Barguzin is the third (by the flow amount) inflow of Baikal, after the rivers Selenga and Upper Angara.

In its middle part, the river flows along the Barguzin Valley or Depression (Russian: Баргузинская котловина), which is 200 km (120 mi) long and up to 35 km (22 mi) wide and runs between the Barguzin Range (to the northwest) and Ikat Range (to the southeast).

In the valley, the river branches, loops, leaves old riverbeds, and creates a swampy water network with more than 1,000 lakes.

In the valley is the Dzherga Nature Reserve (Russian: Джергинский государственный природный заповедник) encompassing 2,387 km2 (922 sq mi).

The air flow rushes onto Baikal from the Barguzin Valley and blows across the lake at its middle, mostly for no longer than a day (starting at sunrise and ending by sunset).