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

SPARE SLIDES

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

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