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for people who care about the West

Idaho’s sewer system is the Snake River

As Big Ag flourishes, this massive waterway suffers.


Begin where the Snake River begins, as crystal-clear, clean water on the calderas of the Yellowstone Plateau, on the edge of the vibrant national park. In late spring, the largest tributary in the headwaters, the Henry's Fork of the Snake River, is still locked in a head-high layer of snowpack. On wind-blown ridges rimming the water, hundreds of elk graze under the late morning sun. A-frames and log cabins hibernate, boarded and silent, awaiting the summer arrival of the fly fishers who treasure this place. Everything appears at peace and as it should be.

But for those who know what to look for, a less pristine reality is evident, even here in the river system's headwaters. It's represented by the 7,000-acre Island Park Reservoir on the Henry's Fork, built in 1938 to benefit farmers downhill from here by holding back and controlling the flow for irrigation diversions. This repurposing of the water becomes obvious 20 miles south of Island Park, where the plateau tips to deliver the Henry's Fork to the Snake River Plain, a rapid descent from the residue of a high-elevation winter to a more recognizable spring, from the postcard Idaho to the real Idaho, from what was to what is.

From here on, the Snake, to use the euphemism of record, becomes a "working river" – wholly subservient to agriculture. There are many ways to describe how a river system gets harnessed to ag, but we'll begin with the most basic, the dams and reservoirs. The Snake's drainage is interrupted by no fewer than 23 large dams that form reservoirs, and there are many smaller dams that divert water for irrigation without stalling the river's flow. The reservoirs impound about half of the river's 1,078 miles. None of this is news; we began damming this river – the largest tributary of the Columbia – more than a hundred years ago, and the dams were only the first step in the creation of one of the world's largest concentrations of industrialized agriculture.

We are not here for elk or fly fishing, but rather for accounting. Industrial agriculture impacts the entire planet, but the Snake's system – sizable, relatively isolated, discrete and significant – is a good place to assess the impacts at a local scale, examining the nuts and bolts as well as the weight of the whole. This accounting process is simple enough for those willing to pay attention: You begin where the water is clean and relatively natural, then follow the big river across an entire landscape defined by agriculture, to where the abused, exhausted water finally ends up.

Acknowledge one basic fact about the vast lowland that the river flows through: The Snake River Plain, sprawling over 15,600 square miles, is a desert. The river system and about 10 inches of rain a year are its water supply entire.

Remember that, as we continue our journey into the realm of industrial ag. Henry's Fork merges with the mainstem Snake near Ashton, a tiny town whose tall silos are monuments to the river's work. In the countryside, farmers are burning last summer's unwanted growth off the irrigation ditches, smoothing the channels for this season's flows. More farmers on massive machines till the soil, generating dust clouds. You can't miss how irrigation has recast the land. What was once drought-tolerant sagebrush is now a green-tiled landscape of clean-cut squares and circles drawn by center pivots.


Whether the irrigation water comes from ditches drawing directly from the river system or from groundwater wells, essentially all of it comes from the river. That's true nearly everywhere farmers operate around rivers, but it's especially true here, because the thermal geologic forces that created the Yellowstone calderas also deposited loose volcanic soil across the plain, soil so porous that the groundwater flows as one with the river. The irrigators here have tens of thousands of groundwater pumps – run on cheap electricity that also comes from the dams – causing the water to circle continuously, from aquifer to surface, and then percolating back to the aquifer. The entire groundwater body – the largest west of the Continental Divide, larger even than Lake Erie – is named in recognition of the close connection: the Snake River Aquifer.

The irrigation has converted 6.5 million acres from grassland to cropland along the Snake – an area larger than Massachusetts or New Jersey. Beyond that, just past the green irrigated fields, there are tawny furzes of unplowed grass, rock and lava flows that amount to millions of additional acres devoted to ag. Most of this land is federal, controlled by the Bureau of Land Management and leased by farmers and ranchers for livestock grazing. In total, the Snake strings together at least 18 counties, and according to the U.S. Census of Agriculture and the Idaho Department of Commerce, fully 87 percent of these counties' land is used for agriculture, either cropland or grazing.

This entirely domesticated landscape's most famous product is the Idaho spud – the russet potatoes that have long been and still are Idaho's dominant cash field crop. But pause near Ashton for a closer look. Some of the spud sheds seem more forlorn than usual, some of them even abandoned. Notice, too, the stubble fields awaiting spring planting – this year, the stubble is corn. Corn in potato country? It's evidence of a recent shift that has intensified the plain's industrial ag. Since 1993, Idaho's potato acreage has declined by 18 percent. Sugar beets, long the region's other mainline crop, have declined by 15 percent in total acreage planted. Same for malting barley (a decline of 14 percent) and wheat (down 12 percent). Meanwhile, corn acreage has almost tripled, and alfalfa – the other up-and-coming crop here – has increased tenfold.

The cause of this revolutionary shift can be smelled as well as seen as we continue down the river. In enormous feedlots dedicated to dairy production, black-and-white Holstein dairy cattle stand shoulder-to-shoulder at feed bunks, gobbling the corn and alfalfa and transforming it into milk and mountains of manure. Since 1993, the number of dairy cows in Idaho has nearly tripled, to 572,000 head, so that Idaho now ranks fourth among the states, just behind New York and just ahead of Pennsylvania.

It's an odd development for a desert like this. After all, cows evolved and were domesticated in wet climates, and corn and alfalfa grow best in places whose annual rainfall is quadruple that of southern Idaho. Milking, processing, washing, moving manure, all suck up massive amounts of water. But the development is deliberate. These dairy operators are not local potato farmers who suddenly fell in love with Holsteins. Rather, most moved here from California's Central Valley, eager to harness this desert's water to grow large quantities of high-quality forage for dairy cows. Wilson Gray, a state agricultural economist, explains the attraction: Idaho supports the dairies through the complete domestication of the Snake River, which allows farmers to meter out X number of inches of water, year-in, year-out. No rain necessary; no floods expected anytime soon.

Hundreds of miles from the Snake's headwaters, we reach the Magic Valley, nicknamed for the miraculous conversion of desert to farms. It's ground zero for Idaho's industrial agriculture. The Magic Valley hosts two-thirds of the state's dairy feedlot cattle, and its eight counties include Gooding County, where more than 99 percent of the land is given over to ag, and Cassia County, which achieves 96 percent. As we enter the valley's hub, Twin Falls, on a bridge spanning the scenic Snake River Canyon, the two immediate impressions are: This town is prosperous, and it values its view of the river. The country club sits on the canyon floor, and tony restaurants, malls and office buildings line the developed side of the rim, commanding the view of the river 500 feet below. All are attached to the dairy sector by tributaries of cash.

You might be surprised by the breakdown of the dairy sector. Only 6 percent or so of Idaho's total dairy production goes to "fluid milk," the stuff you drink. That's because fluid milk is heavy and costs a lot to ship. Better to manufacture and sell dry milk, which is why much of the Snake River Plain's milk leaves in a dehydrated form, bound for food processors in Asian markets. Cheese is also big business here, mostly the processed kind slapped on the burgers in fast-food chains, or in the industry's preferred term, QSRs or "quick service restaurants."

Thus, the top tier of the Snake River Plain ag industry includes the usual suspects: J.R. Simplot, Idaho's homegrown potato-rooted multinational company, with annual sales topping $3 billion, and the Amalgamated Sugar Company, the nation's second-largest sugar producer, which processes the beets for bulk customers such as Pepsi's Mountain Dew. And there's an abundance of new suspects, like the Idaho Milk Products company, whose Magic Valley factory processes 3 million pounds of milk per day – in the company's words, the "largest dedicated milk protein concentrate and milk protein process plant in the world." Glanbia Foods, the world's largest manufacturer of American-style cheese, is also headquartered in the Magic Valley. Cheese- and whey-maker Lactalis American Group, owned by multinational corporations based in Italy and France, also operates here. And so on.

Begin the critical accounting with economics, but deeper than the boosterish summations of jobs and revenue. A couple of decades ago, the famously blunt Dwayne Andreas, head of Archer Daniels Midland, the prototypical U.S. food processor, said that he would never consider steering his company into the business of farming, the front line of ag. He preferred processing, because the risks are lower and the profit margins higher. He also acknowledged that U.S. agriculture is not a free-market economy, but is and always has been a socialist enterprise, supported by pro-industry government policies, such as domestic price guarantees and import restrictions, as well as direct subsidies. The 18 Snake River counties, for instance, received a total of $1.85 billion in various federal farm subsidies between 1995 and 2012, when the dairies were ramping up.

But really, U.S. industrial agriculture is more of a hybrid. Modern entrepreneurs of all stripes succeed by socializing their costs onto the taxpayers while they privatize profits. That's the real magic in the Magic Valley: making the costs disappear.

This magic was begun by no less than President Theodore Roosevelt, a progressive who believed the West could be settled, made prosperous and democratized by irrigation and farming. His seminal legislation in this regard was the 1902 Reclamation Act, which fronted much of the federal cash that began the industrialization of the Snake River by locking the flow behind subsidized dams. Later in the 1900s German social scientist Karl Wittfogel held a diametrically opposed view of this kind of development, warning that "hydraulic societies," from the Chinese on, have been decidedly undemocratic by necessity, more suited for oligarchy. Wittfogel would feel validated by modern Idaho's hydraulic society. There are a lot of farms along the Snake, and so you could say the plain is peopled with yeomen, as Roosevelt envisioned. But follow the money. Gooding County, for instance, has a total of 665 farms, but 14 percent of them account for 95 percent of total sales. Adding up all the farms along the Snake River system, according to the U.S. Census of Agriculture, 8.5 percent of them pull in 85 percent of total sales. These oligarchic farms and the mega-processors perch at the top of a pyramid based on low-wage jobs.

As a recent editorial in the Twin Falls Times-News observes: "Beyond the political shoutouts and grandstanding, beyond the high-brow discussions of economic development and billionaire elbow-rubbing, there lurks the truth of south-central Idaho's economy. The people are left impoverished while the sprawling new factories make a very few rich." This jeremiad is even more remarkable because the Times-News is owned by Lee Enterprises, a pro-business, conservative chain anchored in Midwestern farm states. But the local editors can't ignore the reality in the Magic Valley: About 80 percent of the students in the valley's schools receive free or reduced-price lunches, a common indication of poverty. "These are farm kids," the editorial points out, "and children of laborers and factory workers" mostly associated with industrial ag. In another gauge of poverty, Idaho as a state is dead last in average weekly pay, but the Magic Valley's counties fall below even that dismal average.

The jarring discrepancy between upscale malls and impoverished children living nearby in sub-standard housing was recently, if inadvertently, recognized by Idaho's highly conservative U.S. Rep. Raúl Labrador, who reported that 90 percent of the jobs in Idaho's dairy sector are held by "illegal immigrants." Nonsense, the dairymen countered; it's really only between 75 and 80 percent.

There is nothing unique about this economic angle; it pretty much tracks the demographics and cash flow of industrial agriculture nationwide. We tend to look the other way, because this is how we get food. People gotta eat, don't they? But consider what Idaho's farms produce. Potatoes? Everyone's "gotta eat" potatoes, right? Except that only a sliver of Idaho's total production is sent as whole potatoes to supermarkets. About two-thirds is processed in one way or another, sliced, diced, frozen, dehydrated, typically ending up in a fast-food fryer, filled with unhealthy trans fats. Sugar beets? Like the fries, sugar lies at the root of the nation's obesity epidemic. Barley? The dry farmers who specialize in this crop are typically Mormons growing malting barley for giant beer-makers, Coors, Modelo and Anheuser-Busch, consumption of which is prohibited by the Mormon Church.

Or consider Chobani, the rising-star manufacturer of Greek yogurt. Chobani started small in upstate New York, but is now anchored in a gleaming new 1-million-square-foot industrial building just outside Twin Falls – the world's biggest yogurt factory. Hamdi Ulukaya, the Turkish immigrant who founded the company in the early '90s, is today personally worth $5.4 billion. But even Chobani yogurt's mega-factory doesn't exactly produce "gotta eat" food. Chobani boasts that its product is "delicious, nutritious, natural and accessible," but a recent New Yorker article took issue with some of those adjectives, under the headline "Just Add Sugar," the unofficial credo of the U.S. food processing industry. Chobani has achieved its success not only by adding sugar, but also artificial colors and thickening agents. Its "natural" yogurt is really another kind of fast food derived from feedlots, which has important implications for human health as well as the environment and the economy. To name one, feedlot milk and beef lack the healthy omega-3 fats present in both products when they derive from pasture-fed cows.

All this industrial ag has transformed the environment. The Snake River Plain's original native sagebrush and grasses were much richer in plant and animal life than today's farmed and livestocked plain. Fur trappers in the early 1800s, among the first Europeans to arrive, described "a landscape of grasses shoulder high to a horse, with brush and trees along even the intermittent streams and a riot of bird life, grazing animals and attendant carnivores," write E.B. Bentley and Glenn Oakley in a history of the place published by Boise State University. "Trappers reported bison, antelope, sheep, elk, deer and beaver. Carnivores included grizzly bear, wolves, coyote, lynx and cougar."

Wildlife in any desert is largely dependent on riparian vegetation. From the number of reservoirs alone, you might conclude that half of the region's original riparian habitat has been drowned, but this understates the case. Cottonwood forests were the core of the riparian areas, stabilizing the sediment with their roots and offering shade with their leaves, creating habitat for at least 150 species of grasses and forbs along with the wildlife, according to researchers focusing on a reasonably intact remnant west of Twin Falls. Cottonwoods require flooding, the seasonal rise and fall of water, to survive. The dams ended that ebb and flow so early that we really have no idea how much riparian habitat was destroyed, but it was clearly more than half.

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."

Point sources are typically sewage plants or factories, the sort of Rust Belt polluters that repeatedly set Ohio's Cuyahoga River on fire back in the 1950s and 1960s, one of the triggers for the passage of the Clean Water Act in 1972. Farm fields – the source of most of the nutrient loading, most of the nitrogen, in the Snake system – are considered "non-point" sources and therefore don't count. Yet wherever nitrogen, phosphorus and other fertilizers leach into streams, they stimulate the growth of algae that deplete the oxygen levels in bodies of water, which can eventually achieve a lethal condition called "anoxia." This process is most evident in the famous Dead Zone, where the Mississippi River empties runoff from the Midwest's Corn Belt into the Gulf of Mexico – a state-sized aquatic zone wholly anoxic and therefore dead, devoid of marine life. No doubt: Nitrogen and phosphorus kill rivers.

We can see more regulatory unfairness in the sewage-treatment plants along the Snake: They're forced to limit their discharges into the river, at taxpayer expense, while the privately operated farm fields are not regulated. And we can see some regulatory gray areas just downstream of Pocatello, where another Snake River tributary, the Portneuf River, flows beside a large Simplot factory that renders phosphate from local mines into mountains of fertilizer each year, while generating polluted wastewater. A billboard in front of the factory proclaims: "Fertilizer: Life's main ingredient." Poets might take issue with that, but it's true enough in a limited sense. The fertilizer factory would appear to be an obvious "point source" of pollution contributing to the Portneuf River's failure to meet the Clean Water Act standards. But the regulators have struggled to get leverage on this cog of the industrial agriculture on the Snake River plain, because the fertilizer factory doesn't directly pipe its phosphate-laden discharge into the river. Instead, the company pumps its wastewater to settling ponds, and from there, for many years it percolated through the soil to the Portneuf River.

The company argued that its riverside fertilizer factory was exempt from 303(d), and EPA regulators decided not to attempt a prolonged legal battle on that disagreement. Eventually, the agency found another lever, through an unrelated Superfund site cleanup it's forcing Simplot to do, and the company has agreed to line the fertlizer-factory ponds to reduce the likelihood of leaks into groundwater and the river system (a likelihood that is never reduced to zero because pond liners also have a habit of leaking). In effect, the regulators' victories come inch by inch, while the impacts of industrial agriculture advance by acres and miles.

What about the feedlots? Legislation subsequent to the Clean Water Act designated feedlots as point-source pollution, so the EPA could regulate them under the act if they discharged into the river or had a potential to do so during floods and storms. But the industry successfully sued to remove that provision, so now the EPA can regulate feedlots only if a factory-like pipe conveys liquid manure to the river. Feedlots are completely free to pump that same manure onto sandy soil fields a stone's throw from the riverbanks, even though the U.S. Geological Survey hydrologists have maps, computer models, well samples and 3-D drawings that show how manure flows to the river through the soil. This is another form of magic: A science agency sees it, but the other agency – the one that regulates – doesn't.

The EPA knows full well the threats posed to water quality by the explosion of feedlots along the river, but under the current legal framework, all it's done is institute a voluntary program of self-inspections and self-regulation. How's that going? "We know we have large CAFO (feedlot) facilities, but they have made the business decision to not participate," says Jim Werntz, EPA's director in Idaho. "Right now we have zero participation in Idaho."

As our springtime journey continues downstream of Twin Falls, we pass a wonderful and melancholy stretch of the river called Thousand Springs, where a great deal of the aquifer's underground flow finally gushes from the canyon walls and joins the river proper. Basically, it's all hard-used irrigation water percolated down from the vastness of chemically dosed fields and feedlots, carrying the nitrogen, phosphorus and other components of the fertilizers, and residues of the manure, pesticides and herbicides. Fish farms – another cog, producing millions of pounds of rainbow trout per year (Idaho leads the nation in cranked-out trout) – use the canyon springs to grow their product, a process that generates additional phosphorus and nitrogen discharges into the river, in the form of fish feces, among other things.

Farther down the river, still more cattle feedlots cluster around Marsing, southwest of Boise. These feedlots have discharged manure by spreading it as a liquid three inches thick and miles wide on surrounding farm fields, which are crusted over with dried muck. The feedlots weren't here 10 years ago, and now they confine about 15,000 Holsteins within a half-mile of the river. And so forth.

Just as Idaho's Snake River ag factory has a beginning, it has an end. Where the river approaches the Washington border, there are three final reservoirs directly receiving runoff from the Snake River Plain: Brownlee, Oxbow and Hells Canyon. (The four dams and reservoirs down on the Washington stretch of the Snake River, also built to benefit farmers, are not so directly related to the Snake River Plain.) Here, then, is where we do our final accounting.

We can do this accounting quantitatively, if you like, using numbers for sediment and nutrients sampled in the Brownlee, Oxbow and Hells Canyon reservoirs that exceed EPA standards. Definite readings of rampant algal blooms, anoxia and fish kills. There are even advisories issued by the state government, warning people not eat reservoir fish owing to mercury contamination of the tissue. It's difficult to determine the mercury's source exactly, but industrial ag has an important role. Mercury occurs naturally in soils and gets released into the atmosphere by operations such as crushing limestone to make cement, but that form of the element doesn't bioaccumulate in fish and humans. First, it must be chemically transformed in a process called methylation, which is made possible by the chemical composition of the nutrient-laden sediments of the reservoirs.

In another unusually frank conversation, some USGS hydrologists in Boise discuss the problem. One of them, Greg Clark, is especially blunt. "Every year you get this layer on the bottom (of Brownlee Reservoir) that goes anoxic, and then you get perfect conditions for creating methyl mercury."

Clark corrects the impression that the range of pollutants from industrial ag goes completely untreated. He sees the entire Snake as a sewage system, with the reservoirs at the bottom end acting as de facto sewage-treatment lagoons. Clark explains it using the terminology of that science: The three huge reservoirs/lagoons provide primary, secondary and tertiary treatment. He actually uses those terms.

"We should show the videos of what the bottom of Brownlee looks like," he says. "It looks like a sewage-treatment facility. Fine-grained muck. It's really nasty stuff. It looks like the bottom of a septic tank. We took a rover and went down and took videos, and there's all these little organisms down there decomposing stuff and there is gas bubbling up. It's nasty. It's nasty."

So this is the end, for now. One could argue with a mix of cynicism and dark comedy that this sort of sewage treatment works by sending relatively nutrient-free water downstream to the Columbia, where farmers can repeat the process of fouling it. But even the darkest comedians have no experience with reservoir-sized treatment lagoons hooked to a state-scale sewer. The reservoirs are filling day by day with toxic, mercury-laden sludge in layers to match the mountains. What will happen when – eventually and inevitably – almost 30 square miles of reservoirs fill with enough sludge to cover 2,700 square miles of land a foot deep? No one knows the answer. This problem we leave to future generations, as is our habit.


A few corrections and clarifications: The editing process introduced two mistakes in the version printed in the HCN magazine; both have been corrected in this online version. First, the dams in the Hells Canyon of the Snake River are not easier on salmon than downriver dams; in fact, they allow no fish passage, so those five words have been deleted from this online version. Second, the Chobani yogurt factory in Twin Falls is roughly a million square feet, not 100 million square feet (a mistake by the Idaho Dairymen's Association, which we repeated). And clarifying what we reported about the ingredients of Chobani yogurt: Chobani says its yogurt is natural, because the thickener, colors and flavors are derived from plants; that's an argument, because healthy-food advocates think those additives are artificial, and the federal government has not imposed a legal definition of "natural."


Richard Manning, based in Helena, Montana, has authored nine books including Go Wild, published earlier this year by Little, Brown and Company, and his freelance writing has appeared in a range of national publications including Harper’s and The New York Times.

This story was made possible with support from the Kenney Brothers Foundation.