Workshop: Where land becomes stream

 AHLeGall    15/03/2017 : 13:12
 Aucun    Caroussel


Where land becomes stream: connecting spatial and temporal scales to better understand and manage catchment ecosystems

Where land becomes stream: connecting spatial and temporal scales to better understand and manage catchment ecosystems

Date and location: Rennes, France, 7-8 March 2017.
Number of participants: 24
Number of countries: 5
Number of institutes: 11

On the 7th and 8th of March 2017, 24 international experts on hydrology and ecology held a conference in Rennes France at the OSUR. In addition to colleagues from France, there were participants from the UK, Sweden, Germany, and the USA (see full list of participants below). The workshop was convened by Dr. Gilles Pinay (University Rennes 1, France), Dr Benjamin Abbott (Michigan State University, USA), Professor Florentina Moatar (University of Tours, France), and Dr. Ophélie Fovet (INRA Rennes, France).

Participants worked together to develop new tools and data to address environmental issues of water quality in headwater streams. While headwater streams represent the vast majority of stream length and are the primary conveyor of water, solutes, and particulates, they have such high spatial variability that is difficult to relate concentrations and fluxes to catchment characteristics. Given the high cost of high-frequency water quality monitoring, how can we quantify this heterogeneity in an ecologically meaningful way?

Specifically they addressed the following questions:
• How can we integrate multiple, non-uniform data sources (e.g. occasional synoptic sampling, high-frequency time series, agency water quality data)?
• What are the limits to extrapolating high-frequency data from a single catchment?
• What tools can be used to scale spatially and temporally in headwater catchments to address management issues and improve hypothesis testing?

Specific working groups investigated:
• Analysis of concentration-discharge (C-Q) relationships at multiple spatial and temporal scales, providing a stream network perspective of hysteresis and chemostasis.
• Long-term changes in seasonality as indicators of ecosystem health and efficacy of management actions.
• Optimizing monitoring designs to leverage intensive and extensive water quality sampling depending on the monitoring objectives (e.g. diagnostic, preventive action plan assessment).
• Synchrony and stationarity of headwater catchment water quality.
• Novel modelling techniques to link hydrological and biogeochemical functioning.

Sub-groups of participants contributed to the production of discussion papers prior to the meeting; these provided a basis for discussion at the start of the workshop, feeding into plenary sessions later on.

Where Land Becomes Stream2b
Headwater streams like this one in Brittany France, make up the majority of the terrestrial-aquatic interface and global river habitat. They respond quickly to changes in precipitation, experiencing huge swings in water flow and water chemistry. Photo: G. Pinay.

Where Land Becomes Stream3b
Human activity has profoundly impacted small streams. Urbanization and agriculture alter stream ecology with nutrient-rich runoff, and physical modifications change hydrological behavior, like the diking of this channel near the Mont Saint-Michel World Heritage Site. Photo: B. Abbott.

The main conclusion was that current water quality monitoring schemes are a consequence of historical priorities and choices. Consequently, they are not always able to evaluate whether current regulations are being met. Most regulatory frameworks are focused on not exceeding legal thresholds or annual load limits. If monitoring designs are not able to evaluate these parameters, they are unlikely to usefully inform management efforts to improve water quality. While downstream annual loads in large catchments are relatively well constrained, bias in sampling currently prevents quantification of concentration thresholds through the stream network, which requires higher-frequency and more distributed sampling. This raised four questions for further consideration in a follow-up discussion paper: i) What are the most relevant regulatory goals? ii) What kinds of interventions would be most effective to improve performance in regard to those goals? iii) How long will it take before improved management will be reflected in performance? iv) How can a monitoring framework be developed to better integrate and create synergy between scientific researchers and land managers?

In addition to the discussion paper, other papers will be written as outcomes of the meeting: one on emergent properties, looking at how and why variance in water quality varies with spatial scale; a second paper on the characterization, classification and prediction of solute (co)variability in catchments and in ungauged basins; and a third paper which will consider new metrics of water quality data. Finally, we will prepare two letters, one to be sent by hydrologists to aquatic ecologists and another from aquatic ecologists to hydrologists. In both cases we are interested to learn what disciplinary differences prevent hydrologists and ecologists from working together. The letters will address the following questions: What does the other side get wrong? What is intimidating or confusing about the other side - why are their concepts hard to master? What collaboration opportunities do you wish they would offer? In due course, we aim to produce short commentaries for both communities outlining opportunities for future scientific collaboration.

Participant list:

Nicholas Howden (University of Bristol)
Tim Burt & Fred Worrall (University of Durham)
Jay Zarnetske & Ben Abbott (Michigan State University, USA)
Francois Birgand (North Carolina University, USA)
Andreas Musolff (Leipzig UFZ, Germany)
Sarah Godsey (Idaho State University, USA)
Zhang Qian (USEPA Chesapeake Bay Program, USA)
Kevin Bishop (SLU, Sweden)
Gilles Pinay, Gérard Gruau, Jean Marçais, Jean-Reynald de Dreuzy, Camille Vautier (CNRS, University Rennes 1, France)
Florentina Moatar & Camille Minaudo (University of Tours, France)
Ophélie Fovet, Rémi Dupas, Chantal Gascuel, Patrick Durand, Laurent Ruiz, Zahra Thomas (INRA Rennes, France)

Where Land Becomes Stream4

Contact OSUR
Ben Abbott / @
Gilles Pinay / @

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