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WATER POVERTY INDEX IN SUBTROPICAL ZONES: THE CASE OF HUASTECA POTOSINA, MEXICO
Briseida LÓPEZ ÁLVAREZ1*, Germán SANTACRUZ DE LEÓN1, José Alfredo RAMOS LEAL2 and Janete MORÁN RAMÍREZ2
1 El Colegio de San Luis, A. C. (COLSAN). Parque de Macul 155, Frac. Colinas del Parque, San Luis Potosí, S.L.P., C.P. 78299
2InstitutoPotosinodeInvestigaciónCientíficoyTecnológico(IPICYT).CaminoaLaPresadeSanJosé2005,Col. Lomas 4ta Sección, San Luis Potosí, S.L.P., C. P. 78216
* Autor para correspondencia: [email protected]
(Recibido mayo 2014; aceptado febrero 2015)
Keywords:wateraccess,waterquality,wateravailability,humandevelopment,hydricresources,VallesRiver
ABSTRACT
Toolsareneededinordertoevaluateanintegratedwaterresourcemanagement,andtoencouragethemanagementandcoordinatedusageofwaterresourcesalongwiththeenvironmentalandsocioeconomicfactors.OneofthosetoolsistheWaterPovertyIndex(WPI),whichenablestheevaluationofwaterpovertyintermsofthephysicalandsocioeconomicfactorsrelatedtowateravailability.TheWPI,ascalculatedinthisstudy,isderivedfromtheweightedsumofsixkeycomponents–resources,access,usage,capacity,qualityandenvironment–onascaleof0to100.TheobjectiveofthisworkwastocalculatetheRíoVallesBasinWPIfor2010.Thisregionisasemi-tropicalareawithabundantwaterresources,suchaslargesprings.Itsannualmeanprecipita-tionis1100mm.IntheRíoVallesBasin,thevolumeofsurfacewaterusedperyearis81.33 Mm3,whichrepresents91%ofthetotalresource.Thevolumeofgroundwaterusedperyearis8.17Mm3,representingtheremaining9%.Usually45Mm3/yearisstoredinLaLajilladam.Thesedataindicatethatsurfacewateristhemainsourceofsupplyforusessuchasagriculture,whichistheactivitywiththelargestwaterdemand.AWPIscoreof59wasobtainedfortheRíoVallesBasin.
Palabrasclave: accesoalagua,calidaddeagua,disponibilidaddeagua,desarrollohumano,recursoshídricos,Río Valles
RESUMEN
Paraevaluarlagestiónintegradadelosrecursoshídricossenecesitanherramientasparafo-mentarsuadministraciónyusocoordinadoconelambienteylosfactoressocioeconómicos.UnadeestasherramientaseselÍndicedePobrezadelAgua(IPA),quepermiteevaluarlapobrezadelaguaentérminosdelosfactoresfísicosysocioeconómicosrelacionadosconsu disponibilidad. El IPA, como se calculó en este estudio, se deriva de la suma ponderada deseiscomponentesclave:elacceso,eluso,lacapacidad,lacalidadyelambiente,enunaescalade0a100.ElobjetivodeestetrabajofuecalcularelIPAdelacuencadelRíoVallesparaelaño2010.Estaregiónessemitropical,conabundantesrecursoshídricos,
Rev.Int.Contam.Ambie.31(2)173-184,2015
B. López Álvarez et al.174
comograndesmanantialesyunaprecipitaciónmediaanualde1100mm.EnlacuencadelRíoValleselvolumendeaguasuperficialutilizadaesde81.33Mm3/año, lo que representa el91%deltotaldelrecursoutilizado.Elvolumendeaguasubterráneautilizadaesde 8.17 Mm3/año,loquerepresentael9%restante,normalmentesealmacenan45Mm3/año enlapresadeLaLajilla.Estosdatosindicanqueelaguasuperficialeslaprincipalfuentedeabastoparadiversosusoscomolaagriculturaqueeslaactividadconlamayordemandade agua. El IPA que se obtuvo para la cuenca del Río Valles fue de 59 puntos.
INTRODUCTION
IntegratedWaterResourcesManagement(IWRM)isaprocesstofosterthemanagementandcoordinatedusageofwaterresources,aswellastheenvironmen-tal and socioeconomic factors in order to maximize socialandeconomicbenefitsinanequitablemannerwithout compromising the sustainability of vitalecosystems (IWRM-UNESCO2009).To evaluateIWRM,toolsareneededandthoseshouldtakeintoaccount these elements.Oneof those tools is theWaterPovertyIndex(WPI),whichmakesitpossibletoevaluatewaterpoverty indifferentstudyscales–countries, regions or communities– taking intoaccountphysicalandsocioeconomicfactorsrelatedtotheavailabilityofwater(Lawrenceet al.2002).
TheWPIisevaluatedbasedonfivecomponents:water resources, access, capacity, usage and envi-ronment.These components enable establishingconnectionsbetweenpoverty,socialmarginalization,environmentalintegrity,wateravailabilityandhealth.TheWPIhasbeenappliedataninternationallevelbyLawrenceet al.(2002)andrecentlyinasemi-aridregionsuchastheSanLuisPotosíValley(SLPV)byLópez-Álvarezet al.(2013).
TheobjectiveofthisworkwastocalculatetheWPIinasemi-tropicalregionwithabundantwaterresources,specificallyattheRíoVallesBasin(RVB).ThisregionislocatedineasternMexicoonthebound-aryoftheEasternSierraMadre(Fig. 1),inthestatesofTamaulipasandSanLuisPotosí(SLP).Thelatterisfacingseriousproblemsregardingtheavailabilityofwaterresources.ThestudywasconductedinthespecificregionknownasHuastecaPotosinawhererainfallishigherthanthenationalmean(Santacruz2007).In2010theRVBhadapopulationof255452inhabitants(INEGI2010)with91%dependenceonsurfacewater.
TheRVB comprises the following cities andmunicipalities:municipalityofAquismón,CitiesofMaíz,CiudadValles,ElNaranjoandTamasopoinSanLuisPotosíand themunicipalitiesofAntiguoMorelos, Nuevo Morelos, Ocampo and Tula in Ta-maulipas (Fig. 1).
Development of the WPI for Huasteca PotosinaTheWPI is based on the structure andmeth-
odologies proposed byUNESCO in theHumanDevelopment Index as part of theUnitedNationsDevelopmentProgramme(2002).
ThemethodologyproposedbyLawrenceet al. (2002)includesfivekeycomponents.Nevertheless,theapplicationoftheWPItotheRVBincludedwaterquality as anadditional component (Table I) since Mexico’ssurfaceandgroundwaterhaveseriouslevelsofnaturaland/oranthropicpollution,therebylimitingitsuse(Santacruz2007,Carranco-Lozada2013).
Although thismethodology includes six basiccomponents, depending on different scenarios, subcomponents could be also considered. For in-stance,intheResourcecomponentwhereground-waterisincluded,theaquifersinthesystemcouldbethesubcomponents(López-Álvarezet al.2013).In terms of the subcomponents of surfacewaterthesecouldberepresentedbydifferentwaterbodies(reservoirsandrivers)inthestudyarea.Inaddition,fortheQualityoftheresourceboth,groundwaterorsurfacewatersubcomponenthasitsownqual-ityvalue (López-Álvarezet al.2013).RegardingtheUsage component this could be subdividedinto urban, agricultural and industrial usage as subcomponents. Socioeconomic data related to a population can be used as subcomponent of Access andCapacity.ForthecomponentofEnvironment,data such as land use, erosion rate, flood zones,naturalprotectedareas,vegetation types,anden-dangered and protected animal spatial distribution could be used as subcomponents. In general theevaluationofeachcomponentcanbeascomplexastheamountandqualityofinformationavailable.
ThemathematicalstructureonwhichtheWPIisbased is expressed as:
∑∑
=
== N
i Xi
N
i iXii
w
XwWPI
1
1 (1)
whereWPIi istheWaterPovertyIndexforaparticularregion, wXiistheweightedfactorandXiisthevalue
WATER POVERTY INDEX IN SUBTROPICAL ZONES 175
of component i.TheWPIistheresultoftheweightedsumofthecomponents:Resources(R),Access(A),Usage(U),Capacity(C),Environment(E)andWaterQuality(Q).
Equation(1)canalsobeexpressedinafurtherdevelopedform(equation2).Tostandardizethere-sultsandproduceaWPIvaluebetween0and1,thesumneedstobedividedbythesumoftheweights,asshown:
qeucar
qeucari wwwwww
QwEwUwCwAwRwWPI
+++++
+++++= (2)
Formost components aweight analysis is ap-pliedtodefinetheimportanceofeachsubcomponent(Ramos2002).Theweightanalysisisexpressedas(equation 3):
∑ =
= N
i i
iii
WXwXrWx1
* (3)
whereXri and Xwi arethescoresforeachXi compo-nentandtheirtheoreticalweightsandWiisthesumofthetheoreticalweights.
Sinceeachcomponentcanbeformedbymorethanone subcomponent, theweightw applied to eachsubcomponent(Xai)intheWPIstructurecanbe obtained from the values associatedwith thesubcomponents. For example, in the case of theResource component percentages related to themanagementofthedifferentsupplysourcescanbeusedasweights.FortheAccesscomponent,percent-agesofthepopulationwithaccesstodrinkingwaterorwithwatertreatmentsystemsandpercentagesofagriculturallandswithaccesstoirrigationcanbeconsideredasweightsforthesesubcomponents.FortheCapacitycomponentsocioeconomicconditions,populationincomedata,mortalityratesofchildrenunder5yearsofage,theeducationindexandtheGini coefficient can be used asweight elements.Percentageofwaterusedfordomestic,agricultural
102º0'0'' 100º0'0'' 98º0'0'' 92º20'0'' 99º0'0''
92º20'0'' 99º0'0''
102º0'0''
22º0
'0''
24º0
'0''
26º0
'0''
22º0
'0''
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'22
º40'
0''
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'0''
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º40'
0''
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'0''
26º0
'0''
Latit
ude
Nor
th
Latit
ude
Nor
th
Longitude West
Longitude West
Municipal Head
Legend
Perenial streamIntermittent streamLa Lajilla damState dorder
Ciudad VallesAquismónAntiguo Morelos
Ciudad del MaízEl Naranjo
Tula
Nuevo Morelos
TamasopoOcampo
EE.UU.
100º0'0''
Tamaulipas
San Luis Potosí
Gulf of Mexico
Gulf of Mexico
Pacific Ocean
EE.UU.
98º0'0''
El Naranjo
Nuevo Morelos
Ciudad Valles
El S
alto
rive
r
Los
Gat
os ri
ver
Mes
illas
rive
r
Valles river
Fig. 1. LocationoftheRíoVallesBasin
B. López Álvarez et al.176
andindustrialpurposescanbeusedasweightsfortheUsagecomponent.Whereaspercentagesinlandusechangesinnaturalprotectedareascanbecon-sideredweightsforthecomponentofEnvironment.FinallyfortheQualitycomponentthemanagementofdifferentsupplysourcescanbeusedasweightforindicestoevaluatewaterquality.
Foreachcomponent,thesumofthesubcompo-nentsmultipliedbyaweightfactormustequal1.Toobtainthefinalvalue,theWPIneedstobenormal-izedbyweightingoncemorethesubcomponentsandthesumshouldequal1.Theassignedweightsdependon thedegreeof importanceor influenceofeachcomponentineachregion.Theweightwi is assigned to each component (Xi) in theWPIstructure for that region. It isworthmentioningthattheresultscanbeexpressedasascorerangingfrom0to100.
Theresultsforeachcomponentinthismethodol-ogycanbegraphedasapolygonwhoseedgesrep-resent100%ofeachcomponent.Whennormalized,themaximumis1andthecenterofthepolygonis0. TheidealpolygonisthatinwhichalltheWPIcom-ponentshavevaluesof1andformahexagon.Asmorevalueswithlessthan1arepresent,theymovefurtherawayfromthehexagonandformanirregularpolygon.
Resources (R)TheRVBisinHydrologicalRegion26.Ithasan
approximateareaof3216km2 and is divided into four subbasins: “Río Los Gatos”, “Río El Salto”, “Río Mesillas”and“RíoValles”.Itislocatedinthedrain-ageareaoftheEasternSierraMadreasevidencedbythelargespringsfoundintheHuastecaPotosinaregion (Fig. 1).
The climates are sub-humid with medium andhighhumidityandsummerrains,andsemi-hotand sub-humidwith summer rains.The annualmeanprecipitationis1100mm–higherthanthenationalmean of 772mm (Santacruz 2008).The volumeofwaterused in theRVB is81.33Mm3/year forsurfacewater,whichrepresents91%ofthetotalresource used and 8.17 Mm3/yearforgroundwater,representingtheremaining9%.Usually45Mm3/yeararestoredinLaLajilladam.Thesedataindi-cate thatsurfacewater is theprimaryresource inthestudiedbasin.
TheweightsassignedtotheResourcesubcompo-nentswerederivedfromthepercentagesofsurfaceandgroundwatersourcesusedasseeninequation4in the followingmathematical expression (López-Álvarez et al.2013):
AsubAR 09.0sup91.0 += (4)
TABLE I.KEYCOMPONENTSINTHEWATERPOVERTYINDEX(AdaptedfromLawrenceet al.2002)
WaterPovertyIndexComponent
Definition Sub-components
Resource (R) Physicalavailabilityofsurfaceandgroundwater,consideringitsuseandwaterbalance
•Surfacewater•Groundwater•Volume used
Access (A) Levelofaccesstocleanwaterforhumanuse •%ofthepopulationwithaccesstodrink-ingwater
•%ofpopulationwithaccesstowatertreatment.
•%ofagriculturallandwithaccesstoirrigation
Capacity(C) Efficacyofthehumanpopulation’scapacitytomanagewater
•Income•Mortalityrateofchildrenunder5years•Education index•Ginicoefficient
Usage (U) Waysinwhichwaterisusedfordifferentpurposes, including domestic, agricultural and industrial uses
•Domesticwateruse(L/day)•Adjusted%ofwaterusedforagricultureandindustry,basedonthesector’scontri-butiontotheGDP
Environment (A) Evaluationofenvironmentalintegrityrelatedtowater
•Land use•Natural Protected Areas
Waterquality(Q) Evaluationofwaterqualityforhumanuse •Surfaceandgroundwaterqualitydata
WATER POVERTY INDEX IN SUBTROPICAL ZONES 177
( )Vol. annual precipitation
Stored volumeMmAsur 3 = (4.1)
ExtractionExtractionMmAgrn
2Recharg)( 3 −
= (4.2)
Access (A)Seventy-five percent of the population in the
RVBlivesinCiudadValles,ElNaranjoandNuevoMorelos.Thesethreepopulationcenterscontainmostof the drinkingwater (90%coverage) andwatertreatment (30% coverage) services (Fig. 2).Therestofthepopulation(38694inhabitants)livesinsmallanddispersedlocalitieslackingpublicservices(INEGI2010a).
A total of 81.2%of theEconomicallyActivePopulation (EAP)works in the three populationcentersmentioned,performingsecondaryandtertiaryactivities.The remainingpercentageworks in theprimarysector(agricultureandlivestock).Forthissector thereare84405haofagricultural land,12399ofwhichhavesomekindof irrigationsystem(INEGI2007).
TheAccess(A)componentincludesthepercent-age of the populationwith access to pipedwater(Aap)fortheirbasicneeds,thepercentageofwater
thatistreated(At),andtherelationshipofagriculturallandwithandwithoutaccesstoirrigation(Ai).Theexpression(equation5)thatdefinesthiscomponentis(López-Álvarezet al.2013):
iAAAA tap 1.03.06.0 ++= (5)
Thesubcomponentswereweightedusingaweightanalysis(Ramos2002,López-Álvarezet al.2013)whichshowssubcomponentAapasthemostsignifi-cant and Aiastheleastsignificant.
Capacity (C)InMexico, the HumanDevelopment Index
(HDI)isevaluatedatmunicipallevel.AlthoughtheRVBcoversseveralmunicipalities,onlythreehavenotablesocialandeconomicinfluence(Santacruz2007):NuevoMorelos, ElNaranjo andCiudadValles.ThemunicipalityofNuevoMorelos,Tam-aulipas,hadaHDIof0.753 (placing itat35outof 43) in 2005,whichwasbelow the statemean(0.85)forthatyear.ElNaranjoandCiudadValles,inSanLuisPotosí,hadanHDIof0.810(9outof58)and0.838(4outof58),respectively.Ofthesemunicipalities onlyCiudadValleswas above thestatemeanof0.816.
The(C)componentwasevaluatedbasedontheHDI.Itevaluatesthesocioeconomicvariablesthatcanaffectaccesstowaterorreflectaccessaswellasitsthequality.TheGinicoefficientisintroducedtoadjustthecapacitytoaccesscleanwateraccording toameasurementoftheunequaldistributionofin-come(Lawrenceet al.2002).
Thesubcomponentsare:incomeindex(Ii), mor-tality rate for childrenunder 5 years of age (Mi), education index (Ie)andtheGinicoefficient(CG).
Capacityisevaluatedbytheequation6(López-Álvarez et al.2013):
Geii CIMIC 2.02.01.05.0 +++= (6)
Weightswereassignedtothesubcomponentsus-ingaweightanalysis(Ramos2002,López-Álvarezet al.2013),whichindicatesthatsubcomponentIiisthemostsignificant, Ie and CGhavemediumsignificanceand Miistheleastsignificant.
Usage (U)TheRVBpresents biophysical conditions that
favorcertainwateruses.Itssubbasinshaveparticularconditionsthatmakethemmoreor less“suitable”foraspecificuse.Sincethelastdecadesofthe19th centuryandtheearlydecadesofthe20thcentury,the
22º0
'0''
22º2
0'0'
'22
º40'
0''
22º0
'0''
22º2
0'0'
'22
º40'
0''
Latit
ude
Nor
th
Longitude West99º30'0'' 99º15'0'' 99º0'0''
99º30'0'' 99º15'0'' 99º0'0''
Population ≤ than 100 inhabitants
Population ≥ than 100 inhabitants
Population between 100 and 500 inhabitantsPopulation between 500 and 1000 inhabitantsState border
Urban settlement
Perenial streamIntermittent stream
Legend
Fig. 2. DistributionofthehumanpopulationintheRíoVallesBasin
B. López Álvarez et al.178
waterusagehasreflectedtheadvancesintechnologyoftheperiod.Thevolumeofwaterusedandextractedfromdifferentwater bodies, primarily theVallesRiver is 89.85 Mm3/year,accordingtotheComisiónNacional delAgua (NationalWaterCommission,CONAGUA,Spanish acronym) and theRegistroPúblicodeDerechosdelAgua(PublicWaterRightsRecord, REPDA, Spanish acronym). From this 89.85 Mm3/year,89.2%isused inagricultureforirrigatingcrops,suchassugarcane(Saccharum of-ficinarum).Atotalof81.06%ofthevolumeofwaterused in agriculture comes from surface sources and therestfromgroundwater(Fig. 3).
IntheRVB7.53%ofthewatervolumeextractedis for agro-industrial uses and2.43% for public-urban uses.
Thiscomponentincludesthreesubcomponents:waterfordomesticuse(Ud),waterforagro-industrialuse (Ui)andwaterforagriculturaluse(Ua). It is deter-minedfromequation7(López-Álvarezet al.2013):
aid UUUU 9.008.002.0 ++= (7)
Theweight assigned to the subcomponents isbasedonthepercentageofwaterusedintheRVB.
Itisworthmentioningthatfordomesticuse,theamountofdrinkingwaterusedperinhabitantperdaymustbetakenintoaccount.FortheRVBtheaver-ageamountofdrinkingwaterusedis200L/hab/day(PHE2000).
Todetermineagro-industrialwaterusage,arela-tionshipwasestablishedbetweentheproportionofthegrossdomesticproduct (GDP)generatedfrom
thisactivityandtheamountofwaterused.Thisre-lationshipwasappliedtowaterforagriculturaluseandprovides an approximatemeasurement of theefficiencyofwater usage (Lawrenceet al. 2002).Agro-industryandagricultureintheRVBrepresents 4 and1%of the stateGDP, respectively (INEGI2010b).
Environment (E)RainfedandirrigatedagricultureintheRVBare
basedonsugarcanecrops.Theincreasedareaplantedwiththiscrophadalsoledtoagrowingdemandforirrigationwater andhas expanded the agriculturalboundariesintoareasthatformerlycontainedtropi-cal forests.
Thisexpansionoftheagriculturalboundarieswasevaluatedwithinformationrelatedtolanduseandvegetationtypefromtheyears1970to2000(Table II). Rainfedagricultureexpandedduringthestudyfrom313.2km2to717.79km2.Whilethisactivityissig-nificantinallfoursubbasins,rainfedagriculturegrew177.66km2inthe“RíoLosGatos”and92.55km2 inthe“RíoValles”subbasins(Fig. 4).
Theincreaseinrainfedagriculturalareamostlycoincideswiththedecreaseinthelowlanddeciduousandsub-deciduouswoodlandduringthestudy.Over24yearstheareaofthe“RíoLosGatos”subbasin,with lowlanddeciduousandsub-deciduouswood-land,decreasedfrom546.63km2 to351.00km2.Thatisareductionof195.63km2(35.78%).Thesamesituationoccurredinthe“RíoMesillas”subbasinthatlost173.97km2ofdeciduouswoodlandduringthesameperiodoftime(Santacruz2007).
Total volumeSurface waterGroundwater
Agriculture IndustryWater uses
Urban-Public Others
80
70
60
50
40
30
20
10
Volu
me
(Mm
3 /yea
r)
9089.5
81.33
8.17
807060504030
2010
Volu
me
(Mm
3 /yea
r)
Total volume used in the
basin Rio Valles
Surfacewater
Groundwater
Source type
Fig. 3. Volumeofwaterusedandextractedfromdifferentwaterbodies,mainlyintheVallesRiver.Poner“mm”enminúsculalasdosenambasgráficas
WATER POVERTY INDEX IN SUBTROPICAL ZONES 179
TABLE II.RATEOFCHANGE(%ANDkm2)INVEGETATIONTYPEANDLANDUSEINTHERÍOVALLESBASINBETWEEN1976AND2000
Land use and vegetation
Entire basin
1976 2000Change
(km2) (%)
Irrigated agriculture 82.32 135.19 52.86 64.22Rainfed agriculture 313.02 717.79 404.78 129.31Introduced and cultivated pastures 372.2 481.86 109.65 29.46Junglemediumevergreensub-evergreen 48.4 32.51 -15.88 –32.83Lowlanddeciduousandsub-deciduouswoodland 1857.5 1329.11 –528.38 –28.44Palm forest 88.54 41.23 –47.31 –53.43Humansettlements 9.27 29.32 20.04 216.28Waterbodies 8.16 9.23 1.07 13.11Oakforests 399.94 410.78 10.84 2.71Mountainmesophyticforest 11.21 10.42 –0.79 7.04Xericshrublands 7.74 1.45 –6.28 81.13
Source:Santacruz(2007and2012).
1970
Longitude West
LegendLand use and vegetation
Irrigation agriculture Xeric shrublandsPalm grove
Induced and cultivated pasture
Lowland deciduous woodlandand sub-deciduousHigh evergreen and sub-evergreen jungle
Scale 1:250 000Perennial stream
Rainfed agriculture
Urban settlementBroadleaf forest
Mesophyll mountain forestWater
22º51'
22º00'
22º15'
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''
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0'
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''
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ude
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Longitude West
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''99
º30'
99º1
5'
99º0
0'
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''
Latit
ude
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th
2000
Fig. 4. VegetationtypeandLandUseintheRíoVallesBasinbetween1970and2000.CAMBIAR“Lowdecidu-ousjungleandsub-deciduous”POR“Lowlanddeciduousandsub-deciduoustropicalforest”Y“Highevergreenjungleysub-evergreen”POR“Highlandevergreenandsub-evergreentropicalforest”
B. López Álvarez et al.180
OveralltheRVBlost544.26km2ofitsjunglesand10.84km2ofitsforestsbetween1976and2000,resultinginadeforestationrateof1.18%(Santacruz2007).Thisvalueisslightlyhigherthantheannual0.65and0.76%atnationallevel,withsimilarveg-etationtypesduringthesamestudiedperiod(Reyeset al.2006).
Theevaluationwascarriedoutatascaleof0to100%,wherethecategoryof0to20representsverysmallchanges,20to40smallchanges,40to60me-diumchanges,60to80largechangesand80to100verylargechanges.Therefore,thescoreof0to20%wouldbethemostfavorabletotheWPI,sinceitwouldrepresentlittlechangeinthenaturalvegetation.Ontheotherhand,thescoreof80to100%wouldrepresentnearlyatotallossofnaturalvegetationinthebasin.
Quality (Q)Waterisindispensableforhumanlife.Both,its
qualityandquantityareimportantanditsdegradationimpactstheenvironmentand,inparticular,humanhealth(Azqueta2002,Soares2003).Waterpollutioncanoccurfromnaturaloranthropogeniccauses.Theimpropermanagementofwaterresourcesisoneofthemain reasons for its deterioration.UNESCO(1998)indicatesthatanevaluationofthequalityandquantityofavailablewaterisaprerequisiteforthe
developmentandmanagementofwaterresources.In theRVB,CONAGUA has differentwater
qualitymonitoringstations,primarilyinthe“RíoElSalto”and“RíoValles”subbasins.Intermsofthephysical,chemicalandbacteriologicalinformationregardingwaterqualityatthesemonitoringstations,the temporal behavior of quality parametersweredetermined and comparedwith themaximum al-lowablelimitsaccordingtotheMexicanregulationNOM-127-SSA1-1994. It is important tomentionthat onlyCiudadValles haswastewater treatmentplants(whoseoperationsandefficiencyisquestion-able).Domesticwastewater is discharged directlyintoreceptorwaterbodies,increasingthepresenceofpollutants,especiallythosethatarebacteriological.
Thevaluesfortotalandfecalcoliforms(NMP/ 100mL)wereover0(Fig. 5)inallthesamplestakeninthe“RíoElSalto”subbasin.
Thepresenceofbacteriologicalpollution in themainwater supplysource reducesconsiderably theavailabilityofwaterforhumanusepurposesinthebasin.At themonitoring stationsnamedAADAPAand Birmania by CONAGUA –the latter beingdownstream from the former– themost probablenumber (MPN) in the samples taken in the year2005variedfrom47000to700000MPN/100mL. SánchezandHernández(1996)foundtotalcoliform
1
Sampling date
Total coliformsFecal coliformsNOM-127 (Zero CFU/100 mL)
07/0
8/19
9506
/10/
1995
01/0
3/19
9615
/05/
1996
15/0
8/19
9614
/12/
1996
26/0
2/19
9704
/06/
1997
22/1
2/19
9719
/02/
1998
20/0
5/19
9819
/08/
1998
18/1
1/19
9801
/09/
1999
27/1
0/19
9925
/11/
1999
10/0
2/20
0025
/04/
2000
15/0
6/20
0010
/08/
2000
04/1
0/20
0021
/02/
2001
25/0
4/20
0112
/06/
2001
14/0
8/20
0117
/10/
2001
20/0
2/20
0214
/05/
2002
05/0
8/20
0219
/11/
2002
18/0
9/19
97
100 000
10 000
1000
100
Tota
l anf
feca
l col
iform
s (M
PN
/100
mL)
10
Fig. 5. Bacteriologicalanalysisofwaterfromthe“RíoValles”andthe“RíoElSalto”sub-basins.Source:Santacruz(2007)andNOM-127-SSA1(1994)
WATER POVERTY INDEX IN SUBTROPICAL ZONES 181
valuesof2500MPN/100mLatdifferentpointslocatedthroughoutthemainchannelinthissubbasin.TheyalsodetectedthepresenceofenterobacteriasuchasEscherichia coli, Proteus, Klebsiella pneumoniae, Shigella dysenteriae and Serratia marcescens.
ThiscomponentwasevaluatedusingtheWaterQuality Index (WQI) developed byMcclelland(1974).Thisindexisanumericalrepresentationofthechemicalparameteranalyzed.Theindexisobtainedfromaddingandponderingthespecificweightsob-tained from a geometric mean (equation 8):
=i
ii
PPC
kWQA∑∑
(8)
whereCiisthepercentagevalueassignedtotheparam-eters, Piistheweightassignedtoeachparameter,k is theconstantwhichtakesthevalueof1forclearwaterwithnoapparentpollution,0.75forclearwaterwithaslightcolor,foam,andslightunnaturalapparentturbid-ity,0.50forwaterwithacontaminatedappearanceand0.25forsewagewithfermentationsandodors.
Toobtain thewater quality component for thesurfaceandgroundwateravailableinthestudyarea,thefollowingexpressionisused(López-Álvarezet al.2013,equation9):
AgrnAsur QQQ 09.091.0 += (9)
whereQAsur and QAgrnaretheWQIforsurfaceandgroundwater from the aquifer, respectively.Theweightfactors(0.91and0.09)usedinthiscomponentwereassignedaccordingtothepercentageofusagefromthesesourcesintheregion.
Onascaleof0 to100, themaximumvalueof100representsexcellentqualityandvaluesunder50represent serious pollution problems.
RESULTS AND DISCUSSION
Thefollowingresultswereobtainedafteranalyz-ingtheinformationtoevaluateeachcomponentfortheRVB.
ResourcesGiventheorographicandclimaticconditionsin
theRVB,duringtherainyseasonlargeflowsoccur,frequentlycausingfloodinginthelowerpartsofthebasin.Consequently,surfacewaterisabundantandprovidesthemainsource(91%)ofwaterfordifferentactivitiesintheregion.
Fromageologicalperspective,groundwatercir-culatesinhighlyfracturedlimestonewithdissolutioncavities(karstarea),resultinginlargerechargesoftheaquifer(Morán-Ramírezet al.2013).Theabundantsurfacewatergenerateslowdemandforgroundwater,therefore,theamountofdeepwellsislowcomparedtootherregionsinMexico.Verylittlegroundwaterisused,representingonly9%ofthetotalwateruseintheRVB.
ToevaluatethenormalizedRparameter,value1represents abundantwater resources.Thiscompo-nentwasevaluatedwithanequation that includesextremescenarios,inwhichthevalue0.5representsabalanceoftheresourceintheaquifersandvalueslessthan0.5representthedepletionoftheaquifer(López-Álvarezet al.2013).
InthecaseoftheRVB,avalueof0.97wasob-tainedforthiscomponent,whichisconsistentwiththeclimatologicalconditionsandtheabundantwaterresourcesinthestudyarea.
QualityAlthoughsurfacewaterisabundantandservesas
themainsourceforavarietyofeconomicactivities,itsdomesticuseislimitedbecauseitsqualityisverypoor forhumanconsumption.For example,waterfromtheRíoVallescontainstotalcoliformvaluesofasmuchas273000CFUandfecalcoliformvaluesof170000CFU,causinggastrointestinalandder-matologicalillnessesamongthehumanpopulation(Gómez and Velarde 1996).
TheWQIscorewas51forsurfacewaterand66.7fortheaquifer(SantacruzandRamos2010).Thesevalueswereused inequation (9),basedonwhichthe score of 0.52 for componentQwas obtained.Whilethislimitsitsuseforhumanconsumption,itis acceptable for agricultural irrigation (Santacruz andRamos2010).
UsageRegarding thiscomponent,agriculturalactivity
playsanimportantroleanddemandsahighvolumeoftheresourceforgravityirrigationsystems,whosemaximumefficiencyisestimatedat50%.Thevalueof itsproductionhas little influenceon the state’sGDPandtheregionaleconomy.
Domestic use is deficient becausemost of thedrinkingwaterservicesarelocatedinthemunicipalcapitalofCiudadValleswhiletherestofthelocalitieslacktheseservices.
Theevaluationof thiscomponent resulted inanormalizedUvalueof0.052,whichreflectstheso-cioeconomicconditionsinthestudyzone.
B. López Álvarez et al.182
TABLE III.VALUESOBTAINEDFOREACHCOMPONENTOFTHEWATERPOVERTY INDEXOFRÍOVALLES BASIN
Component Score Weight WaterPovertyIndexResource 0.97 30
59
Quality 0.52 20Use 0.05 10Access 0.31 15Capacity 0.35 15Environment 0.90 10
AccessThe rural population in theRVB is dispersed,
whilemostof theurbanpopulation isgathered inthreemunicipalitieswheredrinkingwaterservicesarecentralized,particularlywastewatertreatmentinCiudadValles.Therestof themunicipalitieshavelessanddispersedpopulation, therefore,access totheseservicesislimited.
Anormalizedvalueof0.31wasobtainedduetothe centralizationof drinkingwater and treatmentservicesinthemainpopulationcentersandthelackofthoseservicesinrurallocalities.
CapacityInthecityofSanLuisPotosí,anotableconcen-
trationofservicesandeconomicactivityexists.Thissituationpolarizesthesocioeconomicconditionsinthe rest of the state, and therefore theHDI in thestudyzoneislow.
Themortalityrate,incomeandGinicoefficientusedtoevaluatetheCapacitycomponentgavesimilarvaluestothoseobtainedintheSLPValley(López-Álvarez et al. 2013),while the education indiceswerelowerthanthoseobtainedintheSLPV,whichisreflectedinthenormalizedscoreof0.35forthiscomponent.
EnvironmentLandusechangesintheRVBwereconsideredto
evaluatetheenvironmentcomponent.Themodifiednaturalareaisapproximately588km2,whichrep-resents24%ofthetotalareaoftheRVB,avalueof0.9wasassignedtothiscomponent.Thisisconsistentwithlandusechangesintheregion,wheretropicalrainforestshavebeenconvertedintoirrigatedagri-culturalland.ThislandusechangehaslessimpactthaninotherregionsofSLPwherenaturalvegeta-tionhasbeenturnedintourbanuseordeforestationwithout recovery had occurred (López-Álvarezet al.2013).
Water Poverty Index for the RVBTheresultingpolygonfortheRVBreflectsseri-
ousproblemswithusage,accessandcapacity.Ontheotherhandwaterquality,forinstance,istheleastproblematicinitsevaluation,andtheenvironmentalandresourcecomponentsalsohavefavorablecondi-tions (Fig. 6).
Table IIIpresentsthescoresobtainedforeachcomponentandtheirweights,aswellastheoverallWPIfortheRVB,withascoreof59.
IfwecomparethisvaluewiththoseobtainedbyLawrenceet al. (2002),thatarenotnormalized,it
isfarfromthescoresofdevelopedcountries,suchasFinlandwithaWPIof78.TheWPIintheRVBis higher than those in underdeveloped countrieswithwaterpovertyproblems,suchasHaitiwithaWPIof35.1,andisevenhigherthantheWPIforMexicoandtheSLPV,withvaluesof57.5and46,respectively.
TheWPIvaluefortheRVB(59)isprobablyduetothehighavailabilityofwaterandthelowenviron-mentaleffectsinthisarea.Neverthelessitindicatesthattheruralpopulationdoesnothaveaccesstotheresource, its socioeconomic situation is unequal and theuseofwaterisdeficient(Fig. 6).
ContrastscanbeseenwhencomparingtheWPIintheSLPVwiththatoftheRVB(Fig. 7).TheresourceisabundantintheRVBwhilescarceintheSLPV.Inaddition,accessandthecapacitycomponentsaredeficientintheRVBwhereasintheSLPVthereisamoreefficientmanagementofthisresource.
0.97Resource
Environment
Capacity
Access
Use
Quality0.52
0.05
0.31
0.35
0.90
1.0
0.8
0.6
0.4
0.2
0.0
Fig.6. NormalizedWaterPovertyIndexHexagonfortheRíoValles Basin
WATER POVERTY INDEX IN SUBTROPICAL ZONES 183
Throughout history, the environment in theSLPVhasundergoneirreversiblechanges,suchasdeforestation and depletion and pollution of surface andgroundwaterresources.Nevertheless,theenvi-ronmental changes in theRVBare reversible anddeforestedzonesmayberecoveredinashortperiodof time. In termsof theresource, recharge ishighandflowsareverydynamicbecauseofthekarsticcharacteristicoftherock.
Theaboveanalysisshowsthattheabundanceoftheresourcedoesnotensurebettersocioeconomicdevelopment in a region.
CONCLUSIONS
Geographic,geological,orographicandclimaticconditionsarefactorsthatenhancetheabundanceoftheresource(R),resultinginavalueof0.97.
LandusechangesintheRVBhavehadlittleim-pactontheenvironmentbecausethelossofnatural
vegetationcoverwasreplacedbyirrigatedagricul-ture,resultinginavalueof0.9fortheenvironmentalcomponent (E).
In termsof thequality(Q)ofwaterforhumanconsumption,treatmentisrequired.Nevertheless,itisadequateforagriculturalusesandavalueof0.52wasobtained.
Regarding capacity (C), a value of 0.35wasachieved,which reflects the centralization of theeconomicalactivityinthearea,thatisfocusedmainlyinonemunicipality,whiletherestofthelocalitiesareleftbehind.
SeventyfivepercentofthehumanpopulationlivingintheRVBislocalizedinCiudadValles,ElNaranjoandNuevoMorelos.Thispopulationhasaccesstocleanwater, but there aredeficientwastewater treatmentservicesandadequateaccesstoirrigationwater.Therestofthepopulation(25%)hasdeficientornoaccess(A)totheresource,asreflectedbyascoreof0.31.
Themainuseofwaterisforagriculture,whichisthelargestactivityintheregion.Nonetheless,theusage (U) does not significantly contribute to thestate´sGDP,asreflectedbyavalueof0.05forthiscomponent. In addition, domestic use is centered primarilyinCiudadValles,whereasservicesfortherestofthepopulationintheRVBaredeficient.
TheevaluationoftheWPIfortheRVBdemon-stratesthatwaterpovertylevelsinaregionarenotdeterminedbythequantityoftheresourcebutratherbyitsefficientmanagementanduse.Therefore,theWPIcouldbeausefultoolforintegratedwaterre-sources management.
REFERENCES
AzquetaD.(2002).IntroducciónalaEconomíaAmbiental.Ed.McGraw-Hill.Madrid,Spain,456pp.
Carranco-LozadaS.,Ramos-LealJ.,Noyola-MedranoC.,Moran-RamírezJ.,López-ÁlvarezB.,López-QuirozP.andAranda-GómezJ.(2013).Effectsofchangeofuseoflandonanaquiferinatectonicallyactiveregion.Nat.Sc.5,259-267.
GómezN.A. andVelardeN.H. (1996).Deteccióndeenterobacterianas en el Río Valles como una fuente de contaminación. Universidad Autónoma de San Luis Potosí,UnidadZonaHuasteca.Mexico,74pp.
INEGI.(2007).Censoagropecuario,VIIIcensoagrícola,ganaderoy forestal. InstitutoNacionaldeEstadísti-ca yGeografía. [Online]: http://www.inegi.org.mx/prod_serv/contenidos/espanol/bvinegi/productos/metodologias/censo_agrope/2007/metodo_2007/Sin-MetCAGyF.pdf10/03/2014.
Fig. 7. NormalizedWaterPovertyIndexHexagonfortheRíoVallesBasinandtheSanLuisPotosíValley
Resource
Environment
Capacity
Access
Use
Quality
Component ScoreSLPV RVB
Resource 0.26Quality 0.74Use 0.29Access 0.75
Environment 0.40Capacity 0.63
0.970.700.050.31
0.900.35
San Luis Potosi Velley (SLPV)
Río Valles Basin (RVB)
1.0
0.8
0.6
0.4
0.2
0.0
B. López Álvarez et al.184
INEGI.(2010a.)Censodepoblaciónyvivienda.InstitutoNacionaldeEstadísticayGeografía.[Online]:http://www.inegi.org.mx/sistemas/olap/proyectos/bd/consul-ta.asp?p=17118&c=27769&s=est15/03/2014
INEGI.(2010b).SistemadecuentasNacionalesdeMé-xico. Producto interno bruto por entidad federativa. InstitutoNacionaldeEstadísticayGeografía.[Online]:http://www.inegi.org.mx/prod_serv/contenidos/espa-nol/bvinegi/productos/derivada/regionales/pib/2007-2011/pibe2011.pdf15/03/2014
IWRM-UNESCO (2009). IntegratedWaterResourcesManagement inAction.WorldWaterAssessmentProgramme, United Nations Educational, Sci-entific and Cultural Organization. Report. Paris, France. 18 pp. [Online]: http://unesdoc.unesco.org/images/0018/001818/181891e.pdf26/02/2014.
LawrenceP.,Meigh J. andSullivanC.A. (2002).Thewaterpovertyindex:internationalcomparisons.KeeleEconomicsResearchPapers,KeeleUniversity,Staf-fordshire,UnitedKingdom,19pp. [Online]: http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.13.2349&rep=rep1&type=pdf7/04/2015
López-ÁlvarezB.,Ramos-LealJ.A.,Santacruz-DeLeónG.,Moran-RamírezJ.,Moran-Ramírez,J.,Carranco-LozadaS.E.,Noyola-MedranoC.andPinedaMartínezL.F.(2013).CálculodelÍndicedePobrezadelAguaen zonas semi áridas: caso Valle de San Luis Potosí. Rev.Int.Contam.Ambie.29,249-260.
McclellandN.(1974).EPA-907/9-74-001.WaterQualityIndex.Application in theKansasRiverBasin.U.S.EnvironmentalProtectionAgency-RegionVII.,KansasCity,Missouri,USA,226pp.
Morán-RamírezJ.,Ramos-LealJ.A.,López-ÁlvarezB.,CarrancoLozadaS.andSantacruz-DeLeónG.(2013).Comportamiento hidrogeoquímico de flujos subte-rráneos en acuíferos cársticos fracturados, aplicando modelacióninversa:CasoHuastecaPotosina.Bol.Soc.Geol.Mex.1,71-82.
NOM-127-SSA1-1994(1994).NormaOficialMexicana.Modificacion a laNormaOficialMexicanaNOM-127-SSA1-1994,SaludAmbiental.Aguaparausoy
consumohumano.Limitespermisiblesdecalidadytratamientos a que debe someterse el agua para su potabilizacion.SecretaríadeSalud.DiarioOficialdelaFederación.20dejuniode2000.Mexico.
ReyesH.,AguilarM.,Aguirre J. andTrejo I. (2006).CambiosenlacubiertavegetalyusodelsueloeneláreadelproyectoPujal-Coy,SanLuisPotosí,México,1973-2000. InvestigacionesGeográficas.Bol. Soc.Geol.Mex.59,26-42.
SantacruzG. (2007).Hacia unagestión integral de losrecursoshídricosenlacuencadelRíoValles,Huasteca,México.TesisdeDoctorado,FacultaddeCienciasQuí-micas,IngenieríayMedicina,UniversidadAutónomadeSanLuisPotosí,Mexico,308pp.
SantacruzG.(2008).Generaciónytratamientodeaguaresidual en la Zona Metropolitana de la ciudad de San LuisPotosí.BoletíndelArchivoHistóricodelAgua.Comisión Nacional del Agua. Secretaria de Medio AmbienteyRecursosNaturales.Mexico,89pp.
SantacruzG.andRamos-LealJ.A.(2010).EstudiodelcomportamientohidrogeológicodelaReservaSierraAbraTanchipaysuzonadeInfluencia.ReporteTéc-nicoGTZ-CONANP-COLSAN-IPICYT. SanLuisPotosí, Mexico, 71 pp.
SantacruzG. (2012).ElEspejismode lacuencahidro-gráficacomoespacioparalagestióndelosrecursoshídricossuperficiales,elcasodelríoValles,Huasteca.Colección Investigaciones, El Colegio de San Luis, A.C., Mexico, 171 pp.
Siles J., SoaresD. andAlemánE. (2003). La fuerzade la corriente: gestión de cuencas hidrográficasconequidaddegénero.IUCN,RegionalOfficeforMeso-America.EditorialAbsoluto.SanJosé,CostaRica, 266 pp.
UNESCO (1998).Evaluaciónde los recursos hídricos:Manual para la estimación de las capacidades nacio-nales.Biblioteca virtual del Programa hidrológicointernacionalparaAméricaLatinayelCaribede laUNESCO,142pp.[Online]:http://www.unesco.org.uy/phi/biblioteca/archive/files/8402cc013900e2e09e3a026b75b704a8.pdf25/03/201.
