Weekly Current Affairs

Surplus river basins face drop in rainfall: IIT study [Environment]

  • A study carried out by a team of researchers from IIT Madras and IIT Bombay has found a decrease in spatial variability of mean monsoon rainfall over major river basins in India.
  • While there is a statistically signifi cant decrease in the monsoon rainfall over major water surplus river basins, there is no statistically signifi cant increase in monsoon rainfall over major water defi cit river basins.
  • Major surplus basins such as Mahanadi, Godavari, Brahmani and West Flow River-I are witnessing signifi cant decrease in rainfall. Other surplus basins also exhibited decrease in rainfall but they are not statistically signifi cant.
  • The decrease in water yield in recent periods in major surplus basins has been more than 10 per cent in the case of Mahanadi and West Flow River-I. In the case of other surplus basins, the decrease has been within 10 per cent.
  • Though water yields in major defi cit river basins such as Indus, Ganga and East Flow River-II have increased during the period 1976-2000 compared with the previous 25 years (1951-1975), the trend is not statistically significant.
  • Ganga, which is a major water defi cit basin, has seen signifi cant increase in rainfall, while Yamuna, Krishna and Cauvery river basins exhibit a decrease.
  • There has been an increase in extreme rainfall events in India but this does not play a significant role in water availability as the surplus water gets wasted.
  • As a previous study had pointed out, the latest study has found that the amount of summer monsoon rainfall over Indian river basins does not support the paradigm “wet gets wetter and dry gets drier”.
  • The changes in rainfall pattern over major river basins in India raises concerns regarding the suitability and viability of interlinking major river water basins.