Ecohydraulic flumes: are we taking full advantage of their potential for symmetrical interdisciplinary research?

Abstract

Leading-edge biological research is thriving and so does advanced research on hydraulics, aided by innovations in technology, instrumentation and respective conventional experimental facilities in laboratories or field stations. In long-established fields, such as ecology and biology or hydraulics, hydrology and geomorphology, state-of-the-art research may be self-sufficient in experimental facilities. In newer interdisciplinary fields, like ecohydraulics, the challenge of conducting cuttingedge research necessitates using innovations and advances in more than one field. In addition, experimental facilities, such as ecohydraulic flumes, are needed to allow studies, measurements and integration of biotic and abiotic variables under controlled conditions. The question then becomes what the appropriate balance between “eco” and “hydraulics” is for leadingedge ecohydraulic research. One may posit that research with ecohydraulic flumes is thriving, at least if the rapid growth of relevant publications is indicative. As ecohydraulic researchers though, we are aware that many studies involving ecohydraulic flumes struggle to balance “eco” with “hydraulics,” and only a limited number achieve suitable symmetry. It takes fully engaged interdisciplinary teams, using state-of-the-art technology, instrumentation, experimental facilities, analyses and integration of observations to reach ecohydraulic symmetry with interdisciplinarity as the overriding principle for all research aspects. How frequently does this actually happen? Ecohydraulic flumes, which have a water surface open to air pressure (as opposed to closed chambers with fluid pressure), facilitate research which integrates ecological/biological and hydraulic/morphodynamic aspects. Such flumes may be fixed or mobile, are used in laboratories or field stations, and are designed for the purpose of studying abilities and responses of aquatic flora and fauna to hydraulic/morphodynamic conditions in prototype to avoid scaling effects on biota and their behaviour (Katopodis 2005). Research on flora and fauna under controlled conditions in ecohydraulic flumes, contributes to improved understanding of the complex interactions between biota and hydraulic variables. Although in recent decades ecohydraulic flumes have been used for research on a variety of flora and fauna, different fish species have been the most common biota studied. The Fisheries-Engineering Research Laboratory adjacent to a fishway at Bonneville Dam was one of the first dedicated to ecohydraulic research on fish passage mostly for anadromous Pacific salmon relating to the hydroelectric generating stations on the Columbia River, USA (Collins and Elling 1960). Without fish tagging technology or videography, and simple hydrometric instruments, observations on fish behavioural responses and swimming performance were limited to average values of basic variables such as velocities, rates of fish movement, endurance times and swim distances. Aspects of fishway design and whether fish would utilize them were also tested. With the development of fish tagging technology, videography and more advanced hydrometric methods, opportunities to study finer scale fish movements, as well as associate them with detailed hydraulic variables, such as velocity distributions and various turbulence characteristics became accessible. Some of the earliest studies utilizing such developments in modernized ecohydraulic flumes were performed in Canada. Many studies in ecohydraulic flumes on a variety of fish species followed, notably at the S. O. Conte Anadromous Fish Research Center, Turners Falls, Massachusetts, USA, the International Centre for Ecohydraulics Research, University of Southampton, Southampton, UK, and the Hydraulics and Environment Department of the National Laboratory for Civil Engineering (LNEC), Lisbon, Portugal. Gradually ecohydraulic flumes became available as research tools in many countries and continue to expand around the globe. Numerous studies on flora and fauna are conducted worldwide, many times repeating similar investigations with different species, usually to provide information for environmental mitigation measures and practical applications. Less frequently, ecohydraulic flumes are used to innovate and pose scientific questions which facilitate discovery and enhance insight. Progress of course has been made over several years using ecohydraulic flumes with a variety of aquatic life forms studied under different hydrodynamic and morphodynamic conditions. Studies have been conducted on many aspects of the ecohydraulic trilogy: (1) movements, abilities and passage of aquatic organisms; (2) e-flows, i.e., environmental, ecological or instream flow regimes for aquatic flora and fauna; and (3) restoration of aquatic habitats and ecosystem morphodynamics. How often though in these studies do we take full advantage of the potential offered by ecohydraulic flumes which enable us to achieve leading-edge research? Using ecohydraulic flumes to combine state-of-theart biology with basic hydraulics or vice versa, limits study design and allows inferences rather than direct observations in interpreting the results. More fully integrated ecohydraulic studies are still evolving with