- 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.