Ottawa River now predicted to rise 50 cm over 2017 levels

The Ottawa River could rise 50 centimetres above peak levels seen during the devastating flooding of May 2017, officials now warn.

Under the worst-case scenario, record-high water levels could be reached in some areas by the middle of next week, according to the latest forecast.

The updated prediction is based on data from the Ottawa River Regulation Planning Board (ORRPB), which controls reservoir levels along the length of the river basin. It comes less than 24 hours after Ottawa Mayor Jim Watson declared a state of emergency based on a prediction of levels rising 11 centimetres over the 2017 peak.

The prediction, issued Friday morning, is "subject to a high degree of uncertainty," according to the board, which keeps records dating back to 1950.

Pembroke

About 150 kilometres up the Ottawa Valley from the capital, the river is expected to peak in Pembroke on Sunday.

The highest water level ever recorded in Pembroke was in 1960. If levels surpass 113 metres above sea level this year, it will mark the sixth time since 1950 that's happened.

Arnprior

The Chats Lake station saw its highest-ever water level in 2017. It could set a new record this year.

The river is forecast to peak there on Monday.

Britannia

The board's monitoring station on Lac Deschênes, which also collects data affecting Aylmer, also set a new record in 2017.

It's expected to peak on Monday.

Hull

This monitoring station for Hull is near the Alexandra Bridge, behind Parliament Hill. It also saw record levels in 2017.

It's expected to peak on Tuesday.

Grenville

This station, on the Quebec side of the river near the Ontario-Quebec border, set its record in 1951.

It's forecasted to peak on Tuesday.

Other areas

Thurso, Que., across from Clarence-Rockland, is monitored by the ORRPB, but isn't included in a graph because it doesn't have historic data.

It could rise by as much as 70 centimetres from its Friday morning levels, which would be 40 centimetres higher than the 2017 peak.

While the ORRPB doesn't have monitoring stations in these areas, local conservation authorities do.

The Rideau Valley Conservation Authority said in its latest update Thursday afternoon water levels in eastern Cumberland, around Boisé Lane, could rise 20 to 40 centimetres higher than in 2017.

The Mississippi Valley Conservation Authority said in that same update water levels in Constance Bay could top 2017's peaks by 50 to 70 centimetres.