Earth Observation

28 esa bulletin 117 - february 2004 www.esa.int

Looking after Waterin Africa

– ESA’s TIGER Initiative meets the challengesposed at the Johannesburg Summit

Major river catchment basins and land-cover distribution in Africa© Geospace/Spotimage 2004

Senegal NigerNigerLake Chad

Volta Nile

JubaShibeli

Congo

Zambezi

Okavango

Limpopo

Orange

Lake ChadSenegal

– ESA’s TIGER Initiative meets the challengesposed at the Johannesburg Summit

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All Life Depends on Water

Almost all aspects of the Earth system involve or relyon water. Ours is unique among the planets becauseits water is maintained in vapour, liquid and iceforms. Water is, in fact, the only known substancethat can naturally exist in gas, liquid, and solid formwithin the relatively small range of air temperaturesand pressures found at the Earth's surface. In all, ourplanet’s water content is about 1.39 billion cubic

kilometres and the vast bulk of it, about97%, is in the global oceans. Onlyabout 3% resides as freshwater on theland.

Furthermore, two thirds of thisfreshwater exists in ice caps, glaciers,permafrost, swamps, and deep aquifers,where it is largely inaccessible. A verysmall fraction of the total is held in theatmosphere, but it plays a critical role inour climate and in the transport ofocean water that precipitates over land.The latter can be considered as therenewable part of the resource,determining the amount of water thatcan be used by humans withoutdepleting the water stored in reservoirsor aquifers.

The TIGER Initiative

Water resources, the ‘blue gold’ of the 21st century, can besuccessfully monitored from space using Earth-observationtechnology. Satellites can measure precipitation, atmosphericwater content, soil moisture, surface run-off, lake and riverlevels, groundwater reservoirs, as well as ice and snowcover. Improved sensors, better modelling and a deeperunderstanding of the underlying science have substantiallyadvanced our knowledge of the global water cycle in recentyears.

However, there are still major shortcomings in both theunderstanding and the observation of key parameters. Theestimation of groundwater resources, for example, poses amajor challenge, as they are not directly visible from space.Indirect methods based on gravity-field measurements, radarinterferometery and altimetric monitoring of rivers need tobe applied to gain knowledge of reservoir volumes andflows. In order to improve our capabilities and to offer thistechnology to people in developing countries, ESA haslaunched a new programme focusing on the use of spacetechnology for water-resource management in Africa. Theinitiative, called ‘TIGER’, is a direct follow-up of ESA’s strongengagement in the 2002 Johannesburg World Summit onSustainable Development, and implements itsrecommendations through concrete actions.

José AchacheDirector of Earth Observation Programmes, ESA, Paris

Josef AschbacherProgramme Coordinator, Directorate of Earth ObservationProgrammes, ESA, Paris

Stephen BriggsHead of ESA Earth Observation Science and ApplicationsDepartment, ESRIN, Frascati, Italy

Wetland ecosystems are a principal source of life on Earth

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Earth Observation

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Water and energy are intimatelyinvolved in driving atmosphericcirculation. Consequently, climate- andweather-prediction systems must considerwater as a primary component. Humansaffect the water cycle not only indirectly asglobal warming affects precipitationpatterns, but also directly as river control,irrigation and general water-managementpractices reorganise the patterns of watermovement. The drying out and over-salinisation of the Aral Sea and theconstruction of the Three Gorges dam are prominent examples of humansinfluencing regional water-resourcemanagement. The complexity ofthese interactions and the rangeof their space and time scalespose major challenges tohydrologists and decision-makers alike.

To represent these variablesadequately, a mix of satelliteand in-situ data is required.Remote sensing, especiallyfrom space, can provide spatialcoverage for rainfall, soilmoisture, snow cover, snowwater equivalent, and vegetationconditions. Remote sensingdoes not, however, remove theneed for ground-based measure-ments. Hydrologists use remotesensing as a major, and in manycases essential informationsource to better understand and monitorthe global and regional water cycle. Thechallenge for space agencies lies in theadequate integration of space-basedinformation into a holistic decision supportsystem, which should lead to betterdecisions and ultimately to better lives forthose who most depend on improvedmanagement of water resources.

The Johannesburg World Summit onSustainable Development

The 2002 Johannesburg World Summit onSustainable Development recognised theimportance of natural resources fordevelopment, and hence stability, on ourplanet. The biggest challenge mankind is

facing over the next 50 years is that ofcoping with a predicted 50% increase inthe Earth’s population, from 6 billion todayto 9 billion by 2050. Heads of State andGovernments committed themselves at the Summit to the Johannesburg Plan ofImplementation for Agenda 21, integratingthe three pillars of sustainable development –economic development, social developmentand environmental protection – at local,national, regional and global levels.

Water is probably the most crucialamong the issues prioritised inJohannesburg, which also include energy,health, agriculture and biodiversity.

Freshwater is a finite and vulnerableresource. Over one billion people still donot have access to safe drinking water, andnearly two billion lack safe sanitation. Anestimated 10 000 people die every dayfrom water- and sanitation-relateddiseases, while thousands more suffer froma range of debilitating illnesses.

Humans currently appropriate more thanhalf of the accessible freshwater run-off,and this proportion is expected to increasesignificantly in the coming decades. Asubstantial amount, namely 70%, of thewater currently withdrawn from allfreshwater resources is used foragriculture. With the rapid increase in theworld’s population, the additional foodrequired to feed future generations will putfurther enormous pressure on freshwater

resources. According to recent globalwater assessments, around 70% of thefuture world population will face watershortages, and 16% will have insufficientwater to grow their basic foodrequirements by 2050. The impact ofinadequate water and sanitation servicesfalls primarily on the world’s poor.

Earth Observation for Water-ResourceManagement

Earth-observation satellites play a majorrole in the provision of information for thestudy and monitoring of the water cycle.

Atmospheric-temperature, water-vapourand cloud-cover measurements areprovided operationally by meteorologicalsatellites such as MSG and MetOp. ERSand Envisat, for example, provide surfacetemperatures, ocean winds, wave heights,and ice-dynamics data, as well asinformation on vegetation cover, soilmoisture, and geology over land surfaces.

Precipitation is clearly a key parameter,but given its high temporal and spatialvariability it is a fundamentally difficultparameter to measure. Until recently,visible/infrared images from geostationarymeteorological satellites provided the bestsource of information from space – withindirect but frequent estimates of rainfallderived from measurements of cloud-toptemperature. The advent of the Tropical

Main components of the Earth’s water cycle

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Rainfall Mapping Mission (NASA/JAXA)in 1997 provided a major step forward with the provision of 3-D information onrainfall structure and characteristics.ESA has joined NASA, JAXA andother partners to continue thiscollaboration and to develop theGlobal Precipitation Mission(GPM), due for launch in thesecond half of this decade. TheGPM constellation of satellites willprovide global observations ofprecipitation every three hours tohelp develop our understanding ofthe global structure of rainfall and itsimpact on climate.

Recognising the central role of thewater cycle in our understanding of theEarth system and climate change, theworld’s space agencies are already operating

or are currently developing a number ofnew missions aimed at addressing keyscientific objectives. These include theAqua mission (NASA), Cloudsat (NASA),EarthCare (ESA/JAXA), GRACE (NASA/DLR) and ESA’s Cryosat. Altimetricmeasurements provided by Topex-Poseidonand Jason from CNES and NASA, andERS and Envisat from ESA, providecontinuous monitoring of lakes and riverswith centimetre accuracy. Revolutionarynew measurement capabilities will beprovided in the future by ESA’s SoilMoisture and Ocean Salinity (SMOS)mission scheduled for launch in 2006.Following GRACE, ESA’s Global OceanCirculation Experiment (GOCE) missionwill determine the Earth’s gravity field andits geoid with high accuracy and will allowthe retrieval of water-table height measure-ments, one of the main parameters of interestto hydrologists.

The TIGER Initiative

Meteosat MSG-1 image taken on 14 July 2003 showing high thunderstorm clouds(yellow) ‘overshooting’ into the stratosphere© ESA/Eumetsat 2003

Artist’s impression of ESA’s Soil Moisture and Ocean Salinity (SMOS) satellite

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Earth Observation

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To ensure the necessary co-ordinationbetween these many satellite programmes,the IGOS Partnership is developing anIntegrated Global Water Cycle Observations(IGWCO) Theme. This Theme provides aframework for guiding international decisionsregarding priorities and strategies for themaintenance and enhancement of water-cycle observations so that they will supportthe most important applications andscience goals, including the provision ofsystematic observations of trends in keyhydrological variables.

The first element of IGWCO is a Co-ordinated Enhanced Observing Period(CEOP), which is capitalising on theopportunity of the simultaneous operationof key European, Japanese, and Americansatellites during the period 2001-2004 togenerate new water-cycle data sets.

New technologies for measuring,modelling, and organising data on theEarth’s water cycle offer the promise of a deeper understanding of the cycle’sprocesses, and of how different manage-ment decisions may affect them. Earth-observation satellites provide synoptic,high-resolution measurement coveragethat is unprecedented in the geophysicalsciences. The challenges to be faced inexploiting these new capabilities include:– converting satellite measurements into

useful parameters that can be applied inscientific models, and which can beinter-compared and inter-calibratedbetween the different satellite missions;

– providing consistent and accurate dataover many years in order to detect thetrends, which is necessary for climate-change studies;

– succeeding in the technology develop-ments aimed at accurately measuringkey parameters from space for the firsttime – including soil moisture and oceansalinity; and, above all,

– mobilising a large scientific communityin the developed and developing countriesto address this fascinating subject.

To complement the satellite data, existingground-based measurement networks andsystems must continue operating to obtaincurrent data that can be comparedmeaningfully with past records.

ESA’s TIGER Initiative

During 2002, under ESA’s Chairmanship,the Committee on Earth ObservationSatellites (CEOS) invested a considerableamount of effort in its participation at theWorld Summit on Sustainable Development,in Johannesburg. This Summit acknowledgedthe important role of Earth-observationsatellites in assisting sustainable develop-ment. Altogether, 12 specific Articles inthe 54-page WSSD Plan of Implemen-tation that was adopted by Heads of Stateand Governments in Johannesburg refer tothe use of Earth observation.

In November 2002, at its 16th PlenaryMeeting held at ESA/ESRIN, in Frascati(I), CEOS adopted a WSSD Follow-upProgramme. This Programme proposesaction in a number of fields, which wereidentified in the Plan of Implementation as

areas where Earth observation plays animportant role for sustainable development.

It is within the framework of the WSSDFollow-up Programme that ESA haslaunched its TIGER initiative, as a directresponse to the challenges identified inJohannesburg. TIGER is aimed atimproving our scientific understanding ofthe water cycle and developing sustainableEarth-observation services for integratedwater-resource management in developingcountries, with a particular focus onAfrica. It consists of two major elements:

(i) a set of individual projects withlimited geographical coverage and scope,which are ‘building blocks’ for the

(ii) political process, which aims atdeveloping long-term, large-scale,sustainable information services for betterdecision making in the water-resourcemanagement domain.

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The TIGER Initiative

The Committee on Earth ObservationSatellites (CEOS)

CEOS was created in 1984 under the auspices of the G7, with the goal ofcoordinating Earth-observation satellite missions among its Members. The 21Members include space agencies that have active Earth-observation satelliteprogrammes, while the 23 Associates include organisations that receive,process or use environmental data gathered from space. ESA is a foundingmember of CEOS and a permanent member of the Secretariat, which carriesout the executive work in support of the annually rotating CEOS chairingagency. CEOS was chaired by ESA in 2002, followed by NOAA in 2003, Chinain 2004 and BNSC in 2005.

The Nile river delta captured by Envisat’s MERISinstrument on 1 March 2003© ESA 2003

Lake Tanganyika, the deepest fresh water lake in theworld, on the border between Tanzania and Zaire.These images were taken using Envisat’s AATSRinstrument during the rainy season in April 2002(left) and during the dry season in July 2002 (right)© ESA 2002

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Earth Observation

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To achieve this long-term goal, strategicpartners with a development mandate areinvolved, such as financing institutions ordevelopment organisations. Other partnersinclude user organisations in Africa andbeyond, as well as providers of spacetechnology and services. Close co-operation with UNESCO has beenestablished, thereby benefiting inparticular from its International HydrologyProgramme (IHP) and World WaterAssessment Programme (WWAP), whichprovide access to a global network ofhydrologists and field officers. UNESCOalso supports training activities anddevelops educational material.

During 2003, the TIGER participantswere identified and the organisationalstructure and work programme defined.Two major consultation meetings withstakeholders were held, one in May in Parisand one in October in Rabat. The topicsidentified as priorities for the first phaseare groundwater resources, wetlands,epidemiology and food security; other topicsmay be added at a later stage. A two-phaseapproach was agreed, with Phase-1 (untilend-2005) serving to demonstrate theusefulness of Earth observation forintegrated water-resource management toAfrican users and decision-makers, whilePhase-2 (2006 onwards) will engage majordonor and development agencies in orderto turn the successful demonstratorprojects into major development program-mes. The precise content of Phase-2 willbe defined in the course of 2005 on thebasis of the Phase-1 results, as well as the results of reviews by African local andnational authorities and potential inter-national donor agencies. A key criterionwill be the prospect of sustainability forselected services.

TIGER Demonstration Projects in Africa

As of early 2004, ESA has launched orinitiated four projects within theframework of TIGER, focusing on variousaspects of water-resource management inAfrica. These projects, implementedthrough the Global Monitoring forEnvironment and Security (GMES) and

Earth Observation Data User Element(DUE) activities at ESRIN in Frascati, are:– Global Monitoring for Food Security– Global Wetland Monitoring– Epidomiology– Groundwater Resource Monitoring.

The goal of the Global Monitoring forFood Security (GMFS) project is toimprove the provision of operationalinformation services to assist food-aid andfood-security decision makers. GMFSaims to consolidate, support andcomplement existing regional-informationand early-warning systems on food andagriculture. It will concentrate initially onSub-Saharan Africa, and will focus on end-users from regional organisations whosemandate is agricultural monitoring forfood security and early warning of foodcrises. The project also aims to meet theneeds of users in international organisationssuch as the UN Food and AgricultureOrganization (FAO) and the EuropeAidCooperation Office (AIDCO).

The Globwetland project is producingsatellite-derived and geo-referencedproducts, including inventory maps anddigital elevation models of wetlands andthe surrounding catchment areas. Theseproducts will aid local and nationalauthorities in fulfilling their obligationsunder the Ramsar Convention for wetlandsconservation. They should also serve as ahelpful tool for wetland managers and

scientific researchers. For much of the lastcentury, wetlands have been drained orotherwise degraded, but scientificunderstanding of their important roles interms of biology and the water cycle hasgrown, spurring international efforts topreserve them. An assessment of themonetary value of natural ecosystemspublished in Nature in 1997 arrived at afigure of 27.7 trillion Euros, with wetlandecosystems making up 12.5 trillion - or45% - of that total. Most of all, wetlandssupport life in spectacular variety andnumbers: freshwater wetlands alone arehome to four in ten of all of the world’sspecies, and one in eight of global animalspecies. Much of human civilisation hasbeen based around river valleys and floodplains. However, global freshwaterconsumption rose sixfold during the 20thcentury - a rate more than double that ofpopulation growth. With wetlands oftenmade up of difficult and inaccessibleterrain, satellites can help provideinformation on local topography, the typesof wetland vegetation, land cover and use,and the dynamics of the local water cycle.In particular, radar imagery provided byESA’s Envisat mission is able todifferentiate between dry and waterloggedsurfaces, and so can provide multi-temporal data on how given wetlandschange with the seasons.

Recharges and discharges of a transboundarygroundwater system (schematic view)

INTERNATIONALBOUNDARY

Discharge fromtransboundary flow

Recharge contribution totransboundary flow

Transboundaryflow direction

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The Epidemio project is aimeddeveloping Earth-observation services forepidemiologists, with a particular focus onmalaria and Africa. Malaria affects 300million people worldwide, and kills up to1.5 million people annually. The incidenceof the disease is influenced by localclimate, which can be monitored bysatellites to help in forecasting malariaoutbreaks. The Epidemio project providesmaps of water bodies - updated through thewet and dry seasons - as well as digitalelevation models and weekly land-surface-temperature maps. Water mapping isespecially useful for malaria riskprediction as mosquitoes begin life asaquatic larvae and the adults rarely travelmore than 2 km from their breedingground during their two- to three-weeklifetime.

The above three projects were alreadystarted during 2003, but another newproject will be initiated in early 2004which focuses on the use of Earthobservation for groundwater monitoring.This project, known as Aquifer, is aimed atusing SAR interferometry measurementsto derive the surface subsidence rates ofthe terrain above the northwest African

aquifer, which is the largest in the worldand spans three countries: Algeria, Libyaand Tunisia. These subsidence measurementswill be coupled with geomorphologicinformation and in-situ measurements tomodel water extraction rates from theaquifer. ERS and Envisat SAR data will bethe main data sources used in this project.

Conclusion

There is no doubt whatsoever that themanagement of water resources will pose amajor challenge in this century, particularlyas the growth in the global population isgreatest in regions with dry and semi-dryclimates. With its TIGER initiative, ESA is

addressing this challenge head-on byfostering a greater understanding of thewater cycle, and by providing crucialinformation to decision makers at local,regional and global levels. Improvedinformation about the use of waterresources not only provides a better basisfor life and health to local people, but isalso a critical factor in supporting peaceand stability among countries desperatelyconcerned about the use of shared waterresources. Hence, information fromsatellites is not only a tool for natural-resource management, but also a confidence-building resource by providing transparentinformation to people in the developingand developed world. s

The TIGER Initiative

Left: Water-extraction pointsfrom the northwest-Africanaquifer Below: Water extraction (inbillions of cubic metres peryear) from 1950 to 2000for Libya (blue), Tunisia(yellow) and Algeria (green)© OSS 2003

Libya

Tunisia

Algeria

2.7

2.4

2.1

1.8

1.5

1.2

0.8

0.6

0.3

01950 1955 1960 1965 1970 1975 1980 1985 1990 1995 2000

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