FRISCO — Some Wyoming watersheds may be showing signs of wear and tear due to coalbed methane development, according to a U.S. Geological Survey study done on the Powder and Tongue river basins in northeastern Wyoming and southeastern Montana.
According to the USGS, three sites on the Powder River show a difference in water quality between the time before coalbed methane development and during the production period. But thirteen other sites, including mainstem and tributaries to the Tongue and Powder Rivers in northeastern Wyoming and southeastern Montana, showed few substantial differences in water quality between the two time periods.
Working with the Montana Department of Natural Resources and Conservation, Water Management Bureau, the USGS analyzed data collected between 1980 and 2010 at 16 sites in the Tongue and Powder River Basins. Eleven water-quality constituents and properties were selected for trend analyses in the report to determine if there were water quality changes.
Three sites on the Powder River showed increases in sodium, alkalinity (an indicator of bicarbonate), and sodium adsorption ratio during the time period of coalbed methane extraction activities.
The site on the Powder River upstream of the coalbed methane activity did not show corresponding increases in these or other evaluated constituents and properties.
“It’s important to understand that the hydrology and water quality of streams in the Tongue and Powder River Basins are complex. Assessing potential impacts of CBM activities using advanced statistical methods was a large undertaking,” said USGS hydrologist Steve Sando said in a statement.
Streams in both the Powder and Tongue River Basins can naturally have high levels of many water-quality constituents and properties, making it challenging to determine if changes are occurring, and what the causes of the changes are.
An increase of water-quality constituents and properties, regardless of the cause, might be a concern if it affects how the water can be used. For example, irrigating with water that has high sodium-adsorption ratio values can result in soil swelling, reduced infiltration rates, and increased soil erosion.
Water that has very high bicarbonate can have adverse effects on aquatic life. However, while the report has general descriptions of water quality at each site, the primary purpose of the report was to determine if changes were occurring, not to determine the usability of the water.