Rivers’ flows must be maintained to protect the services they provide, but India has no legislation
Prayers for a little
How much water should flow in Indian rivers? Hydrologists have been discussing minimum river flows for over four decades now. The churning has resulted in the concept of environmental flow, or e-flow. This implies strategically releasing water downstream of dams and reservoirs to protect the services a river provides.
Two recent studies—by IIT-Roorkee and a multi-disciplinary group of IIT experts—have pushed for the establishment of e-flow. IIT-Roorkee submitted its report in June this year, while IIT experts are hammering out a preliminary draft report on e-flow recommendations for the Ganga. They will present their report within two years.
“Our job is to present the scenario. But there will be trade-offs and the decision may become political,” says Vinod Tare, coordinator of the study by IIT experts and professor at IIT-Kanpur.
Flows are essential for rivers to maintain their regime, says Ramaswamy Iyer, former secretary of the Union Ministry of Water Resources. “They help rivers purify themselves, sustain aquatic life and vegetation, recharge groundwater and support livelihoods. They facilitate navigation, preserve estuaries, prevent incursion of salinity and enable rivers play their role in people’s cultural and spiritual lives,” he says. These functions are possible with a suitable e-flow regime.
Many environmentalists demand that rivers should be left in their natural state. But this option is unviable as it would mean scrapping hydel projects, dismantling canal networks and decommissioning the existing dams.
E-flow is perhaps the best solution. While it would ensure water to all those dependent on the river, it would also secure the river’s ecosystem. What is minimum river flow?
At present, India has no legislation to protect rivers from projects that may dry up long stretches. Himachal Pradesh is the only exception. In 2005, it notified that flows should not be less than 15 per cent of the average lean season—from December to March.
Later, the Union Ministry of Environment and Forests (MoEF) prescribed 10 to 15 per cent flow for projects in river valleys without giving a scientific thought to it. The limit was randomly increased this year. “Twenty per cent of the average lean month flow should now be released downstream of the dam,” says Sanchita Jindal, member secretary, MoEF’s environment appraisal committee for hydel projects.
But setting a minimum flow sanctions maximum diversions, says Iyer. “Project proponents think they are entitled to divert rest of the water. Rivers must flow. We should be wary of interfering with their natural flows,” he says.
The concept of minimum river fl ow was developed in the 1970s. A hydrological estimate, it stipulates a minimum percentage of the mean annual river flow. Studies have established that while a minimum flow may keep the river wet, all elements of the river’s regime—high, medium and low flows—are essential to maintain its ecosystem (see graph on page 26). In the 1990s, methodologies were developed that gave river basin managers release options to protect the rivers’ fauna and vegetation, while meeting people’s social and cultural requirements (see ‘Methodologies for minimum river flow’). These, however, were never implemented.
Requirement is e-flow
Vehement oppositions to many hydel projects led the environment ministry to ask IIT-Roorkee in July 2010 to assess their impact on the Alaknanda-Bhagirathi basins. Its report had also proposed establishment of e-flow, not minimum flow, after studying the river’s discharge, cross-sections and impact of different flows on biotic life.
A project’s installed capacity should be planned conforming to the water available after satisfying the needs of e-flow, it says. But the report does not provide any conclusive takeaways on e-flow, says Jindal. If the percentage of river length affected is high, hydel projects should not be allotted, the IIT-Roorkee report says. A threshold, say 70 per cent, may be fixed for the purpose. “This is an arbitrary figure and in line with the present affected length of the Alaknanda. The report fails to stipulate quantum of water for release,” says Ravi Chopra of the non-profit People’s Science Institute, Dehradun.
A recent study by Delhi University found that regulation of the Bhagirathi by Tehri dam has changed the levels of water temperature, pH value and dissolved oxygen in the reservoir. “The reservoir’s water temperature increased by nearly 16 per cent compared to the natural flowing section. Its pH value increased from 8.99 in the river’s non-regulated stretch to 9.34 in the reservoir,” says Maharaj Pandit, head of the department, school of environmental studies, Delhi University. The upstream river water recorded higher dissolved oxygen compared to the reservoir. Change in temperature led to significant decrease in biotic communities like phytoplankton (microscopic organism at the base of aquatic food web), says Pandit. “Such a loss of biodiversity in the ecosystem has serious implications.
We are a voice to you; you have been a support to us. Together we build journalism that is independent, credible and fearless. You can further help us by making a donation. This will mean a lot for our ability to bring you news, perspectives and analysis from the ground so that we can make change together.
Comments are moderated and will be published only after the site moderator’s approval. Please use a genuine email ID and provide your name. Selected comments may also be used in the ‘Letters’ section of the Down To Earth print edition.