Wearing dark clothing and a blaze orange hat, Greg Brick headed into the snowy woods on a trail at North Sunrise Park Reserve in the St. Croix River valley. In one hand he carried an iPad with a map that showed the topography of the area. Light snow fell atop the inch or so coating the ground—perfect conditions for Brick's search. On this November morning the Department of Natural Resources research analysis specialist was on the hunt for springs, where water flows year-round and can appear as dark rivulets against the snow.

Ten minutes into his hike, Brick saw a culvert alongside the trail with water running through it. He followed the stream upslope, clambering over and around downed trees to a spot where water bubbled out amid black mud. Voila. This particular spring, unlike the picturesque image one might have of water rippling out of a cliff, gurgled up right out of the muck.

He took the water's temperature and measured its flow rate. He also noted other characteristics such as the slight sheen on the water surface, like an oil slick, that told of natural iron oxide in the water. Brick marked the spring on his digital map and left to search for more springs, a forgotten resource.

"Springs were so much better known 100 years ago than today because they were used for drinking water," says Brick. Today, we get our drinking water from municipal sources and wells.

The DNR is on a quest to find and map the state's springs for a project called the Minnesota Spring Inventory. Brick's time at the DNR ended in December 2018, but two other employees will continue the hunt part time. So far, they have charted roughly 5,000 springs on an online map that anyone can access. The reason for the mapping project is simple.

"If you don't know where the resources are, you can't protect them," says Brick.

Springs are important for a variety of reasons. Fairly constant 48-degree temps provide year-round habitat for plants like edible watercress, sentinel species like freshwater shrimp, and trout. Springs are an important and easy place to measure the quantity and chemistry of groundwater, on which roughly three-fourths of Minnesotans rely for drinking water. By measuring water chemistry at the springs, scientists can tell whether pollution from places ranging from feedlots to golf courses enters the aquifers.

Knowing spring locations can also help land managers decide whether to allow industry nearby. By measuring the quantity of water flowing out of a spring, scientists can tell whether people using the water, say for irrigation, are drawing down the resource.

"If the springs are drying up, that's the canary in the coal mine that says you're pumping down these aquifers," says Calvin Alexander, a hydrogeologist at the University of Minnesota.

The map is most complete in the southeastern part of the state, where mapping has gone on for decades, and on public lands. Brick's work over the past couple of years has helped fill in the map outside the southeast.

Anyone can help the project by going to the online map and filling out a form advising where a spring is located. The information will help fuel a project that's really just getting started.

"We have clearly found only a tiny fraction of what's actually out there," says Alexander.

To let the DNR know about a spring, go to mndnr.gov/MnSpringInventory.

Joe Spring, associate editor