For over a century, the federal government has constructed water resource projects for a variety of purposes, including flood control, navigation, power generation, and irrigation. While most municipal and industrial water supplies have been built by non-federal entities, most of the large, federal water supply projects in the West, including Hoover and Grand Coulee dams, were constructed by the Bureau of Reclamation (Department of the Interior) to provide water for irrigation. Growing populations and changing values have increased demands on water supplies and river systems, resulting in water use and management conflicts throughout the country, particularly in the West, where the population is expected to increase 30% in the next 20-25 years. In many western states, agricultural needs are often in direct conflict with urban needs, as well as with water demand for threatened and endangered species, recreation, and scenic enjoyment. Debate over western water resources revolves around the issue of how best to plan for and manage the use of this renewable, yet sometimes scarce and increasingly sought after, resource. Some observers advocate enhancing water supplies, for example, by building new storage or diversion projects, expanding old ones, or funding water reclamation and reuse facilities. Others emphasise the need to manage existing supplies more efficiently through conservation, revision of policies that encourage inefficient use of water, and establishment of market mechanisms to allocate water. Recent proposals to expand the Upper Mississippi River-Illinois Waterway (UMR-IWW) a major transportation route for products moving to and from Illinois, Iowa, Minnesota, Missouri, and Wisconsin have met with significant controversy. Some of this controversy centres on the cumulative environmental effects of the current navigation system and the proposed expansion. The Upper Mississippi River System (UMRS), which includes the navigation channel and surrounding floodplain supports an unusually large number of species for a temperate river. The UMR-IWW navigation system alters UMRS habitat and contributes to a decline in the abundance of some species. For example, locks, dams, and other channel structures inhibit the movement of fish between and within river segments; fill side channels, backwaters, and wetlands with sediment; and suppress plant growth by reducing water clarity.