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In tree rings warning of Brahmaputra floods

Topics Covered: Disaster management.

In tree rings, warning of Brahmaputra floods:


Context:

Existing projections of flooding of the Brahmaputra are based on observations of past rainfall patterns, but they rely on discharge- gauge records that date back only to the 1950s.

  • So, now the scientists have come up with an innovative idea in which they have tried to analyse floods by relating them to tree rings.

What does the new study suggest?

The new study is based on examinations of tree rings, which provided a picture of rainfall patterns going back seven centuries.

  • The rings showed that the post 1950s period was actually one of the driest since the 1300s- there have been much wetter periods in the past.
  • The tree-rings suggest that the recent decades (particularly from the 1950s to 1980s) were unusually dry. Therefore, in general, past conditions were wetter.
  • It also suggests that the future will likely be wetter due to our emissions of carbon-dioxide.

How tree rings helped?

  • As trees grow they incorporate information about the environmental conditions they are living in in their annual growth rings.
  • Tree rings grow wider in years when soil moisture is high. Trees in the region grow more and put on wide rings in wet monsoon years.
  • Conversely, in dry monsoon years (or droughts) they grow less and put on narrow rings.

Since some of these trees can live for a long time, by taking a small, pencil-thin tree-core from these trees and measuring their rings under a microscope scientists could learn more about climate conditions for the past several centuries.

Significance:

The findings are obviously relevant to Assam and Northeast India too. With this, flood risks could be compounded by planned projects in the region.

Sources: Indian Express.