Lac Dollard-des-Ormeaux is a reservoir formed by the Carillon dam, stretching approximately 20 km in length and about 1 km in width along the Ottawa River. It sits at an elevation of 37 m and forms the natural boundary between Ontario and Quebec. Depths vary considerably, ranging between 6 and 30 m in most areas, with a recorded maximum of 94 m. The lake is fed by the Ottawa River and drains downstream into Lac des Deux Montagnes.

The lake is navigable and connects to a broader waterway system. At the downstream end, the Carillon canal lock allows passage between Lac Dollard-des-Ormeaux and Lac des Deux Montagnes, with a 20-metre elevation difference between the two. This lock operates from mid-May to mid-October. Upstream, the waterway connects toward Ottawa and Gatineau, though the Chaudière Falls on the Ottawa River present a significant natural obstacle beyond that point. Paddlers should be aware that this is a working waterway used by larger vessels navigating between these connected water bodies, which has implications for boat traffic and wave action.

Voyageur Provincial Park on the Ontario shore provides a vantage point over the lake and may offer access opportunities for paddlers exploring the area.