This section describes Pakistan’s freshwater resources, and the species that are dependent on it. The major threats to Pakistan’s freshwater Biodiversity are also discussed, as are the conservation measures that have already been taken or are proposed.
8.1 Pakistan’s Freshwater Resources
Pakistan’s freshwater resources are dominated by the Indus River system, which serves as a drainage basin for the Himalayas. The Indus originates in western Tibet and enters Pakistan through Baltistan. Its length up to the Arabian Sea is 2,480 km. As the river flows through the Northern Areas, the Shyok, Astor and Gilgit Rivers join the Indus. In the NWFP it is joined by the Kabul River, this has already joined the Swat River. The Indus then flows into Punjab, where the Jhelum, Chenab, Ravi, Beas and Sutlej Rivers join it. These rivers flow through Punjab and converge to form the much larger Indus River, which then flows through Sindh, before draining into the Arabian Sea through the Indus Delta.
Other than the Indus River system, there are some small rivers in Balochistan province such as the Hub River, Gudri River, and the Nal River, all of which drain into the Arabian Sea on the Makran coast. The area of Pakistan covered by inland water bodies is illustrated below in Figure 8.1.
Figure 8.1 Inland Water Bodies in Pakistan
P akistan has one of the world's largest man-made canal irrigation systems, which consists of a number of large dams, barrages, and a network of irrigation canals and waterways. The three largest dams are the Tarbela, Mangla and Hub Dams. These dams have been constructed to regulate river water for hydropower production, and to provide water for irrigation in Punjab and Sindh. In addition to irrigation canals, a number of link canals connect the rivers. Link canals are used to transfer water from one river to another. In addition to dams, a number of barrages also regulate water flow. Some of the larger barrages are the Chashma, Taunsa, Merala, Rasul, Qadirabad, Guddu and Sukker Barrages.
Pakistan’s extensive irrigation system has resulted in a number of problems. Due to bad drainage, about 2.25 million hectares of agricultural land is presently waterlogged. In addition, a significant portion of these waterlogged areas is saline due to minerals that leach from the soil.
Around 200 multi-purpose mini dams have also been built in Rawalpindi, Chakwal, Attock, Sialkot, and Jhelum and Quetta districts to irrigate small areas.
Pakistan has a number of natural lakes: four in the province of Sindh (Manchar, Bakar, Kinjhar and Halijee); two in Balochistan (Patisar and Hina); one in Kaghan Valley (Saiful Malook), two lakes in the Neelum Valley. Several of other in Skardu and other parts of the Northern Areas. All these lakes receive water from springs and streams, and contain sweet to slightly saline water. A number of moderately saline marshy lakes also exist. Lakes in the Salt Range (Punjab) are generally saline, since they are charged by aquifers in mountains with a high salt content.
8.2 Important Species and their Status
Pakistan is at the peripheral zone of the South Asian region. The Trans-Himalayan area has no South Asian fish. There are 68 genera reported from Pakistan, none of which is endemic. Out of these, nine genera are high Asian. Most of the snow carps are restricted to the Trans-Himalayan part of the Indus system and only few come down to the mountain areas when temperature fluctuations in the water occur.
At least 179 species and sub-species of freshwater fish are reported to exist in Pakistan (15 exotics), including representatives from important groups such as loaches, carps, and catfish (including air-breathing catfish).
8.2.1 Aquatic Plants
Groups such as algae, and submerged and other emergent macrophytes have been studied in freshwater environments. None of these plants is reported to be under threat. However, comprehensive information is absent as research material is scarce.
8.2.2 Amphibian Fauna
There are three families of amphibian fauna in Pakistan:
Twenty species and 4 sub species i.e. 24 taxa of amphibian fauna (frog and toad) are recorded.
8.2.3 Fish and other Aquatic Organisms
An interesting phenomenon that exists in Pakistan is the temperature-related distribution of fish and other aquatic organisms, distinguishing cold water fish from warm water fish. The different temperature zones are described below:
Rithorn Zone: In this zone the water temperature of the river remains below 20C, oxygen concentration is always high, flow is fast and the bed is composed of rocks, stones and gravel. Such areas contain cold water fish and other fauna. Most fish found in this region are carnivorous as the primary productivity of these waters is very low, which results in low algal biomass. About 17 fish are known from this zone.
Deosai Plateau: This is an area of rolling country at an elevation above 4000m including parts of the Himalayan and Pamir-Karakorum Ranges. Three fish are found here viz. Triplophysa stoliczkae, Dyptichus maculatus and Ptychobarbus conirostris.
Potamon Zone: In this zone, the water temperature rises over 20C, the water flow is slow, and the bed is mainly sandy. This zone contains warm water fish. Most parts of Pakistan have elevations lower than 1000 m, and are included in the Potamon Zone. The majority of Pakistan’s fish belong to this zone.
A total of 32 fish species and sub-species are known to be endemic to Pakistan.
Pakistan’s endemic fish species are not yet recognised as endangered at the national level. However, at least two of threatened species, due to their great commercial importance, may become endangered soon, if steps are not taken to conserve them. One of them is the Tor putiptora, which migrates from the flood plains to the Himalayan foothills for breeding, but the construction of the Mangla and Tarbela Dams has blocked its migration. The other species is the Tenualosa ilisha, which requires a 200 km northward run for spawning from the coast in the Indus River. The migration of this fish has been blocked by the construction of the Ghulam Muhammad Barrage and Kotli Barrage (with ineffective fish ladders).
Considerable studies on fish fauna have been carried out in Pakistan to determine their natural distribution. However, a large number of species have not yet been studied in terms of habitat requirement and population. The barrages have physically fragmented the riverine habitat, which is particularly critical for species like the blind Indus dolphin, which is trapped between the barrages of Sindh and the Punjab provinces. During the formulation of this report, it was learnt that two blind dolphins had been strangled to death in the fish ladder of Chashma Barrage in 1997. Ironically, in the records of the Punjab provincial Wildlife Department, its annual dolphin survey does not register the dolphin as being found upstream of the Chashma Barrage.