Prayers for a little
Down to Earth – August 31, 2011
By Bharat Lal Seth
Rivers’ flows must be maintained to protect the services they provide, but India has no legislation
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.
Algae and hydrophytes (aquatic plants) do for water what plants do for land and air,” says Prakash Nautiyal, department of zoology and biotechnology, Garhwal University. Changes in the reservoir also affects the river’s ecosystem downstream. “But engineers have not been sensitised about aquatic biodiversity. They value the physicality of water, but don’t appreciate how nature’s engineers render ecological services,” he says.
River’s flow has an impact on freshwater species. Some organisms require fast water current, others thrive in slow flow. Nautiyal has been campaigning to save the Indian Mahseer, the big scaled carp that prefers cold, clear, fast-flowing water, with stony, pebbly or rocky bottoms, and intermittent deep pools. The Indian Mahseer has already lost breeding grounds in Uttarakhand’s rivers. The barrage at Rishikesh, for instance, has had an adverse impact on its population. “Uttarakhand may lose the fish if an appropriate e-flow regime is not established,” he says.
Studies to improve rivers’ ecosytem
As part of its Living Ganga programme, WWF-India set out to establish e-flows at different sites in 2007. It was India’s first attempt to look beyond hydrology. At Bithoor, a pilgrim centre in Kanpur, people expect the water of the Ganga to inundate a part of a temple. For them, it is akin to washing of Lord Brahma’s feet. “Our study captured these expections from the river,” says Nitin Kaushal, who worked with the WWF-India project.
The multi-disciplinary group of IIT experts has carried forward their approach and is now preparing e-flow recommendations for the Ganga by calculating requirements from the river at 80 sites. “Certain species at the top of the food chain will be selected to understand their dependance on the river’s width, depth and velocity,” says Tare. The team has collected cross-sectional data from 40 sites between Gangotri and Varanasi. It will get data for 40 more sites from the Central Water Commission (CWC), a technical agency on water resource development. The study will take two years to complete.
To draw an action plan for improving the condition of water bodies in India, the MoEF set up Water Quality Assessment Authority in 2001. One of its working groups, did the priliminary work on minimum flows in India. It mostly constituted CWC officials. The group’s report recommended minimum flow of just 2.5 per cent of the mean annual flow of Himalayan rivers.
After several rounds of discussions it was decided that many more studies are required to reach a conclusion. “A lot has changed in the e-flow debate. We need to update the recommendations before ratifying them,” says a senior official in the environment ministry.
Difficulty in quantifying water
Quantifying the amount of water a river must have is difficult because a river’s ecological needs have not been defined yet, say CWC officials. Moreover, 80 to 90 per cent of the annual flow occurs in just 120 days, and India has a water storage capacity of 11 per cent of the annual flow. The irony is, say the CWC officials, that those who favour e-flow oppose large storage projects.
Maintaining e-flow may come at the cost of other requirements. Since India’s is an agrarian economy the trade-off would mainly be with agriculture. “Today, rivers are over-allocated. The only water available for future use is floodwater. We have to learn to distribute it from surplus to deficit areas,” says Ravindra K Srivastava of Uttar Pradesh State Water Resources Agency and member of the group making e-flow recommendations for the Ganga.
Establishing e-flow is also difficult because ecology does not get high priority. It figures fourth on the list of priorities under the national water policy. This means that water for e-flow can be released only after meeting the needs of drinking, agriculture and industry.
On diverting water, a river becomes lean, its aquatic life is disturbed and its aesthetic quality impaired. Any engineering intervention, however small, will invariably impact an ecosystem’s functions and services, says Jayanta Bandyopadhyay of IIM-Calcutta and member of IITs’ working group. “The question is to find an agreeable trade-off in which the diversions of water will be socially acceptable and ecologically sustainable, and all the damages to livelihoods and ecosystems, adequately dealt with,” he says.