Water and sanitation are at the very
core of sustainable development – critical to the
survival of people and the planet – and touch on
many other areas, including food and agriculture,
climate, health, education and poverty reduction.
This means that SDG6 “not only addresses the issues
relating to drinking water, sanitation and hygiene,
but also the quality and sustainability of water
resources worldwide.” Satellites provide repeatable
and objective observations of the water cycle with
consistency across regions and globally, supporting
the implementation and scalability of monitoring
systems.
Observations for integrated water resource
management
Satellite observations of the water
cycle cover a broad range of parameters and at
present hydro-meteorological and space agencies
around the world are operating or planning
instruments to monitor all phases of the cycle.
Satellite capabilities are subject to a
range of accuracies, and include the monitoring of
clouds, precipitation (rain and snow), soil
moisture, groundwater storage, inland water bodies,
river and lake surface levels, the cryosphere (e.g.,
snow, ice, glaciers) and a number of ocean
parameters. These observations support holistic
management approaches, including hydrological
modeling and the implementation of Integrated Water
Resources Management (IWRM), identified as a key
aspect of sustainable water management in the 2002
Johannesburg Plan of Implementation. The development
of IWRM is a focus of water-related overseas
development aid disbursements, with water management
projects representing 5% of the total ($8.6 billion)
in 2015.
One example of Earth
observation support of the development of IWRM is
the Water Observation and Information System (WOIS),
developed as a part of ESA’s TIGER initiative in
response to the 2002 Plan of Implementation. WOIS
helps address problems faced in the collection,
analysis and use of water-related geo-information,
and the software is available free of charge.
Global surface water monitoring
The presence of inland and coastal
surface water affects human and ecosystem well-being
globally. While national and regional inventories,
statistical extrapolation and satellite imagery are
used to produce surface water snapshots,
systematically monitoring long-term changes at high
resolution has remained a challenge. Several efforts
have been undertaken using the long time series of
Landsat imagery (since 1984) to try and address this
challenge, including the European Commission’s Joint
Research Centre’s (JRC) Global Surface Water
Explorer (GSWE).
Leveraging massive
parallel computing capabilities provided by Google
Earth Engine, the GSWE maps the location and
temporal distribution of water surfaces using 3
million Landsat images, quantifying the extent and
change in global surface water monthly over the past
32 years at 30m resolution. The maps show that
between 1984 and 2015, permanent surface water has
disappeared from an area of almost 90,000 square
kilometres, equivalent to slightly more than the
area of all the surface water in Europe, though new
permanent bodies of surface water covering 184,000
square kilometres have formed elsewhere. Over 70% of
the global net permanent water loss occurred in the
Middle East and Central Asia, linked to drought and
human actions, including river diversion or damming
and unregulated withdrawal.
The GSWE
provides a freely available dataset to the public,
scientists, and policymakers to help countries
improve the modelling of surface water, provide
evidence of changes in water-related ecosystems
ecosystems, and inform water management
decision-making including in support of SDG
Indicator 6.1.1.
