Critical reservoirs silting up

The rapidly dwindling capacity of Pakistan's three major water reservoirs, Tarbela, Mangla and Chashma is an issue of grave concern, with the storage capacity of the facilities rapidly depreciating due to silt, adding to the deficit in Pakistan's water resources, a government official told IRIN on Wednesday. "This is of very serious concern. The loss is about 25 percent. I have been there and seen an aerial view of Tarbela and there is an island which is all silt nearing the dam," Aftab Ahmad Khan Sherpao, the Minister for Water, Power, Kashmir Affairs and Northern Areas, said. The Tarbela reservoir is on the river Indus, about 80 km northwest of the capital, Islamabad. Mangla Dam is on the river Jhelum, about 30 km upstream of Jhelum city (120 km from Islamabad). The Chashma Hydropower Project is located on the right abutment of the Chashma Barrage. The barrage is located on the Indus River near the village of Chashma in Mianwali District, about 300 km northwest of Lahore. "Tarbela dam is the most vulnerable as it is the first dam on the Indus and receives most of the silt - Mangla is also eroding, whilst Chasma is not eroding to the same degree," a spokesperson from The World Conservation Union (IUCN), Farhan Sami, told IRIN from Karachi. The Indus River is one of the largest sediment producing rivers globally. This is due to its proximity to glacial landscapes and the erosion caused by steep-sided slopes. It has been estimated that the Indus and its tributaries bring millions of cubic metres of sediment into the system annually. "The Indus River is a unique river because of the speed with which it flows. It erodes the riverbanks and beds and brings down silt. The Indus River has the tenth highest water run in the world. Geological assessments have shown that the sediment discharge is very high," Sami said. Extensive watershed management programmes have been undertaken to reduce the levels of silt flow, but these programmes have run into financial difficulties, according to Sami. Annual silt clearance is undertaken in the canals to assist in the reduction. "Reforestation is also assisting to prevent the build up of silt. Another option is to build a dam further upstream which will act as a holding cell for the silt and minimise impact," Sami commented, adding the life of Tarbela dam was initially 60 years but it had been estimated that it would now be serviceable for 85 years. Yet according to reports by the World Commission on Dams, the usable storage of the dam will decline over this time. The agricultural industry is the most affected by the build up of silt in the water reservoirs, as it reduces the availability of water that can be used, Sami said. "The accumulation of silt impacts heavily on irrigation. The reservoirs are used to irrigate during dry periods," Sami maintained. Research conducted by the United Nations Development Program (UNDP), has found Pakistan's water resources are not adequate to meet present or future demands. The population, which currently stands at 145 million, is adding to the strain, with low water resources impacting on agriculture, industry and households, according to a recent study by the UNDP. It was estimated in 2001 that the deficit was 8.1 billion cubic metres (BCM). This is expected to increase to 18.3 BCM by 2004. The critical threshold of chronic water stress, generally perceived to be 1000 cubic metres per capita per annum is almost nearing that level for Pakistan, according to the report. "We are trying to keep the reservoirs at a level that doesn't disturb the silt towards the dams. In the past because of droughts we had to release water which did disturb the silt. We are now ensuring the level does not go down," Sherpao stressed.