Ontario Low Water Program

The Ontario Low Water Program serves to monitor and assess low water conditions in Ontario, including within Toronto and Region Conservation Authority’s (TRCA) watersheds, based on long term stream and precipitation observations.

low water in stream

Program Background

Fresh water is a natural resource crucial to the economic and environmental well-being of Ontario. Water supports almost all aspects of human activity, including health, industrial development, and recreation.

Because water is critical to so much of our activity, it is managed from several perspectives and by many jurisdictions, groups and individuals.

The Ontario Low Water Program reflects this historical partnership between the province — specifically the Ministry of Northern Development, Mines, Natural Resources and Forestry — and local jurisdictions. Much of Ontario, organized on a municipality and conservation authority basis, has the institutions and the resources to effectively deal with low water conditions at both scales.

Through the Ontario Low Water Program, conservation authorities evaluate developing drought conditions, given their local knowledge and expertise of their watersheds, and communicate this information to municipalities and the interested public.


Level 1 Low Water Condition

Streamflow indicators for the period ending July 15, 2022 are showing < 70% of normal seasonal streamflow rates at most locations across TRCA's watersheds.

What is Drought or Low Water?

Although the term drought can have many implications depending on perspective, from a water-cycle viewpoint it can generally be defined as: conditions involving long-term weather patterns resulting in a lowering of water levels in rivers and streams and in extreme cases groundwater supply shortages.

A drought or low water condition can generally be characterized by one or more of the following:

  1. Precipitation amounts below normal for an extended period of time which can be coupled with high rates of evaporation potentially leading to reduced river and lake levels and groundwater storage
  2. Streamflows are at the minimum required level to support aquatic life with limited surplus water to sustain other water uses and activities
  3. Socioeconomic effects occurring on individual properties and extending to larger areas of a watershed or beyond

low water in stream

What are the Signs of Drought or Low Water?

Precipitation Indicator
Precipitation is the most important and convenient indicator. Reviewing the precipitation data from TRCA and Environment Canada rain gauges, in comparison to typical seasonal volumes, will warn of developing low water conditions.

Streamflow Indicator
Streamflow volumes are often quick to respond to climatic inputs, including periods of lower-than-normal precipitation. Gauges in streams measure streamflow and can be used to assess river conditions against historical low flow periods.

Groundwater Indicator
Groundwater indicators tend to lag in response to drought conditions in comparison to precipitation and streamflow indicators. TRCA relies primarily on precipitation and streamflow indicators as they more rapidly identify developing low water conditions.

How Can We Measure or Assess for
Drought/Low Water?

Conservation authorities and the Ministry of Northern Development, Mines, Natural Resources and Forestry will complete calculations for precipitation and streamflow conditions on a monthly basis. These conditions are then compared to precipitation climate normal and the lowest average summer streamflow.

Below is a summary of the precipitation and streamflow indicators used to determine Low Water status conditions.

Precipitation Streamflow
Level 1 < 80% of precipitation normal Monthly flows < 70% of lowest average summer month flow or <100% during spring
Level 2 < 60% of precipitation normal Monthly flows < 50% of lowest average summer month flow or < 70% during spring
Level 3 < 40% of precipitation normal Monthly flows < 30% of lowest average summer month flow or < 50% during spring

What Can You Do?

Consult with your local conservation authority and municipality, and be aware of water advisories or water-use by-laws for updates and awareness on low water status.

Knowing where to find information on current conditions can help you be mindful of your water usage during low water periods.

For more information on the Ontario Low Water Program and current low Water conditions in Ontario, please visit the Ministry of Northern Development, Mines, Natural Resources and Forestry webpage.