The use of irrigation to combat aridity is an old tradition in this region. Beginning with simple lift irrigation, Pakistan has developed one of the most intricate and complex system of canal irrigation in the world. The development of agriculture in Pakistan is largely dependent on irrigation. More than 80 percent of the total cropped area is under irrigation.
Rainfall is a critical factor in the growth of crops, particularly in Pakistan where most of the land is dry . About 50 percent of the country is arid, 40 percent semi arid and only 10 percent humid. The whole of Sindh, most of Balochistan and a large part of Punjab south of Sahiwal receive less than 250 millimeters of rainfall a year. North of the arid region, a large part of northern Punjab, soutern NWFP and northern Balochistan experience semi arid condition. The only area in Pakistan fortunate enough to experience humid conditions is found in the center towards the north, where rainfall is 750 millimeters in the plains and 625 millimeters in the highlands. In the arid and semi arid regions, irrigation is necessary for successful farming. Even in the humid areas, rainfall is not always adequate during the growing season, with a high year to year variability.