Authored by the European Commission's Directorate-General for Research and Innovation (DG RTD)
The relevance of the water-energy nexus for EU policies
Energy and water systems depend on each other in many ways. The power sector is a clear example, since almost all electricity generation technologies, as well as carbon capture and storage, use significant amounts of water. Water is necessary in the coal sector too, to extract oil and gas and to refine oil products into fuels and petrochemicals; it is also used to grow biomass for the bioenergy sector. Conversely, energy is required to extract, convey, deliver and treat water.
Most energy and climate projections suggest that the waterenergy nexus will be affected by the shifting availability of water resources due to climate change and the increasing penetration of non-dispatchable renewable energy sources. It is therefore crucial to estimate these impacts: water resources shall be accurately incorporated into power systems operations and planning, water use shall be integrated into large-scale grid analyses, and market design studies will have to consider the value of water.
An evolving energy system may affect other sectors beyond the water-energy nexus. It is therefore necessary to establish appropriate allocations of water resources, whilst limiting any negative effect on natural ecosystems. Amongst the many concerned EU policies, we recall the Water Framework Directive  (amended several times since 2000); the Drinking Water Directive (for which the European Commission has recently proposed a revision ); the Common Agricultural Policy (for which several legislative proposals have been put forward ); and water diplomacy initiatives, particularly involving developing countries. Proper consideration of energy-related aspects into water system planning may help to better assess the impact of the nexus on many key policies.
Given the relevance of the water-energy nexus to several EU initiatives, Horizon 2020 (the current Framework Programme for Research and Innovation) supports related projects, from those aimed at reducing the water consumption of concentrating solar power plants to those which propose integrated approaches to energy, sustainable water management and climate change mitigation. Horizon Europe, the recently proposed 2021-2027 Framework Programme for Research and Innovation, aims at exploiting the synergies between sectors even further, which could be beneficial for waterenergy nexus research.
The global profile of the issue offers many opportunities for international cooperation. For example, in the context of the EU-US Energy Council , the US Department of Energy (DoE) and the European Commission have launched a collaboration on integrated water and power systems modelling. In 2016, the Commission’s Joint Research Centre in Ispra hosted an expert workshop. Based on the participants’ input, the DoE and the Commission are now supporting modellers in a challenge to show the way forward for the integration of their power and water system models. Modelling activities are underway and comparative exchanges are taking place between the teams. A second expert workshop will take place in the US in December 2018.
We welcome this new issue of the SETIS Magazine focussed on the water-energy nexus, which reflects the increasing importance of cross-sectorial and multidisciplinary approaches.
 EC Communication (2017) 753: Proposal for a Directive of the European Parliament and of the Council on the quality of water intended for human consumption