SanJuanRiver_small_RachelLee

The San Juan River Basin is fortunate to have an extensive monitoring program that informs managers on how species respond to changes in streamflow. Can we leverage this knowledge for rivers where responses are not as well known? Photo credit: Rachel Lee

Environmental flow assessment is an emerging approach for balancing the water needs of freshwater ecosystems with the water needs of human society. By using knowledge of how freshwater species respond to patterns in streamflow (i.e. their flow-ecology relationships), scientists and managers have been able to use environmental flows to improve native fish spawning and recruitment, restore assemblages of native macroinvertebrates, and promote native riparian vegetation over invasive ones.

But what if we do not have the knowledge of species’ flow responses when we need to implement environmental flows? Because streamflow is so integral to the structure and function of riverine ecosystems, most environmental flow assessments are built on a foundation of understanding species’ flow-ecology relationships. Lacking this foundation may make environmental flows ineffective or even detrimental to the freshwater ecosystem we’re trying to sustain. On the other hand, the problems of increasing water scarcity and growing human water consumption will not wait for the development of the flow-ecology models necessary to prescribe effective environmental flows.

To address this challenge, we are investigating the transferability of species’ flow-ecology relationships across different locations and through time, using a suite of freshwater fishes across five river systems in the American southwest. We are also evaluating use of traits as a currency for transferring flow-ecology knowledge across different species, which can inform management of rarer species that are less likely to have established flow-ecology research.

Fortunately, it turns out that the transferability of species’ flow-ecology relationships is similar across spatial scales, meaning flow-ecology models can likely be transferred across river systems. Knowledge of a species’ flow response at a given location is relatively transferable across time as well, suggesting that we do not need to prioritize the constant verification of flow-ecology models. Finally, flow-ecology relationships appear to be similarly transferable across species of the same trait guild as they are within species, offering the opportunity to share information across taxonomic divides.

This all bodes well for implementing needed environmental flows even when flow-ecology knowledge is limited. We’re currently writing the manuscript for this work, so be on the lookout for the publication!

Will Chen