The work recently published in the journal Aquatic Conservation was conducted by scientists from Wildlife Conservation Society – India Program (WCS-India Program), National Centre for Biological Sciences, Bangalore, India, the University of Florida, Ashoka Trust for Research in Ecology and the Environment, and Foundation for Ecological Research Advocacy and Learning (FERAL).
SHPs are hydroelectric plants with relatively smaller power generating capacity compared to large hydropower plants. They are often promoted as a cleaner and greener alternative to large hydropower projects as they are assumed to have little or no environmental impacts. In India, they are defined as those that generate power up to 25MW. There has been a proliferation of SHPs in India, especially in biodiversity-rich areas such as the Western Ghats and Himalayas. As of 2012 there were 1266 projects commissioned while another 6474 have been identified.
The study was conducted in the upper reaches of river Nethravathi, which is part of the Western Ghats biodiversity hotspot, from February 2014 to May 2014. In the study, two dammed tributaries and one undammed tributary of the west flowing Netravathi river were selected.
It was found that the SHPs affected the river flow by reducing flow immediately below the dam and caused flow fluctuation when the water is released back into the river after power generation – both of which have consequences on fish assemblages. The dammed streams had altered fish composition and reduced number of species.
The SHPs are made of four main components – a diversion weir (this blocks the river’s flow and creates a reservoir), a powerhouse with turbines, a penstock pipe and a tailrace canal. The water diverted at the weir passes through the pipes to the powerhouse to produce electricity. Water is then released back into the river further downstream through its tailrace canal.
Explaining the results, Suman Jumani, the lead author expresses, “Our study was one of the first to holistically assess the impacts of SHPs in the forested regions of the Western Ghats. Ecologically, SHPs severely altered river geometry, water quality, and freshwater fish species assemblages. Since they divert water for long distances, it leaves vast stretches of the river almost completely devoid of water flow in the dry season. Waters in these stretches had lower oxygen levels and higher water temperature. Not surprisingly, these habitat alterations strongly affected freshwater fish assemblages.”
It was also found that the dammed streams had more generalist species of fish (those that are widespread and can survive in harsh environments) compared to specialist species (those that are unique to certain rivers). They also had reduced numbers of migratory fish such as the Mahseer. It was also found that the native species were strongly affected, which is a matter of grave concern since these local species are found only in the Western Ghats and hence are under threat of being driven to extinction.
Spike in Human-Elephant conflict
A couple of years ago, as part of the related study, the research team had conducted a survey to understand the perceptions of local communities towards the SHPs.
It was noticed that there was general discontent amongst the communities who were dependent on the river since they were neither involved in the public hearing nor promises of electrification and local employment were fulfilled. The SHPs have also brought along a new problem: a surge in human-elephant conflicts.
Shishir Rao, from WCS-India, who co-authored both the papers, says, “Our research has shown that the sudden onset of human-elephant conflict in the study area correlated with the beginning of SHP construction. In the year 2005, the number of claims filed for elephant conflict compensation increased by 173% compared to the year before. Coincidentally, this is the same year in which the first SHP was commissioned in this area. Thereafter, the number of claims has peaked every time a new SHP was commissioned. This is a concern since the reserve forests of Sakleshpur are a critical elephant corridor connecting Pushpagiri wildlife sanctuary in the south and Kudremukh national park in the north.”
Apart from the dam, the construction of associated structures such as large pipes, canals and transmission lines hinders the movement of elephants, forcing them to find new routes, thus increasing the incidences of conflicts with humans.
Rampant Growth of SHPs
As noted by Suman, “SHPs are a classic case of good intentions leading to terrible consequences. This is mainly because SHPs are defined not based on their ecological footprint, but rather on their installed capacity. In our country, SHPs are hydroelectric dams that produce up to 25MW of power - an arbitrary threshold. Hence, we have numerous SHPs with weir heights extending beyond 15m, a threshold used by the World Commission of dams to define large dams!”
Multiple SHPs set up in close proximity on the same river have affected both the water quality and habitat. For example, 10 SHPs s currently exist on the 108 km long west-flowing Netravathi River and an additional 44 SHPs have been proposed on the same stretch and this could have a deleterious impact on the ecosystem.
Currently, a new SHP is being constructed on Hongadhahalla, the only free-flowing tributary in this area. Most of the others are also being dammed and diverted as part of the Yettinahole drinking water project. “Given that this region is an important watershed and a part of Western Ghats biodiversity hotspot, there is an urgent need to monitor, regulate and carefully evaluate the impacts of large-scale infrastructure development”, notes Shishir.
Suman adds, “Despite mounting evidence, the Ministry of New and Renewable Energy has plans to build about 6500 additional SHPs without any environmental and social regulations. Given that most of these planned dams are located within biodiversity hotspots of the Western Ghats and the Himalayas, it is imperative that the policy concerning these projects be revised to include mandatory minimum flow requirements and individual and cumulative environmental impact assessments"
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