In the early 1990s, irrigation from the Indus River and its tributaries constituted the world's largest contiguous irrigation system, capable of watering over 16 million hectares. The system includes three major storage reservoirs and numerous barrages, headworks, canals, and distribution channels. The total length of the canal system exceeds 58,000 kilometers there are an additional 1.6 million kilometers of farm and field ditches.

Partition placed portions of the Indus River and its tributaries under India's control, leading to prolonged disputes between India and Pakistan over the use of Indus waters. After nine years of negotiations and technical studies, the issue was resolved by the Indus Waters Treaty of 1960. After a ten-year transitional period, the treaty awarded India use of the waters of the main eastern tributaries in its territory--the Ravi, Beas, and Sutlej rivers. Pakistan received use of the waters of the Indus River and its western tributaries, the Jhelum and Chenab rivers.

After the treaty was signed, Pakistan began an extensive and rapid irrigation construction program, partly financed by the Indus Basin Development Fund of US$800 million contributed by various nations, including the United States, and administered by the World Bank. Several immense link canals were built to transfer water from western rivers to eastern Punjab to replace flows in eastern tributaries that India began to divert in accordance with the terms of the treaty. The Mangla Dam, on the Jhelum River, was completed in 1967. The dam provided the first significant water storage for the Indus irrigation system. The dam also contributes to flood control, to regulation of flows for some of the link canals, and to the country's energy supply. At the same time, additional construction was undertaken on barrages and canals.

A second phase of irrigation expansion began in 1968, when a US$1.2 billion fund, also administered by the World Bank, was established. The key to this phase was the Tarbela Dam on the Indus River, which is the world's largest earth-filled dam. The dam, completed in the 1970s, reduced the destruction of periodic floods and in 1994 was a major hydroelectric generating source. Most important for agriculture, the dam increases water availability, particularly during low water, which usually comes at critical growing periods.

Despite massive expansion in the irrigation system, many problems remain. The Indus irrigation system was designed to fit the availability of water in the rivers, to supply the largest area with minimum water needs, and to achieve these objectives at low operating costs with limited technical staff. This system design has resulted in low yields and low cropping intensity in the Indus River plain, averaging about one crop a year, whereas the climate and soils could reasonably permit an average of almost 1.5 crops a year if a more sophisticated irrigation network were in place. The urgent need in the 1960s and 1970s to increase crop production for domestic and export markets led to water flows well above designed capacities. Completion of the Mangla and Tarbela f1a a reservoirs, as well as improvements in other parts of the system, made larger water flows possible. In addition, the government began installing public tube wells that usually discharge into upper levels of the system to add to the available water. The higher water flows in parts of the system considerably exceed design capacities, creating stresses and risks of breaches. Nonetheless, many farmers, particularly those with smallholdings and those toward the end of watercourses, suffer because the supply of water is unreliable.

The irrigation system represents a significant engineering achievement and provides water to the fields that account for 90 percent of agricultural production. Nonetheless, serious problems in the design of the irrigation system prevent achieving the highest potential agricultural output.

Water management is based largely on objectives and operational procedures dating back many decades and is often inflexible and unresponsive to current needs for greater water use efficiency and high crop yields. Charges for water use do not meet operational and maintenance costs, even though rates more than doubled in the 1970s and were again increased in the 1980s. Partly because of its low cost, water is often wasted by farmers.

Good water management is not practiced by government officials, who often assume that investments in physical aspects of the system will automatically yield higher crop production. Government management of the system does not extend beyond the main distribution channels. After passing through these channels, water is directed onto the fields of individual farmers whose water rights are based on long-established social and legal codes. Groups of farmers voluntarily manage the watercourses between main distribution channels and their fields. In effect, the efficiency and effectiveness of water management relies on the way farmers use the system.

The exact amounts of water wasted have not been determined, but studies suggest that losses are considerable and perhaps amount to one-half of the water entering the system. Part of the waste results from seepages in the delivery system. Even greater amounts are probably lost because farmers use water whenever their turn comes even if the water application is detrimental to their crops. The attitude among almost all farmers is that they should use water when available because it may not be available at the next scheduled turn. Moreover, farmers have little understanding of the most productive applications of water during crop-growing cycles because of the lack of research and extension services. As a result, improvements in the irrigation system have not raised yields and output as expected. Some experts believe that drastic changes are needed in government policies and the legal and institutional framework of water management if water use is to improve and that effective changes can result in very large gains in agricultural output.

Data as of April 1994