Except for its eastern Caspian shoreline and some areas bordering Georgia and Iran, Azerbaijan is ringed by mountains. To the northeast, bordering Russia's Dagestan Autonomous Republic, is the Greater Caucasus range; to the west, bordering Armenia, is the Lesser Caucasus range. To the extreme southeast, the Talysh Mountains form part of the border with Iran. The highest elevations occur in the Greater Caucasus, where Mount Bazar-dyuzi rises 4,466 meters above sea level. Eight large rivers flow down from the Caucasus ranges into the central Kura-Aras Lowlands, alluvial flatlands and low delta areas along the seacoast designated by the Azerbaijani name for the Mtkvari River (Kura) and its main tributary, the Aras. The Mtkvari, the longest river in the Caucasus region, forms the delta and drains into the Caspian a short distance downstream from the confluence with the Aras. The Mingechaur Reservoir, with an area of 605 square kilometers that makes it the largest body of water in Azerbaijan, was formed by damming the Kura in western Azerbaijan. The waters of the reservoir provide hydroelectric power and irrigation of the Kura-Aras plain. Most of the country's rivers are not navigable. About 15% of the land in Azerbaijan is arable.