Environment

Without Proper Impact Assessment, Small Dams Could Cause Great Ecological Damage

Although small dams are considered sources of ‘clean energy’, studies show that the environment suffers as much damage from these dams as it does from larger ones.

The relatively smaller scale of operation, smaller areas of forest submergence and almost no displacement of people make SHPs seem like a source of ‘clean energy.’ Credit: Twitter

The relatively smaller scale of operation, smaller areas of forest submergence and almost no displacement of people make SHPs seem like a source of ‘clean energy.’ Credit: Twitter

Energy security is a critical concern in rapidly developing nations like India. But the issues of ecological sustainability and climate change are often pitted against increasingly resource-intensive lifestyles. Renewable energy could provide the coveted middle ground – provided we plan with a futuristic vision for environmental sustainability.

So far, hydropower has been the most widely used source of renewable energy in India. Massive dams that arrested the flow of big rivers to harness water for power and irrigation formed Jawaharlal Nehru’s vision of ‘temples of modern India’. However, with increasing recognition of the extensive adverse social and environmental impacts of large dams, they now face considerable scrutiny, criticism and regulation. As a result, hydropower development is going ‘small’.

Hydropower goes small

Small hydropower (SHPs) projects, simply put, are smaller dams. Typically, a weir built across a river diverts water to a powerhouse a few kilometers, where it rotates turbines to produce power.

The relatively smaller scale of operation, smaller areas of forest submergence and almost no displacement of people make SHPs seem like a source of ‘clean energy’. SHPs are also thought of as projects that generate local employment, develop infrastructure and provide power to remote areas. Based on these claimed advantages, SHP projects are being actively sold as a clean substitute for large hydro projects. Suddenly, small dams are everywhere.

The issues with small dams, however, begin with its definition. With no consensus on what actually constitutes a ‘small’ dam, every country has its own definition, which is usually based on the quantum of power generated. In India, SHPs are defined as dams generating 2-25 MW of power. However, a definition based on power generating capacity alone does not account for other physical and spatial features of small dams, which determine its ecological impact.

For example, many small dams in India have weir (dam) heights exceeding 15 metres, which according to the World Commission on Dams makes it a large dam. Additionally, what is termed as a small dam could submerge up to 200 hectares of forest, breaking forest connectivity and taking with it a chunk of biodiversity. Roads and power lines associated with access to dam sites and transmission of generated power further fragment forests. These peripheral infrastructures are often not even evaluated when considering forest loss and enumerating trees to cut for small dam construction.

So, why does a definition matter?

Small dams can avail multiple financial and policy incentives from the government just by virtue of their classification. SHPs in India are exempted from the purview of the Environment Protection Act. Not requiring any environmental clearance, these projects do not go through environment impact assessments or public hearings with stakeholders. The current policy environment for small dams lends a perverse incentive to sell every dam as “small” regardless of its wider environmental impacts, so long as the limit to power generating capacity is maintained.

Myriad impacts of small dams

The rationale for excluding these projects from the environment impact assessment notification is based on the assumption that unlike large dams, small dams use up very little space. However, multiple small dams often come up within the catchment of one major river, blocking tributaries and headwaters.

Studies show that when the environmental impacts are compared, for every kilowatt of power generated, river flow, hydrology and aquatic biodiversity suffer as much damage from extensive small dam development as from the development of large dams.

Moreover, many small dams are needed to produce the same amount of electricity as one large dam. Hence, the impact on river flow and riverine biodiversity would have to be calculated cumulatively for every unit distance of river dammed. This means that environmental assessments would also have to be cumulative, which means evaluating each dam in full context of all other dams that exist or are planned in a river catchment or forest area.

Research also indicates that even single small dam has marked environmental and social consequences. The river stretch between the weir and the powerhouse runs nearly dry, disrupting riverine connectivity. River flow becomes highly pulsed since water is released in sudden bursts for short periods during power generation and reduced to a trickle at other times. The highly erratic flow alters riverine ecology, changing physical and chemical water parameters and nutrient cycling.

Changes to flow and water quality, in turn, damages riverine biodiversity. Recent studies from the Western Ghats show that small dams markedly reduce the diversity of fish communities in rivers. Moreover, ecologically sensitive or specialised species such as endemic and migratory fish tend to be most strongly hit.

Ecological changes to the river and forest impact local human communities as well, especially those whose livelihoods depend on the river. Fish catches decline, local irrigation cycles and water mills are disrupted, water-use rights and access to the landscapes becomes restricted and drinking water sources are compromised. Moreover, projected employment opportunities and improvements in electricity supply are almost never realised.

Vague regulations, strong economic incentives and the lack of effective monitoring have also resulted in numerous illegalities. For example, in many instances, one large dam has been shown as two small dams on paper in order to evade scrutiny and garner financial incentives. Unregulated forest clearing around dam sites and sand mining are other common problems associated with SHPs.

Getting the science right for small dam policy

Neglecting the overwhelming scientific evidence of the negative ecological consequences, India’s renewable energy ministry plans to erect nearly 6,500 SHPs. As of 2012, 1,266 SHPs (amounting to a capacity of 4747 MW) had already been commissioned without environmental impact assessments. Most importantly, the highest densities of planned dams fall within the biodiversity hotspots of the Western Ghats and the Himalayas.

India’s new draft National Mission on Small Hydro (2015) is proposing a number of economic and policy incentives to further promote this sector. Considering these staggering numbers, the ambitious targets for SHP development call for cumulative impact assessments. Sustainable planning of SHPs require estimating basin-wide carrying capacities of SHPs, minimum mandated river flows and inter-dam distances. Environmental impact assessments – especially in biodiversity-rich areas – will help identify mitigation measures to limit the ecological damage. For example, mandated minimum river flows and fish ladders can diminish adverse impacts on aquatic fauna. Similarly, dams should be placed away from forested areas to minimise fragmentation.

Environmental impact assessments – especially in biodiversity-rich areas – will help identify mitigation measures to limit the ecological damage. For example, mandated minimum river flows and fish ladders can diminish adverse impacts on aquatic fauna. Similarly, dams should be placed away from biodiversity-rich forested areas to minimise fragmentation.

Further, stakeholder consultations and participatory decision-making can help identify and remedy areas of social conflict or community concerns prior to dam building.

Science, foresight and regulation

Undoubtedly, the growing energy needs of a developing economy require us to pursue alternative energy sources. But we cannot rush without proper assessment of the ecological consequences.

Paradoxically, “green energy” options such as SHPs can damage regional ecology – a fact documented in numerous scientific studies. The key lies in appropriate regulation based on larger considerations of ecological sustainability. Such evaluations will promote long-term feasibility of small dams as an energy solution without compromising regional hydrology and stream biodiversity.

Exercising foresight and using good scientific information can ensure that SHPs can be used sensibly to support energy needs without causing severe ecological damage. Cumulative assessments are essential for planning and placing SHPs at the landscape scale, especially in biologically rich and ecologically sensitive regions. Finding the balance between consuming natural resources versus saving ecological spaces needs getting the science right and using it well.

Suman Jumani is an independent researcher studying impacts of small dams and Meghna Krishnadas is affiliated with the Yale School of Forestry and Environmental Studies.