Building up or taking down: Scientific approaches are needed to balance impacts of dams

Spiros Xanthos via

Building up or taking down: Scientific approaches are needed to balance impacts of dams

Governments and regulators are moving away from large-scale water infrastructure towards smaller hydropower plants. This means both decommissioning aging dams and investing in smaller hydropower plants. But neither of them is a simple solution. Experts have analyzed these global trends and call for detailed scientific assessments and strict regulations as the right way forward.

  • Curry, R.A., Yamazaki, G., Linnansaari, T., et al. (2020). Large dam renewals and removals—Part 1: Building a science framework to support a decision-making process. River Research and Applications, 36:1460–1471. rra.3680   
  • Couto, T., & Olden, J. (2018). Global proliferation of small hydropower plants - science and policy. Frontiers in Ecology and the Environment, 16(2):91-100.   
  • Basso, S., Lazzaro, G., Bovo, M., Soulsby, C., & Botter, G.  (2020). Water-energy-ecosystem nexus in small run-of-river hydropower: Optimal design and policy. Applied Energy, 280:0306-2619.    

In the early morning hours of 7th February 2021, a disastrous Glacial Lake Outburst Flood event in one of the largest Himalayan Glaciers, named Nanda Devi, devasted several villages in India. Over 100 people drowned. However, this was not an isolated event. The Himalayan Region has always been prone to earthquakes and glacial floods. But over the years, climate change and global warming have increased the frequency and intensity of these disasters. The region’s aging dams are inadequate to deal with climate change-induced weather uncertainties like flash flooding and glacial meltdowns. Add to the mix a rapidly urbanizing downstream region, and we have the perfect recipe for calamitous disasters. Globally, countries have now acknowledged these issues and are rapidly decommissioning their large-scale dams and replacing them with smaller, run-of-the-river hydropower plants. Three recent studies on these trends lend insights into a way forward. 

Dr. Allen Curry and a team of researchers published a recent study in the journal River Research and Applications on the need to decommission aging dams in a scientific and streamlined manner. Most dams built during the dam building boom of the 20th century are now aging. It is expensive to maintain and operate these dams as they are vulnerable to increasing climate change-induced natural disasters. Additionally, a change in social conditions and values in the last few decades contributed to the growing popularity of energy infrastructure that minimally disrupts the environment. Governments and dam regulators of aging dams are deciding to decommission dams in favor of other new energy technologies such as solar, wind, and small hydropower plants that are more socially acceptable and environmentally friendly.  

But dam decommissioning is a complicated process. It involves years of technical and impact studies before the extensive infrastructure of dams is removed safely with as minimal impact as possible on adjacent human communities and environment. For example, in the U.S., the Elwha and Glines Canyon River dams’ removal project took two decades to decommission, and the Klamath River dam removal project which began in 2000 is still ongoing. Detailed assessments and other allied studies on the short- and long-term impacts of dam decommissioning must be conducted before commencing such projects. The authors of this study propose a scientific framework to assess dam decommissioning projects that would minimize negative impacts on the ecosystem and maximize economic and social benefits to all stakeholders. They piloted this framework to assess the Saint John River Dam in eastern Canada, and consequently, reduced the time-period of the review process and expanded the range of impacts analyzed. This standardized review process promotes science-based decision making in dam decommissioning projects.  

While dams are being decommissioned, they are often replaced by small hydropower plants (SHPs). These plants, generally called run-of-the-river hydro plants, are touted to require little to no water storage and have minimal impact on river flows and fish migrations. Moreover, these plants are usually small in scale and involve lesser investment and operational costs. The growing popularity of this solution is reflected in energy policies across the world as countries aggressively promote SHPs within their clean energy agendas. Over the last two decades, countries in Latin America have seen up to a five-fold increase in SHPs. The U.S. Department of Energy also reports that there is room in its rivers to generate 65 gigawatts from new SHPs. This could power almost 47 million homes annually. So worldwide there is tremendous enthusiasm for SHPs.   

Despite all this optimism, researchers are increasingly questioning the rationale behind this unchecked political support for small-scale dams. With this in mind, researchers Thiago Couto and Julian Olden investigated the reasons behind SHPs growing popularity and question whether SHPs are really as minimally disruptive to the environment as commonly perceived. Their study, published in Frontiers in Ecology and the Environment, identified over 80,000 SHPs operating across the world. They estimate another 180,000 could be built in our rivers, if this trend continues. This “global proliferation” of SHPs is primarily the result of governmental regulations that incentivize SHPs through simpler permitting processes and easier access to private development. 

However, these SHPs carry ecological consequences. The authors caution against unchecked promotion and growth of SHPs citing insufficient scientific research on the ecological impact of these hydropower installations. Governments have created policies that promote SHPs through lax and arbitrary regulations and exemptions without proper studies to back their decisions. Their policies fail to account for the disastrous cumulative impact of multiple SHPs fragmenting riverine flows and disrupting migrations of riverine species. Alarmingly, their study shows that the cumulative negative impacts from small-scale dams on adjacent ecosystems are actually comparable in intensity to large-scale dams.  

Recognizing these negative impacts, researchers from the Helmholtz Centre for Environmental Research in Germany suggest specific tools to assess SHPs in a recent Applied Energy article. Their article offers mathematical modelling tools for understanding the tradeoffs between money and ecosystems. In their study, the tradeoff between economic profitability of hydropower production and preservation of adjacent ecosystems is modeled. The novelty of the model lies in its inclusion of fish migration and downstream water flow. An ideal SHP would maximize its revenue and minimize changes in species migrations and water flow. In other words, through this modeling, the researchers give equal importance to the preservation of the ecosystems and the economics of the project. Policy makers, communities and private developers often hold the incorrect assumption that small is good for the ecosystem. Instead, a stricter and more holistic approach while designing, siting, regulating, installing, and operating small run-of-the-river projects is needed, along with proper environmental assessments and impact studies. Using these tools, policy makers, communities, and private developers could use SHPs to meet their green energy agenda while also accounting for and mitigating the potential negative impacts of these projects on the local ecosystems.   

As we build and promote infrastructure projects that have minimal impacts on natural ecosystems and are safer to local communities, decommissioning of aging dams and installation of small run-of-the-river hydropower plants may emerge as an essential component. They are important in our efforts to deal with climate change and build resilience against natural disasters. But they need to be approached with caution. Not all of these projects are environmentally friendly in the short- and long-terms. As the impact of climate change uncertainties increases, all water resource-dependent projects, no matter their scale, must be thoroughly studied in a streamlined and scientific manner, their impacts forecasted and catalogued, and the local communities prepared and empowered to participate in decision-making processes. We are heading in the right direction by moving away from larger towards smaller water infrastructure; but, without scientific impact studies and streamlined regulations, even small-scale water infrastructure projects can have serious ecological consequences. 

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