Forecast for 2026-04-28

River conditions forecasts posted on 2026-04-28 by Ottawa River Regulating Committee

Water levels and flows along the main stem of the Ottawa River continue to rise slowly from Mattawa to Pembroke, while they are stable or slightly declining between Lake Coulonge and Carillon. In Mattawa, water levels may exceed the major flood level over the next few days. Snowmelt is increasing in the northern part of the basin, sending more spring runoff downstream. Forecast rain starting today is expected to add more water from the northern and central unregulated areas, with quantities depending on how much rain falls and where over the next few days.  This could lead to water levels and flows increasing gradually in all locations over the next few days. Our website Forecasts section provides expected water levels over a four-day horizon in several areas. The rate of snowmelt in the northern portion of the basin and the potential for rainfall over the coming weeks remain uncertain. As a result, in the coming weeks, a second flood peak remains possible from Pembroke to the Montreal region, as well as the possibility of levels at Mattawa exceeding major flood levels for the first time. A rapid melt combined with rainfall could lead to water levels higher than those observed between April 19 and 22 in all locations.