USGS Aquatic Systems Branch: River Flows, Dams, Contaminants and Trout

The Aquatic Systems Branch of the U.S. Geological Survey's Fort Collins Science Center in Colorado is a group of scientists working across disciplines on water-related environmental problems. Resource managers need more and better science, and demands for water keep growing and competing. The branch's specialities are ecological flows, riparian (riverside) ecology, hydroscape ecology, ecosystem management and contaminant biology. Its tools range from fieldwork, laboratory experiments and remote sensing to simulation, predictive models and decision-support software, using an aquatic experimental laboratory, a greenhouse and a botanical garden. The work happens on the ground, in rivers and from the air.

Research themes

Ecological flows. The central question is how the flow of water shapes populations, communities, ecosystems and whole hydrologic landscapes. Branch scientists untangle how hydrology, landforms, chemistry, living things and people interact, and measure when and where water is needed for ecological purposes. Human changes to river flow are a main cause of damaged aquatic ecosystems and lost freshwater species, and the branch gives decisionmakers methods and tools for flow questions.

Riparian ecology. Riparian ecologists study how flow, channel change and vegetation interact along rivers in the western United States and worldwide, on questions that matter for managing water and public lands: dam operations, climate change, invasive species and restoration. Work runs from pot and growth-chamber experiments — testing how plants respond genetically and physically to drought, frost, root fungi, salt and extra carbon dioxide — to case studies of invasions, dams and climate change, and regional studies across the West.

Aquatic ecology and contaminants. This team studies key processes in aquatic and riverside ecosystems and how human activity affects them, from cells to whole ecosystems: the effects of land use and climate change on streams, native versus invasive fish, and how contaminants move through food webs that link water and land.

Decision support. Setting environmental targets is hard when so many physical, hydrological and biological processes interact and uncertainty is high. The branch builds computer-based decision support systems, chiefly maps of habitat suitability under different flow scenarios. They combine spatial environmental data, alternative flows, local hydrodynamics, water conditions and the habitat needs of key species, and use Bayesian methods to express uncertainty — supporting adaptive management and testing the consequences of climate change.

Hydroscape ecology. A "hydroscape" is a hydrologic landscape, the stage on which water, landforms, chemistry, life and people together provide services to society. Dams, diversions, land conversion and other development have fragmented and tamed hydroscapes, and managers often lack the landscape view needed to restore them. The team develops new conceptual models, modelling and survey methods, and spatial metrics to measure how human changes to water and landforms ripple through ecosystems at many scales.

Selected projects

• Dams. For more than twenty years the branch has studied how dams affect rivers: the recruitment of cottonwoods and other pioneer trees on the Upper Missouri and Bill Williams rivers, and channel shape and vegetation across the Great Plains. That work has guided dam releases that help native trees establish or clear invasive plants from channels. The branch is monitoring floodplain vegetation on the Elwha River in Olympic National Park after two large dams were removed, to guide future restoration, and studies the experimental pulse flow in the Colorado River.
• Contaminants on the wing. Most aquatic insects grow up in water and fly off as adults, and when spiders, birds and bats eat them, contamination crosses from water to land. Field studies from mountain headwaters to the Great Lakes trace how this happens, and experiments at the centre's new aquatic laboratory test the mechanisms. Its mesocosm facility is unusual in reproducing the boundary between stream and riverbank, not just one or the other. The results help managers judge water-quality criteria and plan and assess clean-ups.
• Floods in tree rings. Branch scientists relate the growth and establishment of riverside trees to past flows, then use tree rings to reconstruct river flow over centuries — the frequency and size of past droughts and floods. They pioneered the use of cottonwood for tree-ring work, a real advance in dry regions where old trees of other species are scarce. Climate projections and watershed models then predict future changes in flow and tree growth. Current studies focus on the Upper Missouri basin and China's Tarim River.
• Trout and climate. Cold-water fish such as trout, salmon and charr are especially exposed to warming and more erratic water. Native cutthroat trout of the southern Rockies now occupy only a tiny share of their former range, pushed out by non-native fish, fragmented habitat and poor land management. Using fieldwork and models — including regional models of mountain-lake surface temperatures — the team asks how changing temperature and flow affect trout in linked lake and stream networks, including spawning migrations, and will fold the answers into decision tools for climate-smart conservation.
• Drones. Unmanned aircraft give an affordable, safe way to collect high-resolution imagery for wildlife monitoring, vegetation analysis, habitat mapping and erosion monitoring where data were hard or impossible to get. Branch pilots are testing them with other USGS centres, the U.S. Fish and Wildlife Service, the Bureau of Land Management, the U.S. Department of Agriculture, Colorado Parks and Wildlife and private landowners.

Sources

• Dong, Q., and Walters, K., 2015, Aquatic Systems Branch — Transdisciplinary research to address water-related environmental problems: U.S. Geological Survey Fact Sheet 2014–3073, Fort Collins Science Center. https://pubs.usgs.gov/publication/fs20143073
• Photos: Quan Dong and Robert Zuellig, U.S. Geological Survey, from the fact sheet's PDF. Its photograph from Freshwaters Illustrated is left out.
• Rewritten in hubnx's own words.