The Black Mountains in Bhutan's central region form a watershed between two major river systems: the Mo Chhu and the Drangme Chhu. Peaks in the Black Mountains range between above sea level, and fast-flowing rivers have carved out deep gorges in the lower mountain areas. The forests of the central Bhutan mountains consist of Eastern Himalayan subalpine conifer forests in higher elevations and Eastern Himalayan broadleaf forests in lower elevations. Woodlands of the central region provide most of Bhutan's forest production. The Torsa, Raidak, Sankosh, and Manas are Bhutan's main rivers, flowing through this region. Most of the population lives in the central highlands.