LAHORE, July 11: Two studies carried out by foreign consultants before and after construction of the Mangla dam have been found to have ‘grossly estimated’ the possible flood resulting in under utilization of the dam’s capacity during the past 40 years. This is the finding of a team of Pakistani experts in hydrology and meteorology headed by Abdul Majid, a hydro-meteorologist of international repute and former chairman of working group of hydrology for Asia at the World Meteorological Organization (WMO) who had also been the National Flood Forecasting Bureau director.

In his report to the authorities concerned, including the Wapda chairman, Abdul Majid has said the technical computation of hydro-meteorological factor called the Probable Maximum Flood (PMF) that is simply stated the highest possible flood that could ever occur at any dam site, has a direct bearing on the quantity of water storage in a dam and its operating procedure.

He has suggested that there is an urgent need to review such hydro-meteor studies like the PMF in respect of the major present and proposed dams so as to bring them on the proper scientific footings.

This would not in any way obstruct or oppose ongoing Wapda projects but it would ensure the proper utilization of storage capacities and help in the formulation of most realistic dam operating rules. It would need setting up committees of experts comprising professionals possessing necessary expertise in the hydro-meteorological and the related fields. The PMF study involves about 60 per cent meteorology and 40 per cent hydrology.

Reverting to the foreign consultants’ studies, Mr Majid has pointed out that the Mangla dam’s PMF as estimated by the British and American consultants — Messrs Binnie and Partners and Harza International in 1959 at 2.6 million cusecs had restricted the maximum water level at the dam at 1,202 feet (above seal level) for the dam’s safety.

They were of the view that a peak flood reaching 2.6 million cusecs could occur at Mangla and this in order to enable the safe passage of this flood through the reservoir called for keeping the maximum water level at 1,202 feet.

On the other hand, he said, the highest actual flood ever occurred so far over a period of 100 years was that of September 1992 which was less than 1.1 million cusecs.

We are thus waiting for more than double of the highest historic flood and keeping the reservoir sufficiently empty to provide for its safe routing. He said that no doubt the safety of the reservoir was paramount and sufficient empty space must be provided to enable the absolutely safe passage of flood but it should not mean that we aim at hypothetically high value of the PMF and manipulate the laid down procedures to achieve this value.

He said that in the first study done by Binnie and Partners in association with Harza the lack of sufficient data and knowledge of weather systems influenced the foreigners who in a bid to play safe manipulated some of the rainfall enhancement factors that were not even applicable in the environment thus produced so big rainfall enhancement factors of more than four as against normal enhancement factor ranging from 1.4 to 2.00.

In the second study done by Harza before the occurrence of historic September 1992 Mangla flood, the consultants had not used the enhancement factors but instead produced a fictitious isotherm map, drawn without actual rainfall data, to manipulate the similar results.

The third study of Mangla PMF was undertaken by the Mangla Joint Venture (MJV) led by the Nespak. The MJV in consultation with Harza gave two sets of PMF values, meteorologically computed PMF value of around 1.7 million cusecs and hydrologically computed value of about 2.3 million cusecs.

He said the root cause of the problem was the fact that Harza had been a common factor in all the three studies. Consequently, in all the three studies similar results were manipulated.