A river scientist measuring the shape of the river channel. Photo © Julie Knudson

Spring Flood on the River of Sorrows

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.

USFWS Biologist Doug Osmundsen holds an endangered Colorado pikeminnow (Ptychocheilus lucius) captured in the Colorado River near Grand Junction in western Colorado. Photo © USFWS (Flickr) through a Creative Commons license

Less well-known are the bluehead sucker and the flannelmouth sucker. Contrary to sucker myths you may have heard, these two species are native and — because we’ve so altered their habitat — becoming rare.

With McPhee Dam fully online, farmers now put about two-thirds of the Dolores River’s water on fields of alfalfa and other crops. Spring floods are smaller by half or more. With less water and no big floods, sediment fills deep pools that roundtail chubs need for shelter and smothers the rocks where bluehead suckers forage. Without big floods, streambanks don’t get ripped up and reconfigured in the process of destruction and constant renewal that characterize Rocky Mountain rivers. Native fish now share their home with a dozen non-natives that wouldn’t have been able to survive the natural extremes of southwest Colorado, but now thrive in tamed water.

Can we turn the tide on the decline of western rivers? The Dolores is one place where the Conservancy is working with water users, our state wildlife agency, and river runners to do exactly that. On the Dolores, we started with a simple question: how much water does the river need? We reviewed scientific literature. We brought in fish experts. We analyzed hydrology. For years, we discussed, debated, and argued about how we can create a healthier river while farmers still get the water they need. We drew diagrams of how we thought releases from the dam should be done to create a healthier river, and how we expect the ecology of the river should respond. Then we waited for the snow to come.

Finally, this year, it did.

Scientists love uncommon events, and the expected flood on the Dolores has been no exception. Scientists mobilized from the Conservancy, three different universities, Colorado’s wildlife agency, and the Bureau of Reclamation. Our goal: to assess if the flood renews habitat as we expect it to? And, how can we learn from this rare event to better manage the Dolores, and to better manage western rivers in general?

A staff gauge shows the river level as the flood rises and falls. Photo © Julie Knudson

Before the snowmelt started in earnest, we headed to the field to collect pre-flood data. The Dolores is so remote, even a routine field trip becomes a major expedition. You better be sure you have everything you need with you when you head into the field, because you can expect to drive hours to the nearest hardware store. Of course, there are upsides to this remoteness, like the bighorn sheep I got to see up close on my way to the “office” on the first day.

We expect the flood to scour pools and reshape the river channel, so our before-flood data collection started with the basics: surveying a cross-section of the channel. For this measurement, we used surveying techniques that have been modified only slightly over the past two centuries.

We also used science innovations that are changing conservation. A wildlife camera installed at each research site is taking a photo of a staff gauge every half hour, so we can watch the river change day by day. With luck, it will also catch a photo of an elusive river otter.

Channel measurements will tell us a lot, and we also want to know what happens over the whole landscape. For that, our partner Agrobotix helped us collect high resolution aerial photographs with a drone. Using this imagery, we can see how the flood shifts the channel, moves individual rocks, rips up plants, and lays down sand where cottonwood seeds can germinate and take root.

With high resolution imagery from a drone we can see what happens to individual rocks and shrubs (left) and how vegetation patterns change before and after the flood (green pixels on the right). Images © Tom McKinnon

With the before data collected, we now wait. In anticipation, I check the USGS stream gage near Slick Rock. Today it is showing 2000 cubic feet per second (cfs). Our Southwest Colorado Water Project Director, Celene Hawkins, sent a report from the field yesterday, saying “2,000 cfs is looking good on the river. The water has inundated the willows on the first bench, and I saw some evidence of sediment walls collapsing into the river.” In a bit over a week, we expect it to be at 4000 cfs.

In two months, we will be back on the river collecting post-flood data. We expect to see cobble bars cleared of sediment and riffles deepened, creating better habitat for the suckers and chubs that have struggled on this river in recent decades.  With good science and good collaboration with farmers and rafters, we hope that our efforts will build a future where the Dolores is no longer a river of sorrow.

If you believe in the work we’re doing, please lend a hand.

Add a Comment