Great Salt Lake Information System

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Map of the Great Salt Lake Basin
9,962 km2 / 3,846 mi2

Minimum:  1,279 m / 4,196 ft
Maximum:  3,627 m / 11,899 ft
Range:  2,348 m / 7,704 ft

Minimum:  229 mm / 9 in
Maximum:  1,549 mm / 61 in
Average:  508 mm / 20 in

Utah Lake Watershed

Utah Lake is one of the largest natural freshwater lakes in the western United States. It occupies much of Utah Valley, and is used by Salt Lake Valley as a water source. The Provo, Spanish Fork, and American Fork Rivers are primary inflows, and the Jordan River drains the lake north to the Great Salt Lake. While it is large in surface area, the average depth is only about 10 feet. This allows winds to constantly stir up bottom sediments, resulting in turbid water.

This diverse watershed contains soils of many different types. The vegetation communities consist of all types found in the state. The watershed receives 25 - 152 cm (10 - 60 inches) of precipitation annually. The frost-free season around the reservoir is 120 - 160 days per year. Land use in the watershed is 53% multiple use (logging, mining, grazing and recreation on BLM, State, and USFS lands), 31% agricultural, and 16% Urban which includes industrial areas around the lake. Perhaps the greatest impact that humans have had on Utah Lake has not been changing the biota, dumping sewage and industrial wastes, logging the watershed, grazing the watershed, agricultural runoff, or paving the watershed, but has been the elimination of most of the natural inflow to the lake.

The area between the Wasatch Front and the Sierra Nevada Mountains is stretching and collapsing, leaving the area topographically lower than the mountains to the east and west, forming what is geologically referred to as "the Basin and Range Province." Much of this area does not drain to the ocean (hydrologically, the "Great Basin" includes the entire Wasatch Range and the western Uintas). In moister eras, such as the cold periods of the ice ages, the great basin filled with water, creating Lake Bonneville, and eventually flooding to the north into the Snake River and to the Pacific Ocean. The drainage was not able to maintain itself as decreased precipitation lowered the level of Lake Bonneville, and the remnants are Utah Lake and the Great Salt Lake. Utah Lake remained intact due to its mountainous watershed, which contributes a significant amount of water to the area.

Utah Lake's watershed includes areas east and west of the Wasatch Fault, in both (geologically speaking) the Basin and Range province and the Rocky Mountains. The lake itself, and Utah Valley, are part of the Basin and Range province, while the mountains bordering the valley to the east are part of the Rocky Mountains. The Basin and Range area is generally flat, with small mountains ranges jutting above it. The climate is clearly arid. West Mountain, the Tintics, and the Lake Mountains are classic ranges. The Rocky Mountains are much higher, and consequently have more precipitation and large areas of lush vegetation. Continual uplift (as much as 10'/1,000 yrs) results in rocky outcrops wherever soil building processes are outstripped by erosion. In the high elevations, glaciers turned narrow canyons into broad valleys, and the quantity of rock removed is evidenced by the massive Provo bench, which is the Provo River delta from Lake Bonneville.

The principle inflows are the American Fork River, the Provo River, Mill Race Creek, Hobble Creek, the Spanish Fork River, and Currant Creek. Among the tributaries, the Provo River is the largest. It flows through the Wasatch Range in an ancient canyon, which has carried rivers in the past from west to east. The present Provo River has captured drainage in fairly recent history that has added a portion on the Uintas to the watershed. Man has further augmented the watershed with diversions from the Duchesne River and the Weber River. The Spanish Fork River has been similarly augmented, receiving water carried from the south face of the Uintas, from Upper Stillwater Reservoir in the Rock Creek Drainage to Strawberry Reservoir, including the Duchesne River, Currant Creek, Layout Creek and Water Hollow Creek. All of this water is drained through the Strawberry Tunnel into the Diamond Fork Drainage, which is a tributary of the Spanish Fork River. The American Fork River and Currant Creek are entirely diverted for much of the year. Many other tributaries once flowed into the lake during the spring floods, but have since been diverted for culinary or agricultural uses. Most tributaries are impounded to divert water into culinary systems or onto agricultural lands, or to regulate the flow of water into the lake.


L A N D   C O V E R K M 2 P E R C E N T
Urban 632 6
Forest 3,936 40
Rangeland 3,980 40
Agriculture 724 7
Other 691 7
TOTAL 9,962 100

L A N D   O W N E R S H I P K M 2 P E R C E N T
Bureau of Land Management 525 5
Forest Service 3,166 32
State 584 6
Private 5,114 51
Other 573 6
TOTAL 9,962 100