Wade–Giles romanization  Pei-erh Hu, Mongol  Pinyin  Buir Nur,  lake on the border of the Mongolian People's Republic and China. It has an area of 235 square miles (609 square km). It receives the Ha-lo-hsin River from the southeast, and its outlet, the Orchun River, flows into Hu-lun Lake to the north.