city in the country: quantifying the effects of land … · 2018-09-28 · methods - u.s.g.s....
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CITYINTHECOUNTRY:QUANTIFYINGTHEEFFECTSOFLANDUSECHANGEONTHEHYDROLOGYOFAWATERSUPPLYWATERSHED,SARATOGASPRINGS,NY
Wiles-Skeels,RobinH.1andNichols,KyleK.2,
1EnvironmentalStudiesand
2Geosciences,SkidmoreCollege,SaratogaSprings,NY12866
ABSTRACT
SignificantrecentandprojectedfuturegrowthinSaratogaCounty,NewYork,andinthe
13.7km2LoughberryLakewatershedinparticular,createsimpermeablesurfaces,suchas
roads,parkinglotsandroofs,thatincreaserunoffvolumeandpeakstormwaterdischarge.In
theLoughberryLakewatershed,mostlandusechangeisfromwell -drained,sandyforeststo
themixedimpermeableandgreenspacelandusesofcommercialandresidentialzones.
Suchlandusechangeincreasesthesurfacerunoffanddecreasesthegroundwaterrecharge
thatisimportanttosustainreservoirlevelsthroughthehigh-demandsummermonths.
Wequantifiedlandusechangefrom1980to2001,aperiodofrapiddevel opmentinthe
LakeLoughberrywatershed.WeusedGeographicInformationSystems(GIS)toquantifythe
1980datafromtheEarthResourcesObservationSystems(EROS)DataCenter(EDC)land
useclassificationthatonlyallowsforageneralizedestimateoflanduseareas.Wedigitized
the2001,usingGIS,from12”perpixelhigh-resolutionorthophotographicimages.Forthe
2001data,wedigitizedallimpermeablesurfacesincludinghouses,roads,andparkinglots,
greenspace,andforestedareas.Thus,the2001dataaremoreprecisethanthe1980data.
Basedona10-year24-hourstorm,andusingthecurvenumberapproach,thetotalrunoff
volumehasincreased304%fromundevelopedconditionsof100%forestcover,similartothe
conditionsinthe1870swhenthereservoirwasbuilt.Therunoffvolumefrom1980to2001
forthesamedesignstormhasincreased26%.Usingtherationalrunoffmodel,peak
dischargesin2001are160%overtheundevelopedconditionand54%higherthanthe1980
landusecover.
Suchtime-seriesmeasurementsoflandusechangeprovideusefulresearchexperience
forundergraduatestudentsandalsoprovidesvaluabledataontheexpansionofimpermeable
surfaceswithincriticalwatersheds.InSaratogaSprings,thisprojectisprovidingimportant
informationonlandusepracticesatatimewhenthecityislookingtoexpanditssummer
watersupply.
INTRODUCTION
-LoughberryLakesuppliesSaratogaSpringswithitsdrinkingwater
-Demandforwaterincreasesyearly,anddoublesduringthesummerhorseracing(tourist)
season
-DevelopmentintheLoughberryLakewatershedhasincreasedsignificantlyoverthepast
twodecades
-Developmentandimpervioussurfacesdecreasegroundwaterrechargeareas
-Groundwaterrechargeisessentialforthelaketomaintainreservoirlevelsduringhigh-
demandsummermonths
-GroundwatersustainsLoughberryLakereservoirlevelssuitableforSaratoga
Springsuse
METHODS
-U.S.G.S.1:24,000topographicmapsusedtodefinewatershedboundary
-EarthResourcesObservationSystems(EROS)datausedtoquantify1980landuse
-12''perpixelhigh-resolutionorthophotographicimagesusedtodelineate2001landuse(houses,
roads,parkinglots,greenspace,forestedareas)
-GISusedtoquantify2001landuseareas
-SoilnamesfromEngineeringHandbook4(1972)usedtoverifyhydrologicsoilconditions
-Rationalrunoffmodel(DunneandLeopold,1978)usedtoquantifypeakdischargesfrom1980and
2001landuses
-Curvenumberapproach(DunneandLeopold,1978)usedtoquantifyrunoffvolumefrom1980and
2001landuses
-Calculationsbasedon10-yrdesignstormsof24,6,1,and0.5hourdurations
REFERENCES
Dunne,ThomasandLeopold,LunaB.,1978.WaterInEnvironmentalPlanning:W.H.Freeman
andCo.,NewYork,718p.
SoilConservationService,1972.Nationalengineeringhandbooksection4:Hydrology.
Washington,D.C.,USA:UnitedStatesDepartmentofAgriculture.
curvenumbersfromDunneandLeopold,1978
1980EarthResourcesObservationSystems
DataCenterlanduseclassificationfor
LoughberryLakewatershed
LoughberryLakewatershedsoiltypes
HydrologygroupA:loamysand(mud,silt,clay
andsandmixture)-lowrunoffpotential
HydrologyGroupC:rolling,rocky-highrunoff
potential
2001aerialphotoofLoughberryLake
watershed
2001landcoverdelineationin
LoughberryLakewatershed
A
C
NewYorkState
SaratogaCounty
UnitedStates
ACKNOWLEDGMENTS
WethankBobJonesforGISexpertise.Fundingforthisproject
wasprovidedbytheRathmannFoundationandSkidmore
College.
NEXTSTEP
-SaratogaSpringsislookingtouseSaratogaLakeor
theUpperHudsonRiverasanewwater
source
-Wewillperform
similarhydrologicanalysesforthe
SaratogaLakewatershed
-Wewillevaluateprojecteddevelopmentinthe
SaratogaLakewatershedforthenext20to30years
(basedonzoningandpopulationdata)toseehow
runoffandpeakdischargewillchangeandinfluence
SaratogaLakewaterquantityandwaterquality
IMPLICATIONS
-Bestresults,forsmallbasins,areobtainedfromhighresolutionaerialphotographscompared
to"generalized"EROSlandusedata(tradetimeforaccuracy)
-DevelopmentintheneighboringtownofWiltonsignificantlyincreasesrunoffvolume(26
to58%)andpeakdischarge(54%)for10-yearstorms
-Greatersurfacerunoffvolumesandpeakdischargesincreasepollutanttransporttothelake
-Morerunoffandlessinfiltrationexasperateswatershortageduringdroughtduetoless
groundwaterrechargeintoLoughberryLake
-Continueddevelopmentwillfurtherdiminishwaterquantityandquality
-EffectsofdevelopmentonLoughberryLakenecessitateeither1)waterconservationand
betterwatershedmanagementor2)anewwatersupplyforSaratogaSprings
24hr
6hr
1hr
30min
187050,000
25,000
00
1980161,000
101,000
39,000
31,000
2001203,000
140,000
60,000
49,000
%increase
1980-2001
26
38
53
58
10-yrSTORMRUNOFFVOLUME(m
3)
24hr
6hr
1hr
30min
1870
2.2
6.6
22
37
1980
3.7
11
38
62
2001
5.7
17
58
96
%increase
1980-2001
54
54
54
54
10-yrSTORMPEAKDISCHARGE(m
3/s)
Landuse
Curve#
HydrologicCondition
MixedForest
30
goodcondition
CroplandandPasture
60
goodcondition
Commercial
70
<70%impervious
Builtupareas
40
<25%impervious
Residential
54
goodcondition
Roads
98
paved
soilgroupsfromSoilConservationService,1972
curvenumbersfromDunneandLeopold,1978
CURVENUMBERSUSEDFOR1980DATA
Landuse
Curve#
HydrologicCondition
Forest(sandy)
30
goodcondition
Forest(notsandy)
60
goodcondition,low
infiltration
Greenspace
40
goodcondition
Roads
98
paved
Roofs
98
impervious
soilgroupsfromSoilConservationService,1972
curvenumbersfromDunneandLeopold,1978
CURVENUMBERSUSEDFOR2001DATA
Rainfall(in)
02
46
810
12
StormRunoff(in) 2468
1968aerialphotoofLoughberryLake
Noticeminimaldevelopmentnorthoflake
October2003developmentinLoughberry
Lakewatershed
Cropland
Residential
Builtup
Commercial
Roads
MixedForest
Loughberry
Forestnotsandy
Forestsandy
Roads
Greenspace
Roofs
Loughberry
*Northistothetopoftheposterineachmap,LoughberryLakeis~1.5kmlong