Developing Essential Water Variables (EWVs) to Support Water Cycle
Research and Water Sustainability Applications
Abstract
The initial list of Essential Water Variables (EWVs) evolved from wide
meta-surveys of water data needs for research and applications that were
carried out in 2010 to support GEO Societal Benefit Areas (SBAs). These
EWVs were formalized in the Group on Earth Observations System of
Systems (GEOSS) Water Strategy Report (WSR) “From Observations to
Decisions”, released in 2014. Subsequently, discussions with additional
user communities have augmented the list, for example with Surface Water
Extent. Besides “primary” EWVs that identify key water variables,
including precipitation, soil moisture, and water quality, a set of
“supplementary” EWVs is also needed to complete the information that
the formal list of primary EWVs should provide, such as Digital
Elevation Models. It is clear that all available observing systems,
employing both remote sensing and in situ observing instruments and
networks are required to address the range of space/time resolutions,
accuracies, and data latencies that the end-user applications require.
In fact, there are still gaps in our ability to deliver all variables as
required. In some cases this is a technical challenge, such as remote
sensing capabilities for some water quality variables, while in many
other cases it is a matter of administrative and resource challenges.
This paper summarizes EWVs as currently defined and required by key
end-user research and applications sectors. As a follow up to the WSR,
we highlight the relevance of EWVs to the indicator monitoring
objectives of the UN Sustainable Development Goals (SDGs), various
international Conventions and Frameworks, and the GEO Global Water
Sustainability (GEOGloWS) priority thematic communities.