Greenhouse gas emissions
Hydropower decision-makers are judged on their ability to future-proof projects. A commitment to build and share understanding of hydropower’s relationship with climate change is central both to our strategy and to the future of the industry.
While hydropower is a very low-carbon technology, it is known that some reservoirs in certain conditions can release quantities of methane, a greenhouse gas. Reservoirs can also, in other circumstances, act as carbon sinks.
The processes and conditions are highly complex and require thorough investigation so that the development and the operating regimes of the reservoirs can be optimised to improve the water quality and mitigate emissions.
Much work has been undertaken to measure emissions and the conditions under which they occur, but this work is usually site-specific, complex and not appropriate for widespread use in the great majority of reservoirs where this is not an issue.
We have been working since 2006 with UNESCO and a wide stakeholder group in and around the industry to develop common understanding and metrics for the issue. This has resulted in the publication of the UNESCO/IHA GHG Measurement Guidelines for Freshwater Reservoirs, downloadable here.
We are also continuing the development of a screening tool that will allow the rapid and low-cost assessment of likely GHG emissions from reservoirs allowing developers and operators to assess whether the reservoir is likely to generate emissions, and therefore require further and more detailed examination and modelling.
This project is now moving into a new phase, with a revised screening tool being developed to estimate the impact of a reservoir on the GHG exchanges that occur in a river basin. The GHG Reservoir Screening Tool will allocate any GHG impact to the services provided by the reservoir. A prototype of this revised tool was launched at the World Hydropower Congress in Beijing, in May 2015.
The tool is intended to inform decision makers if there is likely to be any significant GHG footprint associated with the purposes for which the reservoir is being developed. The tool will be applicable for both existing and planned reservoirs. If the tool identifies a reservoir that is likely to cause a significant impact, the recommended action will include the possibility of detailed modelling.
Our work is aligned with that of the International Energy Agency’s Hydropower Agreement (IEA-Hydro), which is currently working on the development of modelling guidelines. These guidelines will relate to the detailed study of the GHG status of reservoirs shown to be vulnerable by the GHG Reservoir Screening Tool.
The GHG Risk Screening Tool
The GHG Screening Tool provides an estimate of the likely level of total (gross) GHG emissions from a freshwater reservoir. It has been developed as an empirical model, making use of existing published data of gross GHG emissions from previous assessments on 169 reservoirs around the world.
The tool output provides an indication of the need for further assessment of GHG emissions.
The GHG Risk Assessment Tool is a living document. As further data are collected and analysed, its formulation will be revised and the level of uncertainty reduced.
We are very keen to work with dataholders and experts to refine the tool further.