Water levels expected to rise along Ottawa River

The Rideau Falls at the Ottawa River in Ottawa on Monday. March 18, 2025. (Brad Quinn/CTV News Ottawa)

Water levels are expected to rise “more rapidly” along the Ottawa River over the next few days and minor flooding may occur in low-lying areas, as heavy rain soaks Ottawa and eastern Ontario.

A total of 25.5 mm of rain was recorded at the Ottawa Airport on Sunday and Monday, and Ottawa has received 52.7 mm of rain so far in April.

The Ottawa River Regulation Planning Board says water levels are expected to increase along the Ottawa River over the next few days.

“Warmer forecast temperatures, combined with rainfall and runoff is expected to accelerate snowmelt across much of the basin,” the planning board said in a statement Monday afternoon.

“Water levels and flows are expected to continue increasing over the coming week, particularly from Pembroke down to the Montreal area. Minor flooding in low-lying areas may occur over the next few days. Low-lying areas (such as recreational trails near water) are those locations that regularly flood during the spring freshet period.”

Officials say the warmer temperatures in the forecast are expected to cause “rapid snowmelt in the southern part of the basin” around the Petawawa River, and increased snowmelt in the Coulonge and Rouge rivers.

“Combined with forecast rainfall of 30 to 60 mm over the next few days across the basin, water levels and flows are expected to rise significantly and may exceed flood levels in many locations later this week,” the board said in a media release with the headline “increasing flood risks along the Ottawa River.”

“Over the next few weeks, the risk of flooding will vary and will depend on weather, in particular events bringing above normal temperatures and heavy rainfall.”

A flood outlook statement was issued on Tuesday for the Lower Ottawa River, between Arnprior and Hawkesbury.

The Mississippi Valley Conservation Authority says while there are “currently no flooding indicators of concern, it is still too early to forecast peak river conditions, which remain dependent on snowmelt and rainfall amounts.”

“Rising levels along the main stem of the Ottawa River could create possible flooding in low-lying areas over the coming weeks,” the conservation authority said.

“Low-lying areas are those that are regularly flooded during the spring freshet period.”

Flood Watch on the Mississippi River

A flood watch has been issued for the Mississippi River Watershed in eastern Ontario due to the recent mild temperatures and rainfall.

“Water levels and flows are now elevated across the system and continue to rise along the Mississippi River and its tributaries,” the Mississippi Valley Conservation Authority said on Monday.

“Snowpack remains in the upper watershed, which—combined with any additional forecasted rainfall—may further increase flows into the system. Ground conditions are saturated, which will limit infiltration and increase runoff.”

Officials say rivers and streams may experience higher water levels, and roads, driveways and properties in flood-prone areas could see minor flooding.

The Mississippi River flows from Mazinaw Lake to the Ottawa River near Fitzroy Harbour.

A flood outlook statement has been issued for the Carp River.

Flood Watch on Rideau River

A flood watch was issued last week for the Tay Valley and Rideau Lakes areas due to rising water levels.

The Rideau Valley Conservation Authority said water levels and flows remained high in the Upper Rideau River Watershed areas, and water levels may approach flooding onset in low-lying areas.

Residents in low-lying areas near Bobs Lake and Christie Lake were advised to take “necessary precautions” to protect their property. Water levels on Upper Rideau Lake, Big Rideau Lake and Wolfe Lake were also above average.

With files from CTV News Ottawa’s Ted Raymond

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