Pakistan can be divided into three main hydrological units: the Indus basin, the Karan desert, and the arid Makran coast. There are 24 rivers in Pakistan, with the largest being the Indus River. Dams are constructed across rivers to control water flow for purposes like irrigation, hydroelectric power, and flood control. Some of Pakistan's major dams include Mangla Dam on the Jhelum River, Tarbela Dam on the Indus River, and Warsak Dam on the Kabul River.