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Densitometric probe based on non-differential pressure the technique allowing to follow suspended matter loads at very high concentrations
Department of Water Pollution Control
D. Petrovic, A. Marescaux, J-P. Vanderborght & M. A. Verbanck
IT4water project
Suspended sediment monitoring: no universal technique
FIT
LISST
WTW ViSolid
Advanced optical probes
Gamma
Alpha
Nuclear probes
UHCM
aDcp
Densitune
Vibrating device
Acoustic methods Remote Sensing Densitometry
(760 - 900 nm)
Manual
Differential pressure
Rapid changes in water depth and suspended sediment concentrations (10 to 30 g/L). Surveillance bridge in
Caojiaquan, Lower Yellow River, Northern China.
Rapid changes in water depth and SSC (10 - 30 g/l) Caojiaquan, Lower Yellow River, Northern China
St Donat-sur-Herbasse, France, 6 Sep 2008
Which sensing method is available to monitor SSC at these high concentrations ?
T°
p
p0
H’
pressure sensor in air
radar limnimeter
H
pressure sensor & thermometer
Densitometric probe – based of absolute pressure measurements
Proxy method based on combination of four sensors
M. A. Verbanck, D. Petrovic & J-P. Vanderborght
International patent application N° PCT/EP2012/054135
5
rw(T) =
rw(T
0)
1+ b(T - T0)
Cv =r
w(T)
rs- r
w(T)
p- p0
rw(T)gH
-1æ
èçç
ö
ø÷÷
suspended sediment volumetric concentration
Densitometric probe – basic principles
p= rLgH
rL
= (1-Cv)rW
(T)+Cvrs
Observed suspended sediment volumetric concentration versus known suspended sediment volumetric concentration (relative error less than 9%)
Test in static conditions
2,5 m deep cylindrical tank
water level at 2 m
water temperature & atm
pressure constant
test of various sensors
Amazon river plume data: - campaign to test DensiTune instrument (acoustic characterization of sediments) - Lab "Acoustics and environmental Hydroacoustics”, ULB , June 2012 , led by Prof. Hermand
Cv =r
w(T)
rs- r
w(T)
p- p0
rw(T)gH
-Cvsalt
rsalt
- rw(T)
rw(T)
-1æ
èçç
ö
ø÷÷
Test in environment with non negligible salt presence
Densitometric probe – validation in natural environment
Ecuador – Jadan river (SSC up to 25g/l) Jan-Apr 2014 – expected rain season
Results application in complex geometry use of sensors with regular sensitivity
Difficulties: unexpected weather conditions influence of air bubbles & floatables water level measurement problems
Ecuador – Jadan river (Jan-Apr 2014 )
Densitometric probe – validation in natural environment
Densitometric probe – (potential) new test site
Laval, Draix – French Southern Alps
Monitoring since 1984
water level: before 1997: bulle-à-bulle,
US, ellan & pressure sensor presently: US &
conductivity based method
SSC – sampling + optical device
Hyperconcentrated black marly slurry 800 g/l on Aug 13, 1997
Densitometric probe concept applied on historical data at Laval maximal SSC in g/l
0
50
100
150
200
250
300
350
400
450
500
31/07/1990 12:00 1/08/1990 00:00 1/08/1990 12:00 2/08/1990 00:00
SSC
(g
/l)
SSC by filtration
densitometric probe
Densitometric probe concept applied on historical data at Laval
13
question & issues we would like to discuss
reliability of water level measurements by pressure sensor
(air bubbles, sediment presence)
when to turn to another methods?
best protection from dynamic effects
search for a new test location – any suggestion?
high concentrations
& fine sediment particles
advantages: monitoring high SSC
continuous real-time monitoring
dynamical alluvial rivers
short time scales: local resuspension
cost reduction
additional water parameters info
disadvantages: limited sensitivity: not appropriate for low suspended sediment
concentrations
15
Densitometric probe – based of absolute pressure measurements