with a total land area of 97,914 square miles is home to 19,347 miles of streams, 427,219 acres of lakes and reservoirs, and an estimated 940,000 acres of wetlands.

The Continental Divide subdivides the state into four major drainage basins, including the Missouri, Columbia, Colorado and the Great Salt Lake basin. This geographic feature makes Wyoming the headwaters of the West. The headwaters of the Green River, a major tributary of the Colorado River, arise in the glaciers and snowpack of the Wind River Mountains.

More than 90 percent of the water flowing through Wyoming originates within the state. Less than 10 percent of Wyoming receives more water as precipitation than is lost back to the atmosphere through evaporation and transpiration.

Although Wyoming's portion of the basin encompasses 16 percent of the land area in Wyoming, it is home to approximately ten (10) percent (50,600 persons from the 2000 census) of the state's population. Communities served by Green River Basin water include Baggs, Pinedale, Big Piney, Farson, Kemmerer, Green River and Rock Springs. The largest transbasin diversion of Colorado River system waters is into the over appropriated North Platte River system. The city of Cheyenne diverts, on average, about 14,4000 acre-feet of water annually from the Little Snake River Basin to replace diversions of Platte River water for municipal use by the City. In addition, two minor transbasin diversions occur for irrigation use.

In the Wind River Mountain Range, precipitation averages between 40 and 60 inches per year. The largest concentration of glaciers in the American Rocky Mountains, occurs in the Wind River Range. Lower elevation portions of the basin receive 7-9 inches per year. By comparison, annual precipitation across the entire state averages 14.5 inches.

The mean annual water balance (precipitation minus evapotranspiration) for the Green River Basin has a negative value. However, runoff, of which about 70 percent is derived from snowmelt, occurs during a period (spring/early summer) when the basin has a positive water balance. Therefore, reservoir storage plays an important role for the Green River water supply during non-runoff months. The total reservoir storage capacity within Wyoming's portion of the Green River Basin is in excess of 4.4 million acre-feet, including Flaming Gorge Reservoir which impounds up to 3,780,000 acre-feet in both Utah and Wyoming. The state of Wyoming has contractually purchased 125,000 acre-feet of Fontenelle Dam storage from the federal government, ensuring the availability of water for Wyoming's agricultural, commercial, industrial, municipal and recreational needs both for the present and the foreseeable future.

Wyoming's economic well-being revolves around three industries -- the extraction of minerals, tourism and recreation, plus agriculture, which is the largest user of water in the state (about 80 percent of total). Infra-red satellite imagery and aerial photography (circa 1999) indicate that 330,408 acres are irrigated in the basin. Alfalfa, native grasses and small grains are the predominate crops due to the short growing season and high elevation of the irrigated lands. The sparse rainfall makes most of the basin agriculturally suitable only for grazing and livestock, unless irrigated.

Millions visit Wyoming each year, flocking to the state's popular vacation and recreation attractions. Many of these are based on water and water what is within the Colorado River Basin. Water-based recreation plays a significant role in the economic base of the basin. Flaming Gorge, Fontenelle, Fremont Lake, the Green River and the Alpine areas of the Wind River Range support fishing, hunting, power boating, sailing, canoeing, rafting, skiing, hiking, mountaineering and wildlife observing. Wyoming has 22 species of game fish, including brook trout (char), brown trout, cutthroat trout, golden trout, kokanee salmon, and lake trout (char) that thrive in the clear and cold environment of the basin's lakes and streams.

To help maintain existing stream environments and fisheries, the Wyoming Legislature enacted an instream flow law in 1986, making instream flow, provided either from natural stream flow or from storage water, a beneficial use of water. Between 1986 and February 2001, thirty-four instream flow applications in the Green River Basin were filed with the State Engineer's Office.  Two filings have been granted permits.

Construction of Fontenelle Dam induced changes in the Green River which Congress anticipated when it established the Seedskadee National Wildlife Refuge in 1965 to help offset the loss of habitat due to the construction of Fontenelle and Flaming Gorge dams. The refuge is domiciled on approximately 26,000 acres of sagebrush plains, cottonwood groves and marshes enveloping roughly thirty-seven (37) miles of the Green River.  The refuge provides habitat for such diverse species as pronghorn, shiras moose, trumpeter swans, sage grouse, raptors, pelicans and trophy trout.  Guests can visit historic Lombard Crossing which was used by emigrants traveling the Oregon, Mormon and California Trails.

Wyoming became the first state in the union to claim state ownership of water when the state constitution was ratified in 1890. Wyoming's water law is based on the prior appropriation doctrine. Wyoming's first territorial engineer and state engineer, Elwood Mead (who later became commissioner of the U.S. Bureau of Reclamation and for whom Lake Mead was named) was largely responsible for writing Wyoming's water laws. It has not been found necessary to change much in those laws during the 100 years of statehood that have followed, and Wyoming's water laws formed the basis of water law in many other western states. Due to being a headwaters state, Wyoming is a party to seven interstate compacts and two U.S. Supreme Court decrees which govern her rights to beneficially use water, including the Colorado River Compact of 1922 and the Upper Colorado River Compact of 1948, which apportioned 14 percent of the Upper Basin water supply to the state of Wyoming.

In a continuing effort to protect and properly manage Wyoming's water resources, the Wyoming Legislature authorized the Wyoming Water Development Commission (WWDC) to initiate a Basin Water Planning Process in 1999 to cover each of the seven major river basins in the state.  The primary objective of the process is to identify and document current and future uses of water within the state.  The Green River Basin Water Planning Process final report was completed in February 2001.  The finished document and all other basin reports completed under this program will be reviewed and updated every five years.  All program documents and finished reports may be obtained from the WWDC Water Planning Web Site (http://waterplan.state.wy.us/).