World Water Day: space tool aids fight for clean drinking water(Forwarded)

ESA News
http://www.esa.int

22 March 2006

World Water Day: space tool aids fight for clean drinking water

According to the UN, safe drinking water remains inaccessible for about
1.1 billion people in the world. To address this global dilemma, the UN
Millennium Development pledged at the World Summit in Johannesburg in 2002
to reduce by half the proportion of people without access to safe drinking
water by 2015.

Meeting this goal will demand reliable, current data and information about
how much water is stored in large lakes, rivers and reservoirs around the
world -- which radar altimetry can provide.

In the past, hydrological information could often be difficult to obtain
by ground-based gauge instruments due to the inaccessibility of the
region, the sparse distribution of gauge stations or the slow
dissemination of data due to national policy.

Radar altimetry can avoid these obstacles because it is located on
satellites 800 to 1300 kilometres above the Earth and is able to measure
large lakes' surface water height to two centimetres accuracy and rivers
to ten centimetres by sending 1800 separate radar pulses over bodies of
water per second and recording how long their echoes take to bounce back.
In addition, these data are available in near-real time.

Today there are several teams in the world involved in radar altimetry
over inland water, using satellite data from ESA, NASA and the French
Space Agency (CNES). Hydrologists from each of these research teams met at
the '15 Years of Progress in Radar Altimetry' symposium, organised by ESA
and the French Space Agency (CNES) in Venice Lido, Italy, from 13-18 March
2006, to discuss the abilities of past and current altimeters for
monitoring the Earth's changing inland water resources.

Professor Philippa A. Berry of the UK's Earth and Planetary Remote Sensing
Laboratory (EAPRS) at De Montfort University said: "This field has evolved
rapidly over the past two decades. Initial work over a handful of large
targets has now expanded to the current capability to monitor thousands of
river and lake heights worldwide."

Although designed for ocean studies, hydrologists undertook great efforts
for radar altimetry to include precise river and lake level monitoring.
Berry, for instance, led a River and Lake Level monitoring development
project, under ESA contract, in an effort to track rivers and lakes to
help manage water resources.

As a result, ESA launched a web-based demonstration in 2005 that allows
for radar altimetry data of African rivers and lakes from its
environmental satellite, Envisat, to be freely available worldwide in
near-real time -- within four days of measurements.

Following the 2002 World Summit, ESA partnered with UNESCO in starting up
the TIGER initiative, which uses satellite data to manage water resources
in Africa. ESA is currently presenting the TIGER initiative at the World
Water Forum in Mexico City. The forum, being held from 16 to 22 March, has
brought government, business, and non-government organisations together to
discuss establishing a water-secure future and the UN goal of halving the
number of people without drinking water by 2015.

The primary objective of TIGER is to help African countries overcome
problems faced in the collection, analysis and dissemination of water
related geo-information by exploiting the advantages of Earth Observation
technology. More than 200 African water basin authorities, universities
and other organisations have become involved in TIGER projects across the
continent.

Although radar altimetry has been successful in measuring the height of
rivers and lakes, scientists are looking for ways to improve the
instrument in the future. More than 150 scientists from more than 20
countries have proposed an Earth Explorer hydrology mission called Water
Elevation Recovery (WatER), which aims to determine how water storage
varies in space and time.

According to Professor Doug Alsdorf of Ohio State University, conventional
profiling altimetry -- which uses a single antenna looking strait down at
Nadir -- limits the spatial and temporal sampling of water surface
elevations, making it essential to obtain a two-dimensional sampling in
order to capture the flow dynamics of highly complex waters.

To this end, WatER will use an interferometric altimeter, which will allow
it to measure elevations over a 120 kilometre wide swath and therefore map
the world's water bodies repeatedly in less than a week.

"WatER is designed to meet high priority targets for all nations and will
provide essential data for the EU Water Framework Directive. WatER will
meet the United Nations' call for a 'greater focus on water related
issues,' " CNES' Dr. Nelly Mognard, lead scientist for the WatER proposal
and part of Laboratoire d'Etudes en Geophysique et Oceanographie
Spatiales, said at the symposium in Venice.

CryoSat-2, the next ESA radar altimetry mission, expected to launch in
2009, is designed to measure changing ice fields, but it will also
contribute to monitoring water resources by acquiring samples of data from
its new generation radar altimeter over inland water bodies upon request
from scientists for experimental purposes.

A follow on to CryoSat, ESA Earth Explorer ice mission, which was lost at
launch in 2005 due to an anomaly in the Russian launcher, CryoSat-2 will
fly an enhanced radar altimeter instrument, called the Synthetic Aperture
Interferometric Radar Altimeter (SIRAL) which will allow it to improve the
resolution of the measurements by increasing the number of separate radar
pulses it sends down to Earth every second from 1800 to up to 17 800. The
experiment will demonstrate how to benefit from novel technologies to
serve emerging science fields, such as hydrology, from space.

Supported as part of the Agency's Earth Observation Data User Element
(DUE), the River and Lake project is aimed at developing, demonstrating
and assessing an information service based on inland water altimetry.

Related news

* Radar altimetry revolutionises the study of the ocean
http://www.esa.int/esaCP/SEMB1RNVGJE_index_0.html
* Envisat tracking Africa's rivers and lakes to help manage water
resources
http://www.esa.int/esaCP/SEMM7B5Y3EE_index_0.html

Related missions

* Envisat overview
http://www.esa.int/esaEO/SEMWYN2VQUD_index_0_m.html

In depth

* River & Lake website
http://earth.esa.int/riverandlake/
* Data User Element
http://dup.esrin.esa.it/
* TIGER
http://www.tiger.esa.int
* Radar Altimetry Symposium
http://earth.esa.int/venice06/

Related links

* WatER mission
http://www.legos.obs-mip.fr/en/reche...mis_partn.html

[NOTE: Images supporting this release are available at
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