Idaho’s sewer system is the Snake River

As Big Ag flourishes, this massive waterway suffers.

  • Kirk Anderson
  • Irrigation headgate on the Henry's Fork, a tributary of Idaho's Snake River.

    Kirk Anderson
  • A panoramic view of the Snake River from the canyon rim just a few miles upriver from the town of Marsing in southwestern Idaho, where the irrigated plain is surrounded by desert.

    Kirk Anderson
  • The Snake River winds through farmland south of Boise, Idaho.

    Kirk Anderson
  • An aerial view of one of the many industrial dairy farms dominating the landscape of southern Idaho.

    Glenn Oakley
  • Agricultural runoff into the Snake near Homedale.

    Leo A. Geis, Idaho Airships Inc.
  • Boats float beneath a depleted Shoshone Falls. So much water is diverted for hydropower and irrigation above the falls that sometimes it's only a trickle.

    Kirk Anderson

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The decline of biodiversity extends across the land far from the riverbanks, and affects the river itself, most obviously its salmon. Historically, these anadromous fish – the youngsters migrate down the Snake to the Columbia and ultimately the Pacific Ocean, and the adults swim back up when they're ready to spawn – ran the river's mainstem all the way up to Shoshone Falls, a natural barrier east of Twin Falls. Now, all four surviving runs of Idaho salmon are listed as endangered or threatened under the Endangered Species Act, mainly because of migration-blocking dams and water diversions. Originally there were five runs, but the Snake River's coho salmon went extinct in the 1980s. And anyone hoping to experience the aquatic roar of Shoshone Falls today needs good timing and luck. Shoshone Falls is still dubbed "the Niagara of the West" because it's a 212-foot cliff in the river channel, a longer drop than the real Niagara Falls on the New York-Ontario border. But so much water above Shoshone Falls is now diverted for irrigation and hydropower generation that it's often only a trickle – fodder for jokes, as in: "I hear they only turn on the falls long enough to let gawkers snatch selfies on their iPhones."

Beyond the changes in wildlife, vegetation and river flow, consider the federal Environmental Protection Agency's rule of thumb that we'll call "cow shit equivalents." Basically, a single cow produces feces the equal of 20-40 humans. There's every reason to go with the high end of the range in the case of Holstein dairy cattle, champions in this regard, but assume a middle ground of 30. Under this math, the feedlots of southern Idaho offer to the environment the equivalent in raw sewage of 17 million people, dwarfing the effects of the state's 1.5 million human residents. And the dairy feedlots cause much more of this impact than an equivalent number of humans would, because the feedlots do not have to funnel their feces through sewage treatment plants or septic tanks. Instead, they pump it onto the ground over the aquifer that is one with the river.

The manure is rich in pollutants – chiefly nitrogen compounds and phosphorus, but also various others including antibiotics, which feedlots pack into cows to ward off the sickness that inevitably results from confinement and a diet lacking pasture grass. Meanwhile, the farm fields are awash in pesticides, herbicides and fertilizer.

These pollutants flow through the porous volcanic soil into the groundwater and eventually into the river, but Idaho's state government does almost no monitoring. Nor do the other governments that have jurisdiction, from the counties on up to Congress and the executive branch in Washington, D.C. Ag economist Gray is one of the few Idaho officials willing to admit publicly that the lax environmental regulations have been a primary reason for the dairy sector's growth.

Among the scanty findings available: Some drinking-water wells sampled along the Snake are in violation of the EPA standard for nitrogen compounds (10 milligrams per liter, more than 10 times the natural background level here). This nitrogen is a concern because it's hazardous to any humans who drink it, especially infants. There is no good reason beyond politics that the monitoring doesn't look for other pollutants and more widely than a relatively few drinking-water wells.

U.S. Geological Survey hydrologists did make a wider assessment of the nitrogen in 2012, using well sampling and computer simulation to trace nitrogen flows in a study area corresponding to the outlines of the Magic Valley. The study considered three scenarios with the understanding that agriculture clearly generates the nitrogen. The first scenario: All nitrogen pollution from feedlots and farm fertilizer ceases immediately – not likely, but a way to calculate how long it would take the water from the mountains to flush the system of pollutants. Another scenario calculated the flows of nitrogen continuing unchanged, as if they could be capped at the annual totals in 2008, when the data were collected. A third looked at the result of another 20 years of growth in the dairy sector on a curve like the last 10. Even in the first scenario – shutting down or somehow sealing off all the dairies, feedlots and farms – excess nitrogen would remain in drinking-water wells for about 40 years, the time it would take the aquifer to recover. The consequences of the other two scenarios? Worse and much worse.

The television gangster Tony Soprano routinely advised colleagues against shitting where they eat, good advice in any situation, but especially for crowds of cows confined on porous soil over an aquifer that people use for drinking water. Yet buried in the USGS study is a graph that suggests we are missing something by focusing on feces. The researchers modeled nitrogen inputs by adding up cow numbers and the chemical fertilizers applied to all fields. Both lines on the graph rise in a steady, steep gradient, the increase in fertilizer being the direct result of the need for cattle feed. But the farm fields are generating about twice the raw tonnage of nitrogen that comes from feedlot manure. The manure piles with their olfactory signature get your attention, but the subtle fertilizer component is of far more consequence. Double, in fact. And the fertilizer and other chemicals on the farm fields effectively extend the feedlots' footprint well beyond their fences, and well beyond the Magic Valley, even beyond the Snake River Plain to the intermontane valleys to the north. The croplands from Ashton on down the river are sucked into the vortex as they churn out alfalfa and corn for the cows.

Both alfalfa and corn require more water than the traditional potatoes and beets. Also worth noting, corn requires as much as 40 percent more nitrogen fertilizer than a field of wheat. Alfalfa's relationship with nitrogen is another matter. As a legume, it has the ability to in effect manufacture its own fertilizer by pulling free nitrogen from the air. That nitrogen also winds up either in the soil or in manure.

The relevant bureaucratic term here is "303(d)," the section of the federal Clean Water Act that tells states to list all streams and rivers that do not meet clean water standards. Idaho has 13,057 miles of streams and rivers that fail to meet the standards, and 204,091 acres of "lakes" (including reservoirs) that also fail. This is mostly the feds' calculation, because Idaho's state government has been reluctant to do the survey. The list includes much of the Snake's system, especially the reservoirs, where slack water backs up nutrients and sediment. A variety of dynamics and pollution sources is to blame, including sewage treatment plants for towns and the natural background levels of the nutrients, but agriculture is the primary culprit, especially nutrient loading from nitrogen and another common fertilizer, phosphorus, along with bacterial contamination and sedimentation.

In theory, the 303(d) listing is meant to trigger remedies, the designation of sources and coming up with "TMDLs" – more government jargon, standing for "total maximum daily load," a designation of how much pollution a stream can bear without violating water-quality standards. Once this calculation is made for a stream, the total permitted discharge is apportioned between the various polluters, with each expected to reduce its discharge to bring the stream into compliance. Idaho's first 303(d) list was composed in 1996, but there is still no real plan to clean up the streams and rivers. And even if a plan does materialize, it wouldn't make much difference. Most of the pollution is invisible to this regulatory process because of a loophole that divides the pollution into classes: "point source" or "non-point source."