Dragana Petrovic (ULB) stelt een methode voor om sediment te meten in rivieren op basis van eenvoudige maar nauwkeurige druk- en peilmetingen.

1. 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

2. 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

3. 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 ?

4. 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. 5
rw
(T) =
rw
(T0
)
1+b(T - T0
)
Cv =
rw
(T)
rs
- rw
(T)
p- p0
rw
(T)gH
-1
æ
è
çç
ö
ø
÷÷
suspended sediment volumetric concentration
Densitometric probe – basic principles
p= rL
gH
rL
= (1-Cv)rW
(T)+Cvrs

6. 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

7. 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 =
rw
(T)
rs
- rw
(T)
p- p0
rw
(T)gH
-C
vsalt
rsalt
- rw
(T)
rw
(T)
-1
æ
è
çç
ö
ø
÷÷
Test in environment with non negligible salt presence

8. Densitometric probe – validation in natural environment
Ecuador – Jadan river (SSC up to 25g/l)
Jan-Apr 2014 – expected rain season

9. 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

10. 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

11. 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

12. 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. 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

14. SPARE SLIDES

15.  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

17. Gray, J. R., and J. W. Gartner (2009), Technological advances in suspended-sediment surrogate monitoring,
Water Resour.Res., 45, W00D29.