Surface water includes water found in oceans, lakes, rivers, wetlands, and glaciers. In Pakistan, surface water primarily comes from the Indus River and its tributaries, and is an important source of fresh water, providing 154 MAF annually on average. It is used heavily for irrigation via Pakistan's extensive canal system of large dams, barrages, and canals. However, surface water availability is declining due to factors like increasing population, water pollution, and more water being used by industries. The three major dams that provide surface water for irrigation are Tarbela Dam on the Indus, Mangla Dam on the Jhelum, and Warsak Dam on the Kabul River.