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Water-related development in the basin
The 4 000-year-old Indus civilization has its roots in irrigated agriculture. Canal irrigation development began in 1859 with the completion of the Upper Bari Doab Canal (UBDC) from Madhopur Headworks on Ravi river. Until that time, irrigation was undertaken through a network of inundation canals, which were functional only during periods of high river flow. These provided water for kharif (summer) crops and residual soil moisture for rabi (winter) crops. The UBDC was followed by the Sirhind Canal from Rupar Headworks on Sutlej in 1872 and the Sidhnai Canal from Sidhnai barrage on the Ravi river in 1886. The Lower Chenab from Khanki on Chenab in 1892, and Lower Jhelum from Rasul on Jhelum in 1901 followed suit. Lower and Upper Swat, Kabul river and Paharpur Canals in Khyber Pakhtunkhwa (Pakistan) were completed during 1885 to 1914.
In the beginning of the 1900s, it became apparent that the water resources of the individual rivers were not in proportion to the potential irrigable land. The supply from the Ravi river, serving a large area of Bari Doab, was insufficient while Jhelum had a surplus. An innovative solution, the Triple Canal Project, was constructed during 1907-1915. The project linked the Jhelum, Chenab and Ravi rivers, allowing a transfer of surplus Jhelum and Chenab water to the Ravi river. The Triple Canal Project was a landmark in integrated inter-basin water resources management and provided the key concept for the resolution of the Indus waters dispute between India and Pakistan in 1960 with the Indus Water Treaty (IWT).
The Sutlej Valley Project, comprising four barrages and two canals, was completed in 1933, resulting in the development of the unregulated flow resources of the Sutlej river and motivated planning for the Bhakra reservoir. During the same period, the Sukkur barrage and its system of seven canals serving 2.95 million ha in the Lower Indus plain were completed and considered as the first modern hydraulic structure on the downstream Indus river. Haveli and Rangpur from Trimmu Headworks on Chenab in 1939 and Thal Canal from Kalabagh Headworks on Indus were completed in 1947. This comprised the system inherited by Pakistan at the time of its creation in 1947. The IBIS, spread over the flat plains of the Indus Valley, is the largest contiguous irrigation system in the world and is the result of large surface irrigation schemes promoted by the British up to 1947 when their Indian colony was divided into India and Pakistan.
At independence, the irrigation system, conceived originally as a whole, was divided between India and Pakistan without considering the irrigated boundaries. This resulted in an international water dispute in 1948, which was finally resolved by the enforcement of the Indus Water Treaty in 1960 under the aegis of the World Bank.
After Partition, Kotri, Taunsa and Guddu barrages were completed on the Indus river to provide controlled irrigation to areas previously served by inundation canals. The Taunsa barrage was completed in 1958 to divert water to two large areas on the left and right banks of the river making irrigated agriculture possible for about 1.18 million ha of arid landscape in Punjab province (Pakistan). Currently rehabilitation and modernization of the barrage is in progress. Also, three additional inter-river link canals were built before the initiation of the Indus Basin Project. The last inundation canals were connected to weir-controlled supplies in 1962 with the completion of the Guddu barrage on the Indus river.
The Indus Basin Project (IBP) was developed in pursuance of the Indus Water Treaty, including Mangla dam, five barrages, one syphon and eight inter-river link canals, completed during 1960-1971, and Tarbela dam started partial operation in 1975-1976. The two main components of IBP were the major storage reservoirs on Jhelum (Mangla) and Indus (Tarbela) to mitigate the effect of diverting the three eastern rivers by India and to increase agricultural production in the IBIS (Table 2). As part of the implementation schedule of IBP, the Mangla Dam Project was taken up first and completed by 1968. In the meantime, the decision was also taken to go ahead with the Tarbela dam after its re-evaluation by the World Bank and lining up of the additional funding. Consequently construction started in 1968, was substantially completed by 1974, and started partial operation in 1975-1976 (WCD, 2000).
As a result of these extensive developments, Pakistan now possesses the world’s largest contiguous irrigation system. It commands a full control equipped area of 14.87 million ha (2008) (36 percent is under Mangla command and 64 percent under Tarbela command (WCD, 2000)) and encompasses the Indus river and its tributaries including three large reservoirs (Tarbela, Mangla, and Chashma), 23 barrages/headworks/siphons, 12 inter-river link canals and 45 canals commands extending for 60 800 km, with communal watercourses, farm channels, and field ditches covering another 1.6 million km to serve over 90 000 farmers’ operated watercourses.
River water in the Indus system is diverted by barrages and weirs into main canals and subsequently branch canals, distributaries and minors. The flow to the farm is delivered by over 107 000 watercourses, which are supplied through outlets (moghas) from the distributaries and minors. The mogha is designed to allow a discharge that self-adjusts to variations in the parent canal. Within the watercourse command (an area ranging from 80 to 280 ha), farmers receive water proportional to their land holding. The entire discharge of the watercourse is given to one farm for a specified period on a seven-day rotation. The rotation schedule, called warabandi, is established by the Provincial Irrigation and Power Department, unless the farmers can reach a mutual agreement.
In Pakistan, more than 95 percent of irrigation is located in the Indus river basin. In 2008, the total area equipped for irrigation throughout Pakistan was estimated at 19.99 million ha. The total water managed area in Pakistan is around 21.20 million ha, and can be divided according to the following classification:
- Full control irrigation schemes cover a total area of 19.27 million ha, of which 14.87 million ha lie within the IBIS and 4.40 million ha outside. The areas outside the IBIS cover minor perennial irrigation schemes, groundwater schemes including tubwells, wells, karezes and springs. They are located in Khyber Pakhtunkhwa and Balochistan.
- Spate irrigation covered a total potential area of 2 million ha in 2004. This area refers to potential spate area, but actual area varies based on flood occurrence and frequency and is around 0.72 million ha in an average year. In Pakistan, these areas are known as Rod Kohi in Khyber Pakhtunkhwa and Punjab, or Bandat in Balochistan, and are often called flood irrigation.
- Flood recession cropping areas covered a total area of 1.21 million ha in 2004. In Pakistan these areas are known as Sailaba, and are often called falling flood irrigation areas. Sailaba cultivation is carried out on extensive tracts of land along the rivers and hill streams subject to annual inundation. The moisture retained in the root zone is used after the flood subsides together with subirrigation owing to the capillary rise of groundwater and any rain.
In 1990, the area equipped for irrigation in Pakistan was estimated at 15.73 million ha and total water managed area was estimated at 16.96 million ha.
The total area equipped for irrigation in the entire Indus river basin is estimated to be around 26.3 million ha, of which Pakistan accounts for approximately 19.08 million ha or 72.7 percent, India for 6.71 million ha or 25.6 percent, Afghanistan for 0.44 million ha or 1.7 percent and China for 0.03 million ha or 0.1 percent. Area actually irrigated is estimated at 24.5 million ha. The equipped area irrigated by surface water accounts for 53 percent while groundwater accounts for 47 percent.
The cropped area in the Indus basin in Pakistan expanded with the increased availability of water from the Tarbela dam. Other factors helped to increase the cropped area: increased numbers of tractors, availability of planting machinery and credit support. A rapid rise in population also encouraged the cultivation of additional areas to meet the growing needs of the population. The major rabi crops in the Tarbela command are wheat, fodder and horticultural crops. Sugarcane also needs irrigation during the rabi season and thus competes for water with rabi crops. There was a significant shift in cropping patterns with the increased availability of water from Tarbela dam. There was a net increase in the cropped area of food grains and cash crops such as wheat, rice, cotton and sugarcane. Consequently, there was a decrease in the cropped area of coarse grains and conventional oilseeds.
In the Indus basin, irrigated agriculture saw an increase in area of 36 percent, 44 percent, 39 percent and 52 percent for wheat, cotton, rice and sugarcane, respectively. The overall increase in the cropped area was around 39 percent (Table 3).
Wheat is the leading food grain for human consumption, while its straw is used as a source of cheap roughage for livestock feed. The increase in the area under sugarcane, in particular, is the result of the availability of additional irrigation water from the Tarbela reservoir as it is a crop that demands at lot of irrigation. Other factors that contributed towards this increase were the development of the sugarcane industry and the road infrastructure, both of which provided the necessary linkages for growth (WCD, 2000).
In 2008, total harvested irrigated cropped area in Pakistan was estimated at 21.45 million ha, most of it in the IBIS. The major irrigated crops in the country are wheat, rice, sugarcane, cotton and fodder. These crops comprise almost 78 percent of the total harvested area, or 16.6 million ha, with wheat covering 7.3 million ha, rice 2.5 million ha, sugarcane 1.2 million ha, cotton 3.1 million ha and fodder 2.5 million ha (GoP, 2008).
When the IBIS was developed, the drainage needs were initially minimal. Water tables were deep and irrigation water supplies were too low to generate much groundwater recharge and surface water losses. Whatever little drainage was required, could readily be accommodated by the existing natural drainage. The drainage needs, however, increased over time as more irrigation water was diverted and the water table rose to harmful levels causing waterlogging and salinity. The drainage systems mostly have been developed over the last 30-40 years (Bhutta and Smedema, 2005).
Total water withdrawal in the Indus river basin is estimated at 299 km3, of which Pakistan accounts for approximately 63 percent, India for 36 percent, Afghanistan for 1 percent, and China for barely 0.04 percent. Irrigation withdrawal accounts for 278 km3, or 93 percent of the total. Surface water and groundwater account for 52 percent and 48 percent of total withdrawals in the Indus river basin respectively.
Most summer rains are not available for crop production or recharge to groundwater because of rapid runoff from torrential showers.
In the Pakistani part of the basin, in 2005, total dam capacity was estimated at 23.36 km3. Currently, there are three large hydropower dams and 50 smaller dams (more than 15 m high), while 11 smaller dams are under construction. The designed live storage capacity of the three large hydropower dams in the Indus river basin is 22.98 km3 (Tarbela 11.96 km3, Raised Mangla 10.15 km3, which includes recent raising of 3.58 km3, and Chashma 0.87 km3). The current live storage capacity of these three large hydropower dams is 17.89 km3, representing an overall loss of storage of 22 percent (World Bank, 2005).
Pakistan can barely store 30 days of water in the IBIS. Each km3 of storage capacity lost means one km3/year less water that can be supplied with a given level of reliability. There is an urgent need for storage just to replace capacity that has been lost because of sedimentation. Given the high silt loads from the young Himalayas, two large reservoirs are silting rapidly. In 2008, because of the raising of the Mangla dam, the loss resulting from sedimentation was recovered (World Bank, 2005). The designed live storage capacity of 50 small dams is 0.383 km3. Information related to sedimentation and loss of live storage of small dams is not available. Therefore, it was assumed that on average 25 percent of the live storage of these small dams has been lost as a result of sedimentation, leading to a current live storage capacity of these small dams of 0.287 km3.
There are more than 1 600 mini dams (less than 15 m high), which were constructed for small-scale irrigation purposes, but the capacity of these mini dams is low as a mini dam is normally constructed for an individual farmer. Information on the live storage capacity of mini dams is not available and it is negligible compared to small dams. According to certain estimates, the total designed capacity of these mini dams would be in the order of 0.036 km3.
The Pakistani part of the Indus river basin has a hydroelectric potential of about 50 000 MW. Its main gorge, between the Skardu and Tarbela, has a potential of almost 30 000 MW. These include Bashan (4 500 MW), Disso (3 700 MW), Banjo (5 200 MW), Thicket (1 043 MW), Paten (1 172 MW), Racicot (670 MW), Yuba (710 MW), Hugo (1 000 MW), Tunas (625), and Sakardu or Kithara (possibly 4 000 to 15 000 MW). Almost 20 000 MW potential is available on various sites on the rivers: Swat, Jhelum, Neelam, Punch and Kumar (Qazilbash, 2005).
In 2010, India had six large dams in the Indus basin, with a total dam capacity of 18.6 km3. Bhakra and Nangal dams are on the Sutlej river, Pandoh and Pong dams are on the Beas river and Salal and Baglihar are on the Chenab river.
Table 4 shows the large dams in the Indus river basin.
Table 5 shows the barrages in the Indus river basin.