From The Nature Conservancy (John Sanderson):
Like a Frenchman knows good years and bad years for wine, I remember years in Colorado for their snowpack. In 1995, deep snow remained well into summer. In 2002, the snow never came and Coloradans were reminded of how bad drought can be. In 2011, the snow at my family’s favorite backcountry ski trailhead was still 10 feet deep in early May. In 2012, it was drought again; later that summer fires raged west of my home in Fort Collins.
Water from this snowpack is the proverbial lifeblood of Rocky Mountain rivers. In fact, water is the lifeblood of the entire economy of the West—for brewers in cities, for corn growers east of Fort Collins, and for angling guides in our high county. Competition for water can be fierce.
Residents of the Southwest weren’t yet competing for water in 1776 when two Spanish priests — Francisco Atanacio Dominguez and Silvestre Valez de Escalante — christened one of our lifeblood rivers, El Rio de Nuestra Senora de las Dolores. Better known as the Dolores — the Sorrows — many view this epithet as reflecting the current state of the river. In 1983, the gates closed on the McPhee Dam, one of the last projects during the United States Bureau of Reclamation’s era of big dams. Within a decade, a series of dry years came along and a fight exploded over the impacts of the dam on the ecology of the river.
With its origins in the high, remote mountains near Telluride in southwest Colorado, the Dolores is a river of extremes. Fed by snowmelt gushing off the Rocky Mountains, spring flood flows before the dam could reach 1000 times the low flows of late summer. The reason people dam rivers is to make the water supply — in this case irrigation water — more predictable. Capture the spring snowmelt in a reservoir. Send the water to farm fields later in the summer. That’s good for farmers. But it’s bad for native fish.
At the time of Dominguez and Escalante, only about half a dozen fish species lived in the 175 miles of river now below McPhee Dam. These fish are all built for extremes. Aerodynamic bodies help them withstand huge floods. Tolerance for hot temperatures allow them to wait out low, warm waters during drought. Some of these fish can detect chemical and electrical signals of their prey, so they can hunt in dark murky water. Many can live for decades, allowing populations to survive a string of bad years with little or no reproduction.
The best known native of the Dolores is America’s largest minnow: the Colorado pikeminnow. The pikeminnow can reach 6 feet long and weigh up to 80 pounds. One hundred years ago, pikeminnow were so abundant that fishermen would haul them out of rivers with pitchforks. Pikeminnow harvests even supported a commercial cannery near Yuma, Arizona. This species has been around for more than 3 million years. But after just a few decades of 20th century dam building, they were nearly extinct.