In the decades ahead, fresh water is expected to become oil’s successor as the next prize in the world’s resource wars, especially if the consequences of Global Warming, such as increased desertification and longer heat waves, come true.
Articles in our water quality series:
PFCs from 3M: an ongoing source of debate by Anna Pratt
Measuring water quality in Minneapolis, St. Paul lakes by Anna Pratt
Twin Cities water: good to the last drop? by Rich Broderick
Drinking across the river in Minneapolis by Rich Broderick
Water as an economic resource by Rich Broderick
Still to come:
Savage water: a suburban study by Rich Broderick
Minnesota, of course, is singularly blessed with sources of fresh water. But even here, there is no reason for complacency. Challenges like those facing the metro region’s two biggest water utilities have led to a growing realization that our approach to water safety and potability has to shift from a nearly exclusive focus on treatment to one that includes just as urgent an emphasis on water source protection.
And when it comes to water sources for the metro area, we are talking the Upper Mississippi whose watershed drains approximately 19,000 square miles from the headwaters to the northern suburbs: a small nation-sized network of tributaries, sub-tributaries, ponds, lakes, wetlands, and aquifers. Everything – natural and unnatural – that enters the river has the potential of entering metro water supplies, including whatever seeps, leaks, erodes, or is dumped out of thousands of point – meaning self-contained, identifiable sources – and non-point sources of contamination. In addition to everything else, where the Mississippi’s water comes from also means understanding the state’s singular geological history.
“Rivers in Minnesota are still reacting to late glacial events,” explains Carrie Jennings, a glacial geologist with the Minnesota Geological Survey. Jennings’ work focuses on the Minnesota River watershed, originally a spillway for Lake Agassiz, the huge inland body of water that formed some 10,000 years ago at the end of the Ice Age. Though the Minnesota feeds into the Mississippi below the intake for either Minneapolis or St. Paul, its geological composition is similar to less-studied tributaries that empty into the Mississippi upstream from the metro area. “As the glaciers retreated, drainage systems evolved,” she says. “The Mississippi was a braided stream choked with sediment that flowed from the foot of the glaciers. Once you get upstream, you can see how it’s still a braided stream with a low gradient.”
|Talking about water |
aquifer – a layer of permeable, sand or gravel that contains large amounts of water
groundwater – water that is underground, as opposed to surface water in lakes and rivers
potable – fit for drinking
point source –specifically site of contamination, such as a wastewater outlet
non-point source – diffuse source of pollution, such as run-off from lawns
watershed – a region that drains into a particular river or body of water
Over time that drainage system “adjusted,” reaching a natural balance in which erosion slowed and sediments entered the river at much lower levels. What’s happening now, Jenning explains, is that the natural rate of adjustment has been upset.
“First we logged the eastern part of the Mississippi basin and loaded the system with sediment that way,” she says. “Since then we have completely organized the drainage in the uplands in places like the Crow watershed [which drains into the Mississippi about 50 miles north of the Twin Cities] because we wanted to build farms and homes on otherwise not very well-drained lands.” Curbs, gutters and tile systems – tiled ditches meant to slough excess water away from cropland – all hasten the movement of water out of the soil and into the river, speeding up erosion and raising sedimentation levels. “As tributaries of the Mississippi ‘erode up’, more sedimentation is deposited in the waterway,” she says. That sediment is not only rich in phosphates and nitrogen it also binds with other less-natural contaminants, like heavy metals.
As a result, treatment plants drawing water from the Mississippi have to have special equipment and processes for dealing with overloads of sediment and what the sediment brings with it. The answer, she says, is a “holistic solution” that weaves together the efforts of the many different federal and state agencies, as well as different local government bodies, that play some role in soil and watershed conservation and water treatment.
Information about sediment also happens to be what Dave Brostrom looks for as part of his work. He is an independent consultant who serves as project manager with the Upper Mississippi River Source Protection Project, a four-year program begun last summer with almost $1 million in funding from the cities of St. Cloud, St. Paul, and Minneapolis, the Minnesota Department of Health, the Minnesota Rural Water Association and the Metropolitan Council, among other agencies.
Under the decade-old Federal Safe Drinking Water Act, the Minnesota Department of Health was required to create source water assessments for the state, a task that was completed in 2001. Although the Act doesn’t require it, the three cities decided to push forward on their own to develop source water protection plans for their drinking water.
The project Brostrom helps coordinate thus has an ambitious agenda that includes a detailed geological mapping of the watersheds that provide water to St. Paul, Minneapolis and St. Cloud, identifying all potential point and non-point sources of contamination, including groundwater, and figuring out a way to get local, state, and federal government agencies and entities to buy into source water protection plans when they are completed.
One of the biggest of the Upper Mississippi watersheds is the 2,700 square mile Crow system; because of its glacial geology, it is also the single largest source of sediment contamination for water drawn from the Mississippi by St. Paul and Minneapolis.
“As you move south across the Crow watershed, the soil becomes finer,” says Brostrom. “The worst of it is along the south fork of the Crow River where the soil is light clay and the sedimentation increases commensurately.” A problem, he adds, that’s exacerbated by the region’s steep ravines and “deeply incised streams,” the cultivation of the uplands for row crop production, and the spread of urbanization.
Over the next four years the Source Water Protection Project will begin to implement methods for reducing sedimentation and other sources of contamination. In turn, the project has begun to draw other government agencies into its field of influence, offering a potential model for how water in general will be managed in the future. The Minnesota Pollution Control Agency is keenly interested in the project’s plans to ameliorate sedimentation on the Upper Mississippi because it is the agency charged by the EPA with primary responsibility for cleaning up Lake Pepin as required under both the Clean Water and the Safe Drinking Water Acts.
“From our perspective, the way you protect drinking water is watershed by watershed,” says Brostrom. “It’s the only way to do it.” But, he points out, federal agencies like the EPA often have no record of working with local units of government, like soil conservation districts or water utilities. Projects such as the one he is involved with are creating a mechanism for doing so, thus offering the prospect of a whole new way of dealing with the question of drinking water.
“In the U.S. we’ve relied on the ‘public works model’ in which water suppliers alone are expected to keep water safe, and that’s been accomplished through treatment,” Brostrom says. “What approaches like ours do is not to take away emphasis on treatment but to expand it to include pollution prevention. What happens upstream is important because to the degrees we can reduce sedimentation, we get cleaner, safer water for less money.” Why, he asks rhetorically, spend $160 million on an ultrafiltration treatment plants but not spend, say, $16 million to pay upstream farmers to change some of their cultivation practices, leaving strips of native vegetation as barrier between a field of soybeans and a creekbed?
Of course, even if that were done, the challenges would remain formidable. From its headwaters to the metro region, the Mississippi River and its tributaries are dotted by more than 3,000 potential point sources of contaminants, of which only a handful, like chemical storage sites, and rail and pipeline crossings, even require a permit. And that does not even take into account “emerging” sources of contaminants, like PFOA and PFOS, perflourochemicals once produced by 3M, or endocrine disruptors leaching into the watershed from pharmaceutical plants and other sources.
“For us to exert influence upstream is difficult,” admits St Paul’s Jim Bode. “It’s hard to develop awareness up there that the river is the drinking water source for downstream communities. Today, watersheds are typically managed on a tributary by tributary basis. What we need to do is create a watershed district on a grand scale. Right now there are zillions of government and non-governmental organizations connected to the Mississippi. And when it comes to comprehensive planning and setting limits on contamination, every one of them has different parameters.”
However, creating such an “uber-watershed district,” with the power to bring about changes across the whole Upper Mississippi basin will be, Shahin Rezania concedes, “almost impossible to do.”
“But it’s our only choice,” he argues. “We have to convince communities upstream that if we have problems with water here, it affects them as well. That means asking farmers to give up part of the land they farm for conservation reasons, and towns and cities to consider how their development might affect the river. And it means creating incentives to buy up land along runoff areas and leaving it undeveloped.
“But that’s going to take money – and where is that money going to come from?”