[1] The primary outflow is an unnamed creek in the southwestern corner of Lower Twin Lake, which eventually flows via Rabbit Creek, Rabbit Lake, the Matabitchuan River, Lake Timiskaming and the Ottawa River into the Saint Lawrence River.

A railway point named Doherty lies at the southwestern corner of Lower Twin Lake.

[1] Situated on an abandoned railway siding near Upper Twin Lake is a 10 cm (3.9 in) wide calcite-quartz vein mineralized with minor pyrite, arsenopyrite and smaltite.

This mineral showing, known as the Upper Twin Lake Occurrence, is hosted in diabase of a Nipissing sill just north of a contact with pebbly greywackes and conglomerates of the Coleman Member of the Gowganda Formation.

The vein strikes in a southeast direction and is traceable for a distance of 2 to 3 m (6.6 to 9.8 ft).