KARACHI, June 5: The year-to-year data collected with the help of tree-ring chronologies from the main upper Indus basin has shown that the river flow has considerably increased over the last 21 years, possibly the highest sustained flow period of the past 500 years.

This remarkable finding that could be linked to large-scale global climatic changes is part of the final report of a four-year study “Upper Indus river flow reconstruction using tree-rings implication for agriculture and hydroelectricity” conducted under a Pakistan-US project for science and technology through the Higher Education Commission (HEC).

Not only the method — tree-ring-based reconstructions of stream flow — used in the study is unique, but the research is the first paper that traces the flow of the Indus over the past 500 years. The Water and Power Development Authority (Wapda) has only 45 years’ data on the Indus flow.

The study, according to experts, would be helpful in the scientific and sustainable management of water resources. Dr Moinuddin Ahmed, an HEC foreign professor specialising in dendochronology/ plant ecology teaching at the Federal Urdu University of Arts, Science and Technology, and Dr Edward R. Cook, one of the top scientists in dendochronology working at the Lamont Doherty Earth Conservatory, Columbia University, USA, led their teams from Pakistan and the United States, respectively.

Dr Connie Wood House from the University of Arizona and Dr Jonathan Palmer from the Gondwana Tree-ring Laboratory, New Zealand, also gave their input in the study.

“Whether this recent change in the river flow is due to the enhanced glacier melting on account of global warming or an increase in precipitation and snowmelt in the primary runoff producing regions is unclear at this time. However, knowing the answer would have a big impact on the projections of future Indus river flow based on climate change scenario,” the study says.

The other interesting aspect, the research highlighted, was the occurrence of a major sustained low-flow period from 1640 to 1660.

“It is unprecedented in the record and would clearly be impossible to anticipate or model as it is based on a short instrumental record. Should such a ‘mega drought occur in the future, its impact on hydroelectric power generation and irrigation-based agriculture would be devastating to Pakistan,” the study further says.

A collection of 32 tree-ring chronologies from six different species located in the northern Pakistan were evaluated in terms of their potential for dendrohydrologic and dendroclimatic reconstructions. Two species — C.deodara and P.gerardiana — were found to have the best prospects for the study.

Speaking to Dawn, Dr Moinuddin Ahmed said that Pakistan’s population and economy were heavily dependent on an annual influx of water primarily from melting snow into the Indus river system and efforts to understand how past river-flow changes had developed and persisted could be helpful in the sustainable management of water.

“The Indus river basin is the largest watershed in the country and a severe decline in the flow of the Indus River poses a great threat to Pakistan. The Indus basin is highly vulnerable to environmental change and is already experiencing considerable water deficits due to severe pollution, land use and development,” he said.

Explaining the role of dendochronology (tree-ring research) in water management, Dr Ahmed said it was scientifically proven method for the management of water resources, which was being widely used across the world.

“The tree-ring based reconstructions of stream flow could provide significant insight into the hydrologic variability of the river basin over time. This will help prepare a better response to the natural fluctuations in river flows, most crucial of them are drought conditions,” he said, adding that trees were not cut but rather instruments were used to get the images of tree rings.

“The annual growth rings formed in the trunks of some trees recorded the effects that occurred due to climatic, hydrologic and soil conditions. We record the variations that occur in the normal pattern of a tree-ring. The selection of site and tree species depends on the nature of the study,” he said.

Dr Ahmed questioned the reliability of the 45 years data on the Indus water flow currently available with Wapda and contended that it was simply not adequate for a sustainable management of water resources.

“For sustainable management, one needs to know the water flow patterns that prevailed over centuries in order to be able to predict the situation of water availability in coming years. And, trees are the best source to get such information.

Wapda essentially needs a tree-ring research laboratory.”Giving suggestions, Dr Ahmed said that the government must immediately take measures for forest conservation that should include sustainable grazing and banning cutting of old trees.

“Old trees are an asset. They are, perhaps, the only source available today that can help us know the environmental changes over thousands of years. Destruction of forests means erasing our history,” he said, adding that about 60 per cent of forest cover in Azad Kashmir had already been lost mainly to timber trade and cutting of wood for fuel purposes.