OHMS Overview
This website serves as the access point for the Ontario Hydrologic Modelling System (OHMS), which includes full model configurations and model outputs describing historical (1980-2024) variation in surface water flows and water levels.
The OHMS model covers 100% of Ontario over the 1980 to 2024 period, simulating at a daily time step:
- streamflow at 32,000 locations which include all Points of Interest as decribed in OLLRPv2
- lake levels of 10,000 lakes
This website currently provides access to a large subset of OHMS model instances across Ontario. Clicking on individual points provides access to model results via the RavenView model interface. 'Simulated Headwater Stations' include map of subbasins and surface water bodies simulated and typically multiple locations with simulated hydrographs and lake/reservoir levels. 'Simulated Nested Stations' only include access to the outlet hydrograph. Website will be updated by end of summer enabling users full access to complete OHMS Raven model setups and model predictions of all standard hydrologic variables (e.g., streamflow, water levels, SWE, etc.) in our Ontario Hydrologic Atlas (with models downloadable for hundreds of calibration locations and by the nine+1 regions of Ontario).
Some OHMS Facts
- Research supported by 2022-2026 collaborate research agreement between Ontario MNR and Prof. Bryan Tolson at the University of Waterloo
- Built in the Raven hydrological modelling framework
- An AI-free, regional-scale hydrologic modelling system
- Semi-distributed model with multiple HRU types per subbasin
- Core hydrofabric for subbasin and lake delineation derived from the Ontario Lake and River Routing product v2 (OLLRPv2)
- Explicitly simulates all lakes in the province over 1 km 2 in surface area (~10,000 lakes)
- Driven with CaSR v3.1 ECCC reanalysis forcings, see here for CaSR data
- 1000 km 2 watershed runtime is ~10 seconds for a 45-year simulation
- Median 1992-2024 calibration period KGE of all calibration basins is 0.88
OHMS Developers and License
- OHMS development was led by Dr. Bryan Tolson and Dr. Hongren Shen at the University of Waterloo. Other core contributors to the work include Dr. James Craig, Dr. Robert Metcalfe (MNR), Dr. Ming Han, Madeline Tucker, Amir Al-Bayati.
- All data and models are provided 'AS IS' without warranties of any kind, including those of fitness for a particular purpose
- If you use any data downloaded from the OHMS website, you must cite/acknowledge this fact in any oral/written presentation material, or any website, using the downloaded data.
- Email Dr. Bryan Tolson with any questions
- Lake level observations for the 02KB001 model collected by Dr. Robert Metcalfe (MNR)).