1950 to 42 percent in 2000 (Hutson 2004). The nation’s aquifers have been estimated to receive about one trillion gallons of recharge each day (Nace 1960) but the recharge rates vary greatly both from region-toregion as well as within regions. Even with this vast resource beneath our feet, many parts of the country are experiencing regional and local declines in water levels in aquifers (more than 800 feet in some areas), salt water intrusion along the coastline, land subsidence (Leake 1997), declining water quality due to over pumping, contamination from human activities, and reduced flows to streams. Twenty-six of 28 state agencies responding to a National Ground Water Association (NGWA) survey perceive current or anticipate ground water supply shortages at a statewide or local level in the next 20 years. A separate NGWA survey of public and private sector ground water professionals adds to the state agency assessment. Ground water professionals in 41 of 43 states believe ground water shortages currently exist or will exist in the next 20 years in their states or localized areas of their states (NGWA 2003a;
Twenty-six of 28 state agencies… anticipate ground water supply shortages at the state or local level in the next 20 years.
To protect our citizens, our economy, and the environment, it is important that we understand the factors that contribute to local, regional, or statewide ground water shortages; the strategies that can be implemented to promote a sustainable ground water supply; and what resources or tools are needed to implement these strategies successfully. Factors that Contribute to Ground Water Shortages Population Growth and Distribution Patterns High population growth rates in arid and semi-arid areas and the urbanization of America have a direct impact on the balance of supply and demand on our nation’s ground water resources. The largest census-to-census growth took place from 1990 to 2000, which accounted for an increase of 32.7 million people. The arid Western states experienced the fastest growth rate in the nation at 19.7% during this period, forcing many to struggle to find new sources of water (Perry 2001). The continued concentration of population within or adjacent to metropolitan areas stresses localized ground water sources, even in so-called water rich areas. The legal and political mechanisms of allocating water are struggling to adapt to new priorities and rising demands.
The Chicago-Milwaukee metropolitan area: a case study of population growth and