Let's take a trip along the Snake River, from beginning to end, from its headwaters at the edge of Yellowstone National Park, all the way to where it joins the Columbia River, along the Idaho/Oregon border. It's a journey that author Richard Manning made for High Country News - not to take in the grandeur of the river's 1,078 miles, but to see the effects of industrial agriculture on both the waterway and the surrounding environment.

Here's Manning's explanation:

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.

Most of the river's journey is across the Snake River Plain; an area of high desert, where the Snake is just about the only source of water, other than the few inches of annual rain. So that river water is key to the biggest industry in this area - agriculture. It used to be potatoes and sugar beets that dominated Idaho farmland but more and more, farmers are planting corn and raising dairy cattle, two very water-intensive commodities.

Manning gets into the politics of this - the subsidies for big agriculture, the poverty of many of the farm workers versus the wealth of factory farm owners, the fact that much of what is grown and raised on the Snake River Plain isn't exactly good for our health - and it's worthwhile to read what he has to say on these issues.

But I want to focus on his main point - that the rise of agriculture has had a tremendously negative effect on the environment here. Much of land around the river has been converted to crop and grazing land, at the expense of native plants and wildlife. The dams and reservoirs that punctuate the water's flow prevent the natural rise and fall of the river, destroying the ability of many species to survive - I'm thinking of cottonwood trees, which rely on intermittent flooding; and salmon, which must swim upstream from the ocean to spawn in the Snake's many tributaries.

And then there's the cow shit:

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.

Here's what blows my mind. That sewage isn't even treated. It's pumped out over the ground, where it filters through the porous volcanic soil back into the groundwater and back into the river itself. All those nitrogen compounds from the poop, plus the antibiotics fed to the cows to keep them healthy in unhealthy living conditions, plus the pesticides and fertilizers - all of that makes its way back into the groundwater (into people's wells) and into the river.

Now where, you might ask, is the federal government in all of this? Aren't there limits on pollution? Something called the Clean Water Act? The state hasn't shown much interest in dealing with this but, according to Manning, the federal government believes Idaho has 13,057 miles of stream that fail to meet clean water standards. 204,091 acres of lakes/reservoirs. Agriculture - surprise! - is the biggest contributor to this pollution. But there are a lot of bureaucratic and legal loopholes that allow big ag to keep doing what they're doing - and regulators have no real recourse.

So all this nasty stuff ends up at the western end of the river, in the last few reservoirs before the Snake joins the Columbia. There it sits in what could be considered giant-sized sewage treatment lagoons, these reservoirs that are slowly filling up with toxic sludge. These are reservoirs are used for both recreation (swimming, fishing) and water supply, but there's no plan in place to clean them up or stop the ongoing pollution that stretches back across the state.

Drink up.