The Indus River has provided water to the people of the Pakistan centuries. This water is used for irrigation on the plains of the Indus Valley and transportation of goods. The management of this resource and the distribution has always been vital to the area, but it has also caused many problems. Since Pakistan’s economy is based mainly on agriculture and related industry, and because most of Pakistan is arid or semi-arid, the Indus River System is vital to their growth and survival. "80% of Pakistan's 21.5 million hectares of farmland is irrigated from this river and the canals built from the river." Without the water from the Indus River, the country would be in economic freefall within months. Both India and China have built major damns on this river but so far the supply from the glaciers and tributaries has not harmed the Pakistani economy or irrigation.
as post#3 said....
pakistan is an agriculture country and almost 70% of its people are assosiated with it.Since pak is a arid country mostly with scanty of rainfall thus water from rivers is used for irrigation.
it also provide water for industrial purpose like as coolent in industry.
it also make the land fertile ..giving more area for agriculture.
rivers also are used for transportation and for domestic use of water in ruler areas.
pakisatan is also having a good fish farming industry.rivers of pak are providing it with rare and excellent fish which are exported all over the world like trout fish.