Water-Energy Nexus Initiatives

“Metrics are important. Benchmarks help us to understand where we are, where we have been, and what we need to do to get to where we want to go. The ability to comprehensively assess the relationships among water, energy and greenhouse gas emissions will lead to more efficient investments, more effective programs, and more resilient markets.”

– Fran Spivy-Weber, Prior Vice-Chair, California State Water Resources Control Board










In the U.S., energy and water are intricately connected, as there is a significant amount of energy embedded in the water supply.  From the extraction, storage, and conveyance, to the treatment, delivery, and disposal of water, water and wastewater utilities alone account for about 5% of overall U.S. electricity use.[1] As a result, water resource management and water consumption contribute significantly to greenhouse gas (GHG) emissions both through their direct emissions and the indirect emissions associated with consumed electricity. Optimal management and conservation of water across the complete water use cycle will help reduce GHG emissions. However, transparent methodologies designed to measure, account for, and track the GHG emissions embedded in water have not been available.

To address this, The Climate Registry (TCR) has been working to provide standardized methodologies to quantify the GHG emissions embedded in the complete water use cycle, and to develop reporting registries based on these methodologies.

Water-Energy Nexus Registry

In March of 2018, TCR began working with the California Environmental Protection Agency on a 3-year program to develop a voluntary registry and protocols for quantifying GHG emissions related to water management.  TCR will be coordinating this work with water agencies and other stakeholders in the state to design the protocols and methodologies, which may then be used to estimate GHG reductions.  Registry membership will be open to water agencies and other entities doing business in California.  We are planning to open the online reporting tool and help desk services by mid-2019. For more information on the Water-Energy Nexus Registry, see our website here.

Water-Energy-GHG (WEG) Guidance and Pilot

In 2015, TCR developed the Water-Energy GHG (WEG) Guidance, a new methodology to quantify, compare, and analyze the GHG emissions embedded in delivered water, as part of the Cool Planet Project in partnership with Southern California Edison (SCE). Reporting the WEG intensity metrics provides water suppliers, their customers, funders, and the public with a clear means to quantify, compare, and analyze the GHG emissions embedded in delivered water using consistent and transparent methodology.

TCR will work with stakeholders throughout 2018 to expand the WEG Guidance so that it includes guidance for measuring the emissions intensity of operations related to wastewater and recycled water. For more information on TCR’s WEG Guidance work, see our website here.

Water-Energy GHG Protocol Development

To better support water agencies across the U.S, TCR is exploring opportunities to develop a national Water-Energy GHG Protocol through a consensus-based stakeholder process. By engaging sector-specific experts and all interested stakeholders, TCR plans to develop reporting guidance to quantify the GHG emissions embedded in water across the entire water use cycle (i.e., upstream and downstream processing) reflecting local conditions across the U.S.

A national Water-Energy GHG Protocol will ensure that water suppliers and consumers can accurately and consistently account for the GHG emissions embedded in water, in order to:

  • Compare data using consistent and transparent methodology;
  • Benchmark trends in GHG intensity of water over time;
  • Highlight reduced energy use and GHGs associated with water; and,
  • Better communicate the benefits of improved water, energy, and GHG reduction efforts to stakeholders.

For more information about TCR’s water-energy GHG nexus work, please contact our policy department at policy@theclimateregistry.org.


[1] Electric Power Research Institute (EPRI). 2002. “Water and Sustainability (Volume 4): U.S. Electrical Consumption for Water Supply and Treatment – The Next Half Century.