At least in America, the era of big new dams is probably over for good. But the era of big new ditches and water pipes may just be starting. This merits close attention.

Earlier this month, federal and Washington state officials celebrated a large canal that will transport irrigation water from Lake Roosevelt behind Grand Coulee Dam to dryland farmers in Eastern Washington.

There are some significant benefits from this project. But it is not the unalloyed good that politicians would have us believe.

On the positive side of the equation, farmers produce food. This is no small benefit in a world that is becoming ever-more crowded. In many areas, farmland is being swallowed up by urbanization, soil erosion, desertification, poor farming practices and other problems. Eastern Washington and Oregon are producing large quantities of crops. Water of course is a primary limiting factor.

Irrigators have been using wells to draw down fresh-water aquifers at an unsustainable rate. This “fossil water” accumulated underground over the course of thousands of years. It is not quickly replenished. Canal water can substitute for well water, possibly preserving aquifers and greatly extending the future of dry-side agriculture.

Water is key to the economic survival of the region east of the Cascades. This canal is just the start of finding more efficient ways to move it around.

This is true worldwide. In a world that is generally becoming hotter and drier, fresh water is an essential asset that will increasingly spark wars and migrations as the century goes on.

The Columbia River will be much coveted. All the water pulled out for irrigators will be subjected to evaporation, heating and contamination. This comes at the same time scientists are recognizing the importance of leaving enough water in the river for fish and wildlife.

It may be only a matter of time before long-whispered plans for pipelines are seriously proposed to carry Columbia water to the U.S. Southwest.

There will be winners and losers in the 21st century’s water wars. More water for irrigators in our own region may be acceptable. Shipping our water to desert cities will be something else entirely. We must be prepared to defend our region’s basic resource.