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24 May 2018

A new study of the greenhouse gas footprint of almost 500 reservoirs worldwide, which applied the G-res Tool for assessing net emissions, indicates that hydropower is one of the cleanest energy sources.

The greenhouse gas footprint of hydropower has long been questioned in both scientific and policy spheres, especially with regard to emissions caused by the creation of a reservoir. There has been a lack of scientific consensus on how to quantify this footprint, and this uncertainty has proved a significant obstacle for policy and decision makers concerning the financing of hydropower projects and whether they achieve the designation of being climate-friendly.

The Intergovernmental Panel on Climate Change (IPCC), in its Fifth Assessment Report published in 2014, noted that only onshore and offshore wind and nuclear power have lower median lifecycle greenhouse gas emissions than hydropower. However the panel cautioned that few studies had appraised the net emissions of freshwater reservoirs, allowing for pre-existing natural sources and sinks and unrelated human emission sources.

The challenge of assessing net climate emissions

Over the years, a number of researchers have measured gross reservoir emissions at sites around the world, but the results of each study cannot be reliably applied to other reservoirs, even in the same region. The biochemical processes leading to emissions from a reservoir are highly complex, and life-cycle emissions are very specific to the siting and design of each hydropower facility.

Emissions relating to the construction and operation of a dam, due to fossil fuel combustion and cement/steel production, can vary depending on its type and size. Once filled, factors such as a reservoir’s depth and shape, the amount of sun reaching its floor, and wind speed, affect the different biogeochemical pathways by which CO2 and CH4 are created and released to the atmosphere.

The process of taking measurements to determine the greenhouse gas (GHG) footprint of a hydropower facility or reservoir can be cumbersome or prohibitively expensive. Calculating the net change in emissions caused by a reservoir is highly challenging.

Development of the G-res Tool

Against this backdrop, the GHG Reservoir (G-res) Tool was developed by IHA and UNESCO in cooperation with researchers from the University of Quebec at Montreal (UQÀM) in Canada, the Norwegian Foundation for Scientific and Industrial Research (SINTEF) and the Natural Resources Institute of Finland (LUKE). This research was supported by the World Bank and sponsors from the hydropower sector.

The tool was devised to enable companies, investors and other stakeholders to more accurately estimate the net change in GHG emissions attributable to the creation of a specific reservoir. It takes into account the state of the land pre-impoundment, considering naturally occurring emissions and emissions related to other human activities over the lifetime of the reservoir. It also provides a method for apportioning the net GHG footprint to the various freshwater services that a reservoir provides, such as water supply for irrigation and cities, flood and drought management, navigation, fisheries and recreation.

The G-res tool was formally launched, after more than a decade of development work, at the World Hydropower Congress in Addis Ababa, Ethiopia, in May 2017.

Worldwide study of hydropower reservoirs

During 2017, researchers from IHA undertook a study of 498 reservoirs worldwide using the G-res Tool. The study looked at reservoirs in boreal, temperate, subtropical and tropical climates more than 50 countries in North and Central America, South America, Europe, Africa, South and Central Asia, East Asia and the Pacific.


The study used the G-res tool to estimate the GHG footprint of 178 single purpose hydropower reservoirs and 320 multipurpose reservoirs, excluding emissions caused by construction activity. This data was coupled with project-specific installed hydropower capacity and average annual generation data to obtain the emissions intensity of each site’s hydropower operations.

The global median GHG emission intensity of the hydropower reservoirs included in the study was 18.5 gCO2-eq/kWh; this is the grams of carbon dioxide equivalent per kilowatt-hour of electricity generated allocated to hydropower over a life-cycle. The majority, or 84 per cent of reservoirs, exhibited emissions less than 100 gCO2-eq/kWh. For a comparison with the median values of other electricity sources, see figure 1.

Temperature is one of the variables that has, in theory, a significant effect on reservoir emissions. However mean annual temperature is only one of many variables that influence GHG emissions. The G-res Tool includes other input variables such as the soil carbon content of the reservoir, depth of the thermocline, reservoir drawdown area and the catchment annual run-off. The second figure above shows the emissions intensity attributable to hydropower reservoirs categorised by their respective climate zones.

The IHA study, which is to be submitted for peer review, confirms in part that the vast majority of hydropower reservoirs are producing very low-carbon power, some reservoirs in every climate category can potentially have high emissions exceeding 100 gCO2-eq/kWh (defined by the Climate Bonds Initiative to be an important threshold).

Figure 2 shows the relationship between the GHG emissions intensity (gCO2-eq/kWh) plotted against the power density of the projects (W/m2). High emissions intensities are possible from hydropower reservoirs, even on the same order of magnitude as fossil fuel generators, but only at extremely low power densities. Low power density however does not necessarily translate to high emissions intensity, as many projects with low power densities have emissions intensities well below 100 gCO2-eq/kWh (left of the red line).


It bears noting that the emissions intensity identified from this study applies only to hydropower projects with large reservoirs; many hydropower projects, often run-of-river, do not flood significant areas of land and consequently will have even lower emissions. It should also be noted that hydropower facilities equipped with reservoir storage provide many other valuable power and water benefits. By storing water in a reservoir, a project can offer balancing and ancillary services, delivering dispatachable power when needed. A reservoir also provides water for vital non-power uses such as flood control and drought management, and water supply for municipalities and agriculture.

This article is featured in the 2018 Hydropower Status Report.

11 July 2018

A multi-stakeholder coalition of civil society, industry, governments and financial institutions today launched an expanded suite of tools for assessing hydropower projects against sustainability performance criteria.

The Hydropower Sustainability Assessment Protocol, the world’s leading scoring framework for evaluating hydropower projects, has been updated to examine hydropower’s carbon footprint and resilience to climate change. In addition, a new tool will enable project proponents and investors to identify and address gaps against international good practice.


The new suite of tools was developed over 18 months by the Hydropower Sustainability Assessment Council, which is constituted by organisations such as the World Bank, The Nature Conservancy, the International Union for Conservation of Nature, WWF, the Inter-American Development Corporation, hydropower companies and governments.

“Today marks the most significant expansion in the tools available to assess hydropower performance in almost a decade, following extensive consultation within and beyond the hydropower sector,” commented Mr Roger Gill, Chair of the Hydropower Sustainability Assessment Protocol’s governance committee.

“This is good news for both project proponents and concerned stakeholders who want to measure projects against international practice. Developers and investors now have a targeted, cost effective way of assessing sustainability, while governments and communities can be confident that evaluations are based on robust, objective criteria,” he added.

The new suite of tools comprises:


An expanded sustainability protocol

An expansion of the Hydropower Sustainability Assessment Protocol, first launched in 2010, to cover best and good practice in climate mitigation and resilience. A project that scores well under the new criteria will have a low carbon footprint and be resilient to the impacts of climate change.




A targeted gap analysis tool

A new Hydropower Sustainability Environmental, Social and Governance Gap Analysis Tool. Modelled on the Protocol’s evaluation framework, the ESG Tool offers a targeted assessment across 12 core sections, including biodiversity, downstream flows, project affected communities, cultural heritage, working conditions, and infrastructure safety, as well as climate change.


The International Hydropower Association (IHA) supports the Hydropower Sustainability Assessment Council as the Protocol’s management body, overseeing the training and accreditation of independent assessors. Assessments can be made at all stages of a hydropower project’s lifetime, from preparation, to development and operation.

Richard Taylor, Chief Executive of IHA, commented: 

“With this announcement, the hydropower sector now has two ways to demonstrate the sustainability credentials of a project. The ESG Tool will allow companies to identify good practice and address gaps through a management plan, providing vital reassurance to investors and other stakeholders. For companies that require a more comprehensive assessment, the Protocol remains the first choice for benchmarking a project and showcasing how it performs against international good practice and proven best practice.”

Doug Smith, an accredited assessor who helped to develop the expanded suite of tools, said: 

“The Hydropower Sustainability Assessment Protocol’s new climate change topic will underline its status as the leading tool for hydropower assessment, reflecting newly built consensus in both greenhouse-gas emissions and climate resilience. The ESG Tool’s impact on the sector could also be profound, as the assessments will be systematic and rapid, without compromising rigour, and will include an action plan to close any gaps against good practice.”

Dr James Dalton, Director of the Global Water Programme at the International Union for Conservation of Nature (IUCN), commented: 

“Developing tools and guidelines to help guide society with the resource management choices we face is critical to our future economic, social and environmental development. The hydropower industry has learned from the last eight years of Protocol experience. Building this experience into the Protocol and the new ESG tool is critical to help industry and investors learn, gain confidence in the tools, and expand the use of the Protocol.”

Luiz Gabriel Todt de Azevedo, Chief of the Environmental, Social and Corporate Governance Division of IDB Invest, part of the Inter-American Development Corporation, commented that the new ESG Tool aligns with the Protocol’s goal of promoting sustainable hydropower. 

“The new ESG Tool responds to industry demands. It is an agile and low-cost alternative to be employed by developers and operators in the first level assessment of their projects,” he said.

The tool was developed by the International Hydropower Association (IHA) under the mandate of the Hydropower Sustainability Assessment Council and with the support of the Swiss State Secretariat for Economic Affairs (SECO).

Further information:

The Hydropower Sustainability Assessment Protocol was developed in response to the World Commission on Dams, which showed the need for the hydropower sector to have a global tool for reporting sustainability.

The Hydropower Sustainability Assessment Council, which governs the Protocol, includes environmental NGOs and IGOs (The Nature Conservancy, WWF, IUCN), social NGOs (Transparency International, Women for Water Partnership), development banks (World Bank Group, Inter-American Development Corporation), governments (Norway, Switzerland), and hydropower sector owners and contractors.

The new ESG Tool focuses on 12 sections: Environmental and social impact assessment and management; Labour and working conditions; Downstream flows, sedimentation and water quality; Project-affected communities and livelihoods; Resettlement; Indigenous peoples; Biodiversity and invasive species; Cultural heritage; Infrastructure safety; Climate change mitigation and resilience; Communications and consultation; and Governance and procurement.

To download the suite of tools and find out more information, please visit:

27 June 2018

There is growing demand for energy access across Africa, a continent with a total installed hydropower capacity of 35.3 GW and large untapped potential for new hydropower projects.

Water scarcity however remains a main challenge in many countries, so it is vital that resources are managed sustainably.


IHA's Frank Faraday addresses participants at the Protocol workshop.

The International Hydropower Association (IHA) led a recent workshop in Nairobi, Kenya, where representatives from hydropower companies, government and a range of other sectors learned how an internationally recognised sustainability tool can be used to assess planned or existing projects.

The workshop, part of the International Water Stewardship Programme’s (IWaSP) Water Stewardship for Sustainable Hydropower conference, looked at how the Hydropower Sustainability Assessment Protocol works and the value it provides, as well as a number of recent enhancements to the tool.

In Africa, the Protocol has been used to assess the sustainability of operations at the Cahora Bassa hydropower plant in Mozambique, as well as to undertake early stage assessments of several projects in Ghana. Several operators in the Zambezi river basin have also applied the Protocol in self-assessments, having been assisted by accredited assessors.

The Protocol has proven to be highly valuable when promoting stakeholder awareness and involvement, and addressing environmental and freshwater management, according to Frank Faraday, IHA’s Sustainability Programme Manager.

“The challenge is working out how to get sustainability mainstreamed within decision-making in places where resources are much more constrained,” he said. “We need to think about how the Protocol can be embedded more into internal processes within companies.”

The 7 June workshop was attended by 25 participants and held with the support of GiZ, the German government’s international development agency. The programme included a discussion on applying the Protocol for use on small-scale hydropower projects in developing countries.

João Costa, IHA Sustainability Specialist, said: “A lot of the small-scale hydropower developers in attendance were very interested in the Protocol as it provides a clear reference for good practice in sustainability. Training opportunities and building internal staff capacity were discussed as good starting points for incorporating use of the Protocol into small-scale projects.”

The IWaSP conference explored how water stewardship approaches can address current scarcity challenges and add value to existing models of hydropower development and operation. IHA participated in an IWaSP conference workshop on hydropower benefits.

One of the participants of the conference workshop, Anton-Louis Olivier, CEO of Renewable Energy Holdings Group, discussed the role of stakeholder participation in increasing the value of hydropower infrastructure.

“We, as project developers, contribute as good neighbours to the uplifting and maintenance of society, ecology and system infrastructures,” said Mr Olivier, recipient of IHA’s Mosonyi Award at the 2017 World Hydropower Congress.

“Project development requires us to navigate through a highly complex set of interrelated factors – technical, environmental, social, legal and commercial – in order to structure a viable and sustainable project.

“The Hydropower Sustainability Assessment Protocol provides a clear set of principles to refer to and check throughout the development process in order to manage risks and improve project sustainability, specifically relating to social and environmental factors,” he added.

“In order to fairly share the benefits of a project with local communities and other stakeholders, it is important to understand its impacts by identifying and quantifying both the power and non-power benefits,” said Cristina Diez, IHA Hydropower Analyst, who also spoke at the conference workshop.

“As many of hydropower’s benefits are often misunderstood or under-reported, part of our work has been to provide a framework for collecting evidence.”

IHA has been building and sharing knowledge on the wide-ranging benefits of hydropower since it was founded in 1995. To find out more about the Hydropower Sustainability Assessment Protocol visit the Hydropower Sustainability website. Learn more about IHA’s hydropower benefits work programme.

For the latest information and statistics on hydropower in Africa, download the 2018 Hydropower Status Report

19 June 2018

The International Hydropower Association has signed a Memorandum of Understanding with the Global Women’s Network for the Energy Transition.

The partnership represents IHA's commitment to promoting the role and contribution of women in the energy sector, particularly in the transition to a low carbon future. It also includes the promotion of mentoring, networking and coaching opportunities to encourage the increased participation of women in decision-making positions.


Photo credit: GWNET

The Memorandum of Understanding (MoU) was signed by Richard Taylor, IHA’s Chief Executive, and Christine Lins, founding member of the Global Women’s Network for the Energy Transition (GWNET) on 6 June.

Mr Taylor said: “Our mission to advance sustainable hydropower includes building a vibrant, inclusive and proactive community. We’re proud to be a strategic partner of GWNET, a network which shares these values, as we look towards decarbonisation and a clean energy future.” 

GWNET was founded in 2017 to address the energy sector’s current gender imbalance and promote gender-sensitive action around the energy transition worldwide.

According to its founders, GWNET empowers women in energy through interdisciplinary networking, advocacy, training, coaching and mentoring, and services related to projects and financing.

“GWNET is thrilled to work with the International Hydropower Association to raise the voice of women in hydro, thereby bringing fresh perspectives to the development of societies, attracting and retaining a richer pool of talent in the sector and advancing the energy transition more quickly,” commented Ms Lins.

The new partnership advances on IHA’s recent support of the Women in Hydropower Mentorship Program, which provides a platform for women to connect, make friendships and share experiences in a supportive environment.

Christine Cantin, IHA Board member and Senior Advisor at Hydro-Québec voiced her support for IHA's new partnership with GWNET. Ms Cantin has been an advocate of the Women in Hydropower Mentorship Program since it started in 2016.

“Inclusion and diversity foster and enrich the work environment. Hydropower and women are key actors in the global energy transition, so it is by being associated with initiatives of this kind that we will promote gender diversity progress and a more sustainable world,” she said.

Find out more about GWNET by visiting its website.

18 June 2018

The International Hydropower Association addressed the challenges of managing freshwater and the opportunities provided by hydropower at an Institute of Mechanical Engineers seminar in London.

Participants at the event heard how worldwide hydropower installed capacity had reached 1,267 GW in 2017 – an increase of over 20 GW from 2016.

“Hydropower plays a role in more than 150 countries; it’s a widely distributed technology and industry,” said IHA’s Chief Executive Richard Taylor during his keynote speech. 

“The management of freshwater is probably the biggest challenge faced by mankind this century," and we will need water infrastructure, especially as the developing world needs increased water services.


“To be able to deliver on the increasing demand, with a finite resource, we will need infrastructure to store water. Hydropower can contribute to that infrastructure by providing services and revenues which can justify the investment.”

Mr Taylor also explained how IHA’s work programmes can help to fill sector knowledge gaps and discussed the reporting benefits of the Hydropower Sustainability Assessment Protocol, an internationally recognised tool used to assess the performance of projects at various stages in their life cycles. 

The Institute of Mechanical Engineers (IMechE) seminar was entitled ‘Hydropower Engineering: Technologies, Projects and Future Developments’.

IHA was a supporting partner at the 14 June event, which featured presentations on key hydropower projects and recent sector developments, as well as a panel discussion on hydropower potential in the UK.

IHA members Andritz Hydro and Voith Hydro were represented among the day’s speakers, where asset management and pumped storage hydropower proved common themes of discussion.

Lars Meier, Head of Proposal Management at Voith Hydro, shared technical details on the upcoming modernisation of the Ffestiniog Power Station in North Wales, which was the UK’s first major pumped storage facility.

Ffestiniog, having been commissioned in 1963, is considered an “ageing plant” and modernisation work is due to start in January 2019.

Sean Kelly, project manager at SSE Generation Development, discussed the importance of pumped storage for a grid which is “changing fundamentally since it was set up in the early twentieth century.”

Mr Kelly said: “Pumped storage is an essential tool for system operators to balance the grid. We need to find a way to ensure that all the benefits pumped storage brings to the grid are recognised.” A decrease in pumped storage investment would mean finding alternative solutions, leading to “higher costs to the consumer, slower decarbonisation and probably less energy security.”

Other topics of discussion included tidal power, hydropower technology and the future of hydropower.

For more information on hydropower’s current challenges and opportunities worldwide, download the 2018 Hydropower Status Report.

To find out more about the IMechE event, visit its webpage.