Abkhazia is richly irrigated by small rivers originating in the Caucasus Mountains. Chief of these are: Kodori, Bzyb, Ghalidzga, and Gumista. The Psou River separates the region from Russia, and the Inguri serves as a boundary between Abkhazia and Georgia proper. There are several periglacial and crater lakes in mountainous Abkhazia. Lake Ritsa is the most important of them.