Jordan River (Utah) - Watershed

Watershed

The Jordan Subbasin, as defined by the United States Geological Survey, is located entirely within Salt Lake and Davis counties in a roughly rectangular area of 791 square miles (2,050 km2). The Subbasin is part of the larger 3,830-square-mile (9,900 km2) Jordan River Basin that includes the upper Jordan River, Utah Lake, Provo and Spanish Fork Subbasins. Four of the five largest cities in Utah are in Salt Lake County. The Jordan River flows through Sandy, with a 2008 population of 96,660; West Jordan, population 104,447; West Valley City, population 123,447; and Salt Lake City, population 181,698. Flanked on either side by mountain ranges, the topography of the land varies greatly. The Wasatch Mountains rise on the east, with a high point of 11,100 feet (3,400 m) above sea level at Twin Peaks, near the town of Alta. The Oquirrh Mountains rise on the west, with a high point of over 9,000 feet (2,700 m) above sea level at Farnsworth Peak. The low point of 4,200 feet (1,300 m) is at the river's mouth, where the river enters the Great Salt Lake. Both the Oquirrh and Wasatch Mountains are fault-block mountains created from normal-slip faults where the mountains rise at the fault and the valley floor drops. The Wasatch Fault runs along the western edge of the Wasatch Mountains and the Oquirrh Fault runs along the eastern edge of the Oquirrh Mountains.

From approximately 75,000 to 8,000 years ago, much of what is now northern Utah was covered by a Pleistocene lake called Lake Bonneville. At its greatest extent, Lake Bonneville reached an elevation of 5,200 feet (1,600 m) above sea level and had a surface area of 19,800 square miles (51,000 km2). The lake left behind lacustrine sediments, which resulted in a relatively flat lake bed, and the valley floors seen today. As the region experienced increasingly warmer and drier climate over time, Lake Bonneville's water levels receded, leaving the Great Salt Lake and Utah Lake as remnants. The river's greatest slope, 27 feet per mile (5.1 m/km), is in the Jordan Narrows, while the rest of the river has a more gentle slope of 2 to 4 feet per mile (0.4 to 0.8 m/km).

Approximately 237,000 acres (960 km2) (46 percent of land area) of the Jordan Subbasin is in the Wasatch, Oquirrh and Traverse mountains. The United States Forest Service manages 91,000 acres (370 km2) of land in the Wasatch Range. The vast majority of the Oquirrh Range is privately held, with Kennecott Copper Mine owning most of the land. The State of Utah has scattered land holdings of 9,800 acres (40 km2) throughout the subbasin and owns the beds of all navigable streams and lakes.

The Jordan Subbasin has two distinct climate zones. The lower elevations are characterized as a cold, semi-arid climate, with four distinct seasons. Both summer and winter are long with hot, dry summers and cold, snowy winters. Salt Lake City receives 61 inches (150 cm) of snow annually, part of a total of 16.5 inches (420 mm) of precipitation per year. The mean maximum temperature is 91 °F (33 °C) in July and 37 °F (3 °C) in January Areas of higher elevation have two distinct seasons, summer and winter. One of the areas of highest elevation, Alta, Utah, receives 544 inches (1,380 cm) of snow annually, part of a total of 52 inches (1,300 mm) of precipitation per year. The mean maximum temperature is 71 °F (22 °C) in July and 29 °F (−2 °C) in January.