This river starts in Bobs Lake and flows through Christie Lake. The river then travels through Glen Tay, continuing to Perth. The river splits into two main channels as it flows through downtown Perth. The two channels have recombined by the time it leaves Perth and continues to the Rideau River. It is 95 km in length and drains an area of 800 km². A canal connects the river to the Tay Canal, and Rideau Canal systems at Beveridge Bay on Lower Rideau Lake.
Lakes in the Tay watershed include:
A controversy erupted in 2002 when Swiss multinational OMYA applied for a permit to take up to 4,500 m³ per day from the Tay at its Glen Taycalcium carbonate plant. As a result, the permitted amount was reduced to 1,500 m³ per day, subject to review in 2008.