The validation of an FVCOM hydrodynamic model to support aquaculture on the West Coast of Vancouver Island

Description

Previous work in aquaculture regions of British Columbia (e.g., the Broughton Archipelago and the Discovery Islands) demonstrates the advantage of having a hydrodynamic model that can provide information on current flow, temperature and salinity in three dimensions.

This project examined and quantified uncertainties in the Finite-Volume, primitive equation Community Ocean Model (FVCOM) developed for the West Coast Vancouver Island under a previous ACRDP project (15-1-P-03). The model has been shown to be well suited for simulating the circulation and ecosystem dynamics, particularly for regions characterized by irregular complex coastlines, islands, inlets, creeks, and inter-tidal zones. The model resolution varies from 9 km along the continental shelf to 60 m in the coastal inlets.

The model was initiated at the offshore boundary using output from a pre-operational run of the Coastal Ice-Ocean Prediction System for the northeast Pacific (CIOPS-W) conducted by Environment and Climate Change Canada (ECCC). Atmospheric forcing was taken from the High Resolution Deterministic Prediction System (HRDPS), also run at ECCC. River discharge volumes were either taken directly from observations made by Water Survey of Canada (ECCC), or estimated from historical observations and/or watershed area ratios.

The results were compared at several locations with current data collected by Acoustic Doppler current profilers (ADCP) and the water properties data collected at the fish farms. The research sought to validate the model through identifying the degree of confidence that can be placed in the model results, and also sought to optimize the model for applications in support of aquaculture. Using the FVCOM output as input to particle tracking models already developed at Institute of Ocean Sciences (IOS), the dispersion of virtual particles was modeled and compared to the tracks of surface drifters released at key locations in the model domain. The results of this model map where virtual particles are adverted.

Ultimately, the project provides a FVCOM model for West Coast Vancouver Island aquaculture that can generate three dimensional fields of temperature, salinity and current within confidence limits determined by a clear validation process.

Findings

The validation process of the FVCOM model included examining and quantifying uncertainties in the model output, identifying the degree of confidence that can be placed in the model results, and identifying how to improve the model for applications in support of aquaculture. Several changes were made to the model as a result of this work.

The validation process showed the influence of non-tidal forces, such as intense rainfall events, offshore storms and local squalls, and the summer daily sea breezes in some inlets were important to the movement of the water and evident in the data but not always represented in the model results. Modifications to the model included changing the model grid and the forcing at the open ocean boundary, and better resolving the freshwater runoff and local wind conditions. Atmospheric forcing using the 2.5 km HRDPS wind fields was found to be insufficient to resolve some of the inlet wind events and further work is being carried out to apply wind data from the 1.0 km HRDPS model and from a network of weather stations located at fish farms.

Comparisons of water elevation between the model results and CHS tide gauge data differed on average by only 5%. However, the tidal currents in the model were less than those observed at the current meter locations. There was acceptable agreement in the temperature fields produced by the model when compared to the data measured at fish farms. When compared to the salinity data collected at fish farms in Nootka Sound, the model consistently showed conditions that were saltier than those observed. The mixing parameters used by the model were reviewed to provide a better fit with the observations at the fish farms.

Publications

• Foreman, Chandler, Wan, Thupaki, Bianucci, Krassovski, Spear, et al. A Circulation Model for Inlets along the Central West Coast of Vancouver Island; in preparation.
• Chandler, Foreman, Wan, Thupaki, Bianucci, Krassovski, Spear, et al. The Physical Environment along the Central West Coast of Vancouver Island; in preparation.

Program name

Aquaculture Collaborative Research and Development Program (ACRDP)

Years

2017 – 2019

Principal investigator

Peter Chandler, Oceanographer, Fisheries and Oceans Canada, Institute of Ocean Sciences, Pacific Region
Email: Peter.Chandler@dfo-mpo.gc.ca

Team member(s)

• Mike Foreman, Research Scientist, Fisheries and Oceans Canada, Institute of Ocean Sciences, Pacific Region
• Pramod Thupaki, Postdoctoral Student, Fisheries and Oceans Canada, Institute of Ocean Sciences, Pacific Region
• Di Wan, Physical Oceanographer, Fisheries and Oceans Canada, Institute of Ocean Sciences, Pacific Region
• Maxin Krassovski, Physical Scientist, Fisheries and Oceans Canada, Institute of Ocean Sciences, Pacific Region

Collaborator(s)

• Barry Milligan, Chief Veterinarian and Fish Health Manager, Cermaq Canada Ltd.
• Tim Hewison, Fish Health and R&D Manager, Grieg Seafood BC Ltd.