Drain tiles that lead from farm fields into ditches and then into the Minnesota River contribute to the sediment now being deposited in Lake Pepin. (Star Tribune/The Minnesota Star Tribune)

For those of us who worry about the future of Lake Pepin, Bruce Tiffany poses an important question: Why, he asks, should his fellow "upriver" farmers care about the troubles of Pepin?

Tiffany grows cash crops -- corn and soybeans -- on a 1,700-acre farm near Redwood Falls. As a conscientious land steward, he knows that some of the rain that falls on his farm makes its way to the Minnesota River and, ultimately, to the Mississippi River and Lake Pepin.

In designing his farm, Tiffany has taken sensible steps to manage runoff. In some instances, such as the width of perennial plantings along critical buffers, he has exceeded legal obligations.

Expressing his ethos to Minnesota Public Radio, Tiffany said, "If you wouldn't do a breast stroke in your runoff, you can do better."

That's a laudable sentiment. If it were more widely acted upon, Lake Pepin would not be facing such a dire future.

But the sad fact is this: Lake Pepin -- a natural wonder along our nation's most iconic river, its rich vistas adored by sailors, birders and gawkers of all stripes -- is filling rapidly with muck.

Most hydrologists have concluded that these mountains of sediment come principally from the Minnesota River. This stands to reason.

Most of the original prairies and wetlands of the Minnesota River watershed have been converted to farmland. With the installation of extensive drainage systems, the land is highly productive but also sheds water more quickly than in the past.

In heavy rainfalls, torrents transport sediments -- and fertilizers, pesticides and other pollutants -- from the fields to the river. The increased volume of water entering the rivers, meanwhile, erodes the river itself, adding to the sediment load.

Propelled by current, the muck finally settles when the flow slows as the Mississippi enters Lake Pepin. Researchers estimate that the bays and backwaters of the upper lake are now filling at 10 times the historical rate.

The alarm has been sounded, so the question is what we will do.

In a book called "The Vanishing American Outhouse," there is a picture of a rickety old privy overhanging Canyon Creek in Burke, Idaho. During the mining boom there, author Ronald Barlow explains, such "creek-drop biffies" outnumbered conventional outhouses by a 10-to-one margin.

Not surprisingly, the once-pristine waterway was soon transformed into an open sewer.

"There were so many privies along the stream," Barlow writes, "that locals changed its name from 'Canyon Creek' to a four-letter designation."

The story of Canyon Creek is a small embodiment of what ecologist Garret Hardin famously termed "the tragedy of the commons." A public resource -- in this case, Canyon Creek -- was used by people who were acting in a rational self-interest.

While their quick and easy method of waste disposal made sense to individuals, collectively it spelled disaster.

Today on Lake Pepin, a similar tragedy is unfolding. Thanks to modern sanitation and water treatment technologies, people at Lake Pepin do not face human health hazards like dysentery or cholera.

But at the core, the problem is the same: our individual use of a common resource -- in this case, the use of the river to drain former prairies and wetlands -- has taken a brutal toll on Pepin.

None of this is meant to vilify farmers. Row-crop agriculture isn't going away, and neither are drain tiles.

As a practical matter, the framework of our agricultural economy effectively encourages some farm pollution. But many of the harms can be mitigated, and, fortunately, there are incentives for farmers to do just that.

Under a pilot program announced just this month, for instance, Minnesota farmers will be able to have a share in up to $10 million in federal grants if they agree to employ farming techniques that prevent soil erosion and limit runoff.

For years, government policy in regard to farming and the environment has been more carrot than stick.

While the Clean Water Act of 1972 eliminated some of the most serious sources of pollution (such as the dumping of raw sewage and other harmful industrial effluent into waterways), it specifically exempted agriculture.

So why should farmers care about Pepin? Aside from an altruistic recognition of its value, they should care because their future will be linked to the lake's future.

As the science surrounding farm pollution grows, there will be inevitable pressure on farmers to employ best practices.

While the future of Pepin is important on its own merits, its health is also an indicator of larger concerns. After all, the same farm runoff that imperils Pepin contributes to the dead zone in the Gulf of Mexico.

Like Pepin, the Gulf has vocal advocates who will work the political process and demand change as a bad problem becomes worse.

Those farmers who choose to take advantage of conservation programs that exist today will have a leg up on their colleagues who don't. In the years to come, it's a fair bet that some of those voluntary programs will turn to mandates.

Why? For the same reason you don't see creek-drop biffies along Canyon Creek anymore: When public waters are degraded, after a while people stop asking for change and start demanding it.

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Michael McKay is executive director of the Lake Pepin Legacy Alliance.