Recent Study Reports Natural Flow of Most US Rivers Is Hindered by Land and Water Management Practices

The natural flow of most US rivers is altered by human land and water management practices, according to a recent study by the United States Geological Survey (USGS).

“The USGS has been monitoring river flows at thousands of streams across the country for decades,” explains Daren Carlisle, a USGS aquatic ecologist with the National Water Quality Assessment program in Reston, Virginia.  “We said let's use this wealth of data that's out there and try to see what it tells us about how much the natural flows of rivers have changed around the country.”

“Our first surprise was that altered river flows are not a local or regional problem, we see them everywhere,” says Carlisle.

“The fact that we can, at a large geographic scale, detect ecological impairment in streams with altered flows, implies that a national goal of restoring more natural streamflows would go a long ways.”

Carlisle and his colleagues found that 86% of 2,888 river and streams across the United States had seen changes in their natural stream flow due to interventions like reservoirs, diversions, wastewater input, and that hallmark of urbanization, impervious paved surfaces. The study was published in the journal Frontiers in Ecology and the Environment last week.

The Rhythm of the River

“The very essence of a river and a stream is dynamically changing flows,” he says. “Think of it as the master conductor in this ecological symphony of rivers and streams.”

An unfettered river’s flow changes through the seasons and years but us humans are like Goldilocks when it comes to rivers. Floods are bad but so is drought. We want even controlled river flows so we dam our rivers and mete out their water resources as we see fit.

The problem is that virtually every species that depends upon rivers - sports fish, semi-aquatic birds, amphibians, even the cottonwoods that green small strips of the arid southwest – relies on the river’s dynamic and changing flow.

Alter the river’s flow and rhythm and you get negative ecosystem consequences, Carlisle explains. The more severely a river’s natural flow is altered, the more degraded the river’s biological communities are, the USGS study found.

Let Her Flow!

“What we don't recognize is that many of the things about rivers and streams that we value - whether its those lush wonderful forests along rivers, whether it's important sports fishing or whether it's white water rafting - cannot be maintained without some semblance of the natural flow dynamics,” he says.

Instead of confounding or correcting a river’s natural flow regime we must embrace it, Carlisle says. “Almost everywhere we look across the country we see the same potential of restoring ecological integrity by managing water in ways that more closely resemble the natural dynamics of stream flow.”

Whether it’s the removal of dams (like the Edwards Dam that was removed from the Kennebec River in Maine in 1999) or the management of river dams to mimic natural flows (such as the Flaming Gorge Dam on the Green River in Utah) the outlook is good, he concludes: “There are a lot of instances where we're finding yes, all we need to do is put some water back in the stream and things get better."

It's a lesson that we've seen time and time again over the past 4.5 months as we've journeyed through North America's watersheds and the timing couldn't be better to have a scientific study affirm and underscore what we've experienced for ourselves: give Nature an inch and she takes a mile.