In the Land of 10,000 Lakes, clean water is considered a birthright. Our state bird is the loon, which relies on clear waters to feed. Prized by anglers, our state fish is, of course, the walleye. The state's name comes from the Ojibwe words for sky-tinted water. Three of North America's great bodies of water — the Mississippi River, Hudson Bay and the Great Lakes — are fed by water that starts its journey in Minnesota.

So, figuratively and literally, clean water starts here in Minnesota.

That's why the news that more than half of the rivers, lakes and streams tested in the state are considered impaired was so unsettling ("State finds 56% of Minnesota's lakes and streams are 'impaired,' " Nov. 13).

Now that all of Minnesota's major watersheds have been evaluated, we need to direct our attention to protecting the most significant waters that remain relatively clean.

The St. Croix River, a national scenic riverway, is immensely popular with kayakers and canoeists. And even though it has exceeded federal limits for chemicals that contribute to nutrient pollution, the river is still in reasonably good shape.

In fact, the St. Croix is uncommonly rich in freshwater mussels, with approximately three dozen species, making it a hot spot for mussel diversity. Filter feeders, mussels are not only great indicators of water quality, they also help improve water quality by filtering out pollutants. But too much pollution, bacteria or sediment can wipe them out.

The Mississippi River's headwaters area, which stretches from Lake Itasca to the metro area, is another example of a river system that is so ecologically and economically significant that we must prioritize it for protection and restoration. The lands surrounding the Mississippi, and the rivers and streams that flow into it, support more than 350 species of mammals, birds and other wildlife, including most of the endangered, threatened and rare species listed in Minnesota. The Mississippi River flyway is also a vital migration corridor for nearly half of North America's bird species and about 40% of its waterfowl.

In all, the Mississippi River and its almost 13 million-acre headwaters area provide drinking water for 2.5 million Minnesotans — more than 44% of the state's residents. This water-rich area is also important for agriculture, forestry, manufacturing, tourism and recreation, all key sectors of Minnesota's economy.

Forests, grasslands and wetlands slow runoff, absorb pollutants and trap sediment to keep our lakes, rivers and groundwater clean. Despite their significance, we're losing natural areas in the Mississippi headwaters at an alarming rate. Over the past decade, almost 600,000 acres of land in the region has been converted to cropland or urban development. That's an area nearly three times the size of Voyageurs National Park.

Our scientists have identified land within the river's headwaters area that is the most critical for protection and restoration. With the help of Ecolab, we've also analyzed the economic impact of preserving water quality in the region. Taking action starting now would yield $490 million in direct and indirect benefits including avoided water treatment costs, retained property values and taxes, reduced flood damages, retained tourism revenue and jobs and avoided public health costs.

Protecting the river and its surroundings also avoids billions in future costs, as cleaning dirty water is more expensive than protecting clean water before it is polluted.

Putting conservation on the ground costs money, most of which is currently coming from Minnesota's Clean Water, Land and Legacy Amendment. The Nature Conservancy favors investing more of the amendment's Clean Water Fund money in the region to keep healthy waters healthy.

Minnesota has been a national leader in monitoring, planning and restoring degraded waters. It's time we prioritize taking action and become a national leader in protecting our clean waters. That's the only way to ensure that the state's list of impaired waters does not get any longer.

Rich Biske is director of freshwater conservation for the Nature Conservancy in Minnesota.