Forecast for 2026-04-21

River conditions forecasts posted on 2026-04-21 by Ottawa River Regulating Committee

Water levels and flows are stabilizing between Lake Coulonge and Lake Deschenes as spring runoff from the central unregulated portion of the basin is slowly starting to decrease and northern reservoirs continue to retain runoff from those regions.  Between Gatineau-Hull and Carillon, water levels and flows are expected to start stabilizing later today.  As spring runoff from the central unregulated portion of the basin recedes, spring runoff from the Abitibi-Timiskaming area will increase, leading to a gradual increase in water levels and flows between Mattawa and Pembroke over the next few days. Our website Forecasts section provides expected water levels over a four-day horizon in several areas. Note that uncertain weather factors and measurements of basin conditions play into estimating peak levels. Forecasts are updated daily at around 4:30 p.m. with the most recent information. On April 21 peak level estimates remain close to peak levels reached on May 4-5, 2023, as follows: Pembroke (113.20 m), Lake Coulonge (108.6 m), Chats Lake (75.85 m), Lake Deschenes (60.25 m), Gatineau -Hull marina (44.55 m) and Thurso (43.10 m). These are lower than the 2023 peak levels by 10 cm (Pembroke), 15 cm (Lake Coulonge), 5 cm (Chats Lake), 10 cm (Lake Deschenes/Britannia), 10 cm (Gatineau -Hull marina) and 10 cm (Thurso). Over the next two weeks, levels from Lake Coulonge to Carillon are expected to slowly decline, with the rate of decline depending on weather.  Risk of further increase in levels in late April and early May is higher from Mattawa to Lake Coulonge given the high snowpack remaining in the northern part of the basin.