Measuring and evaluating ecological flows from streams to regions: Steps towards national coverage

Abstract

Living aquatic communities are largely determined and maintained by the volume and quality of flowing waters, both within lotic systems and in receiving waters of coastal systems. However, flow is one of the most frequently and extensively altered features of rivers and streams; alteration effects are likely to be exacerbated by climate change. Lotic systems vary and different fish species need different environmental conditions, and distinct problems are evident at various spatial scales. New synoptic flow and biological information now make it possible to evaluate the effects of altered flows throughout the Great Lakes Region at scales from the stream reach to the Region. We used estimates of river and streamflow and observed fish abundances to develop tools that specify the response of fish to alterations in those flows. We fit the logistic model to a cumulative fish abundance curve as a function of yield providing an empirical means to develop models of the response of cumulative fish abundance to flows. Response zones of yield for each species in each system type (based on size and thermal class) illustrate how criteria may be developed that can be used in decision‐making for management of flows. In our example application, we evaluate both the general response of brook trout (Salvelinus fontinalis) abundances (and fish diversity) to changes in flows and assess the sensitivity of each stream fish community to flow alteration. Mapping stream sensitivity to flow alteration throughout the US Great Lakes Region with a multiscale spatial framework showed how regional variability in sensitivity for any fish species or assemblage may be evaluated and provides managers with information to help determine where the best opportunities for protection or restoration of streamflows and associated communities exist. These results provide valuable tools and critical information to managers responsible for balancing water uses and maintaining high quality lotic ecosystems. These methods may be applied to any geographic region and can be extended nationally or globally, where flow, temperature, fish and landscape data are available.

Recent advances in environmental flows science and water management—Innovation in the Anthropocene

“…Other papers in this issue demonstrate the utility of developing a strong regional hydrological foundation as a platform for more detailed ecological studies in areas of particular concern (e.g. Hain et al, 2018;Mazor et al, 2018;McKenna, Reeves, & Seelbach, 2018).…”

“…Contributions to this Special lssue demonstrate the increasing interest in basin‐ and regional‐scale hydrological modelling to support ecological risk assessment and setting priority restoration actions (Hain et al., ; Mazor et al., ; McKenna et al., ; Sengupta et al., ; Zimmerman et al., ). Several papers focus on river restoration in the Murray–Darling Basin, Australia, where the health of aquatic ecosystems has deteriorated over decades of excessive water withdrawals, largely to support irrigated agricultural production.…”

The Laurentian Great Lakes: A case study in ecological disturbance and climate change

“…New synoptic flow and biological information now make it possible to evaluate the effects of altered flows throughout the Great Lakes basin at scales from the stream reach to the region. McKenna, Reeves and Seelbach () developed a tool that characterises the response of fish to flow alterations, using cumulative fish abundance curves as a function of yield. This allows users to examine both present conditions and the potential for improved or degraded flow conditions.…”

Incorporating fish habitat requirements of the complete life cycle into ecological flow regime estimation of rivers

“…Numerous case studies have proved that, to restore different natural ecological processes, the ecological flow is not constant but changing over time (Fanaian, Graas, Jiang, & van der Zaag, ; Bruckerhoff, Leasure, & Magoulick, ). It has been long and widely accepted that the ecological flow needs to incorporate natural variability rather than simply allocating a minimum flow to maintain the ecological integrity of rivers (Haghighi & Kløve, ; Koutrakis et al, ; McKenna, Reeves, & Seelbach, ).…”