A new Boise State University study has found that a warming climate could decrease the water in the aquifer for both the Spokane River and Boise River basins, which provide drinking water for much of Idaho and parts of eastern Washington.
Boise State civil engineering researchers Venkataramana Sridhar and Xin Jin simulated more than 100 different climate change modeling scenarios to evaluate how changes in precipitation, temperature, soil moisture and timing of snow melt would affect the aquifer during the next 50 years.
The results showed that from 2010 to 2060:
- Changes in temperature for the Treasure Valley region could range from an average increase of 2 to 4 degrees Fahrenheit, or a half a degree per decade. Precipitation could increase an average of four inches; however, some models showed precipitation rates could range from a 3 percent decrease to a 36 percent increase.
- In the Spokane River basin, changes in temperature could range from an average increase of 2 to 4 degrees Fahrenheit, or a half a degree per decade. Precipitation could increase an average of 5 inches; however, some models showed precipitation rates could actually decrease up to 6 percent or increase 17 percent.
- Snow melt timing is predicted to shift to 2-3 weeks earlier, with the peak melt occurring during April instead of May, which could change hydrological patterns. Increased stream flows and aquifer recharge sequences also could change.
The results of the study appear online in the Journal of the American Water Resources Association.
“The warmer temperatures could trigger more precipitation to fall as rain instead of snow in the mountains, which means less gets into the groundwater and ultimately the aquifer,” said Sridhar, an assistant professor of civil engineering. “In terms of peak flows, the high flows in the future will probably be higher than historic high flows, with it being earlier than now. Notably, the low flows are expected to be lower than historic low flows.”
To conduct the study, the researchers simulated the basin-scale hydrology by coupling the downscaled precipitation and temperature outputs from many global climate models and the Soil and Water Assessment Tool (SWAT). The researchers said knowing the possible hydrological impacts on the aquifer and watershed due to climate change will help policy makers in their decision-making process.
The study was funded by the National Science Foundation Experimental Program to Stimulate Competitive Research (EPSCoR) in Idaho, as well as seed funding provided by the U.S. Geological Survey through the Water Resources Research Act.