The Gundlakamma is a seasonal river that flows through the east central part of the state of Andhra Pradesh
. It arises in the Nallamalla Hills, an offshoot of the Eastern Ghats. Its main headwaters lie some 6 kilometers from the village of Ardhaveedu, Prakasam District at an altitude of 425 m. above MSL. Numerous mountain streams join it as it descends down the thickly forested hills through a series of curves and tight bends. It follows a north-easterly direction and enters the plains near Cumbum, after flowing through a town named after it. Gundlakamma is the largest of all the rivers that originate from the Nallamalla Hills.
A 15th-century dam built by the Gajapati kings straddles the river on its entry into the plains. It is an earthen dam that plugs the narrow outlet of a wide gorge that the river flows through. Called the Cumbum Dam, it is 57 feet (17 m) high, has a drainage area of 430 square miles (1,100 km2) and a capacity of 3,696,000,000 cubic feet (105,000,000 m qb). The river then flows past the town of Markapur
and towards the Coromandel Coast. It finally enters the Bay of Bengal, some 19 km east of Ongole
after having covered a distance of 225 km.
Apart from the ancient dam at Cumbum mentioned above, a modern dam called Gundlakamma Reservoir Project too has been constructed across the river at Chinna Mallapuram, Prakasam District. Some 80 feet (24 m) high, this dam has a capacity of 3,800,000,000 cubic feet (110,000,000 m qb) and can irrigate 80,600 acres (330 km2) of land. It will also provide drinking water for the 250,000 people living in Ongole and its surrounding hamlets.