FLOOD WARNING for North Bay-Mattawa watershed

FLOOD WATCH for Lake Nipissing Shoreline (Callander and North Bay)

Watershed Conditions Statement – Flood Outlook for Mattawa River downstream of Hurdman Dam

Message Number: 2026-10

Issued: April 17, 2026 at 2:30 PM EDT

From: NBMCA Duty Officer, Angela Mills

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.

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 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.

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.

A Flood Watch has been issued for the Lake Nipissing Shoreline in North Bay and Callander. A FLOOD WARNING remains in effect for the remainder of the North Bay – Mattawa watershed, except where a Watershed Conditions Statement – Flood Outlook remains in effect for the Mattawa River downstream of Hurdman Dam.

This Message is an update to the previous Message Number 2026-09 dated April 15, 2026.

Current Conditions:

Approximately 80 mm of rain fell across the watershed between April 12 and 14. Month-to-date, more than 200% of normal April precipitation has been recorded at the North Bay Airport. Water levels and flows have increased significantly in response to several days of significant rainfall, and snowmelt in the last couple of weeks. Area lakes remain ice-covered.

Water level on Lake Nipissing has been rapidly rising in response to significant inflows. Water levels have reached summer navigational levels and continue to rise. Runoff from recent rain and melt remains extremely high flowing into Lake Nipissing.

Flood water from Chippewa Creek impacted homes and streets in North Bay yesterday (Apr 14). The volume of water moving through the system was highest since data collection began in 1974, with daily flow was recorded as 18% higher than the next highest flow from April 9, 1980. Water level on Chippewa Creek remains high.

Water level on the La Vase River is receding but remains very high. Corbeil Conservation Area is closed due to flooding. Water level on the Wasi River has begun to recede. Roads in Chisholm remain flooded.

Water levels in the Mattawa River system have largely stabilized as water drains through the watershed. Turtle/Trout Lake is 13 cm higher than its past maximum from 2019 (data since 2018). Lake Nosbonsing is 2 cm less than its previous maximum in 2019 (data since 2018). Lake Talon is 24 cm higher than its previous maximum in 2023 (data since 2018). Mattawa River below Boullion Lake has increased by more than 83 cm since Sunday (Apr 12) and Chant Plein Lake is 7 cm less than its past maximum from 2019 (data since 2018). Mattawa Island Conservation Area is closed due to flooding.

The snowpack has had significant melt in the last week. Corbeil and North Bay are now classified as snow-free, while some snow remains in forested areas and areas of higher elevation. As of April 15, 48 mm of snow water equivalent remains in Chisholm. Many wetlands and low-lying areas across the watershed are inundated and there is minimal storage for any additional inputs.

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 and Climate Change Canada has issued a Yellow Warning for Rainfall for tomorrow (Apr 18), forecasting a cold front bringing 20-30 mm of rain that may at times be heavy and a risk of a thunderstorm. Strong southerly winds are also forecast for Saturday as front passes through. Temperature is forecast to be well above freezing today and tomorrow and then drop to near freezing for a couple days. Minimal precipitation is forecast for the remainder of the week.

Water levels and flows on local creeks and rivers will rise in response to the forecasted rain and remaining snowmelt as the water drains through the landscape.

The water level of Lake Nipissing has been rising at a rate of about 10 cm per day and is expected to continue to increase in response to higher inflows. Water level on Lake Nipissing are forecast to exceed non-damage levels by early next week and conditions through the coming weeks are likely to be comparable to 2019’s flooding levels. It is possible they may exceed levels recorded in 2019. The changes to water levels on Lake Nipissing depend on the amount of water flowing in from rivers, precipitation, and the amount of water flowing out through the control dams to the downstream French River. https://www.canada.ca/en/public-services-procurement/services/infrastructure-buildings/bridges-docks-dams/frenchriver-dam.html

Water levels and flows are above normal for this time of year in Mattawa and are increasing at all locations and along the main stem of the Ottawa River per the Ottawa River Regulating Committee. The Ottawa River water levels are managed by dams and reservoirs operated by provincial and federal governments. The Ottawa River Regulation Planning Board posts current data and forecasts on their website https://ottawariver.ca/

Historic Flood Conditions:

For comparison, when lake-based flooding occurred on Lake Nipissing in May 2019, the water level on Lake Nipissing at North Bay reached a maximum daily average level that is about 78 cm higher than the present level.

Risk:

A Flood Watch has been issued for the Lake Nipissing shoreline in North Bay and Callander. Water levels have been rapidly rising in response to recent rain and snowmelt and are expected to continue to rise. Start of flooding is expected by early next week. The Parks Creek Backflood Control Structure is being activated today to prevent forecasted high water levels on Lake Nipissing from impeding drainage from Parks Creek and surrounding urban area.

A Flood Warning continues for the North Bay-Mattawa watershed, including the Wasi River, La Vase River, and Mattawa River upstream of Hurdman Dam and its tributaries. Water levels remain high as the recent rain and snow melt moves through the watershed. Water levels on smaller creeks and rivers has been receding but could respond rapidly to tomorrow’s forecasted rain.

A Watershed Conditions Statement – Flood Outlook continues for the Mattawa River downstream of Hurdman Dam. Water levels are rapidly rising as snowmelt continues in the Sturgeon River watershed and Upper Ottawa River watershed and may approach flood conditions within the next few weeks.

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 fast moving cold open water, pose a serious hazard. The public is encouraged to keep children and pets away from watercourses and waterbodies.

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, April 22, 2026 at 4:00 PM EDT.

Media Release

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: