April 23, 2014
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Platte and Bear River Groundwater Resources Boosted Above Average Snowpack
New reports by the Wyoming State Geological Survey (WSGS) on the groundwater resources of the Platte and Bear River basins show that the amount and quality of water in each basin varies considerably. What is certain among water scientists, however, is that snowpack plays a key role in the natural variability of Wyoming’s groundwater resources.
“Snowpack is important for water supplies in the Rocky Mountain West and for recharging the state’s aquifers from year to year. It is also important for sustaining healthy water resources in the future,” said Karl Taboga, WSGS geohydrologist.
WSGS Platte River Basin Water Plan Update (481 pages) and the Bear River Basin Water Plan Update (262 pages) are available on the WSGS website by individual chapters through a clickable Wyoming basin map.
“This year snowpack levels are at or above average for all of Wyoming,” said Tony Bergantino, service climatologist with the Wyoming Water Resources Data System-Wyoming State Climate Office. “Levels are currently well above the median for the Platte River Basin, while the Bear River Basin stands just a little above the median,” he said. According to the Natural Resources Conservation Service Snow Precipitation Update, the Upper and Lower North Platte are at 122 percent of median while the South Platte River Basin is at 170 percent. The Upper Bear River Basin is currently at 103 percent of the 30-year median.
“Adequate snowpack is especially important in a semiarid state like Wyoming,” said Taboga, WSGS basin plans project leader. “Abundant streamflows in the state’s major river basins ensure that alluvial aquifers are adequately recharged, and melting snowpack provides direct recharge to geologic formations that outcrop along the margins of Wyoming’s structural basins."
The Platte and Bear River basin reports are part of a series of assessments on the groundwater resources of the state’s river basins. The reports are being developed for the Wyoming Water Development Commission (WWDC), and designed for state basin planning. In addition to the Platte and Bear River basins, the WSGS completed a report in 2012 on the Wind/Bighorn River Basin and is currently assessing the groundwater resources of the Snake and Salt River basins.
What seems to be consistent with all the basin reports, Taboga said, is that groundwater quality varies widely, even within a single hydrogeologic unit. “Similar findings with the Platte and Bear River reports show that water quality tends to be better near outcrop areas where recharge occurs, with noted deterioration as the distance from those areas increases,” Taboga said. Groundwater quality also tends to deteriorate with depth, as noted in both reports, as well as in the Wind/Bighorn Basin report.
The WSGS groundwater assessments include detailed text and maps of the Platte and Bear River basins as well as locations where the best quality, quantity, and highest aquifer recharge rates have occurred. “This information will be used for managing the state’s groundwater resources, including future development of those resources,” said Phil Ogle, supervisor of River Basin Planning with the Wyoming Water Development Office.
“Groundwater is very important to the state since it supplies over half of the municipal and rural domestic water needs,” Ogle said. In the Bear River Basin, about 34 percent of the municipal and rural domestic water needs are supplied by groundwater. While in the Platte River basin, 72 percent of rural domestic and municipal water supplies come from groundwater. About 37 percent of industrial water use is supplied from groundwater on a statewide basis. “Agricultural irrigation is the largest water user in the state, but it depends primarily on surface water,” Ogle said. “However, where irrigation is supplied from groundwater resources large quantities of water are often used,” he added.
The Platte River Basin covers approximately 24,000 square miles or one quarter of the state’s surface area in southeastern and central Wyoming. Nearly 230,000 residents, or more than 40 percent of the state’s population live in the area.
The Bear River Basin, located in southwest Wyoming, ultimately drains into the Great Salt Lake in Utah. It covers approximately 1,500 square miles of the state as well as areas in Utah and Idaho, and serves more than 14,500 people, or 2.4 percent of the residents of the Wyoming.
The WSGS groundwater assessments are developed in partnership with the U.S. Geological Survey. Each report includes an evaluation of the basin’s groundwater resources, including the measurement and characterization of the resources. The reports also include text and analyses, color maps and graphs, databases, metadata, and tables.