The Mimbres River in New Mexico's Mimbres Valley Photo by Carla DeMarco.

Autumn slips across the desert quietly. Although nights grow chill, summer's heat lingers in the afternoons, and the greenery brought on by summer rains simply fades to dusty olive, bleached straw, and weathered brown. As the soil dries out, mesquites, desert willows, and ocotillo drop their leaves without any fanfare. But here and there where water flows - a spring, stream, an irrigation ditch, or a river - autumn shows in the rich yellows and golds of cottonwood trees.

The Rio Mimbres, "River of the Willows," in Southern New Mexico, is an ordinary Chihuahuan Desert river, born high in the mountains, fed by winter snows and summer thunderstorms, and eventually flowing out into the open desert.

Like most Chihuahuan Desert rivers, the Mimbres disappears after it exits the mountains. Its normally-shallow flow simply sinks into the desert, leaving an empty bed to wind for miles through the landscape like a ghost river.

Thomas Antisell, mapping a route for the Southern Pacific Railroad through Southern New Mexico in 1856, described the terminus of the Mimbres as "a large collection of fresh standing water in pools or lagoons, surrounded by willow thickets." One sunny spring day, Richard and I took a gravel road that paralleled the course of the Mimbres, he

aded upstream through the desert to find the river's lagoonlike end.

At first there was no sign of either river or arroyo in the dry grasslands that we drove through. Then we spotted a shallow valley breaking the line of the grasslands to the north. But still no water.

Past a ranch, and the bright green rectangles of its irrigated hayfields, the road suddenly dropped down a small bluff right into the valley. A dense swath of native sacaton grassland, the dried flower stalks as tall as the roof of our truck, filled the valley bottom from bluff base to bluff base. Off to the left, a dotted line of willows, hackberries, box elders, ashes, and the occasional cottonwood marked the river channel.

We searched for a way through the curtain of sacaton and finally found a narrow track that headed for a grove of thick-trunked cottonwoods. Down the track, through the tall sacaton, past a small pond surrounded by old willows, along an irrigation ditch chattering with flowing water, we headed, sure that we'd found the river at last.

At the cottonwood grove, we indeed found the Rio Mimbres - and its end. A raw, recently bulldozed gravel dam several feet high plugged the river channel. Below the low dam, the channel was empty, dry. Above the dam, the river pooled, and, siphoned by an open headgate, the entire river ran into the irrigation ditch. The grove of cottonwoods, all old and misshapen, massive trunks slightly askew, circled the pond like sentinels at a gravesite.

New Mexico's water law gives no status to rivers as such. All of the water in a river and then some can be legally diverted for "beneficial" uses, depriving fish, insects, cottonwoods, ducks, beavers, and the rest of the river community of water. With no water, the vibrant river community slowly dies. Hence the modern-day terminus of the Mimbres, no longer the lagoonlike pools, rich with life, described by Antisell in 1856-instead, the premature, but legal, death of a Chihuahuan Desert river.