Warming Temperatures and Rain Expected to Increase Water Levels Across Watershed

(WCS – R01/2025)

March 3, 2025 – The freshet season is expected to begin this week as Environment and Climate Change Canada forecasts above-freezing temperatures and widespread rainfall across the Rideau Valley Watershed.

Warmer temperatures and precipitation will initiate snowmelt, increase runoff, and contribute to rising water levels. While significant flooding is not anticipated, localized flooding in low-lying areas may occur and ice conditions may become unstable. Residents are advised to exercise caution near waterbodies, as slippery banks, shifting ice, and fast-moving water could pose safety hazards.

Weather Forecast: Environment and Climate Change Canada is forecasting a period of above-freezing temperatures and widespread rainfall that will impact the Rideau Valley Watershed. Daytime temperatures above 0°C, along with light precipitation of 3 to 5 mm on Tuesday, March 4, are expected to prime conditions ahead of heavier rainfall beginning Wednesday, March 5. Temperatures are forecast to reach 10°C between March 5 and March 6, with 15 to 25 mm of precipitation expected during this period. While a return to zero or sub-zero temperatures is anticipated on Thursday, a warming trend expected by March 10 may mark the beginning of the freshet season.

Environmental Conditions: Water levels and flows across the Rideau Valley Watershed are generally at or below seasonal normal. Soils across the watershed are still frozen, reducing their ability to absorb water. The snowpack is slightly above seasonal normal, but is within normal range for annual maximums, and recent warmer temperatures have caused some densification.  

Risks: While significant flooding is not anticipated at this time, the following risks are present:

• Warmer temperatures and rainfall will initiate snowmelt, increasing runoff and contributing to higher water levels across the watershed. 
• Frozen ground conditions and densified snow may limit water absorption, leading to ponding in low-lying areas, ditches, and stormwater systems. Smaller tributaries may respond quickly to increased precipitation and runoff. 
• Rising water levels and faster flows may weaken ice cover, leading to hazardous conditions near lakes, rivers, and streams (slippery or unstable banks). Ice may become unsafe for recreational activities, and shifting ice could pose risks to infrastructure.

Location-Specific Considerations: While significant flooding is not anticipated at this time, all water levels and flows across the Rideau Valley Watershed are expected to increase. Depending on the location and rainfall intensity, localized flooding in low-lying areas, including ditches and stormwater features, may be possible. 

Action & Safety Recommendations: Residents are advised to exercise caution when near rivers, streams, and other waterbodies due to risks described above. Parents should inform their children of these dangers and provide appropriate supervision.

Property owners in flood-prone areas should take necessary precautions, such as:

• Ensuring sump pumps are clear, in good working condition, and have a backwater valve.
• Keeping a portable backup generator and pump easily accessible.
• Ensuring downspouts are clear and directing water at least 3 m away from the dwelling.
• Securing items that might float away as flows increase.
• Removing valuable items from basements or lower floors that could be subject to flooding.
• Keeping emergency phone numbers handy.
• Familiarizing yourself with your municipality’s Emergency Preparedness Plan.

Duration: This Flood Outlook statement is in effect until March 8 at 11:59 pm or until an update has been issued.

RVCA monitors water levels and weather forecasts as part of its Flood Forecasting and Warning Program. Updates will be provided as conditions change.

Water Safety – High flows, unstable banks, melting ice or other factors that could be dangerous for recreational users such as anglers, canoeists, hikers, children, pets, etc. Flooding is not expected.

Flood Outlook – Early notice of the potential for flooding based on weather forecasts, calling for heavy rain, snow melt, high winds or other conditions that could lead to high runoff, cause ice jams and/or lakeshore flooding or erosion.

Flood Warning – Flooding is imminent or already occurring in specific watercourses or municipalities.

Flood Watch – Flooding is possible in specific watercourses or municipalities. Municipalities, emergency services and individuals in flood prone areas should prepare.