Enviornment Prelims cum Mains

Centre sets ‘minimum river flows’ for the Ganga

The News

  • The Union government for the first time has mandated the minimum quantity of water or E-flow (environmental flow) that various stretches of the Ganga must necessarily have all through the year.



  • The E-flow for the river is notified in order to restore and maintain continuous uninterrupted flow of river Ganga (‘Aviralta’).
  • Accordingly any dam or structure meant for diversion of river flows for the purpose of irrigation, hydro-power and domestic or industrial use will now have to maintain the minimum flow under the notification.
  • There are 784 dams, 66 barrages, 92 weirs and 45 functional lift schemes located, at present, in the Ganga river basin.
  • Central Water Commission is the designated authority to collect and monitor the flow data.
  • The CWC further submits monitoring-cum-compliance reports on a quarterly basis to the NMCG.
  • Hydropower projects located along the river are required to comply with the norms within 3 years.
  • However the norms do not apply to mini and micro projects.


E-Flow specifications for Ganga

National Mission for Clean Ganga has laid down the flow specifications:

From its origins to Haridwar:

  • Minimum flow should be
  • 20% of the monthly average flow of the preceding 10-days between November and March.
  • 25% of the average during the ‘lean season’ of October, April and May;
  • 30% of monthly average during the monsoon months of June-September.

From Haridwar in Uttarakhand to Unnao, Uttar Pradesh:

  • Minimum flow is specified at various barrages
  • Bhimgoda (Haridwar)
  • 36 cubic metres per second (cumecs) between October-May,
  • 57 cumecs in the monsoon
  • Barrages at Bijnor, Narora and Kanpur
  • 24 cumecs in October-May,
  • 48 cumecs during June-September.



What is E-flow?

  • The E-Flows are a pattern of flows that are required by a river to maintain itself in a desired environmental condition.
  • Ecological services offered by the rivers in India are getting adversely affected by changes in quantity, quality and flow regimes.
  • This is particularly true with Ganga.
  • During its 2,525 km journey from Gangotri to Ganga Sagar, there are complex, nested sets of challenges that threaten the existence of the river.
  • In the upper Himalayan reaches, the flow in the river is vulnerable to water abstractions by hydropower projects.
  • From the time the river enters the plains, abstractions for agriculture, urban and industrial uses leave the river lean and polluted.
  • As the river makes its way to the sea, and more pollution is added to the lean flows, the stress on the Ganga increases.
  • E-Flows are recognised as a key to the maintenance of ecological integrity of the rivers, their associated ecosystems, and the goods and services provided by them.

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