presentation - University of Delaware

ce.udel.edu

presentation - University of Delaware

Tamar BarkayJean-Claude BonzongoRosemary CarrollDan CrawfordJadran FaganeliKen HeimMark HinesMilena HorvatPaul LechlerBerry LyonsJerry MillerGregor PetkovsekRudi RajarDavid WayneDusan ZagarCollaborators


Funding Sources NIEHS NSF USEPA NSF NSF


Carson RiverModeled domain from USGS gageCCG through Lahontan Reservoir(~110 Km)Semi-arid river with peak flowsgenerally occurring in the springFlowFlow Catastrophic floods (e.g.. 1997-flood) are generated with rare,rain-on-snow events that occurduring the winter monthsThe meandering river isentrenched with steep sides ofcomplexly structured alluvial fill


WASP5 RIVMOD WASP5 MERC4


RIVMOD Floodplain flow WASPModel Augmentation Real sediment transportcapabilities (3 separateparticles and colloids) Bank moisture history Overbank Deposition MERC4 No changes


Minimal Calibration Bank Erosion Evaluate fine sedimentand areal erosionestimates Adjust 3 parameters Mercury May 1994 (Med. Flow) June 1995 (High Flow) Adjust 2 parameters


700600Discharge (m 3 /s)50040019001910192019301940195019601970198019902000201025,00020,00015,00010,0003005,00020001997 FloodEstimated 100-YearFlood1997 Flood100Year0Discharge (ft 3 /s)


1997 FloodPhotos by Rhea Williams, USGS


Geomorphic SurveyExtensive surveyconducted in the spring of1997 using geomorphictechniques of aerialphotography (taken in1991 and 1997) andfloodplain mapping


Geomorphic SurveyRiver dividedinto 10 reachesbased on valleyslope andfloodplain width


1. Handles a morecomplex shape2. Computesdynamic widthadjustment inwhich erodedmass updateschannel width3. Divided channelapproach wasapplied to themomentumequationModifications to RIVMOD


Validation of RIVMOD Code Modifications20618165Depth (ft)14121086432Depth (m)420Previous RIVMOD Modified RIVMOD HEC-UNET0 5 10 15 20 25 30 35 40 45Time (day)10


Modeling Bank Erosion: In-Channel FlowsAssumptions The mass erosion rate, MER (Kg/s) is proportional to the shear stressapplied to the bank MER is inversely proportional to the square-root of the channel bottomslopeMERψρ s γnD21w=1 /2S023v2LsWhere D is the water depth starting at the vertical face of the channel bank(m), and S o is the bottom slope, v is the water velocity (m/s), n isManning’s coefficient, and L S is the segment length (m)


Modeling Bank Erosion: Overbank FlowsA second term was added to account for the underlying change of characteras the river exceeds bankfull flow (Ervine et al., 2000) such that, when D>hMEROB=22322ψργnDvLψργn( D−h)1swS1 /20s+2swh13S1 /20v2LsWhere h is the height of the vertical bank face.


Modeling Overbank DepositionCourse Suspended LoadModified version of Walling and He (1997)cc c ⎛Rs= κVsCmain⎜1⎝−e−X fκ⎞⎟⎠WashloadWEPP (Foster et al., 1995)Rws=Vqfw( G − T )wβ 2s1.66maincTc=ψ3 qfS0


Calibration In-Channel Bank Erosion (Ψ 1 ) andWashload Overbank Deposition (Ψ 3 )3,000Washload Concentration (mg/L)2,5002,0001,5001,000500USGS ObservedModeled WashloadCalibration of ψ 1Calibration ofψ 300.01 0.1 1 10 100 1000 10000Discharge (m 3 /s)


Calibration Overbank Bank Erosion (Ψ 2 )1001010.10.010.12%0.04%Modeled ValuesObserved Values0.66%0.07%7.3%4.9%87%Calibration ofψ 20.0011991199219931994199519961997Obs. MinModeledTotalObs. MaxSediment Eroded (10 6 x tons)


403020100-10-20Channel Width IncreasesObservedPredicted1 2 3 4 5 6 7 8 9 10ReachWidth Increase per Unit ReachLength (m/km)


Overbank CSS Deposition3.02.5ObservedPredictedOverbank CSS(10 6 x Tons)2.01.51.00.50.00 1 2 3 4 5 6 7 8 9 10 11Reach


Overbank Washload DepositionOverbank Washload(10 6 x Tons)1.00.80.60.40.20.0ObservedPredicted0 1 2 3 4 5 6 7 8 9 10 11Reach


Sources of Hg to the Water ColumnMill TailingsBank Erosionathigh flowsQ ~ 43 m 3 /sOld Flood PlainOld Flood PlainDiffusion


Inorganic Hg from Bank Erosion0.008Bottom Slope0.0070.0060.0050.0040.003Reach 1Reach 2Reach 3Reach 4Reach 5Reach 6Reach 8Reach 10Reach 7 Reach 9[ Hgin]bank=λS10.500.0020.00100 10 20 30 40 50 60 70 80Distance from CCG (Km)


Mercury SpeciationComplexedInorganic MercuryMethylationComplexedOrganic MercuryWashloadWashloadLogK d= 4.78LogK d= 3.63CSSLogK d= 1.19SolubleHg 2+SolubleMeHgCSSLogK d= 0.90BedloadLogK d= 0.32DemethylationBedloadLogK d= 0.24


MeHg Bank Concentrations Water contentPercent MeHgMethylation ratesNon-linear contribution ofMeHg from bank erosion?


Inorganic Mercury & MeHg Calibration & VerificationFlow at FCH (ft 3 /s)100,00010,0001,000100101Bank erosiondominates HgloadingDiffusion frombottomsedimentsdominates HgloadingOverbank Flows1997 FloodOct-91Oct-92Oct-93CalibrationVerificationOct-94Oct-95Oct-96Oct-97Oct-98Oct-99


Calibration Hg in Transport: Pre-1997 floodλ 1 = 2,500 µg/kg100,00010,000May 16, 1994 (medium flow Q = 600 ft 3 /s)Hg (ng/L)1,000100100,00010,0001010 10 20 30 40 50 60 70Distance from Upstream Boundary (Km)Hg (ng/L)1,00010010100,00010,00010 10 20 30 40 50 60 70Distance from Upstream Boundary (Km)Hg (ng/L)1,000100June 10, 1995 (higher flow Q = 1,960 ft 3 /s)1010 10 20 30 40 50 60 70Distance from Upstream Boundary (Km)June 16, 1994 (low flow Q = 62 ft 3 /s)


Verification Hg in Transport: 1997 flood and beyond100,000THg at FCH (ng/L)10,0001,0001997 Flood EventShadded regionpertain to periods ofdiffusion dominatedHg loading10012/20/962/8/973/30/975/19/977/8/978/27/97


Verification Hg in Transport: 1997 flood and beyond100,000Shadded regions pertain toperiods of diffusiondominated Hg loadingTHg at FCH (ng/L)10,0001,00010010/1/9711/20/971/9/982/28/98Data associated withMineral Canyon flashflood event4/19/986/8/987/28/989/16/9811/5/9812/25/98


Verification using July 23-29, 199710,000(low flow Q = 43 ft 3 /s)Inorganic Hg (ng/L)1,0001001010 10 20 30 40 50 60 70Distance from Upstream Boundary (km)


Mercury Rates and CalibrationMethylationDemethylationLocation K 20 (day -1 ) Q 10 K 20 (day -1 ) Q 10 Range (Km)Water Column 0 2.03 0 2.03 0 - 115.0River Bed 0.0041 2.03 0.4483 2.03 0 - 79.25River Bank 0.0060* 2.03 0.4483 2.03 0 - 79.25Reservoir Bed 0.0028 2.03 1.2522 2.03 79.25 - 115.0* calibrated


MeHg (ng/L)108642Calibration MeHg Transport: Pre-1997 floodK 20 (Μ bank ) = 0.0060 day −1May 16, 1994 (medium flow Q = 600 ft 3 /s)10800 10 20 30 40 50 60 70Distance from Upstream Boundary (Km)Hg (ng/L)64102MeHg (ng/L)864200 10 20 30 40 50 60 70Distance from Upstream Boundary (Km)June 10, 1995 (higher flow Q = 1,960 ft 3 /s)00 10 20 30 40 50 60 70Distance from Upstream Boundary (Km)June 16, 1994 (low flow Q = 62 ft 3 /s)


Verification MeHg Transport: 1997 flood andbeyond25TMeHg at FCH (ng/L)20151051997 FloodEventShadded regions pertainto periods of diffusiondominated MeHg loading012/20/962/8/973/30/975/19/977/8/978/27/97


Verification MeHg Transport: 1997 flood andbeyondTMeHg at FCH (ng/L)252015105Shadded regions pertain to periods ofdiffusion dominated MeHg loading010/1/9711/20/971/9/982/28/98Dataassociatedwith MineralCanyon flashflood event4/19/986/8/987/28/989/16/9811/5/9812/25/98


Ongoing Activities Reservoir physicalcharacterization Reservoir net settling Characterize erosionuncertainty Perform Monte Carloanalysis to determineprobable range of predictedsystem behavior


Conclusions Simplistic model of bank erosion predicts in-stream sedimentconcentrations well over a large flow domain and channelwidening well over a large spatial domain Overbank deposition of Course Suspended Sediment ispredicted well without calibration over a large spatial domain Overbank deposition of Washload is correctly over-predicted,but this does not validate the approach In-stream inorganic and methyl mercury concentrations arepredicted well over a large spatial and flow domain


Recommendations Determine measures ofmercury bioavailability Re-define mercurymethylation anddemethylation kinetics First-order? Important environmentalfactors and associatedcorrections Deal with and expressimpacts from parameteruncertainties

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