Canada Reservoir Transparency

For the COVERED subset (~150 reservoirs across ECCC/WSC, BC Hydro disclosure portals, Ontario Power Generation reservoir reports, Manitoba Hydro public information, and Quebec Hydro public dashboards), data is published primarily daily where WSC operates a hydrometric station, and weekly-to-monthly for many provincial utility reservoirs. Daily for >50% of covered places this in the lower end of the 80-99 band; some utility-only reservoirs lag at weekly cadence which pulls toward the 60-79 boundary.

The ECCC MSC Geomet OGC API is publicly accessible, well-structured and requires no authentication for WSC stations within the COVERED subset. The Hydat SQLite database provides bulk download. However, the COVERED subset includes ~150 reservoirs of which only roughly half are accessible via WSC API; the remainder live across provincial utility portals (BC Hydro, OPG, Manitoba Hydro, Quebec Hydro), some of which expose structured downloads but most provide HTML dashboards or PDF bulletins. The dominant access mechanism across the covered subset is therefore a mix of documented API (WSC half) and structured-data-via-scraping (utility half), placing this in the upper 60-79 band.

Methodology v1.3.0 (capacity-weighted), conservative denominator. Reported Canadian national reservoir storage capacity is approximately 700,000 hm³ — among the largest in the world, dominated by Hydro-Québec's James Bay and North Shore reservoirs (Caniapiscau ~53,800 hm³, Robert-Bourassa ~61,700 hm³, La Grande 3 ~60,000 hm³, La Grande 4 ~19,000 hm³, Manicouagan/Manic-5 ~141,851 hm³, Gouin), BC Hydro's reservoirs (Williston ~74,300 hm³, Kinbasket, Mica), Manitoba Hydro's Lake Winnipeg-regulated storage and several Churchill River reservoirs, Ontario Power Generation's facilities, and the federal Hydat-monitored reservoirs. Applying a +10% conservative uplift to account for the large estate of provincial-utility-owned smaller reservoirs (Quebec/BC private hydropower partners, Newfoundland & Labrador's Churchill Falls upstream regulators, prairie irrigation districts, municipal supply reservoirs) and the mining-tailings/mill-pond population in remote provinces that never enters Hydat, the realistic denominator is approximately 775,000 hm³. Covered capacity: WSC hydrometric stations (~80 reservoirs incl. Williston, ~150,000 hm³) + BC Hydro public reports (~150,000 hm³) + OPG + Manitoba Hydro public data (~50,000 hm³ Lake Winnipeg regulation) + Hydro-Québec's limited disclosures for Manicouagan, Robert-Bourassa, Caniapiscau, Gouin (~100,000 hm³) + provincial agencies in Alberta, Saskatchewan, Atlantic provinces — totals approximately 450,000 hm³. Coverage = round(100 × 450,000 / 775,000) = 58. The structural gap remains the bulk of Hydro-Québec's reservoir estate where granular operational storage is internal, plus the long tail of private hydropower operators in BC and Quebec.

Median historical depth across the ~150 covered reservoirs is well above 20 years. The Hydat database contains daily values going back to the 1970s or earlier for most active WSC stations, with continuous records spanning 50+ years for many federal stations. BC Hydro's strategic reservoirs (Williston, Mica, Kinbasket) have multi-decade public records dating to commissioning in the 1960s-1970s. OPG's Niagara records extend back many decades. Even where provincial utility records are shallower online, the WSC-monitored majority of the covered subset pulls the median firmly into the 20+ years band.

For the COVERED subset, WSC hydrometric stations publish daily mean values with a short lag; near-real-time data (sub-daily) is available for some priority stations via Geomet API. BC Hydro and OPG publish daily-to-weekly reservoir data. Hydro-Québec's limited public disclosures are weekly. Daily cadence dominates the covered subset, placing this in the 80-99 band.

WSC publishes thorough documentation on station metadata, measurement methods and quality flags for the federal portion of the covered subset. Hydat includes station information, datum references and data grades. The Canadian Dam Association publishes guidelines on dam safety and reservoir management. Provincial utility data, where it exists, comes with mixed methodology documentation: BC Hydro publishes some reservoir operating curves; OPG publishes Niagara River regulation methodology; Hydro-Québec publishes limited methodological notes. The federal portion is strong, pulling the dominant standard into the 60-99 'partially published' band.

Canada is officially bilingual. The Water Office portal and API documentation are available in both English and French. Provincial utility portals are primarily English (with French in Quebec). The interface is modern and usable. Both languages are equally supported, making it one of the most internationally accessible portals from a language standpoint.