The Minnesota Department of Natural Resources is trying to improve the way it manages the state's underground water supply.

Cities, industries and farms are all using more water. State scientists have found evidence that pumping too much water from underground is damaging lakes, streams and wetlands, particularly during summer, said Andrew Streitz, a hydrologist at the Minnesota Pollution Control Agency.

"We're a water rich state, and I think for the first time we're bumping up against limits to what we thought of as a limitless resource," said Streitz, who studies the interaction between groundwater and surface water.

To help preserve a precious natural resource, the DNR plans to test a new water management model that would give local officials a greater role in conserving water.

Dave Leuthe, deputy director for the DNR's division of ecological and water resources, said the department doesn't have the resources to effectively manage water everywhere in the state. Besides, he said, those should be local decisions.

"What we really are moving towards is a management system that engages the users and the local units of government that are making decisions," Leuthe said.

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Little Rock Creek just north of St. Cloud is an example of what state officials want to avoid.

Heavy groundwater pumping in the area causes the stream to shrivel in the summer. As a result, trout in the stream died. Downstream at Little Rock Lake, low water causes massive summer algae blooms.

Every year, Minnesotans pump more water for personal, industrial and agricultural needs, Streitz said.

"We're seeing evidence that this is affecting the rivers and streams and lakes that we love," he said. "And we need to understand that this is happening. We need to understand it now when we can still do something about these trends."

Streitz said the state could begin to address the problem by more closely monitoring wells that tap underground aquifers and pump more water for cities, industries and agriculture. In those areas where more water is pumped from the aquifers, streams have less water. DNR officials say they don't have enough people to closely monitor and regulate that water use.

The big users of water in order of the quantity they consume are public water supplies, industry, and agriculture. Large urban areas like the Twin Cities are using more water per person. Farms in central and north central Minnesota are pumping more to irrigate crops.

Jeanette Leete, who supervises the groundwater unit at the department, said underground water is difficult to measure and monitor. As a result, it's taken years to prove the relationship between water underground and water on the surface, she said.

"Now we know," said Leete, who has studied groundwater for 30 years. "We would be negligent if we didn't try to address some of these problems."

Leete said there are areas where underground pumping makes streams and wetlands dry up in the summer. She said water returns again when snow melts each spring, but by then the damage is done, "because fish can't breathe air for the whole summer, because if you dry out a wetland the plant community will change.

"Even if you do wet it up again the next year, the fish are dead and the plants have changed," she said.

The state now has about 750 wells to measure groundwater levels. Most are in areas of heavy groundwater use, or where there's been a problem with depleted groundwater. But many areas of the state have no monitoring wells.

State officials estimate they would need 7,000 wells to monitor groundwater across the state. The goal is to install those wells over the next 30 years.

The DNR is selecting several pilot sites for its new water management model. It will identify the sites in the next year.

DNR officials want to allow local officials to make informed decisions about how to solve water problems.

"We would work with people to have that baseline knowledge of what's beneath them, what's the monitoring information, so we can help them understand how the system works and flows and moves," Leuthe said. "Then the decisions really have to flow back out locally."

State officials say one of the biggest challenges they face is convincing Minnesotans water is not an endless resource.