Drought monitoring and early warning: concepts, progress and future challenges

WMO - No. 1006

Weather and climate information for sustainable agricultural development

WMO-No. 1006© 2006, World Meteorological OrganizationISBN 92-63-11006-9

Cover illustration: Maasai tribesman walking through drought-stricken landscape, Kenya. © Jonathan and Angela (Getty Images)

NOTEThe designations employed and the presentation of material in this publication do not imply the expression of any opinion whatsoever on the part of the Secretariat of the World Meteorological Organization concerning the legal status of any country, territory, city or area, or of its authorities, or concerning the delimitations of its frontiers or boundaries.

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ContentsForeword . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....2

Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....4

Drought as a hazard: concepts and definitions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....6

Types of drought . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ....8

Characterizing drought and its severity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..10

The challenges of drought monitoring and early warning . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..11

Integrated drought monitoring and delivery: the way forward . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..12

Drought monitoring activities: case studies . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..15

China . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..15

IGADClimatePredictionandApplicationsCentre(ICPAC). . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..17

SouthAfrica. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..19

Portugal. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..20

Australia . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..23

Conclusion . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . ..24

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FoReWoRDThroughout thecourseofhumanhistory,droughthasbeenaproblemaffectingourwelfareandfoodsecurity.Ofallhumanendeavours,agriculturewasperhaps the first sector for which humans recog-nized the strong relationships between crops andweather.Short-termrainfalldeficitspromptedearlyhumans to find alternative food crops. However,evenasingleyearwithaseveredroughtduringtherainyseasonresultedincropfailures,whichmostlikelyledtohumansmigratingtootherareas.There-fore,inearlyhumanhistory,evenlimiteddroughtshadlargeimpacts.

In recent times, short-term drought adaptationmechanismshaveimproved,butextendedperiodsof drought are now the main concern for humanwelfareandfoodsecurity.Theseperiodsofdryness,whencoupledwithotherclimatic factors,suchasextremerainfallandwindeventsorunsustainableagricultural and development patterns, can resultinlanddegradationand,ifunchecked,inincreasesin desert land areas or desertification. During the1970s and 1980s, West Africa experienced anextendedperiodofdroughtthatledtowidespreadconcernabout these issuesTheaggregate impactofdroughtcanbequitenegativeontheeconomiesofdevelopingcountries, inparticular.Forexample,GDPfellby8to9percentinZimbabweandZambiain1992and4to6percentinNigeriaandNigerin1984.Over250millionpeoplearedirectlyaffectedbylanddegradationanddesertification.Inaddition,someonebillionpeopleinover100countriesareatrisk.Theyincludemanyoftheworld’spoorestandmostmarginalizedcitizens.Hence,combatingdeser-tificationisanurgentpriorityintheglobaleffortstoensurefoodsecurityandthelivelihoodsofmillionsofpeoplewhoinhabitthedrylands.

Asvulnerabilitytodroughthasincreasedglobally,greaterattentionhasbeendirectedtoreducingtherisks associated with its occurrence through theintroduction of planning to enhance operationalcapabilities such as climate and water supplymonitoringandbuildinginstitutionalcapacity,andmitigationmeasuresthatareaimedatreducingtheimpactsofdrought.

Importantcomponentsofeffectivedroughtmanage-ment are improved drought monitoring and earlywarning systems. The fight against drought anddesertification receives a high priority in WMO’sStrategic Plan, particularly under the Agricultural

Meteorology Programme, the Hydrology andWater Resources Programme and the TechnicalCooperation Programme. WMO actively involvesthe National Meteorological and HydrologicalServices (NMHSs), the regional and sub-regionalmeteorological centres and other bodies in theimprovement of hydrological and meteorologicalnetworksforsystematicobservationsandexchangeandanalysisofdata.WMOalsoworks closelywithother UN agencies and international organizationsto develop long-term strategies aimed at promot-ing meteorological and hydrological activities thatcontributetobetterdroughtmonitoringanduseofmedium- and long-range weather forecasts and toassistinthetransferofknowledgeandtechnology.

Atits58thordinarysession,theUnitedNationsGeneralAssemblydeclared2006 tobe the InternationalYearof Deserts and Desertification (IYDD). In doing so,the General Assembly underlined its deep concernfor the exacerbation of desertification, particularlyin Africa, and noted its far-reaching implications forthe implementation of the Millennium DevelopmentGoals(MDGs),whicharetobemetbytheyear2015.TheIYDDpresentsagoldenopportunitytoconveythemessage strongly and effectively in the sense thatissues of drought, land degradation and desertifica-tion are global problems that must be addressed. Italso provides an impulse to strengthen the visibilityandimportanceofthedrylandsissueontheinterna-tionalenvironmentalagenda,whileprovidingatimely

M. Jarraud, Secretary-General

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remindertotheinternationalcommunityofthehugechallengesthatstilllieahead.

TheUnitedNationsConvention toCombatDesertifi-cation (UNCCD) and WMO have been longstandingpartners in developing and promoting the issuesrelated to drought monitoring, preparedness, miti-gation, land degradation and desertification. Aspartof its implementationactivitiesfor IYDD,WMOhas prepared this brochure to explain the variousconceptsandchallengesofdroughtmonitoringandearly warning systems. This brochure also detailsthe considerable progress that has been made ontheseissuesinsomedrought-pronecountriesbyhigh-lightingseveralcasestudiesfromaroundtheworld.

IwishtothankMrDonaldWilhite,DirectoroftheNationalDroughtMitigationCenterandProfessoroftheSchoolof Natural Resources of the University of Nebraska(USA),forpreparingthisinformativebrochure.Wehopethatthisdocumentwillbeusefultocountrieslookingtodeveloporenhancetheirowndroughtmonitoringandearlywarningcapabilities.

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IntRoDUCtIonDroughtisaninsidiousnaturalhazardcharacterizedbylowerthanexpectedorlowerthannormalprecip-itationthat,whenextendedoveraseasonorlongerperiodoftime, is insufficienttomeetthedemandsof human activities and the environment. Droughtisatemporaryaberration,unlikearidity,whichisapermanentfeatureofclimate.Seasonalaridity,thatis,awell-defineddryseason,alsoneedstobedis-tinguished from drought, as these terms are oftenconfusedorused interchangeably.Thedifferencesneedtobeunderstoodandproperlyincorporatedindroughtmonitoringandearlywarningsystemsandpreparednessplans.

Droughtmustbeconsideredarelative,ratherthanan absolute, condition. It occurs in both high andlowrainfallareasandvirtuallyall climate regimes.Droughtisoftenassociatedonlywitharid,semi-aridandsub-humid regionsbyscientists,policymakersand the public. In reality, drought occurs in mostcountries,inbothdryandhumidregions.Droughtisanormalpartofclimate,althoughitsspatialextentandseveritywillvaryonseasonalandannualtime-scales.Inmanycountries,suchasAustralia,China,India and the United States of America, droughtoccurs over a portion of the country each year.Owingtothefrequentoccurrenceofdroughtandtheprofound impacts associated with it, governmentsshoulddevotemoreattentiontothedevelopmentof

anationalstrategyorpolicytoreduceitseconomic,social and environmental consequences. A criti-calcomponentofthatstrategyisacomprehensivedrought monitoring system that can provide earlywarningofdrought’sonsetandend,determine itsseverityanddeliverthatinformationtoabroadclien-teleinmanyclimate-andwater-sensitivesectorsinatimelymanner.Withthisinformation,theimpactsofdroughtcanbereducedoravoidedinmanycases.

Drought is a regional phenomenon and its charac-teristics differ from one climate regime to another.Afewexamplesof thecontrastingtemperatureandprecipitationregimesofvariousregionsareshowninFigure1.Droughtoccurs ineachof these locations,but characteristics such as frequency and durationvary appreciably. New Delhi’s precipitation patternisdistinctlymonsoonal,withmaximumprecipitationoccurring from June to October, with the greatestconcentration inJuly,AugustandSeptember.Tunishas a distinctly Mediterranean-type (dry summer)climateregime.Nairobi’sprecipitationdistributionisdistinctlybi-modal,withpeakrainfallexpectedfromMarch through May and a second concentration inNovember and December. London’s precipitationis evenly distributed throughout the year. In eachexample,asignificantdeparturefromtheseregimesforanextendedperiodoftimewillresultinimpactsinclimate-andwater-sensitivesectors.Impactsarealso

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regionalinnature,reflectingexposuretothehazardandthevulnerabilityofsocietytoextendedperiodsofprecipitationdeficits.Impactsareameasureofvul-nerability.Riskisaproductofexposuretothehazardandsocietalvulnerability.

Droughtbyitselfisnotadisaster.Whetheritbecomesa disaster depends on its impact on local people,economiesandtheenvironmentandtheirabilityto

copewithandrecoverfromit.Therefore,thekeytounderstanding drought is to grasp its natural andsocial dimensions. The goal of drought risk man-agement is to increase society’s coping capacity,leading to greater resilience and a reduced needforgovernmentordonorinterventionsintheformof disaster assistance. Drought monitoring andearly warning are major components of droughtriskmanagement.

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Figure 1. Climographs illustrating monthly temperature and precipitation regimes for New Delhi, Tunis, Nairobi and London. (Source: National Drought Mitigation Center, University of Nebraska–Lincoln, USA)

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Economic impacts Social impacts

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Natural climate variability

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Plant water stress, reduced biomass and yield

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Reduced streamflow, inflow to reservoirs, lakes, and ponds;

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DRoUght as a hazaRD: ConCepts anD DeFInItIonsDrought differs from other natural hazards in vari-ous ways. Drought is a slow-onset natural hazardthatisoftenreferredtoasacreepingphenomenon.Itisacumulativedeparturefromnormalorexpectedprecipitation,thatis,along-termmeanoraverage.This cumulative precipitation deficit may build upquicklyoveraperiodoftime,oritmaytakemonthsbefore the deficiency begins to appear in reducedstreamflows,reservoirlevelsorincreaseddepthtothegroundwatertable.Owingtothecreepingnatureofdrought, its effectsoften takeweeksor monthstoappear(Figure2).Precipitationdeficitsgenerallyappearinitiallyasadeficiencyinsoilwater;therefore,agricultureisoftenthefirstsectortobeaffected.

Itisoftendifficulttoknowwhenadroughtbegins.Likewise, it is also difficult to determine when adrought isoverandaccording towhat criteria thisdeterminationshouldbemade.Isanendtodroughtheraldedbyareturntonormalprecipitationand,ifso,overwhatperiodoftimedoesnormalorabovenormal precipitation need to be sustained for the

droughttobedeclaredofficiallyover?Sincedroughtrepresents a cumulative precipitation deficit overan extended period of time, does the precipitationdeficitneed tobeerased for theevent toend?Doreservoirs and groundwater levels need to returntonormaloraverageconditions? Impacts linger foraconsiderableperiodoftimefollowingthereturnofnormalprecipitation.Therefore,istheendofdroughtsignalledbymeteorologicalorclimatologicalfactors,or by the diminishing negative impact on humanactivitiesandtheenvironment?

Anotherfactorthatdistinguishesdroughtfromothernaturalhazardsistheabsenceofapreciseanduni-versallyaccepteddefinition.Therearehundredsofdefinitions,addingtotheconfusionabouttheexist-ence of drought and its degree of severity. Defini-tions of drought should be region and applicationspecific or impact specific. Droughts are regionalinextentand,aspreviouslystated,eachregionhasspecificclimaticcharacteristics.DroughtsthatoccurintheNorthAmericanGreatPlainswilldifferfrom

Figure 2. Sequence of drought occurrence and impacts for commonly accepted drought types. All droughts originate from a deficiency of precipitation or meteorological drought but other types of drought and impacts cascade from this deficiency. (Source: National Drought Mitigation Center, University of Nebraska–Lincoln, USA)

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those inNortheastBrazil,southernAfrica,WesternEurope,easternAustraliaor theNorthChinaPlain.The amount, seasonality and form of precipitationdifferwidelybetweeneachoftheselocations.

Temperature, wind and relative humidity are alsoimportant factors to include in characterizingdrought from one location to another. Definitionsalsoneedtobeapplicationspecificbecausedroughtimpactswillvarybetweensectors.Droughtconjuresdifferentmeaningsforwatermanagers,agriculturalproducers,hydroelectricpowerplantoperatorsandwildlifebiologists.Evenwithinsectors,therearemanydifferentperspectivesofdroughtbecauseimpactsmaydiffermarkedly.Forexample,theeffectsofdroughton crop yield may vary considerably for maize,wheat, soybeans and sorghum because they areplanted at different times during the growing sea-sonanddonothavethesamewaterrequirements

andsensitivitiestowaterandtemperaturestressatvariousgrowthstages.

Drought impacts are non-structural and extendoveralargergeographicalareathandamagesthatresult from other natural hazards such as floods,tropical storms and earthquakes. This, combinedwithdrought’screepingnature,makesitparticularlychallenging to quantify impacts and even morechallenging to provide disaster relief for droughtthan for other natural hazards. These characteris-tics have hindered the development of accurate,reliable and timely estimates of the severity andimpacts, such as drought early warning systemsandultimately, the formulationofdroughtprepar-edness plans. Similarly, it is difficult for disasterofficialstaskedwithrespondingtodroughttodealwith the largespatialcoverageusuallyassociatedwithitsoccurrence.

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types oF DRoUghtDroughtsarecommonlyclassifiedbytypeasmeteo-rological, agricultural, hydrological and socio-economic.

Meteorological droughtisusuallydefinedbyapre-cipitationdeficiencythresholdoverapredeterminedperiodoftime.Thethresholdchosen,suchas75percentofnormalprecipitation,anddurationperiod,forexample, sixmonths,will varyby locationaccord-ingtouserneedsorapplications.Figure3illustratesthreecharacterizationsofdroughtforthreedifferentcountries based on precipitation departures fromnormal, deciles and the Standardized PrecipitationIndex (SPI). Meteorological drought is a natural

eventandresultsfrommultiplecauses,whichdifferfrom region to region. Agricultural, hydrologicalandsocio-economicdrought,however,placegreateremphasisonthehumanorsocialaspectsofdrought,highlightingtheinteractionorinterplaybetweenthenatural characteristics of meteorological droughtand human activities that depend on precipitationtoprovideadequatewatersuppliestomeetsocietalandenvironmentaldemands.

Agricultural drought isdefinedmorecommonlybytheavailabilityofsoilwatertosupportcropandfor-age growth than by the departure of normal pre-cipitationoversomespecifiedperiodoftime.There

Figure 3. Meteorological drought expressed as percentage departure from normal precipitation for India, precipitation deciles for Australia and the Standardized Precipitation Index for Canada. (Sources: Indian Meteorological Department, Australian Bureau of Meteorology and Prairie Farm Rehabilitation Administration and Agriculture Canada, respectively)

Figure 4. Interrelationships between meteorological, agricultural, hydrological and socio-economic drought. (Source: National Drought Mitigation Center, University of Nebraska–Lincoln, USA)

Meteorological

Decreasing emphasis on the natural event (precipitation deficiencies)

Increasing emphasis on water/natural resource managementIncreasing complexity of impacts and conflicts

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isnodirect relationshipbetweenprecipitationandinfiltration of precipitation into the soil. Infiltra-tion ratesvary,dependingonantecedentmoistureconditions,slope,soil typeandtheintensityoftheprecipitation event. Soil characteristics also differ:somesoilshaveahighwater-holdingcapacitywhileothersdonot.Thelatteraremorepronetoagricul-turaldrought.

Hydrological droughtisevenfurtherremovedfromthe precipitation deficiency since it is normallydefined by the departure of surface and subsur-facewatersuppliesfromsomeaverageconditionatvarious points in time. Like agricultural drought,thereisnodirectrelationshipbetweenprecipitationamounts and the status of surfaceand subsurfacewatersuppliesinlakes,reservoirs,aquifersandstreamsbecausethesehydrologicalsystemcomponentsareusedformultipleandcompetingpurposes,suchasirrigation, recreation, tourism, flood control, trans-portation,hydroelectricpowerproduction,domesticwatersupply,protectionofendangeredspeciesandenvironmental and ecosystem management andpreservation.There isalsoaconsiderable time lagbetweendeparturesofprecipitationandthepointatwhichthesedeficienciesbecomeevidentinsurfaceandsubsurfacecomponentsof thehydrologicsys-tem.Recoveryofthesecomponentsisslowbecauseoflongrechargeperiodsforsurfaceandsubsurfacewatersupplies. Insomedrought-proneareas,suchas the western United States, snow pack accumu-latedduringthewintermonthsistheprimarysourceofwaterduringthesummer.Reservoirsincreasetheresilienceofthisregiontodroughtbecauseoftheirability to store large amounts of water as a bufferduringsingle-ormulti-yeardroughtevents.Socio-economic droughtdiffersmarkedlyfromtheother types of drought because it reflects therelationship between the supply and demand forsomecommodityoreconomicgood,suchaswater,livestock forage or hydroelectric power, that isdependentonprecipitation.Supplyvariesannuallyasa functionofprecipitationorwateravailability.Demandalsofluctuatesandisoftenassociatedwithapositivetrendasaresultofincreasingpopulation,developmentorotherfactors.

Theinterrelationshipbetweenthesetypesofdroughtis illustrated in Figure 4. Agricultural, hydrologicaland socio-economic drought occur less frequentlythanmeteorologicaldroughtbecauseimpactsinthese

sectorsarerelatedtotheavailabilityofsurfaceandsubsurface water supplies. It usually takes severalweeks before precipitation deficiencies begin toproducesoilmoisturedeficienciesleadingtostresson crops, pastures and rangeland. Continued dryconditionsforseveralmonthsatatimebringabouta decline in stream flow and reduced reservoirand lake levels and, potentially, a lowering of thegroundwatertable.Whendroughtconditionspersistfor a period of time, agricultural, hydrological andsocio-economicdroughtoccur,producingassociatedimpacts. During drought, not only are inflows torecharge surface and subsurface supplies reducedbutdemandfortheseresourcesincreasesdramati-callyaswell.AsshowninFigure4,thedirectlinkagebetweenthemaintypesofdroughtandprecipitationdeficienciesisreducedbecausewateravailabilityinsurfaceandsubsurfacesystemsisaffectedbyhowthese systems are managed. Changes in the man-agementof thesewatersuppliescaneitherreduceoraggravate the impactsofdrought. Forexample,the adoption of appropriate tillage practices andplanting more drought-resistant crop varieties candiminishtheimpactofdroughtsignificantlybycon-servingsoilwaterandreducingtranspiration.

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ChaRaCteRIzIng DRoUght anD Its seveRItyDroughts have three distinguishing features: inten-sity, duration and spatial coverage. Intensity referstothedegreeoftheprecipitationshortfalland/ortheseverityofimpactsassociatedwiththeshortfall.Itisgenerallymeasuredbythedeparturefromnormalofaclimaticparametersuchasprecipitation,anindicatorsuchasthereservoirleveloranindexsuchasSPI.

Anotheressentialcharacteristicofdroughtisitsdura-tion.Droughtscandevelopquickly insomeclimaticregimes, but usually require a minimum of two tothreemonthstobecomeestablished.Onceadroughtbegins,itcanpersistformonthsoryears.Themag-nitude of drought impacts is closely related to thetimingoftheonsetoftheprecipitationshortage,itsintensityandthedurationoftheevent.Forexample,adrywintermayhavefewimpactsinmanymiddlelatitude,temperateclimatesbecauseofthereduceddemandforwaterduringthosemonths.Developinga better understanding of the frequency, durationandspatialextentofdroughtfromthepaleo-record,for example, tree rings or lake sediments, can bevery instructive because it provides planners withcritically important information from periods out-sideoftheinstrumentalperiodofrecord.

Droughtsalsodiffer in their spatial characteristics.Theareasaffectedbyseveredroughtevolvegradu-ally,andregionsofmaximumintensity,suchasepi-centres,shiftfromseasontoseasonandyeartoyearintheeventofmulti-yeardroughts. In largercoun-tries,suchasBrazil,China,India,theUnitedStatesorAustralia,droughtwouldrarely,ifever,affecttheentirecountry.During1934,oneofthemostseveredroughtyearsinUnitedStates’history,65percentof the country was affected by severe or extremedrought (Figure5).That was themaximum spatialextentofdroughtbetween1895and2005.

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Figure 5. Percentage of the United States affected by severe to extreme drought, January 1895 to May 2006. (Source: National Drought Mitigation Center, University of Nebraska–Lincoln, USA; based on data from the National Climatic Data Center/NOAA)

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the Challenges oF DRoUght monItoRIng anD eaRly WaRnIngAdroughtearlywarningsystemisdesignedtoiden-tify climate and water supply trends and thus todetect the emergence or probability of occurrenceandthe likelyseverityofdrought.This informationcanreduceimpacts ifdeliveredtodecisionmakersinatimelyandappropriateformatandifmitigationmeasures and preparedness plans are in place.Understandingtheunderlyingcausesofvulnerabilityisalsoanessentialcomponentofdroughtmanage-mentbecausetheultimategoalistoreduceriskforaparticularlocationandforaspecificgroupofpeopleoreconomicsector.

There are numerous natural drought indicatorsthatshouldbemonitoredroutinelytodeterminetheonset and end of drought and its spatial character-istics. Severity must also be evaluated on frequenttimesteps.Althoughall typesofdroughtsoriginatefromaprecipitationdeficiency,itisinsufficienttorelysolelyonthisclimateelementtoassessseverityandresultant impacts because of factors identified

previously.Effectivedroughtearlywarningsystemsmust integrate precipitation and other climaticparameterswithwaterinformationsuchasstreamflow, snow pack, groundwater levels, reservoirand lake levels,andsoilmoisture intoacompre-hensiveassessmentofcurrentandfuturedroughtandwatersupplyconditions.

Monitoring drought presents some unique chal-lengesbecauseofitsdistinctivecharacteristics.Someofthemostprominentchallengesareasfollows:

• Meteorologicalandhydrologicaldatanetworksareofteninadequateintermsofthedensityofstationsforallmajorclimateandwatersupplyparameters. Data quality is also a problembecauseofmissingdataoraninadequatelengthofrecord;

• Data sharing is inadequate between govern-ment agencies and research institutions, andthehighcostofdatalimitstheirapplicationindrought monitoring, preparedness, mitigationandresponse;

• Information delivered through early warning

systemsisoftentootechnicalanddetailed,lim-itingitsusebydecisionmakers;

• Forecastsareoftenunreliableontheseasonaltimescale and lack specificity, reducing theirusefulnessforagricultureandothersectors;

• Droughtindicesaresometimesinadequatefordetectingtheearlyonsetandendofdrought;

• Drought monitoring systems should be inte-grated, coupling multiple climate, water andsoilparametersandsocio-economicindicatorstofullycharacterizedroughtmagnitude,spatialextentandpotentialimpact;

• Impact assessment methodologies, a criticalpart of drought monitoring and early warningsystems,arenotstandardizedorwidelyavail-able,hinderingimpactestimatesandthecrea-tion of regionally appropriate mitigation andresponseprogrammes;

• Deliverysystemsfordisseminatingdatatousersin a timely manner are not well developed,limitingtheirusefulnessfordecisionsupport.

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IntegRateD DRoUght monItoRIng anD DelIveRy: the Way FoRWaRDAcomprehensiveandintegratedapproachisrequiredto monitor drought more effectively and provideearlywarning.Thecollectionofclimaticandhydro-logicdataisfragmentedbetweenmanyagenciesorministries in most countries. Often these data arenot reported in a timely fashion. Automating thedata collection process can substantially improvethetimelinessandreliabilityofdroughtmonitoringandearlywarningsystems.

The analysis of climate and water data is mosteffective when it is coordinated under a singleauthority. This authority could be an agency orministryoraninter-agencyauthorityandwouldberesponsibleforanalysingdataandproducingusefulendproductsordecision-supporttoolsfordeliveryto end users. Stakeholders must be involved fromtheearlystagesofproductdevelopment toensurethat the information will serve their varied timingandcontentneeds.Adeliverysystemshouldreflecttheneedsofthisdiverseclientele.TheInternetisthemostcost-effectiveway todeliver information,butit is inappropriate inmanysettings.Acombinationof Internet, extension, print and electronic mediadeliverymayberequiredinmanyinstances.

Todate,monitoringandearlywarningsystemshavebeenbasedonasingle indicatororclimatic index.Recent efforts to improve drought monitoring andearlywarningintheUnitedStatesandothercoun-tries have provided new early warning and deci-sion-supporttoolsandmethodologiesinsupportofdroughtpreparednessplanningandpolicydevelop-ment.Thelessonslearnedcanbehelpfulmodelsforother countries to follow as they try to reduce theimpacts of future droughts. An effective monitor-ing,earlywarninganddeliverysystemcontinuouslytrackskeydroughtandwatersupplyindicatorsandclimate-basedindicesanddeliversthisinformationtodecisionmakers.Thisallowsfortheearlydetec-tionofdrought conditionsand timely triggeringofmitigationandemergencyresponsemeasures, themainingredientsofadroughtpreparednessplan.

Untilrecently,acomprehensive,integrateddroughtmonitoring, early warning and delivery systemdid not exist in the United States. Between 1996and 2006, severe droughts have been widespreadin their occurrence and have affected most of thecountry,reinforcingtheneedforamorehighlyinte-gratedmonitoringandearlywarningsystem.Duringthisperiod,many regionshavebeenaffectedover

several consecutive years and on more than oneoccasion. Some regions of the country have experi-encedasmanyasfivetosevenconsecutiveyearsofdrought. These drought events have highlighted thedeficiencies of the nation’s drought monitoringeffortsand theneed todevelopamorecoordinatedapproachthatwouldmakeoptimumuseoftheInternetfor data sharing and analysis, communication andproduct delivery. In 1999 the National Oceanic andAtmosphericAdministration(NOAA),theUnitedStatesDepartment of Agriculture (USDA) and the NationalDrought Mitigation Center (NDMC) at the UniversityofNebraska–Lincolnformedapartnershipaimedatimprovingthecoordinationanddevelopmentofnewdroughtmonitoringtools.TheUnitedStatesDroughtMonitor(USDM)becameanoperationalproducton18August1999.USDMismaintainedontheNDMCwebsite (http://www.drought.unl.edu/index.htm),whichhasbecomeaweb-basedportal fordroughtandwatersupplymonitoring(Figure6).

USDM successfully integrates information frommultiple parameters—climate indices and indica-tors—andsourcestoassesstheseverityandspatialextentofdrought intheUnitedStatesonaweeklybasis.Itisablendofobjectiveanalysisandsubjec-tiveinterpretation.Thismapproducthasbeenwide-lyacceptedandisusedbyadiversesetofuserstotrackdroughtconditionsacrossthecountry.Itisalsoused for policy decisions on eligibility for droughtassistance.USDMrepresentsaweeklysnapshotofcurrentdroughtconditions.Itisnotintendedtobeaforecast.Thisassessmentincludesthe50USstates,Pacific possessions and Puerto Rico. The product

Figure 6. US Drought Monitor website. (Source: National Drought Mitigation Center, University of Nebraska–Lincoln, USA,http://www.drought.unl.edu/dm)

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consistsofacolourmap,showingwhichpartsoftheUnitedStatesaresufferingfromvariousdegreesofdrought,andaccompanyingtext.Thetextdescribesthe drought’s present impacts, future threats andprospectsforimprovement.USDMisbyfarthemostuser friendly national drought monitoring productavailableintheUnitedStatestoday.TheInternetiscurrentlytheprimarydistributionvehicle,althoughthemapalsoappearsinlocalandnationalnewspa-persandon television.Figure7 illustrates thepat-ternofdroughtconditionsacrosstheUnitedStatesfrom2002to2005.Asingleweeklymapillustratesthe drought pattern in each year. All USDM maps

since1999arearchivedonthewebsiteandavailabletousersforcomparison.

Sincenosingledefinitionofdroughtisappropriateinallsituations,agriculturalandwaterplannersandothersmustrelyonavarietyofdataorindicesthatare expressed in map or graphic form. The USDMauthors rely on several key indicators and indices,suchas thePalmerDroughtSeverity Index (PDSI),the Standardized Precipitation Index, stream flow,vegetationhealth,soilmoistureandimpacts.Ancil-lary indicators such as the Keetch-Byram DroughtIndex,reservoirlevels,SurfaceWaterSupplyIndex,

Figure 7. Spatial extent and severity of drought conditions in the United States, 2002 to 2005, as per the US Drought Monitor. (Source: http://www.drought.unl.edu/dm)

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riverbasinsnowwaterequivalent,andpastureandrange conditions from different agencies are inte-gratedtocreatethefinalmap.Electronicdistributionofearlydraftsofthemaptofieldexpertsthroughoutthecountryprovidesexcellentgroundtruthforthepatterns and severity of drought illustrated on themapeachweek.

USDMclassifiesdroughtsonascalefromonetofour(D1–D4),withD4reflectinganexceptionaldroughteventsuchasa1in50-yearevent.Afifthcategory,D0, indicates an abnormally dry area. The USDMmap and narrative identify general drought areas,labelling droughts by intensity from least to mostintense.D0areasareeitherheadingintodroughtorrecovering from drought but still experiencing lin-geringimpacts.

USDM also shows which sectors are presently ex-periencing direct and indirect impacts, using thelabels A (agriculture: crops, livestock, pasture andgrasslands), and H (hydrological) and/or W (watersupplies).Forexample,anareashadedandlabelledasD2(A)isingeneralexperiencingseveredroughtconditions thatareaffecting theagriculturalsector

moresignificantlythanthewatersupplysector.Themapauthorsarecarefulnottobringanareaintoorout of drought too quickly, recognizing the slow-onsetcharacteristicsofdrought, the longrecoveryprocessandthepotentialforlingeringimpacts.

The methodology associated with USDM has nowbeenappliedtotheproductionoftheNorthAmericanDrought Monitor (NADM), a collaborative projectbetween the United States, Mexico and Canada.Thepartnershipbeganin2002inanattempttomapdrought severity and spatial patterns across theNorth American continent. Figure 8 illustrates theNADM for May 2006. Multiple indices and indica-torsareusedtomapdroughtconditions,similartotheprocedureusedtogeneratetheUSDM.Respon-sibility for this product is shared between NOAA’sNational Climatic Data Center, the US DepartmentofAgricultureand theNationalDroughtMitigationCenterattheUniversityofNebraska–LincolnintheUnited States; the National Water Commission inMexico; and Environment Canada and AgricultureandAgri-FoodCanada.Thisproductispreparedonamonthlybasisandisanexcellentexampleofinter-nationaldroughtmonitoringcooperation.

Figure 8. North American Drought Monitor, May 2006. (Source: North American Drought Monitor, http://www.ncdc.noaa.gov/oa/climate/monitoring/drought/nadm/index.html)

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Figure 8. North American Drought Monitor, May 2006. (Source: North American Drought Monitor, http://www.ncdc.noaa.gov/oa/climate/monitoring/drought/nadm/index.html)

DRoUght monItoRIng aCtIvItIes: Case stUDIesConsiderable progress is being made in droughtmonitoring and early warning systems in manycountries. The increased emphasis on improvingthesesystemsislargelytheresultofthemountingimpacts of drought, reflecting greater societal vul-nerability.Heightenedmonitoringcapability,includ-ing the expansion of automated weather stationnetworksandsatellitesandtheInternetarecontrib-utingtosuchimprovements.TheInternetallowsforimprovedaccesstocriticaldataandinformationtoassist inclimateanddroughtassessmentsandthedeliveryofthisinformationthroughawiderangeoftoolsordecision-supportproductstousersinmanysectors.Afewexamplesfromvariouscountriesare

includedtoillustratesomeoftheapproachesbeingtakenindrought-proneregions.

ChIna

The authority that monitors drought developmentinChina is theBeijingClimateCenter (BCC)of theChinaMeteorologicalAdministration(CMA).BCChasusedtheStandardizedPrecipitationIndexsince1995tomonitordroughtoccurrenceanddevelopmentinChinaona10-daybasis.ThemonitoringresultsarepublishedintheChinaDroughtMonitoringBulletinissuedbyBCC.Between1995and1999,aChinese

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droughtmonitoringandearlywarningsystemwasdeveloped and put into operation on a daily basisin1999.Thissystemprovidesaccurateinformationon drought to various related governmental agen-cies and to the general public, which helps in thedevelopmentofmeasurestomitigatetheimpactsofdrought.ThecoreofthesystemisaComprehensive

Index(CI)fordroughtmonitoringdevelopedbyBCCasaresultofitslongexperienceindroughtmonitor-ingandimpactassessment.

CIisafunctionofthelast30-dayand90-daySPIandthe corresponding potential evapotranspiration.Based on CI and soil moisture monitoring froman agricultural meteorological station networkand remote-sensing-basedmonitoring fromCMA’sNationalSatelliteMeteorologicalCenter,anumberof drought monitoring products have beingproduced:

• BulletinofChinaDroughtMonitoring,whichtar-getsgovernmentalagenciesandispublishedatvaryingintervals;

• Adroughtmonitoringand impactassessmentbriefing,broadcastonCCTVeveryWednesdaysince2004;

• Daily drought monitoring maps, which havebeen available on the BCC homepage sinceFebruary2003(http://www.bcc.cma.gov.cn/en).

Figures 9 to 11 provide examples of drought moni-toring products such as drought monitoring maps,soilmoistureassessmentandremote-sensing-basedproducts.SpringdroughtinNingxiaprovincein2006hadasignificantimpactonthewinterwheatcrop.

Figure 9. Drought monitoring for China, 9 June 2006; the colour scale from eggshell (in the middle) to red indicates increasing drought severity. (Source: China Meteorological Administration)

Figure 10. Soil moisture monitoring of the top 20 cm of soil from 21 to 31 May 2006. The higher the values, the wetter the soil. (Source: China Meteorological Administration)

Figure 11. Remote-sensing-based drought monitoring for 1 to 8 June 2006. The colour scale on the left from blue to brown indicates the degree of drought severity. (Source: China Meteorological Administration)

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IGaD ClImaTe PreDICTIon anD aPPlICaTIons CenTre (ICPaC)

The Greater Horn of Africa, like many parts of thetropics, isprone toextremeclimateevents suchasdroughts and floods. In an effort to minimize thenegative impacts of extreme climate events, WMOand the United Nations Development Programmeestablished theregionalDroughtMonitoringCentre(DMC)inNairobiandasub-centreinHararein1989covering 24 countries in the eastern and southernAfricansubregion.In2003,DMCNairobibecameaspe-cializedinstitutionoftheIntergovernmentalAuthorityonDevelopment(IGAD)andwasrenamedtheIGADClimatePredictionandApplicationsCentre (ICPAC).The participating countries of ICPAC are Burundi,Djibouti, Eritrea, Ethiopia, Kenya, Rwanda, Somalia,Sudan,UgandaandUnitedRepublicofTanzania.TheCentreisresponsibleforclimatemonitoring,predic-tion,earlywarningandapplicationsforthereductionofclimate-relatedrisksintheGreaterHornofAfrica.

ICPAC’smainobjectiveistocontributetoclimatemoni-toring and prediction services for early warning andmitigationof theadverse impactsof extremeclimateeventsonvarioussocio-economicsectorsintheregion,suchasagriculturalproductionandfoodsecurity,waterresources,energyandhealth.Theearlywarningprod-uctsenableuserstoputmechanismsinplaceforcopingwithextremeclimate-andweather-relatedrisksintheGreater Horn of Africa. The Centre also promotescapacity-buildingforbothclimatescientistsandusers.

ICPACprovidesregularregionalclimateadvisories,including10-day,monthlyandseasonalclimatebul-letinsaswellastimelyearlywarninginformationonevolvingclimateextremesandassociatedimpacts.

Regional Climate Outlook Forums are also beingheldbeforetheonsetofthemajorrainfallseasonstoprovideconsensusclimateoutlooksandtodevelopmitigationstrategies.Belowaresomeoftheactivi-tiesundertakenbyICPAC:

• Development and archiving of regional andnationalquality-controlledclimatedatabanks;

• Data processing, including development ofbasicclimatologicalstatistics;

• Timelyacquisitionofnearreal-timeclimateandremotelysenseddata;

• Monitoring space-time evolutions of weatherandclimateextremesovertheregion;

• Generationofclimatepredictionandearlywarn-ingproducts;

• Delineation of risk zones of extreme climate-relatedevents;

• Timelydisseminationofearlywarningproducts;

• Conducting capacity-building activities in thegenerationandapplicationofclimateproducts;

• OrganizationofclimateoutlookforumsforthecountriesintheGreaterHornofAfrica;

• Enhancementofinteractionswithusersthroughuserworkshopsandpilotapplicationprojects;

• Climate change monitoring, detection andattribution.

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Figures 12 to 14 illustrate a range of climate- anddrought-relatedproductsproducedbyICPAC(http://www.icpac.net). The products depict cumulativerainfall deviations from the mean for Marsabit,

Kenya;a regionalclimateoutlookmap;andamapillustrating the food security outlook for the coun-triesintheGreaterHornofAfrica,respectively.

Mean

2005/2006

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Figure 12. Examples of cumulative decadal rainfall over parts of Kenya from June 2005 to early April 2006. (Source: ICPAC)

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DecadsJUN1 JUN3 JUL2 AUG1 AUG3 SEP2 OCT1 OCT3 NOV2 DEC1 DEC3 JAN2 FEB1 FEB3 MAR2 APR1 APR3 MAY2

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Figure 13. Climate outlook for the Greater Horn of Africa, March to May 2006. (Source: ICPAC)

Figure 14. Food security outlook for the Greater Horn of Africa, September to December 2005. (ICPAC)

A Above normalN NormalB Below normal

Percentage probability

Extremely food insecure

Highly food insecure

Moderately food insecure

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souTh aFrICa

Droughtisanormal,recurrentfeatureoftheSouthAfricanclimate.Droughtshaveinthepastresultedin significant economic, environmental and socialimpactsandhighlightthecountry’scontinuingvul-nerabilitywith regard to thisnaturalphenomenon.During low rainfall periods, policymakers, agricul-turalists, businesses and the general public oftenrequireadditional rainfalldata fordecision-makingandplanning.

InresponsetorecurringdroughtinSouthAfrica,theSouthAfricanWeatherService(SAWS)establishedadroughtmonitoringdeskwhereinformationregard-ingobservedrainfallandlong-rangeforecastscould

be presented in one place for easy access. It alsoprovides an opportunity for people to compare thecurrent year’s rainfall with amounts from previousdryperiodstoassistthemintheirdecisionandplan-ningpractices.

Neither the percentage of normal nor the decile-based drought indices can assist decision makerswith the assessment of the cumulative effect ofreduced rainfallovervarious timeperiods.Neitherof these indicescandescribethemagnitudeof thedrought compared with other drought events. SPIcan alleviate both of these principal shortcomingswhile at the same time being less complex to cal-culatethansomeoftheotherdrought indicesnowinuseattheSouthAfricanWeatherService.SPIisanindexbasedontheprobabilityofrainfallforanytimescale;itcanbeusefulinassessingtheseverityof drought and can be calculated at various time-scalesthatreflecttheimpactofthedroughtontheavailabilityofwaterresources.TheSPIcalculationisbasedon thedistributionof rainfallover long timeperiods, preferably more than 50 years. The long-termrainfallrecordisfittoaprobabilitydistribution,which is thennormalized so that themeanSPI foranyplaceandtimeperiodiszero.SPIvaluesabovezero indicate wetter periods and values less thanzeroindicatedrierperiods.

On23November2005,theDepartmentofAgricultureissuedareportindicatingthateightofSouthAfrica’snine provinces were being severely affected bydrought,theexceptionbeingthedenselypopulatedGautengprovince,aminorplayerinagriculture.Atthattime,thenorthernmostprovince,Limpopo,hadhad districts flagged as disaster areas since 2003and2004,with27of its37municipalitiesaffected.Thedamsoftheprovincewereattheirlowestlevels,anaverageof36percentofcapacity,comparedwith64percentthepreviousyear.

TheseverityofthesituationwasclearlyreflectedinthedifferenttimescalesoftheSPImapsontheSAWSDrought Monitoring Page (http://www.weathersa.co.za/DroughtMonitor/DMDesk.jsp),updatedat thebeginningofDecember2005.Averydrywinterandthe lack of good spring rains exacerbated the dryconditionsinsomeareas.

ThemainrainfallfeaturesinNovember2005werenearnormalrainfallovermostofSouthAfrica,butwetcondi-tionsoverpartsoftheWesternCape,theEasternCape,©

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KwaZulu-Natal and Mpumalanga (Figure 15, top).Accordingtoavailabledata,nopartof thecountryreceived rainfall much below the normal value forthemonth.

FromSeptembertoNovember2005,therewassomealleviation of the dry conditions in the northernprovincesaswellasthefarsouth(Figure15,middle).However,somedrynessremainedinthenorthernmostprovince,Limpopo.

The rainfall for the six-monthperiod, as shownbytheSPImapforJunetoNovember2005,showsnearnormal conditions over the largest part of SouthAfrica,butmoderatetoverydryconditionsinseveralareas, most notably in the Southern Cape, southernpartsoftheNorthernCapeandthefarnorth(Figure15,bottom).EventhoughsomepartsofLimpoporeceivedgood rains during November 2005, there was still astrainonwaterresources.

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ThePalmerDroughtSeverityIndexisusedtochar-acterize drought in Portugal. This index has beenadaptedandcalibratedtothespecificclimaticcon-ditionsofmainlandPortugal.ThePDSIperformsaparameterizedcomputationofthesoilwaterbalanceand compares the estimated soil moisture contentwithitsclimatologicalmean.

Evolving drought patterns are presented in monthlyPDSImapsthatshowthespatialdistributionofdroughtinPortugal.Thesemapsareused tomonitor spatialand temporal variations in drought across mainlandPortugal,whichishelpfulindelineatingpotentialdis-asterareasforagricultureandothersectors,allowingforimprovedon-farmdecisionstoreduceimpacts.

The2004–2005hydrologicalyearbeganwithfavour-ableamountsofprecipitationinOctober,except inthe southern region, where it was dry to normal.The months that followed were dry to extremelydry,resulting inthedevelopmentofavery intensedrought. Figure 16 and Table 1 show the monthlyPDSI variations expressed as percentages of areaaffected in mainland Portugal. In addition, theyrevealadeteriorationofdroughtconditionsduringthewintermonths,withsomeattenuationinMarchbecause of the occurrence of precipitation in thecountry’snorthernandinnerregions.DuringJune,

Figure 15. Standardized Precipitation Index (SPI) for South Africa, November 2005 (top); September to November 2005 (middle); June to November 2005 (bottom). (Source: South African Weather Service)

Extreme drought

Severe drought

Moderate drought

Mild drought

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Palmer Drought Severity Index (PDSI)

area affected by drought in 2004–2005 (per cent) 2004 2005

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moderately wet 5 0 0 0 0 0 0 0 0 0 0 0 0 0 0

slightly wet 47 0 0 0 0 0 0 0 0 0 0 0 6 5 5

normal 22 1 0 0 0 0 0 0 0 0 0 0 6 12 11

mild drought 20 47 30 0 0 26 15 4 0 0 0 0 52 81 83

moderate drought 5 47 48 25 23 22 22 28 3 0 0 3 36 2 1

severe drought 1 5 20 53 44 28 20 20 33 27 29 36 0 0 0

extreme drought 0 0 2 22 33 24 43 48 64 73 71 61 0 0 0

July and August, the drought situation worsened.Thesemonthsnormallycontribute,onaverage,only6percentoftheannualprecipitation.Precipitation

Table 1. Percentage of mainland Portugal affected by drought in 2004 and 2005. (Source: Instituto de Meteorologia, I.P., Portugal)

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Figure 16. Percentage of Portugal affected by drought, October 2004 to December 2005. (Source: Instituto de Meteorologia, I.P., Portugal)

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received during the first 15 days of Septemberlessenedtheseverityofdroughtinthenorthernandcentralregions.

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Period

affected population

Withsupplemented

water

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insupply

1st half april 14175 213

1st half may 8395 2635

1st half June 26500 26781

2nd half June 23440 25217

1st half July 26004 26350

2nd half July 54831 53312

1st half august 48500 60061

2nd half august 94372 100500

1st half september 73097 66127

2nd half september 69588 39429

2nd half october 48883 30083

2nd half november 11921 13354

2nd half December 10238 13445

maximum 94 372 100 500

Table 2. Number of people affected directly or indirectly by drought in Portugal, 2005. (Source: Instituto de Meteorologia, I.P., Portugal)

Figure 18. Number of municipalities with supplemented water (blue) or cuts/reduction in household supply (red). (Source: Instituto de Meteorologia, I.P., Portugal)

Figure 17. Spatial representation of consecutive months in severe and extreme drought situations in Portugal, October 2004 to September 2005. (Source: Instituto de Meteorologia, I.P., Portugal)

Figure17showsthenumberofconsecutivemonthsinsevereandextremedrought through theendofSeptember2005.

Theimpactsofthedroughtonagriculture,energyandurbanwatersupplyweresignificant.Figure18illus-tratestheseimpactsontheurbanwatersupply.ThenumberofpeopleaffectedbydroughtfromApriltoDecember2005,asshowninTable2,isalsoagoodindicatorofthewidespreadimpactsassociatedwiththisdroughtevent.

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Figure 19. The extent of serious or worst rainfall deficiencies at the peak of the last El Niño-related drought in 2002 and 2003. (Source: Australian Bureau of Meteorology)

thepeakof the lastElNiño-relateddroughtduring2002–2003.

Althoughanextendedperiodofrainfalldeficiencyinanyareaisvirtuallyaprerequisitefordrought,thereiswidespreadrecognitioninAustraliathattheformaldeclaration of a drought is a more complex issue.It involves consideration not only of the rainwatersupplybutalsothesubsequentusesforthatrainfallonceithasfallenontofarmlands,runsintostreamsandrivers,isstoredindams,isusedtodrivehydro-electricpowerstationsandissuppliedtocitiesandtownsacrossthenation.Furthermore,giventhesizeandgeographicallocationofAustralia,itisunusualfortherenottobeoneormoreareasofvaryingsizeat any given time experiencing serious or severerainfalldeficiencies.Whetherornotsuchareasaredeclared drought stricken and then whether thedroughtisofsufficientintensity,durationandextentforthoseaffectedtobeeligibleforgovernmentreliefinvolvesacomplexseriesofassessmentsbynationalandstateauthorities.

The recognition that drought is a “normal” featureofAustralia’snatural,economic,andsocialenviron-mentshasledthenationalandstategovernmentstoagreethatclimate-sensitiveindustriesandenterpris-esmustlearntomanagedroughtrisk,alongwithalltheotherattendantandongoingrisksthattheyface.Nonetheless, the governments do recognize that,fromtimetotime,somedroughtsbecomesosevere,chronic or widespread that there is a need to offersupporttothoseworstaffected.SuchoccurrencesinAustraliaarecalled“exceptionalcircumstances”.

In 2002–2003 Australia experienced an especiallysevere and widespread drought, accompanied byrecordhightemperaturesinmanyregions.Atthepeakofthedrought,57percentoftheAustralianmainlandhadregistered10monthsormoreofserioustoseverecumulativerainfalldeficits,and90percent,belowthemedian(Figure19).Withtheexperienceofthedroughtfreshinmind,andalsorecognizingtheneedforamoreobjective, fair and transparent process underpinningthe declaration of exceptional circumstances, thePrimary Industries Ministerial Council of Australia in2005commissionedtheestablishmentoftheNationalAgriculturalMonitoringSystem(NAMS).

NAMSwasdevelopedoverthenext12monthsunderthe leadership of the Bureau of Rural Sciences incollaboration with the Bureau of Meteorology and

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TheislandcontinentofAustraliastraddlesthesouth-ern subtropical zone, with its mainland extendingfromaround11ºSacross the“TopEnd” to39ºS inthesouth-east.Thenorthernregionsareseasonallytropicalwhiletheeastern,south-easternandsouth-western coastsand near inland regions aregener-allywellwateredbutpronetohighinterannualandseasonalvariabilityintheirrainfall.Themoreinlandregions range from arid to semi-arid. Droughts,sometimes covering vast tracts of the continent,arearecurringfeatureofAustralia’sclimate.Manyof the more severe and widespread droughts areassociatedwithElNiñoevents.

Given that rainfall is by far the dominant factordeterminingthesuccessorfailureofthegrowingseasonacrossAustralia,droughtmonitoringhasformany years been synonymous with the monitor-ingofrainfalldeficiencies.TheAustralianBureauofMeteorology’sDroughtWatchService,inoperationsince1965,hasusedaccumulatedrainfallpercentilesoversuccessivemonthstoidentifyregionsofrainfalldeficitandexcess.Areaswithrainfallaccumulationsbelowthe10thor5thpercentileforperiodsofthreemonthsormoreare referred toasbeingseriouslyorseverelyindeficit,respectively.Figure19showstheextentofseriousorworserainfalldeficienciesat

rainfall deficiencies: 10 months1 april 2002 to 31 January 2003

DistributionbasedongriddeddataProductoftheNationalClimateCentre

Serious deficiency

Severe deficiency

Lowest on record

Rainfall percentile ranking

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Droughtaffectsmorepeoplethananyothernaturaldisasterandresults inseriouseconomic,socialandenvironmental costs. The development of effectivedrought monitoring, early warning and deliverysystems has been a significant challenge becauseof theuniquecharacteristicsofdrought.Significantstrideshavebeenmadeinrecentyearstoimprovetheeffectivenessof thesesystems.With the increasingfrequencyandseverityofdroughtinmanyregionsoftheworldandincreasedsocietalvulnerability,moreemphasisisnowbeingplacedonthedevelopmentofdroughtpreparednessplansthatareproactiveratherthanreactiveandemphasizerisk-basedmanagementmeasures. Improved drought monitoring is a keycomponent of a drought preparedness plan and anational drought policy. Early warning systems canprovide decision makers with timely and reliableaccesstoinformationonwhichmitigationmeasurescanbebased.Therearemanychallengestoimprov-ingthesesystems,butacomprehensive, integratedapproachtoclimateandwatersupplymonitoringisprovingtobesuccessfulinmanycountries.

theCommonwealthScientificandIndustrialResearchOrganization(CSIRO).Theoutcomeisafreelyacces-siblewebsite containingcurrentmaps,graphsandreports on the state of the climate system acrossAustralia,and informationonproduction formajordrylandbroad-acreagriculturalsystems.Aswellascurrentdata,NAMSalsocontainshistoricalinforma-tiononmeasuredandmodelledproduction,finan-cialimpacts,remote-sensingindicesandclimate.

TheNAMSwebsitepresentsinformationonscreenandintheformofprintablereports,providinggen-eral background, current climatic conditions andproduction and resource statistics for regions thatcanbespecifiedby theuser.Regionscanrange insizefromtheentirecountrytoindividuallocalgov-ernmentareasorthestatisticallocalareasusedforsummarizingAustraliancensusdata.

Collectively, NAMS information shows the statusof current conditions for the major agriculturalproduction systems and production prospects forthe upcoming growing season. NAMS is initiallydirectedatmonitoringandsupplyingdata fordry-landbroad-acreindustries,withplanstoextendthesystem to cover the extensive irrigated regions ofAustraliaandalsoformoreintensiveindustriessuchashorticulture.

AsNAMSdrawsonacommoninformationdatabasefor the entire country, it will facilitate a more con-sistentapproachtothedroughtdeclarationprocessthroughtheuseofthefollowing:

• Acommontemplateandlanguagefordescrib-ingdroughtintermsofprobabilities;

• Acommonsetofdeclarationcriteria;

• A common process for the subjective “on-ground”assessmentofdroughtimpacts.

The NAMS website is at http://www.nams.gov.au.DetailedinformationonAustralia’snationaldroughtassistance measures, including the declaration ofexceptional circumstances, can be found at http://www.daff.gov.au/droughtassist, while informationontherainfalldeficiencymonitoringsystemcanbefound at http://www.bom.gov.au/climate/drought/drought.shtml.

ConClUsIon