Elin vanlierde sediment measurements

Elin Vanlierde05-10-2015

Sediment Measurements @ FHR

Overview of presentation• What do we monitor and where?• Translating measurements into sediment

concentrations• Translating sediment concentrations into fluxes

* ISCO sampler- Automatic sampling

(every seven hours)

* Grab samples/weighted bottle sampling

- Manual sampling (every week)

* EWI sampling- Manual sampling (every

week)

Monitoring physical parameters

• water samples for determining: SSC, LOI, grain size

Localisation of water sampling

High water and low water slack(highest and lowest conductivities)

Half tide ebb(highest flow velocities)

Dock sampling

- Water sampling: SSC, Cl-, Cond

- YSI: T°, pH, Cond

- Water sampling: SSC- YSI: T°, pH, Cond

- Water sampling: SSC, Cl-, Cond

- YSI: T°, pH, Cond

Monitoring physical parameters (continued)

• Monthly sailing campaigns:• Sampling with centrifugal pump• Measurements with YSI

Localisation of sailing campaigns

Half tide ebbSlack tide HW & LW

Monitoring physical parameters (continued)

• Measuring physical parameters with multi-parameter probes

• CTD (Conductivity, Temperature Depth)

• Aanderaa (Flow velocity, Flow direction, Temperature, Conductivity, Pressure, Turbidity)

• YSI (Temperature, Conductivity, pH Pressure, Turbidity, Oxygen content)

Where do we measure?

ProsperpolderBoei 84

Liefkenshoek

Oosterweel

Hemiksem

Driegoten

Melle

GavereZulte

Wondelgem

Appels

EppegemAarschot

Duffelsluis

Grobbendonk

Herenthout

Overview of presentation• What do we monitor and where?• Translating measurements into sediment

concentrations• Translating sediment concentrations into fluxes

Translating measurements into SSC

• Sampling• Grab samples• Automatic ISCO samples• Pump samples

yield SSC (mg/l)

• continuous measurements• Turbidity• Discharge• Conductivity• …

yield various proxies needs translating

into SSC (using rating curves)

Creating rating curves• Approach Aanderaa differs from approach YSI

Location driven • Seascheldt = Aanderaa• influx into Seascheldt = YSI

Aanderaa approach• Aanderaa locations have 1 summer and 1 winter

sampling campaign (multiple hours) per year

Aanderaa approach• All campaigns plotted on one graph• 95% Upper and Lower Confidence intervals are

calculated

Aanderaa approach• R²: high• RMSE: 27 – 58 mg/l• MSPE around 20% or lower

Boei84 Regressiemodel R² RMSE MSPE N Turb_Min Turb_Max SSC_Min SSC_MaxSG5 y = 0.000776x2 + 1.133978x 0.91 45.9 23.1 670 19 515 16 872

SG25 y = 1.232555x 0.95 41.7 20.6 549 22 818 16 1004

Oosterweel Regressiemodel R² RMSE MSPE N Turb_Min Turb_Max SSC_Min SSC_MaxSG5 y = 0.000227x2 + 1.237918x 0.86 51.46 14.96 408 40 510 41 804

SG25 y = 1.397138x 0.87 57.85 13.62 597 53 553 52 841

Driegoten Regressiemodel R² RMSE MSPE N Turb_Min Turb_Max SSC_Min SSC_MaxSG5 y = 0.003491x2 + 1.274708x 0.89 45.3 22.8 522 19 340 15 923

SG25 y = 0.003349x2 + 0.999738x 0.91 27.23 14.87 344 20 259 15 523

YSI approach• Continuous on field measurement data

• YSI: Turbidity, Conductivity, etc. (5min)• Discharge (5 or 15 min Daily or Tidal Mean)

• High-frequent calibrational data:

• automatic sampling SSC (7h)

YSI approach• USGS (Rasmussen et al., 2009)

• Simple linear regression (Turb): when MSPE <20%• Multiple linear regression (Turb. + 1 other variable) when:

• MSPE > 20%• p-value (probability value) of the partial F statistic for extra

predictor< 0.025• Pearsons r < 0.95 (no collinearity issues)

Model R² p-value RMSE MSPE PRESSTu 0,31 <2e-16 144 53,62 0,31Tu-Qtij 0,42 <2e-16 132 49,06 0,42Tu-Cond 0,37 <2e-16 142 53,8 0,36

Regression analysis: Sub-relations

• Sub-relations:• Diff. series

• difference between measurement and predictions

• testing different periods• summer-winter• trimester• year

• using Chow test

Quality of the relationExample Melle• R²: low• RMSE:

• MLR: 121 mg/l• SLR (Turb): 144 mg/l

• MSPE:• MLR: 47%• SLR (Turb)= 55%

Meetlocatie Regressiemodel SSC_Var R² p-value RMSE MSPE N Min_Turb Max_Turb Min_QTij Max_Qtij Min_SSC Max_SSClogSSC=f(log Turb, log QTij) 0.42 <2e-16 121.1 46.99 3236 6.9 549.2 0.174 318.297 35 2419

logSSC=f(log Turb) 0.35 144.362 55.45 3261 6.9 549.2 nvt nvt 35 2419

SSC=f(Qtij) 0.20 <2e-16 205.8 73.2 3507 nvt nvt -29.139 318.297 35 3465

Melle

Quality of the relation• 95% Upper and Lower Confidence Intervals

Discussion points• Hysteresis effects

• The variability observed is due to hysteresis • YSI:

• individual peaks, or even individual rising and descending limbs of SSC peaks give very good relations

• Not feasible within framework of data validation• Aanderaa, less hysteresis observed

Campaign 7/11/14 Oosterweel

150 200 250 300 350 400 450 500 5500

100

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320588outliers 320outliers 588

Turb (FTU)

SSC

(mg/

l)

0

20

40

60

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100

120

D50D90µm

• Masterthesis student requested for further research

Overview of presentation• What do we monitor and where?• Translating measurements into sediment

concentrations• Translating sediment concentrations into fluxes

Translating SSC’s into SSF’s • Fluvial flux towards the Seascheldt

= ∑ fluxes tributaries• Flux tributary = SSC tributary x discharge tributary

• Historical approach (weekly grabsamples)• Assumptions:

• Grabsample = daily average value• Rating curve Q-SSC to determine daily values for

the other 6 days of the week• Results: relationships with wide 95% confidence

bands

Weekly grabsamples (Melle)

Translating SSC’s into SSF’s • Flux towards the Seascheldt = ∑ fluxes tributaries• Flux tributary = SSC tributary x discharge tributary

• Historical approach (weekly grabsamples)• New proposed approach (high frequency

measurements) problem: SSC’s measured or sampled are all point samples

not representative of the cross-sectional SSC

Fluxes based on grabsamples (+CI’s) and ISCO (Melle)

Translating SSC’s into SSF’s • Equal Width Increment

method sampling• results in a depth and

width integrated SSC sample

• Creating rating curves between EWI and grab samples (historically) and ISCO samples (new approach) to correct the calculated flux

EWI corrections (Eppegem)

EWI (mg/l) ISCO (mg/l) Grabsample (mg/l)10 6 250 43 47

100 89 103700 641 777

EWI corrections (Melle)

ISCO (mg/l) EWI (mg/l)10 -8050 8

100 1181000 2094

Translating SSC’s into SSF’s • Equal Width Increment method sampling

• results in a depth and width integrated SSC sample

• Creating rating curves between EWI and grab samples (historically) and ISCO samples (new approach) to correct the calculated flux

• Promising with enough sampling points

To do’s• Establishing good EWI correction factors• Calculating SSF and confidence intervals for SSC’S

corrected with these factors for• grab samples• ISCO samples• Turbidity + other variables

• Comparing the results and confidence bands and selectnig the least demanding approach.

The end…• but let’s have some discussions

Discussion questions• Is the better quality of the Aanderaa relations

compared to YSI relationships due to:• the location, the equipment, the sampling

frequency, less hysteresis between sediment peak and discharge peak in the Seaascheldt…

• Does the increase in predictability of SSC merit the inclusion of other variables in a Multiple Linear Regression?

• Should fluxes be calculated based on measurements (ISCO) rather than (even) higher frequency YSI data?