The test results for a medical checkup 24 years in the making for the state's namesake river are back from the lab.

The Minnesota River remains one of the state's most troubled waterways. But its newly confirmed sign of health -- the ability to sustain aquatic life during extreme heat and drought -- suggests that the river is starting to recover from decades of pollution. And that a 2004 state push to gradually clean up city sewage plant discharges, plus other initiatives to better manage storm water, is making a critical difference.

That's a cause for celebration in a state that has long treasured its lakes and rivers. But it's also a moment to focus on other stewardship measures needed to ensure the Minnesota River's continued recovery and to restore the health of the state's other impaired waterways.

Months of drought this past summer and a July that was one of the hottest on record in the metro gave state scientists a long-awaited opportunity to measure the Minnesota River's health under conditions comparable to those in 1988. That hot, dry summer drastically dropped the Minnesota River's water flows, spawned an algae bloom downstream at Lake Pepin and is generally regarded as a nadir year for state river health.

Under the August sun, state Pollution Control Agency (PCA) staff tested water from a 20-mile metro stretch of the Minnesota River -- from Savage to Fort Snelling. The agency announced the results earlier this month.

Even under maximum stress, the stretch of Minnesota river tested this summer maintained enough dissolved oxygen to support the food chain of organisms that live in it or on its banks -- from insects to minnows and the bigger creatures that eat them. In human medical terms, the river's dissolved-oxygen readings are the equivalent of having strong vital signs, such as a healthy pulse and blood pressure, said PCA Commissioner John Linc Stine.

Stine and other environmental officials linked the improvement to efforts that reduced phosphorus from wastewater treatment plants. Phosphorus spurs algae growth. Bacteria that feast on the algae also use up the oxygen in the water.

While the initiative to reduce phosphorus discharges has been controversial and expensive, the test results suggest that the effort is working. Progress has been slow on cleaning up the Minnesota River; this is a milestone. The positive results also come on the heels of a historic report this fall showing that key water-quality indicators have improved in the Mississippi River's meander through the metro.

The health of these rivers, and other Minnesota waterways, remains seriously challenged by sediment, bacteria, nitrogen and other pollutants. But what the newly documented improvements show is that targeted decisive action to reduce pollution -- largely set in motion by the 1972 federal Clean Water Act -- does work.

Agriculture was exempted from this landmark law. The industry's lobbying might make this difficult to change. But many farmers in Minnesota soon will have a first-in-the-nation opportunity to participate in a voluntary water-quality program to reduce runoff and other pollutants.

Municipalities have stepped up to clean up wastewater discharge. Voters have stepped up by passing the 2008 Legacy Amendment, which targets sales tax dollars toward water quality. Now it's time to see if one of the key sources of pollution in the Minnesota River and other waterways -- the agriculture industry -- is willing to voluntarily do its part.