FLOOD WATCH – Mattawa River watershed and its tributaries; Chippewa Creek and La Vase River in North Bay

Watershed Conditions Statement – Water Safety – North Bay-Mattawa Watershed

Message Number: 2025-13

Issued: June 26, 2025, at 4:30 PM EDT

From: NBMCA Duty Officer, Githan Kattera

FLOOD WATCH notifies that the potential for flooding exists within specific watercourses and municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.

Watershed Conditions Statement – Water Safety indicates that high flows, unsafe banks, melting ice or other factors could be dangerous for users such as anglers, boaters, swimmers, children, or pets. Flooding is not expected.

If you have a flood emergency, please contact your municipality. If you live in an unincorporated township, please contact the Ministry of Natural Resources (MNR) – North Bay District. For Flood Messages related to the Ottawa River, please refer to the MNR North Bay District.

A FLOOD WATCH remains in effect for the Mattawa River and its tributaries, including North River, Kaibuskong River, Amable du Fond River, Sharpes Creek, Pautois Creek, and Boom Creek, as well as for Chippewa Creek and La Vase River within the City of North Bay.

A Watershed Conditions Statement – Water Safety has been remainder of the North Bay–Mattawa watershed.

This is an update to the previous Message Number 2025-12 dated June 23, 2025.

Current Conditions:

A severe thunderstorm recently caused localized flooding in multiple areas, with the Mattawa River watershed receiving the highest rainfall—approximately 70 to 90 mm—and experiencing the most significant impacts. Rivers and creeks across the region are now receding in response to the earlier rainfall.

Water levels along the Mattawa River system—including Turtle Lake, Lake Talon, the Mattawa River below Boullion Lake, and Hurdman Dam—are gradually declining from recent peaks. Levels at the confluence of the Mattawa and Ottawa Rivers remain within normal ranges.

In the City of North Bay, water levels in the La Vase River are receding, and Chippewa Creek has returned to normal levels.

Current water levels can be viewed by searching Station Names “Ottawa River”, “Mattawa River”, “Chippewa Creek”, “La Vase River”, “Wasi River”, and “Lake Nipissing” at https://wateroffice.ec.gc.ca/search/real_time_e.html

Forecasted Conditions:

Environment Canada has issued a Rainfall Warning in effect for North Bay – Powassan – Mattawa. Heavy showers and thunderstorms are expected on Friday. Rainfall amounts of 30 to 50 mm are anticipated, with locally higher amounts possible in thunderstorms. 50 to 70 mm of rain over the next five days, with locally higher amounts possible. The ground, already near saturation, has little ability to absorb further rainfall.

Water levels along the Mattawa River system—including Turtle Lake, Lake Talon, the Mattawa River below Boullion Lake, and Hurdman Dam—are expected to rise in response to the forecasted rainfall.

In the City of North Bay, water levels across the watershed are also expected to rise again with the incoming precipitation. Meanwhile, Chippewa Creek—due to its flashy nature—is likely to peak quickly and recede just as rapidly during the upcoming rain events.

The Ottawa River Regulation Planning Board posts current data and forecasts on their website https://ottawariver.ca/

The water level on Lake Nipissing is regulated by dams operated by the federal government. Water levels have reached normal summer navigable water levels. More information is available at https://www.canada.ca/en/public-services-procurement/services/infrastructure-buildings/bridges-docks-dams/frenchriver-dam.html

Risk:

Water levels are expected to rise along the Mattawa River and its tributaries in response to the forecasted rainfall, including in Chippewa Creek and the La Vase River. A Flood Watch is in effect for these areas. The recent storm has already triggered elevated flows in all of these creeks, and the upcoming rainfall is likely to cause rapid responses again.

A Watershed Conditions Statement – Water Safety is in effect elsewhere in the North Bay–Mattawa watershed.

All residents, especially those in low lying areas, are encouraged to monitor the conditions that are developing. Banks adjacent to rivers and creeks are very slippery at this time and when combined with cold open water, pose a serious hazard. The public is encouraged to keep children and pets away from watercourses and waterbodies.

A Watershed Conditions Statement – Water Safety remains in effect for the remainder of the North Bay–Mattawa Watershed, where localized flooding in low-lying and flood-prone areas is possible.

Municipalities are encouraged to monitor water crossings for debris that may affect the movement of water through culverts and bridges. A close watch on local conditions and updated forecasts and warnings from Environment Canada is also recommended.

Staff at the North Bay-Mattawa Conservation Authority will continue to monitor weather and watershed conditions and update this message based on the changing weather and streamflow conditions.

This message will be in effect until (or updated before) Wednesday, July 02, 2025, at 4:00 PM EDT.

The general public is advised of these messages through the www.nbmca.ca website with the flood status icon and a link to information about current conditions. NBMCA also circulates these messages to local media and social media, posting on Twitter (@theNBMCA), Instagram (nbmcainfo), and Facebook (NBMCA).

The public is invited to share photos of watershed conditions on social media using #NBMCAFlood.

Terminology: Notification Levels

WATERSHED CONDITIONS STATEMENT: general notices of potential flooding or other conditions that pose a safety risk. There are two kinds of statements:

Water Safety: indicates that high flows, unsafe banks, melting ice or other factors could be dangerous for users such as anglers, boaters, swimmers, children, or pets. Flooding is not expected.

Flood Outlook: gives early notice of the potential for flooding based on weather forecasts calling for heavy rain, snow melt, high wind or other conditions that could lead to high runoff, cause ice jams, lakeshore flooding or erosion.

FLOOD WATCH

FLOOD WATCH: notifies that the potential for flooding exists within specific watercourses and municipalities. Municipalities, emergency services and individual landowners in flood-prone areas should prepare.

FLOOD WARNING

FLOOD WARNING: notifies that flooding is imminent or already occurring in specific watercourses or municipalities. Municipalities and individuals should take action to deal with flood conditions. This may include road closures and evacuations.

MAP: North Bay – Mattawa Watershed

North Bay-Mattawa Conservation Authority Subwatershed map — *^{NBMCA Subwatershed Map}*

Lake Nipissing

Flows through the dams are based on daily analysis of the current status of the lake and river and as agreed to by the Sturgeon-Nipissing-French-Wanapitei Water Management Group. Weather forecast is considered, along with the inflows from the upper watersheds and outflows through the dam to the French River.

You can view the current level on Lake Nipissing at North Bay on the graph below and the French River at the Water Survey of Canada (WSC) website. Fluctuations in the levels are a result of the strong winds affecting the movement of surface water. Water level and flow information for the South River and Sturgeon River systems is available from Ontario Power Generation (OPG).

Flood warnings for Ontario can be found on the Ontario Flood Forecasting and Warning website.

Why the fluctuation in water level readings on Lake Nipissing? Lake Nipissing can sometimes act like a bathtub, with water shifting in the lake, depending upon wind direction, speed and atmospheric pressure - known as a wind surge or seiche. At times the wind can have such an impact that it may result in the level being higher or lower at the French River gauge compared to the gauge located on the North Bay shoreline.

Mattawa River

The current Ottawa River water level may be viewed at the Water Survey of Canada (WSC) website (note that there is a delay of several hours, and 100m should be added to the gauge reading for metres above sea level).

The Ottawa River Regulation Committee and Ontario Power Generation which operates the Otto Holden Dam provide information online regarding the management of water levels on the Ottawa River. To view water levels and current conditions on the Ottawa River visit the Ottawa River Regulation Planning Board and Ontario Power Generation.

Watercourses and Monitoring throughout the Watershed

There are other watercourses within the NBMCA jurisdiction which are monitored by NBMCA and other agencies. These gauges are maintained by Water Survey Canada - Environment Canada and can be viewed in real-time online.

In addition to the Water Survey of Canada gauges, there are other staff gauges which are monitored by NBMCA or the Ministry of Natural Resources and Forestry: