Flow augmentation

During the summer and fall, the GRCA releases water from its seven multipurpose reservoirs. This is called flow augmentation. We do it in order to maintain minimum flows in the Grand River system.

During the augmentation season, a graph posted here will show the percentage of river flows coming from the GRCA’s multipurpose reservoirs.

The minimum flows ensure there is enough water to support the operation of municipal wastewater and drinking water plants. It also means there is enough water for other uses and the ecosystem.

Target minimum flows

We release water from the reservoirs to maintain target minimum flows at these locations from May to September. Flows are measured in cubic metres per second (m³/s).

• Grand Valley (Legatt gauge - Upper Grand River): 0.42 m³/s
• Guelph (Edinburg Road gauge - Speed River): 1.7 m³/s
• Doon (Doon gauge – Central Grand): 9 m³/s
• Brantford (Brantford gauge - Lower Grand): 17 m³/s

Augmentation charts

The following charts illustrate the flow augmentation at different locations along the Grand River and in the Speed River at the Edinburgh Road gauge. Charts are updated twice a month from April to November.

Please Note: Augmentation charts are currently offline.