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Thursday, December 16, 2021 3153

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On a November day downstream of McPhee Dam, an earthen plug located in southwest Colorado, Fort Lewis College Geology students battled dense willow thickets and pools filled with mud as they measured the width of the Dolores River and elevation of its riverbed. With no measurable flow in the river, the team had a rare opportunity to examine the state of a river that is severely affected by the operation of the dam upstream and a decades-long drought.

Unless monsoonal moisture drops into the river system, the Dolores River runs at a slow trickle, with drought and diversions reducing the available water. This low-flow scenario has been a longtime regional challenge. To help inform future management decisions, FLC students and faculty are lending a hand with data collection.

“People have been scratching their heads, watching the Dolores change for decades,” says Associate Professor Jon Harvey, whose Geomorphology class was collecting data in November. “Our lens is focused on the presence of the three native fish species that are struggling in the low water environment, but the research approach we’re taking looks at the health of the whole river system, from the floodplain down to the riverbed.”

Last year, the Four Corners Water Center at FLC received a five-year, $165,000 grant from the Colorado Department of Natural Resources to form the Dolores River Adaptive Management Support project. Experts from around the region are collaborating on the project with the ultimate goal of collecting four years of geomorphic and vegetation field data. The data will be shared with the Dolores River Native Fish Monitoring & Recommendations Team, a group who makes flow recommendations to the Bureau of Reclamation in the interest of native fish habitat maintenance below the dam.

“All of this work has been very collaborative, and everyone involved has been conducting research on the Dolores for years,” says Gigi Richard, director of FCWC and instructor of Geosciences. “We’ve identified a lot of questions that need data and we’ve realized we need a formal, nimble, and responsive team to collect that data.”

At three sites below McPhee Dam, FLC biology, ecology, geology, and hydrology students and faculty are studying how the altered streamflow and sediment supply impact the shape and functioning of the Dolores River system. Implementing a standard monitoring program and building a better understanding of how the channel responds to altered water and sediment conditions will help inform river managers as they make annual flow management and dam release decisions.

“Students get motivated when they know there’s a stakeholder,” Harvey says. “Not all undergraduate projects have that level of impact. They’re motivated by the fact that people care about this and that it matters down the line.”

Fish out of water

Professor of Biology Cynthia Dott was introduced to the Dolores River study sites in 2004 by Preston Somers, professor emeriti of Biology. For years while he was teaching at FLC, Somers took students to the sites to collect vegetation data. Since inheriting the datasets, Dott has used them for research through various grants focused on the changes in vegetation below McPhee Dam.

“Preston had the foresight in the late 1980s to start monitoring vegetation soon after the completion of the dam, and my colleagues and I have been lucky enough to be able to build upon those long-term datasets,” Dott says.

Since the dam’s completion in 1984, years of low flow events have considerably altered fish habitat. FLC data shows vegetation has grown thicker and has encroached into the channel. Harvey’s geomorphology data reflect much the same, that sediment deposition and channel erosion aren’t happening in a fish-friendly manner. Fish thrive when there is diverse riverine habitat, including shallower side channels to mate and protect their offspring in, pools in the river channel that are deep and cool in the hotter months, and clean cobble bars that are ideal for spawning. When water isn’t released from the dam—or when too much is released at the wrong time—conditions for fish become suboptimal.

“Up to now, it has been difficult to determine what the optimal discharges are for getting side channels wet while not blowing out the river into one wide, rapid channel,” Harvey says.

With the geomorphology and vegetation datasets, river managers should be able to point to different discharge levels that create particularly good fish habitat. For the next four years, Harvey’s class will measure elevation change in the riverbed to determine where the channel is being scoured or filled in with sediment. Additionally, his senior thesis and GIS Certificate students are looking at air photos from the 1950s and satellite images from the early 2000s to see how the river has narrowed and responded to the modern flow regime. Dott will be taking thesis students into the field as well to measure vegetation density and the number of species growing.

“One of our goals is to help managers decide what flow regimes best support fish while also acknowledging the many other uses for water on the Dolores River,” Dott says. “We also hope it will inform decisions on how to design potential restoration projects going forward. Would it make sense to shift from relatively passive to more active habitat restoration? Passive approaches involve releasing water and seeing what happens; an active approach could involve removing vegetation from some sections of riverbank or side channel entrances, to reconnect potential fish habitat with the main channel.”

A river runs through it

In between its headwaters in Colorado’s San Juan Mountains and its confluence with the Colorado River in the Utah desert, the Dolores River cuts through 241 miles of the Colorado Plateau, exposing canyons of perplexing strata and sustaining abundant desert flora and fauna.

“The Dolores is a fascinating natural classroom,” Dott says.

Students get to conduct research among a complex of geologic and ecologic wonders, like 300-million-year-old rock and impenetrably thick willows. In their research, the team may not set foot on the shores of the water diversion canals and reservoirs that feed agricultural fields and communities, but they understand their significance within the Dolores River system.

“When I think of the river corridors of the Southwest, the Dolores is perhaps the most unique and essential in that landscape,” Harvey says. “We emphasize to students the importance of their work and you see them wrap their heads around the bigger societal issues of how to best use our collective water supply.”

The Dolores River is a tributary to the Colorado River, one of the most over-allocated rivers in the world. Richard sees the DRAMS project as an exciting opportunity to collaborate with multiple agencies on making a more sustainable impact on water in the West.

“Water has value for multiple uses including recreationists, municipalities, and farmers,” Richard says. “What we want to do is make our use of water sustainably across the environmental, social, and economic landscapes. We want to use water in a way that also sustains our ecosystems.”

For more information and to view the Dolores River Adaptive Management Support story map, visit doloresriver.org.