Silting is destructive for life of reservoirs and for agricultural development

Scarcity of water and the crippling load shedding have infuriated the nation and caused the nation of billions of dollars loss. But no one has paid attention to the silting of reservoirs that destroys reservoir lifespan, the source of water, that severely affect agricultural development. Silting is equally dangerous as shortage of water and power if not more. Tarbela, Mangla and Chashma reservoirs have silted up by 6.6 maf in 36 years. This is alarming. Rapid silting of reservoirs and shortage of water has created inter-provincial water dispute between Sindh and Punjab. Rapid silting of reservoirs has adversely affected the storage created under the Indus Water Treaty. The lost replacement of storage due to silting created under the Indus Waters Treaty urgently requires to be replenished, as part of the Indus Waters Treaty. This great loss is not yet realized by the Government. Silting of reservoirs destroys storage capacity and adversely affects agricultural production for which dams are built and water is stored. Similarly, flood control like silt control is equally vital to avoid losses of life and property in billions of dollars and preserve water for agriculture.

Watershed Management is a vital pre-requisite to stop silt flow and increase the life of reservoir. Watershed Management is carried out in the catchment area of storage dams before and after the construction of dams. It is a continued process till silt erosion and silt movement is stopped. Watershed Management is done by building check dams all over the catchment area, by growing forests and greenery to check soil erosion and reduce the speed of rainwater runoff to slow down velocity flow and silt movement.

It is vital to stop soil erosion, and silt flow so that the life of reservoirs increase indefinitely in the interest of agricultural development and food production.

Storage dams are first built in the upstream reach of the river to function as Watershed Management infrastructure so that reservoirs built on the downstream increase their lifespan.  Moreover, the upstream dams generally have better capacity-inflow ratio and longer lifespan.

There are other measures for Watershed Management to reduce silt flow so that it is not deposited in the reservoirs to shorten their lifespan. One of the vital measures is to select dam site on a river where the capacity-inflow ratio is the best. This will prolong the life of reservoirs because the inflow at the proposed dam site would be very less than the reservoir’s storage capacity. This will create more space for silt deposition and give longer life. Dam sites are selected on this basis all over the developed world.

Dams are built in most of the countries at a site on a river that have several times more storage capacity than the river inflow at the dam site so as to have longer lifespan.

 Pakistan is most unfortunate and self-destroyed country to select storage dam at the tail end of the valley where the catchment area is maximum, the river runoff is the maximum, sediment flow is maximum, the storage capacity of the reservoir is minimum and lifespan is short due to rapid silting. WAPDA selected dam site at the end of the valley at Kalabagh that has 20 to24 years lifespan and the other at Tarbela that has a lifespan of 50 to 60 years. No Watershed Management measures are carried out in the catchment area for these dams to increase their lifespan by reducing silt flow.

The example of Hoover Dam or Boulder Dam on Colorodo River in USA is quoted. Its lifespan at the time of its construction was 100 years. After carrying out continuous watershed Management in the catchment area, its lifespan now is extended to 1000 years. 

Pakistan is again unfortunate to have created only 9% storage of its total runoff from rivers. Most countries have created storage on rivers more than 40% and above of the runoff. Reduced storage is the reason that Pakistan is a victim of scarce water and crippling load shedding. Besides the victim of silting, it is the victim of inter-provincial water dispute and a victim of the Indus Waters Treaty as its storage created under the Treaty has rapidly disappeared due to silting. No body bothers about this disturbing fact and about its legal side to replenish the lost storage due to silting.

Tarbela Reservoir has a vast catchment area, spreading over many countries with harsh terrain. Therefore, Watershed Management is beyond the reach of Pakistan. While selecting Tarbela Dam site, no attention was paid to the capacity-inflow ratio and to its estimated short lifespan of 50 years. Tarbela was compared to a downstream dam at Kalabagh, that has the worst capacity-inflow ratio and short lifespan of about 20 to 24 years in the entire reach of the Indus. Out of the two poor most dam sites, the dam site at Tarbela was selected for construction under the Indus Waters Treaty. Surprisingly, the  principle of capacity-inflow ratio for the selection of dam site was ignored or not known to the planners. The unique and multipurpose dam site in the upper reach of the Indus at Katzarah with excellent capacity-inflow ratio was ignored though Katzarah has a lifespan of 1000 years. After first building Katzarah, then Tarbela its lifespan would have been about 200 years.

Indus is the only river in Pakistan where few mega dam sites are available for creating storage reservoirs. Unfortunately, each dam site is less attractive than the one on its upstream. Therefore, storage dams on the Indus be selected with priority so that it has the best capacity-inflow ratio. It is unfortunate that no dam site on Kabul River, Chinab River and Jehlum River exist in Pakistan’s jurisdiction.

The only choice and the excellent choice of a dam site with unique and multipurpose benefits on the Indus is at Katzarah about 20 miles downstream of Skardu town. It is unique because it will control silt erosion from the world’s highly erodible soil in Skardu valley that is the source of silt in the Indus water. It means, Katzarah Dam and its 35maf huge reservoir will submerge the source of silt. Katzarah will function as Watershed Management infrastructure. It will not allow silt to flow down. This means, the estimated life of Basha Dam of about 80 years will increase to about 800 years. The life of Tarbela will also increase by about another 70 years.  This will give economic benefit worth billions of dollars each year. Had Katzarah on the Indus, and Guroh Dop on Panjkora Rivers existed, about 85% flood water that passed below Kotri would have been stored and flood havoc avoided.

Katzarah Reservoir has the best capacity-inflow ratio in the entire reach of the Indus River. Katzarah Dam site has most probably the narrowest bed width in the world after the Khajuri Katch Dam site on Gomal River also discovered by me in 1959. Katzarah Dam site has bed width  between 250 feet to 300 feet at the river bed level and Khajuri Katch Dam site is 85 feet wide at the bed level. Kalabagh Dam site is two mile long. Tarbela is 8000 feet long. I discovered Katzarah Dam site in 1962 and confirmed by Dr Pieter Lieftnick of the World Bank in 1968. Similarly, I discovered Khajuri Katch Dam site on Gomal River in 1959 after stopping work going on at wrong dam site at Gul Katch in the head reach of Gomal River. My proposal was highly appreciated and approved by Harza International Consultants of USA.

Katzarah Dam’s storage capacity of 35 maf is 6 times the storage capacity of Kalabagh Dam or of Basha Dam. Katzarah Dam’s storage capacity is more than 3 times the storage of Tarbela Dam. Katzarah will generate between 10,000 to 15,000 MW of hydropower depending on the fixation of its height. It will control super-floods during climate change. It will irrigate millions of acres of barren lands in Pakistan. The life of Katzarah is more than 1000 years.

During 1962, I proposed to build Katzarah Dam to create huge storage. I then suggested to build All Pakistan Grand Canal to irrigate the Kachi plain of Baluchistan from Chashma barrage on the Indus. No body paid attention to this wonderful project. 

WAPDA is allergic to the construction of Katzarah Dam though China has offered to build this dam in the year 2000. WAPDA has promised before the Parliamentary Committee headed by Nisar Memon to prepare and submit Katzarah Dam’s feasibility report to the Government by September, 2005. WAPDA failed to do so. It failed to build dam after Tarbela in 1974 though the Authority is created for water and power resources development of Pakistan. WAPDA’s headquarter essentially needs to be shifted to Islamabad like that of IRSA so that it is contacted by all concerned and make it active and responsible to meet the water and power needs of the country to avoid ugly situation as the country is facing crippling load shedding and water scarcity besides the devastating record floods this year due to WAPDA’s negligence.. 

The selection of dam site has therefore a great bearing on the rate of silting and the life of the reservoir and its usefulness for sustained irrigated agriculture to produce food for the fast growing population. Silting of dams is therefore an extremely serious matter. Reservoirs must be given full protection by Watershed Management and by proper dam site selection for a longer lifespan. It is surprising silt problem is ignored while planning dams and reservoirs.

I believe it is the media and no body else, who can invite serious attention of the Prime Minister to take notice as the matter is very serious on many counts.