HGS RESEARCH HIGHLIGHT – The HypoSalar project: Integrating hyporheic exchange fluxes into Atlantic salmon (Salmo salar) spawning habitat models
Matteo Roncoroni (matteo.roncoroni@inrs.ca) [1], Carole-Anne Gillis [2], Allen Beck [2], René Therrien [3], and Normand Bergeron [1]
Eau Terre Environnement Research Centre, Institut National de la Recherche Scientifique (INRS), Québec, QC, Canada
Gespe'gewa’gi Institute of Natural Understanding (GINU), Listuguj, Gespe’gewa'gi, QC, Canada
Department of Geology and Geological Engineering, Université Laval (ULaval), Québec, QC, Canada
Fig. 1. The Sautariski River study site. A) Orthomosaic with HGS model domain (dashed red line); B) Shaded Digital Elevation Model; C) Zoomed-in orthomosaic; D) Zoomed-in Digital Elevation Model. The Digital Elevation Model has a resolution of 0.08 m.
In this research highlight ultra-fine resolution HydroGeoSphere models are used to simulate hyporheic exchange fluxes in river reaches used by Atlantic salmon for spawning. The HypoSalar project is contributing to demonstrate that the capabilities of HydroGeoSphere are not exclusively related to the field of hydrogeology, but can be used for both fluvial geomorphology and ecological studies due to HydroGeoSphere's flexibility and superior modeling approach. Stay tuned for news.
Rationale and aim of the HypoSalar project
Habitat modeling is a valuable tool for predicting the likely availability, quality and quantity of spawning habitat for Atlantic salmon and other salmonids. Indeed, habitat models provide the information needed for protecting salmon populations and/or restoring habitats. Unfortunately, current habitat models tend to overestimate the likely availability, quality and quantity of spawning habitat, with important consequences for the protection of salmon populations and the implementation of habitat restoration projects.
The problem with current models is that they rely solely on flow velocity, depth, and more rarely grain size. Evidence suggests that salmonid spawning sites are often located at pool-riffle transitions, which are known to induce significant hyporheic exchange fluxes that provide dissolved oxygen to the eggs and simultaneously dispose metabolic waste associated with egg development (see Kondolf et al., 2008). Although the importance of hyporheic exchanges has long been recognized, to date there is a lack of spawning habitat models that integrate these exchanges. This lack motivates the HypoSalar project, whose aim is to evaluate whether integrating hyporheic exchanges into habitat models can lead to a more robust means of predicting the location of Atlantic salmon spawning sites. To test this integration, two study sites have been selected in Quebec, Canada: the Sautariski and the Restigouche rivers.
River bathymetry
River bathymetry is an essential component in any study that attempts to simulate hyporheic exchanges in riverine environments. Chow and colleagues (2018) demonstrated that detailed, high-resolution bathymetric models lead to more accurate representations of small-scale hyporheic exchanges than low-resolution bathymetric models. Small-scale exchanges that occur in response to bed morphology can have a great influence in defining suitable spawning sites and therefore need to be simulated accurately. The acquisition of high-resolution bathymetric information is challenging: on the one hand, traditional geomatic surveys (e.g., total station, dGPS) do not provide the spatial resolution needed to appreciate small-scale bedforms; on the other hand, bathymetric LIDAR is expensive and its use depends on budget rather than need. The HypoSalar project acquires high-resolution bathymetric information through drone-based Structure-from-Motion (SfM) photogrammetry and post-processing correction for the effect of the water-air interface (the two-media photogrammetry problem; see Roncoroni and Lane, 2019; Roncoroni et al., 2024). This approach is capable of delivering a very accurate representation of the riverbed, including small-scale bedforms and individual pebbles that are within the resolution of the Digital Elevation Model (see Figure 1).
Building a realistic surface-model for the Sautariski River
The reference bathymetric model for the Sautariski River was built from images collected on August 8, 2024. From this model, a high-quality triangular mesh was constructed in AlgoMesh, consisting of 193’225 triangular elements and 97’227 nodes over an area of approximately 12’000 m2 (Figure 1a).
It was decided to simulate the surface flow first and parameterize the model until the predicted hydraulics for the surface flow converged to the measured hydraulics (i.e., 58 control points with known average flow velocities and depths). For this purpose, 11 initial models were run with different values of Manning's n (from 0.03 to 0.06) and steady-state flow conditions (discharge was set at 10.9 m3/s, based on field measurements). To date, the best results were obtained with n equal to 0.052, yielding an average depth error of 0 m (StD of error = 0.05 m) and an average velocity error of -0.03 m/s (StD of error = 0.13 m/s).
Next steps and final considerations
In the coming months, the surface flow model will be continuously parametrized to achieve greater agreement between measured and predicted flow hydraulics. When agreement will be found sufficiently good, coupled surface-subsurface flow simulations will be run to retrieve hyporheic exchange fluxes in the Sautariski River study site. The same approach will be used for the Restigouche River. These data are expected to improve current spawning habitat models. Future results of the HypoSalar project will be presented at the 155th annual meeting of the American Fisheries Society (Aug. 10-14, San Antonio, Texas, USA).
The HypoSalar project
The HypoSalar project is supported by the Swiss National Science Foundation (SNSF) through fund P500PB_217903 awarded to Dr. Roncoroni. The project is currently being carried out at the Institut National de la Recherche Scientifique (INRS), Québec, in close collaboration with Prof. N. Bergeron (INRS). Also collaborating in the HypoSalar project are Prof. R. Therrien (ULaval), Dr. C.-A. Gillis (GINU) and A. Beck (GINU).
References:
Chow, R., Wu, H., Bennett, J. P., Dugge, J., Wöhling, T., & Nowak, W. (2019). Sensitivity of simulated hyporheic exchange to river bathymetry: The Steinlach River test site. Groundwater, 57(3), 378-391.
Kondolf G. M., Williams, J. G., Horner, T. C., & Milan, D. A. V. I. D. (2008). Assessing physical quality of spawning habitat. In American fisheries society symposium (Vol. 65, pp. 000-000).
Roncoroni, M., & Lane, S. N. (2019). A framework for using small Unmanned Aircraft Systems (sUASs) and SfM photogrammetry to detect salmonid redds. Ecological Informatics, 53, 100976.
Roncoroni, M., Ballu, A., Selitaj, A., Mancini, D., Miesen, F., Aguet, M., Battin, T. J., & Lane, S. N. (2024). Ecosystem engineering by periphyton in Alpine proglacial streams. Earth Surface Processes And Landforms, 49(1), 417-431.