In an era of rising nervousness about water supplies, Dakota County is increasingly eyeing its groundwater reserves.

. It's one of the state's most groundwater-dependent counties.Homes, farms and businesses rely mainly on water brought up by wells from underground layers of rock. Only , along with two microsuburbs, Lilydale and Mendota, use Mississippi River water."Four Dakota County cities — Eagan, Apple Valley, Lakeville, and Burnsville — are among the top 20 municipal groundwater users in the state,'' said Jill Trescott, the county's groundwater protection supervisor. "We are also the county that is the second-largest user of groundwater for crop irrigation."

So far, groundwater dependence has not been cause for alarm. Minnesota is water rich compared with many states, Trescott said."We have water that goes back to the glacial era and we get lots of snow and rain which is one of the reasons we have been able to take it for granted for so long."

But because Dakota County's population is growing and rainfall patterns are changing, communities are trying to plan for a range of future situations so they can be prepared regardless of what happens, Trescott said. She

"Cities are working together to identify ways to make the long-term water supply more secure. They are looking for ways to connect with each other in case of emergencies.''

Rosemount, Inver Grove Heights and Hastings are considering forming a groundwater consortium similar to one that Savage and Burnsville have established, Trescott said.

Burnsville decided to capture underground water brought to the surface at a stone quarry and use it to provide water to Savage as well."It was water that was just going to waste that is now being pumped out of the quarry and being put to good use. That is the kind of innovation that every community is going to have to look for as an option to consider for the future.''

The Department of Natural Resources issues permits for all groundwater use. The agency is in the midst of an ambitious study of how much groundwater the state is using.

"We are embarking on a new realization that we do not have an infinite supply of groundwater or any resource in Minnesota,'' said Steve Thompson, supervisor of the DNR's hydrogeology and groundwater unit.

Among other things, the DNR is trying to develop a standard evaluation procedure to define what volume of groundwater use is too much, Thompson said.

Using monitoring wells, the agency's goal is to come up with a water budget for each watershed district in the state that would track how much groundwater is in storage in that watershed, how much precipitation is falling and how much is being pumped out for use. That way it will be clear "at what point are we extracting more groundwater than would adequately be recharged,'' he said.

The new information will be the basis for making so-called "appropriation" decisions, permit by permit, meaning the volume of water allowed. That's the primary tool for regulating water resources, Thompson said. The DNR is taking a hard look now at appropriation requests for high capacity users.

"We are not in a crisis situation in Minnesota,'' Thompson said. "We are not saying the sky is falling. But it is appropriate for us to do some planning.''