500 years of Indus river flow modeling with tree rings
500 years of Indus River flow modeling with tree rings
Suhail Yusuf
KARACHI: A team led by foreign professors at the Federal Urdu University of Arts, Science and Technology (FUUAST), has successfully modeled the past five centuries of Indus River Flow with the help of Dendrochronology – the study of tree rings.
Prof. Dr. Moinuddin Ahmed, the head of Dendrochronology and Plant Ecology told Dawn.com that his team has reconstructed the past river-flow levels of Indus while using dendrochronology as a tool. However the data still needs verification by various statistical tests.
The eureka moment came during the six-day international conference on dendrochronology held a month ago in Karachi, where experts decided to reconstruct 300 years of the Indus River flow by analyzing tree rings.
International collaboration
The three-year project is a joint Pak-US venture and two key researchers are also involved in it. The key findings will be shared by national and international agencies and the data will be archived in the “international tree ring data base.”
Dr. Connie Wood House and Dr. Jonathan Palmer are team members in this project of applied dendrochronology.
Dr. Wood House did the reconstruction of the water flow level in River Colorado in the US. She is working on a similar project for River Indus by looking at tree rings.
Speaking to Dawn.com, Dr Moinuddin Ahmed said that tree rings are not only used to assess the age of a tree, but also a powerful tool for water flow modeling, forest ecology, archaeology, drought, rainfall, glaciology and climate change. Wood chips from archaeological sites can also be used for dating and other purposes. Thus tree rings provide amazing other details rather than just counting their age. Juniper and Pine trees are often used in dendrochronology.
How it works
The team used 28 tree-rings sites from the northern areas of Pakistan. For more than two years, hundreds of trees were bored by a hollow tube which collects a narrow stick of wood from the trunk to the core of the tree.
This is a nondestructive way to collect dendrochronology samples. The team also used fallen dead trees from the areas and compared them with the living trees.
The samples were then analyzed under a highly accurate “tree rings measurement system”, in which every ring is observed carefully and details are registered.
Various statistical techniques are then applied to assess the water flow of the Indus for more than 500 years, which is 10 times longer than any instrumental record of the flow. Advanced software is also used for numerical modeling of the data.
Modeling the ancient waves
The initial data from the tree rings not only matches the data provided by the Water and Power Development Authority (WAPDA) but also provides an initial picture of 500 years of the Indus River flow level.
After compiling the final report, the data can be used for better and long term planning and management of water resources.
The researchers got 45 years of data from Wapda monitors at Partab Bridge, and then collected tree-ring samples from 28 different sites on upper Indus and northern areas. By using software and statistical models they reconstructed the Indus water flow of the past 500 years. Upper figure shows the complete 500 year flow history (from 1505 to 2008). The discharge shown in cubic meters per second (CMS) is based on a network of 28 tree-ring sites. The Black line shows monitored data, the red line depicts constructed river-flow, while blue line shows 30 years running mean. Lower figure shows the strength of the similarity between the 45 years monitored record by Wapda (blue line) and the tree-ring based reconstruction (red line) – courtesy Dr. Moinuddin Ahmed.
Thus, tree rings provide a great window to observe the various scenarios of past. For instance, rings of trees at any archeological or earthquake hit site can be used to shed light on the event. It is possible to know any past event with the help of dendrochronology just by looking at the trees at any particular site.
To reconstruct the Indus River flow, the team chose the trees on slopes of the mountains in northern areas where water from glaciers poured in the Indus Basin, because the flow of Indus River heavily depends upon the water from glaciers. Rain contributes very little to the flow.
Talking to Dawn.com, Dr. Ahmed said that dendrochronology techniques are applicable to probe many important disciplines. He said that three stations of WAPDA hold only 100 years of data while dendrochronology can easily provide 500 years of information of Indus River flow.
Dr. Ahmed is also interested in reconstructing the climate change, and drought situation of the past in the northern areas. Many proposals have been sent to authorities but they don’t have any person or referee to judge this new emerging field.
Dr. Ahmed urged the authorities to get the proposal checked by foreign experts in case of unavailability of local experts.
“Reconstruction of Indus River flows will be helpful in irrigation, water management, hydrology and water distribution among the provinces,” Dr. Ahmed added.
