Pakistan Agriculture News, Water

Capacity of Tarbela, Mangla to reduce 33pc by 2020

ISLAMABAD – A report of UNDP and Ministry of Planning has said that the live storage capacity of tarbela and mangla reservoirs is likely to reduce by 33 percent by 2020, due to resulting reservoir sedimentation and recommended Construction of an upstream Dam (e.g Bhasha) to Reduce Siltation in tarbelaDam.

The problem of soil erosion in Watershed Areas which results in the over sedimentation of the main reservoirs is a matter of serious concern as it is estimated that the Indus and its tributaries carry about 0.35 MAF (0.435 BCM) of sediment annually of which 60 per cent remains in the system where it is deposited in the reservoirs, said report on “Inclusive and Sustainable Development: Analytical basis and policy framework” jointly launched by the United Nation Development Programme Pakistan (UNDP) and Ministry of Planning, Development and Reforms.

According the report Pakistan has abundant hydroelectric potential of about 100,000 MW.

A strategic intervention for facilitating sustained economic growth is to accelerate the development of hydro power projects which would generate abundant and clean electricity and at the same time provide storage for irrigation purposes.

The live storage capacity of tarbela and mangla reservoirs was estimated to have reduced by 20 per cent by the year 2000, and is likely to reduce by 33 per cent by 2020 due to resulting reservoir sedimentation, said the report.

The rate of soil erosion in the watershed areas is accelerating mainly due to overgrazing, deforestation, poor land use practices, cultivation of marginal lands enforced by the rapid population growth, and lack of alternative sources of fuel wood, as well as economic opportunities in the mountain communities.

The rapid deforestation estimated at 7000 – 9000 ha annually be strictly checked in order to decrease soil erosion.

According the report an important policy initiative that should no longer be postponed is the urgent construction of an upstream dam (e.g. Bhasha Dam).

This can possibly increase the life of tarbela dam by 30 to 40 years as is widely known in WAPDA. The government has rightly announced that the Diamir-Basha project has the highest priority. Construction of Bhasha 4500 MW should not be delayed any further and almost simultaneously with Dasu 4320 MW.

Basha would not only provide 8.1 MAF gross water storage, it would increase the life of tarbela by 30-40 years. Acceleration of work on the hydel projects given below is imperative.

According the report, Pakistan has 14 mega or very large hydroelectric projects to be completed: Bhasha 4500MW, Dasu 4320MW, Bunji, 7100MW Kalabagh, 3600MW, Pattan, 2800MW; Thakot 2800MW, Shyok/Yugo 2800 MW, Yulbo 2800 MW, Tungas 2100 MW, Duudhnial 960MW, Neelum-Jehlum 969 MW, Kohala 1100 MW, Karot720 MW, tarbela 4th Extension 1410 MW, totaling 45089 MW.

Only one project is controversial, Kalabagh. But there are a whole range of hydel projects that can be completed in no more than three years.

In addition to the 14 above mentioned sites, there are 75 large and medium sites that are in various stages of development. The total number of hydropower sites is about 950, according to GTZ, including hundreds of small hydels.  The 87 identified site can produce about 65,000 MW.

Regarding the flows below Kotri Barrage, the report said that the scarcity of water for irrigated agriculture and temporal and flows of the Indus river system demands a spatial variation inflows that must pass below Kotri Barrage.

The average below Kotri barrage is about 32 million acre feet, whereas the flow to the sea to check sea water intrusion has been minimum  estimated as 10 million acre feet.

As per the report currently, Pakistan is storing only 15 per cent of its annual river flows, which is far less than required to ensure sustainability of? irrigated agriculture.

In the past few years, the government has been emphasizing the construction of small dams to provide irrigation facilities to the small scale irrigation sector. The small dams may address the poverty issues in selected villages but would not help in eradicating poverty at large.

This may be enough to meet small scale irrigation and domestic water requirements but cannot be a substitute for large dams. For instance, to store water equivalent to Kalabagh dam would require construction of 750 small dams, and that too will be exclusive of power generation.

Therefore, the importance of large dams should not be ignored as they are imperative for sustained national economic growth both from the point of view of food as well as energy security.

Regarding the canal water charges, the report said that existing canal water charges are far lower and inconsistent with the economic benefits. Furthermore, recovery of water charges (abiana) is far lower than its original value. Therefore, an increase in the current abiana rates and improvements in the recovery system are needed to enable Irrigation Departments to improve maintenance of the water infrastructure for increased water supply reliability.