This verse segment from "The Rime of the Ancient Mariner" is becoming more and more recognizable in western agriculture.

Water is becoming the most valuable ingredient in farming and will become more so in the future. Global warming is beginning to reduce rainfall, and virtually all western rivers are projected to have lower flows in coming years. Runoff is occurring earlier, and we no longer have the "reservoirs" of vast snowfields into May and June.

The second-largest U.S. river emptying into the Pacific is the Colorado, which drains vast regions of Wyoming, Colorado, Utah, New Mexico, Arizona, Nevada and California. It used to drain about 20 million acre feet per year into the ocean. Today that natural flow is reduced to about 15 million acre feet. Aquifer drainage has also outpaced recharge.

Any sensible person can see that without more precipitation, water will soon be "nor any drop to drink." The only remedy is less usage.

Because agriculture uses at least 70 percent of the world's fresh water - and even more from the Colorado River - farming will be the first place to look for water savings.

Those savings should be achievable by focusing on different crops. Instead of growing low-value crops like alfalfa that's shipped to China, we can produce high-value vegetables, flowers or grains. If water were priced at full value, including opportunity-cost value, marginal crops would disappear and water conservation would appear.

Moving north from the Colorado to the largest U.S. river emptying into the Pacific, we see a vastly different picture. Although the Columbia is 200 miles shorter than the Colorado and drains a smaller land mass, its water volume annually is almost 10 times that of the Colorado. There are more than 400 dams in the Columbia drainage, mostly for irrigation, with some for hydroelectric generation and transportation. Despite the number of dams and canal systems used for agriculture, total water withdrawal from the Columbia Basin is estimated at less than 5 percent of river flow.

Idaho uses far more of that water per capita than any other state in the basin, tapping an estimated 13,000 gallons per person per day. Wyoming is No. 2 at about 1,000 gallons per day. I didn't believe that statistic at first, but it has been corroborated by authoritative federal agencies. Considering our small population and the fact that 99 percent of all water usage in Idaho is for agriculture, the numbers ring true.

When we look at the disappearance of water in most of the West and the need for 100 percent more food within 50 years, we know that conservation is a must despite the tremendous water assets of the Columbia Basin. Many things can be done today to diminish usage. Most are relatively simple. About a third of all Idaho acreage is flood irrigated, and by investing in sprinkler and drip irrigation, much of that water could be saved. Lining irrigation ditches, monitoring soil moistures to irrigate only when needed, contour farming and no-till agriculture all would contribute to reduced water usage - although as farmers and ranchers, we must be attuned to probable increases in costs.

Finally, what we don't know today might be the most exciting parts of the solution. Desalinization, bio-engineered crops that drink almost nothing, rivers that run uphill - we cannot fathom what is possible.

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Chas Bonner, vice president of business development, Scythe & Spade Co., Eagle. chasb@ag-management.com