“Hopefully we get plenty of rain and don’t have to worry about it,” Krahn said.
Geology the determinant
Even rain is in short supply here. Annual precipitation is as much as 10 inches less than in eastern Minnesota. That means there’s less high quality water to recharge the region’s few aquifers.
“It all comes back really to the history, the geologic history, of Minnesota,” said Jim Stark, director of the U.S. Geological Survey’s Minnesota Water Science Center. Glaciers left the southwest corner of the state with little underground structure favorable to aquifers — such as sandy soil, or porous limestone and sandstone formations. Instead, Stark said, much of southwest Minnesota has clay soils that are great for growing crops but make poor water sources. And underneath the clay typically is hard rock.
“Very old Precambrian and igneous rocks and metamorphic rocks that don’t hold or transmit water very readily,” Stark said.
Activities taken for granted in other parts of the state can be limited in the southwest by geology. The JBS hog slaughter plant in Worthington is one of the region’s biggest employers, but the operation has been forced to drop some plans to expand for lack of water.
It’s not uncommon for a town to tell a potential new business that there’s not enough water to meet its needs. And when a new business does start up, sometimes it disrupts the local water supply.
That’s what happened just outside Granite Falls, a picturesque town of 3,000 on the Minnesota River about 90 miles north of Mountain Lake. Soon after the Granite Falls Energy ethanol plant began operations in 2005, the water table started dropping, and some residential wells ran dry.
One homeowner wrote state regulators that he was afraid of “running out of water and not being able to live in my home anymore”. MPR News contacted the company and some of the affected residents, but all declined interview requests.