When the days heat up here in western Montana, our rivers are go-to spots for boaters, anglers, and people just wanting to enjoy some clear, cool water. But often in summer, in some parts of the river, we find stringy green algae or moss-colored slime mucking up the river rocks.
This algae growth is a result of high levels of nutrients, mainly nitrogen and phosphorous, entering our waterways. It turns out all fresh water streams and rivers contain varying amounts of nutrients. In fact, nitrogen and phosphorous are essential to the growth of aquatic plants that become a food source to other organisms. However, high levels of nitrogen and phosphorous can be a problem because they cause rampant algae growth.
Besides coating our riverbeds with unsightly green slime, mats of algae block sunlight from reaching more beneficial organisms below the river’s surface. Algae also makes it hard to wade and fish and can clog irrigation intakes and canals. To top it off, as algae dies, the decomposition process sucks oxygen out of the water and has a suffocating effect on trout and bugs.
Algae and the nutrients that contribute to its growth are hard to control in our rivers, partly because nitrogen and phosphorous come from many sources. Some of these sources, such as wastewater treatment plants, can be measured, monitored, and controlled. But many other sources of nutrients are difficult to track, such as dense networks of septic system drainfields and fertilizer-rich storm and agricultural runoff.
How is Montana tackling the problem?
The Clark Fork basin has set an example for how to tackle this slippery problem with a combination of education, regulations, and innovative partnerships. One tool that has garnered nationwide acclaim for reducing nutrient pollution is the Clark Fork Voluntary Nutrient Reduction Program (VNRP), a 10-year cooperative agreement from 1998 to 2008 that included the basin’s four largest point-source dischargers—the municipal wastewater treatment plants in Butte, Deer Lodge, and Missoula, and the (former) Smurfit-Stone Mill. The VNRP was created and implemented by the Tri-State Water Quality Council based in Sandpoint, Idaho, as a collaborative effort involving state governments, municipalities, private industries such as Avista, and citizen groups like the Clark Fork Coalition. Read more about the VNRP.
What activities have contributed to lower nutrient levels?
Do these efforts make a difference?
Every five years the monitoring program produces a report showing water quality trends in the basin. See a map of nitrogen, phosphorus, and algae trends from HydroSolution’s 1998-2017 trend report here:
Even with these strides toward cleaner water, though, you’ll still notice algae while you’re on the river in the summer, particularly during low-flow years. That’s because point source dischargers like the wastewater treatment plant only contribute a portion of the nutrients entering our rivers and streams.
It’s harder to manage nutrient pollution that comes from non-point sources like septic systems, stormwater runoff, livestock operations, forestry, and eroded stream banks. Fortunately, a few simple actions by property owners and watershed residents can pay off. Check out our Landowner Guide and Stream Care Guide to see how you can reduce the nutrient impact of your septic system, lawn, garden, or livestock on the river.
Want more detail about nutrient monitoring and results?
The Tri-State Water Quality Council (including Montana, Idaho and Washington) coordinated a nutrient monitoring program from the 1980’s until 2012. Currently, the monitoring program for the Clark Fork River is conducted by Montana DEQ, the University of Montana Watershed Health Clinic, the City of Missoula Wastewater Treatment Plant, and Avista Corporation. The Clark Fork Coalition manages the nutrient monitoring program for this committee. Here are links to current and past nutrient monitoring data/reports: