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The first step to managing water resources fairly and sustainably is understanding the river’s natural cycles of river flows that change across the seasons, and to mimic the natural cycle of flows, even in more heavily managed rivers with less water - as “environmental flows” – or e-flows – requirements. 

That means knowing the quality and quantity of water that needs to be flowing at any given time in order to meet the needs of people and wildlife and maintain the river’s natural processes. For example, many fish species can’t spawn if the river is too slow or shallow, while some religious activities require the river to be at a certain depth.

We assessed e-flow requirements on a 500-mile stretch of the Ganges in northern India, comparing the current state of the river against the desired future state, from the different perspectives of the groups that depend on it.

We looked at issues including:

  • Livelihoods – the depth, width and other aspects of water needed to maintain important jobs like ferrying and rafting
  • Spiritual needs – the depth and water quality needed for religious and cultural purposes, like ritual bathing
  • Biodiversity – the natural flows needed across the seasons to maintain freshwater habitats and the breeding and migration patterns of river dolphins, Golden Mahseer fish, gharials, turtles, otters and other species
  • Physical features – the depth and speed needed to move and deposit sediments so as to maintain the river’s natural channels

This enabled us to work out the e-flows required to meet all these needs at different times of year – especially during the driest months and the monsoon season. For example, we were able to test our e-flows methodology during the 2013 Kumbh Mela, a Hindu pilgrimage that attracted an estimated 80-100 million pilgrims to the banks of the Ganges in Allahabad. We worked with the government to help ensure flows were sufficient to meet the ritual bathing needs. 

The project was the first time such a comprehensive assessment had been attempted for a river system as large and complex as the Ganges.

Using these results along with climate change data, annual rainfall patterns can help to plan and manage irrigation, dams and other water uses in a way that meets environmental and human needs. We’re starting to put this into practice in the Ramganga, one of the rivers that flows into the Ganges. In future, we aspire to see e-flow requirements assessed and respected for every river in India.