Of the more than 1,000 rivers in Azerbaijan, only 21 are more than 60 miles (97 km) long. The Kür (1,515 km), the longest river in the Caucasus, originates in Turkey and after crossing Georgia flows through Azerbaijan from the northwest to the southeast and empties into the Caspian Sea. The most important tributary of the Kür River is the Araz (1072 km). Most of Azerbaijan’s rivers are located in the Kür basin. In the plains the rivers are used to irrigate crops. Both the huge Mingəçevir hydroelectric power plant and the Mingəçevir reservoir with an area of 605 square km are located in the Kür region.
Most of Azerbaijan’s 250 lakes are small. Lake Sarısu with an area of 65.7 square km is the largest and Lake Ağgöl with 56.2 square km is the second largest, while Lake Göygöl is the deepest.