Interactions between sediments and water

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  • Hydrobiologia 494: 14, 2003.B. Kronvang (ed.), The Interactions between Sediments and Water. 2003 Kluwer Academic Publishers. Printed in the Netherlands.

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    Interactions between sediments and waterSummary of the 9th International IASWS SymposiumEllen L. Petticrew1, Ian G. Droppo2 & Brian Kronvang31Geography Program, University of Northern British Columbia, Canada2National Water Research Institute, Environment Canada3National Environmental Research Institute, Denmark

    Introduction

    The important role of sediment in aquatic systems hasgarnered much attention in the last few decades fromboth an applied and a research perspective. Recogni-tion of the environmental influence of both sedimentand sediment-associated chemical (nutrients and con-taminants) transfers and storage on aquatic ecosystemshas generated much concern within both research andregulatory agencies. Studies have been undertaken bya variety of individuals in a wide range of disciplinesas the environmental problems are found in rivers,lakes, wetlands, estuaries and oceans and affect thebiological, chemical, physical and social componentsof the system. Since 1976 an interdisciplinary groupof international researchers have met tri-annually toshare their knowledge about sediment water inter-actions. The International Association for SedimentWater Science held its ninth symposium on the Inter-actions Between Sediments and Water in May of 2002in Banff, Canada. This paper presents the highlightsand a summary of that symposium.

    Background

    In the 1970s a growing concern over the changing con-dition and fate of aquatic systems led to a researchemphasis on the interactions of sediments and water.Sediments act as both a pollutant in natural habit-ats as well as a vector for the transfer of chemicalssuch as nutrients and contaminants. The sedimentwater research was being undertaken worldwide andthroughout a wide variety of disciplines but the ques-tions, approaches and concerns were similar, so agroup of scientists arranged to meet to share theirknowledge and problems in Amsterdam in 1976. Thusbegan the International Association for Sediment Wa-ter Science (IASWS), which brought together a wide

    range of researchers from disciplines including limno-logy, oceanography, hydrology, biogeochemistry, geo-morphology, sedimentology, aquatic ecology, aquaticchemistry and environmental engineering. The sym-posium that began in Amsterdam, Netherlands (1976)has continued on a three-year cycle, meeting inCanada (1981), Switzerland (1984), Australia (1987),Sweden (1990), U.S. (1993), Italy (1996) and China(1999). These tri-annual symposiums provide a forumfor interdisciplinary discussions with the aim of betterintegrating knowledge of the biological, physical andchemical processes between sediments and water. Thescale of the meeting is such that the exchange of ideas,techniques and approaches is fostered encouragingthis integration and enabling future collaboration.

    Symposium venue and structure

    The 9th International Symposium on the Interactionsbetween Sediments and Water was held in Banff,Canada between May 5 and 10, 2002. At the 9thsymposium, 140 delegates attended, representing 31countries. Of this group of researchers attending theCanadian symposium, 24 were students representingcountries as distant as Korea, Australia and the U.K.Banff, Canada was an excellent venue for a sedimentand water symposium, as it provided a superb visualsetting among sedimentary mountains and gravel bedrivers. These past and present sedimentwater activ-ities were a constant reminder of the scientific focusfrom our vantage point at the Banff Springs Hotel,nestled in the Rocky Mountains along the Bow River.Delegates and accompanying persons took a full dayfield trip into the mountains mid-week to view andhear about the geologic and general history of BanffNational Park, a UNESCO World Heritage Site andYoho National Park, the location of the Burgess

  • 2Shales. Commentary on the wildlife, ecology and parkmanagement issues were provided as well.

    Symposium focusGenerally, the IASWS explores issues concerning as-pects of fresh and salt-water systems and their sed-iments. At the 9th Symposium three themes withinthis broad interest area were selected, the evaluationand/or restoration of disturbed watersheds, linkagesbetween terrestrial and aquatic environments, and therole of sediment and water interactions in evaluatingchange in aquatic habitats. Three concurrent sessions,one representing each of the themes comprised 110presentations in 29 sessions. Of these, five sessionsfocused on sediment budgets, three sessions on bio-logical and sediment interactions, eight sessions onsediment associated contaminants or nutrients, six ondisturbed catchments, two on sedimentwater dynam-ics and one on risk assessment. A well-attended postersession had 28 presentations covering the full range ofthemes.

    Theme A assessing and/or restoring disturbedwatersheds

    The first theme was introduced with a plenary talk byDr. Gordon Grant of the United States Department ofAgriculture, Forest Service, who spoke on EmergingIssues for Water, Sediment and Rivers an Interna-tional and Cross-Cultural Comparison. This initialpresentation set the stage for the meeting by presentingan overview of how strongly water and sediment issuesare conditioned by their social and geomorphic set-tings. A range of international settings were providedas case studies.

    One of the main foci within this theme was theenvironmental impact of physical catchment disturb-ances, including dam implementation and removal,mining activities and urbanization. The Electric PowerResearch Institute (EPRI) sponsored the two sessionson the impact of dams. The research presented evalu-ated the extent and severity of sedimentation problemsin reservoirs, with various best management practicesevaluated to minimize the impact of dams on sedi-ment transport and riparian zone degradation. Con-taminant evaluations and remediation options werealso discussed with the impact of sedimentation andsediment remediation on the benthic and fish com-munities presented from specific projects. EPRI iscurrently working on developing guidelines for sedi-

    ment management specifically related to the impact ofdams.

    The source and fate of metals within watershedsinfluenced by mining activities was another focus.Modeling was emphasized as an appropriate tool forevaluating the significance of various processes as-sociated with sediment contaminant interactions andtransport. Two common concerns were the require-ment for more data for model validation and the needto more fully understand the processes at work in thesedisturbed basins.

    The emphasis of the research presentations on urb-anized basins was towards identifying and measuringthe source, fate and effect of sediment related con-taminants. The role of variable flow regimes on themovement and storage of these sediments was also ad-dressed. Papers in these sessions incorporated a rangeof chemical, biological and physical indicators toassess these anthropogenically modified catchments.

    Two sessions on particle behavior emphasized howrelevant particle dynamics are in controlling materialfluxes in aquatic systems. This included both inorganicand organic matter. While the process-oriented studiesof particle behavior were predominantly undertaken atsmall scales, the effect of these behaviours on sedi-ment transfers and storage act on much larger scalesthereby linking these results to the larger concerns ofcatchment sediment transfers and sediment associatedcontaminant transport.

    While many of the talks in this theme identified aneed for predictive ability regarding impacts for res-toration or assessment, a specific session on sedimentrelated risk assessment addressed the current state ofsome available approaches. The lack of a more quant-itative approach was recognized as a limitation forecologically-based risk assessment. Uncertainty andcost-benefit tradeoffs associated with modeling an-thropogenic impacts again emphasizes a requirementfor more site specific data if more quantitative modelsare to be used or developed in the future.

    Theme B sedimentwater linkages in terrestrial andaquatic environments

    The second theme comprised two foci, the first beingsediment budgets which addressed issues of catchmentsediment supply, transfer and storage. The source, fateand effect of sediment related nutrients and contam-inants was the other focus of the terrestrial-aquaticlinkage theme. The plenary speech was delivered byDr. Olav Slaymaker from the University of British

  • 3Columbia Geography Department. He discussed thestrengths and weaknesses of using sediment budgetsas a conceptual tool for integrated watershed manage-ment. A main point was that most studies emphasizeonly one of the three components of mass transfer(clastics, solute and nutrients) while the problemsthat currently exist in catchment management requireknowledge and information of all three.

    The critical importance of accuracy and precisionin measurements of sediment fluxes was emphasizedin several talks, discussions and posters. Errors as-sociated with the measurement of inputs and outputsneed to be minimized but also they must be quantified.The inevitable result of not having these values resultsin the error being transferred to the unknown terms,potentially increasing their perceived importance. Itwas clear that our ability to distinguish sampling andanalytical variability from true spatial variability needsto be improved if we expect to understand the naturalprocesses. This requirement also reflects on the needto ensure the selection of representative field sites sothat we are better able to characterize the true spatialvariability.

    Techniques presented in these sessions were broadand from a range of disciplines. They included geo-chemical fingerprinting, GIS, remote sensing, isotopicdating and numerical modeling. Several presentationsdealing with sediment budgets reflected back on pointsidentified in the first plenary talk by Gordon Grantin that differences in socio-political and/or culturalresponses to anthropogenic disturbance were identi-fied as important factors in changing sediment deliveryover given time periods through recent history.

    Inevitably the transfers of sediment throughaquatic environments incorporates the flux of contam-inants and nutrients. The papers presented in thesesessions highlighted the importance of consideringand integrating processes occurring at different spatialand temporal scales to understand the transport andretention of nutrients and contaminants in rivers, lakesand marine environments. While the efforts to studyaquatic systems (rivers, lakes and oceans) are gener-ally independent the methods and questions are oftenvery similar.

    Theme C evaluating change in saline and/orfreshwater habitatThe third theme incorporated papers and posterson biological and hydrodynamic interactions insedimentwater systems, often in the context of

    sediment-associated contaminants. While the oppor-tunity to address long-term change was an option,the bulk of the papers dealt with spatial or short-term changes in sediment and/or water conditions. DrMarkus Huettel from the Max Planck Institute forMarine Microbiology was the plenary speaker for thisthird theme. He addressed the hydrodynamic impactof biogeochemical processes in aquatic sediment. Hepresented data from a number of experiments em-phasizing that the diffusive boundary layer near thesedimentwater interface changes as a function ofmicrotopography, benthic activity and sediment poros-ity, resulting in complex biogeochemical transportprocesses.

    In the three sessions addressing bio-sediment in-teractions, the range of biological systems includedbacteria, benthic organisms, macrophytes and fish. Asan example of the connectivity between sessions, themacrophyte papers integrated the hydrodynamic pro-cesses with biological components of the system todetermine their influence on sediment storage and/orquality. Several of these talks and some posters con-nected back to the first theme, restoration of wa-tersheds, as they dealt with the response of fishpopulations to altered sediment regimes associatedwith riparian restoration techniques. Applied aspectsof sediment remediation both from a biological andchemical perspective were also presented in several ofthis themes sessions.

    Another group of papers dealt with the geochem-ical changes of particles in water. The applied andtheoretical components of this work demonstrated thevalue of integrating chemical bench research withfield-based sediment-contaminant issues. Some of thefield-based research projects were complimented byspecific techniques and approaches to quantify hydro-dynamic processes at the sedimentwater interface.The rationale for much of this work was to gain moredetailed information on the magnitude and scales oftransport, deposition and erosion processes associatedwith sediment and sediment-associated contaminantsin aquatic systems.

    Symposium proceedings

    This symposium proceedings represent 43 of the 138papers delivered in Banff, Canada. They are presen-ted and ordered here according to the three themesoutlined above. The full set of published abstractsfor the meeting is located on the IASWS website:www.wsc.monash.edu/au/iasws/ninthconference.htm1.

  • 4Summary

    Following what we felt was a successful symposiumin Canada, we look forward to meeting again to dis-cuss advances in sedimentwater issues at the 10thSymposium. It is to be held at Lake Bled, Slovenia inSeptember, 2005. Anyone wishing to obtain informa-tion or join the International Association for SedimentWater Science can contact the IASWS secretary DrCarolyn Oldham at c.oldham@cwr.uwa.edu.ca.

    Acknowledgements

    The Organizing Committee would like to acknow-ledge the financial and in-kind support from theInternational Association for Sediment Water Sci-ence (IASWS), the University of Northern BritishColumbia (UNBC), the National Water Research Insti-

    tute (NWRI), Environment Canada, the National En-vironmental Research Institute, Denmark (NERI), theAluminum Company of Canada (Alcan), the ElectricalPower Research Institute (EPRI), and the GeographyProgram, University of Northern British Columbia. Aswell thanks go to people whose efforts ensured thesymposium ran smoothly, including the co-ordinatingassistants (K. Mawhorter, K. Petticrew) the UNBCgraduate student volunteers (J. Rex, J. McConnachie,C. Luider, E. Radomske), the IASWS Scientific Com-mittee (J. Bloesch, I. Droppo, B. Kronvang, M. Meili,J. Ni, C. Oldham, E. Petticrew, J. Skei, D. Walling)and all those individuals who volunteered to chairsessions and review manuscripts.

    The Organizing Committee and the Editor alsogreatly acknowledge the work of Anne-Dorthe Vil-lumsen, NERI, Denmark who kept a record of thepapers submitted for review from the Symposium andassisted in contact with the authors and the Publisher.

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