July 18, 2014
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WSGS Study Shows Snake and Salt Rivers Are Healthy
The Wyoming State Geological Survey (WSGS) has determined that there is a sufficient quantity of good-quality groundwater in the Snake/Salt River basin to provide for the future. The WSGS completed its latest groundwater study on the Snake/Salt basin in northwest Wyoming for the Wyoming Water Development Commission (WWDC).
“Aquifers in the combined Snake/Salt basin generally show fair to very good potential to meet expected groundwater resource demands in the next 20 years and probably well beyond,” said Karl Taboga, WSGS hydrogeologist. “Most notably, the widely used Quaternary-age alluvial aquifers, along the Snake and Salt rivers, continue to show the highest potential for sustainable development.”
The “Snake/Salt River Basin Water Plan, Available Groundwater Determination (2011-2014)” – 424 pages with color graphics and foldouts – is available on the WSGS website at Snake/Salt River Basin Plan.
The Snake/Salt basin study is part of an overall effort by the agency to assess groundwater in river basins throughout the state, a multi-year project funded by the WWDC.
“Groundwater is especially important in the arid West, from freshwater drinking supplies to irrigating crops,” said Taboga, WSGS basin study project leader.
The river basin plans are part of the WWDC’s efforts to develop and maintain state water plans for each basin. “These plans are used to make decisions regarding the extent and location of groundwater resources within each basin,” said Jodie Pavlica, project manager with the Wyoming Water Development Office. “In many cases, the plans provide the first step in determining which aquifers yield sufficient groundwater to meet a project’s water quality and quantity requirements,” she said.
Geologists with the WSGS, in partnership with the U.S. Geological Survey, conducted a full assessment of the aquifers of the Snake and Salt River Basin as well as a small upstream watershed in Idaho. They also estimated and mapped water-related information and evaluated other related studies and groundwater models for the final published report.
With its headwaters in Wyoming, the Snake River is the largest tributary of the Columbia River, which ultimately empties into the Pacific Ocean. The Salt River, named for several exposed beds of salt and briny springs, drains Star Valley in Lincoln County. Both the Salt and Snake rivers enter the east end of Palisades Reservoir near Alpine, Wyoming.
Overall, the Snake/Salt River basin provides water to more than 34,500 people in Wyoming, or 6 percent of the state’s population. This includes five municipalities (Jackson, Afton, Star Valley Ranch, Alpine, and Thayne), numerous subdivisions, and a large rural population.
Approximately 90 percent of the land area of the Snake/Salt River basin is federally owned. The remaining land includes privately owned properties, concentrated along rivers and streams, land owned by the state, and land owned or managed by other entities.
Land use in the region includes recreation, logging, and agriculture. Approximately 3 percent (99,071 acres) of the basin’s surface area consists of irrigated cropland.
Both the Snake and Salt rivers weave their way through rugged mountains and along rolling plains that make up this diverse basin and watershed. The elevation ranges from 5,623 feet where both rivers enter Palisades Reservoir, to 13,779 feet at the summit of Grand Teton. Annual temperatures can vary from 50°F below zero to more than 100°F. Unlike many of Wyoming’s semi-arid basins, the climate in this region is semi-humid. Annual precipitation averages about 33 inches in the basins.
From Wyoming, the Snake River runs northwest through southern Idaho. During the previous Ice Age, massive glaciers formed, retreated, and flooded the area – events that contributed to carving out canyons and ridges along the middle and lower Snake.
The Snake River Aquifer underlies portions of Yellowstone National Park, where the river’s headwaters are located. Snowpack from the surrounding high peaks is the main source for replenishing its water resources. As a result, hydrogeologists consider the Snake River Aquifer to be one of the most productive in the United States.