TRAC�Project A�software�to�interpret�tracer�tests in�porous�medium GUTIERREZ�Alexis 1 ,�KLINKA�Thomas 1 , 1 BRGM - Water Division 3 avenue C. Guillemin BP 36009 THIERY�Dominique 1 45060 Orléans Cedex 2 France Tracer�6�Conference Oslo�6�8�June 2011 International�Conference�on�Tracers�and�Tracing�Methods Water Division 1 07/09/2016 Plan�of�the�presentation > Uses�of�tracer�tests�in�hydrogeology • Applications • Tracers > Motivations�to�develop TRAC > Example of�application • Interpretation > TRAC�features > Conclusion EAU\GDR 2 07/09/2016
Uses�of�tracer�tests�in�hydrogeology > Qualitative�:�existence�of�hydraulic connection between two points? > First�known scientific tracer�test�in�hydrogeology in�1887 (Immendingen,�Danube�<�>�Ach spring) Injection�of�fluorescent�tracers in�skinholes EAU\GDR 3 07/09/2016 Uses�of�tracer�tests�in�hydrogeology > Quantitative�:�characterize the�transport�properties of�the�aquifer,� i.e.�:�kinematic porosity ( � c ),�dispersivity ( � ),�filtration�velocity (u) � � � � � � � � � � � � � � C C C C C � � � � � u D D D � � � � � � � � � L � � T � � V � � � � � t x x x y � y � z z V Ki � � � � � � � � D u D D u D u u L L T T V V � � c c > Possibility to�take into account of�others process : � • Adsorption�:����������������������������(linear equilibrium adsorption) K � � d R 1 � ln 2 • Degradation : � � � � � � � � M t M 0 exp t t ; 1 2 � EAU\GDR 4 07/09/2016
Applications > The�interpretation�of�the�restitution�curve�is�very�instructive�on�the�potential� transfer�of�contaminants�and�in�the�description�of�hydrodispersive�parameters > To�improve�management�and�protection�of�groundwater�resources > Groundwater : • Delineation of�the�catchment; • Study�of�the�respective�contributions�of�different�waters > Areas�of�groundwater protection�: • Study�of�transit�time�/�protection�zone • 50�days�transit�time > Determine the�transport�parameters of the�aquifer�for�discretized�modeling EAU\GDR 5 07/09/2016 Tracers > To�track�the�movement�of�water�molecules,�one�must�choose�a� tracer�that�is�(ideally): • chemically�stable�and�inert�to�mineral�constituent�rocks�of�the�aquifer,�so�that� the�tracer�is�not�disturbed�sorption�reactions; • still�detectable�in�very�high�dilution,�its�movement�can�be�tracked�over�long� distances; • nontoxic�to�humans�and�the�environment; > The�type�of�tracer�used�depends�on: • objectives�tracing • constraints�of�the�tracing�(water�chemistry,�etc.). • means�(technical�and�financial)�available�(sampling,�analysis,�...) > The�artificial�tracers�commonly�used�are�water�soluble�tracers EAU\GDR 6 07/09/2016
Tracer�comparison > Source�:�Utilisation�des�traceurs�artificiels�en�hydrogéologie�– SSH,�2002 EAU\GDR 7 07/09/2016 Motivations�to�develop a�tool > Lack of�simple�tool > CATTI�software�(Sauty,�Kinzelbach,�1991) > A�tool that helps the�interpretation and�design�of�tracer�tests > Based�on�the�use�of�analytical�solutions�(no�spatial�discretization)�: • Homogeneous�aquifer; • Infinite�in�terms�of�extension; • Dimensions�of�flow�(1D,�2D,�3D,�radial); • Monolayer; • Uniform�flow�(not�for�radial). EAU\GDR 8 07/09/2016
Analytical solutions > TRAC�offers�a�panel�of�12�analytical�solutions • Compared with numerical�models, analytical�models are generally useful at�a�first�stage of a project�when�information regarding� the complexity of�the�environment is�not�known • Advantage of numerical�models is�their�ability to take into account this� complexity, including heterogeneity of�the geology or the�boundary� conditions • Analytical�solutions�assume that the geometry�of�simulated� domain is relatively simple. Despite their�limitations,�analytical�models can be very useful for simplified analysis and are therefore widely�used in�practice. EAU\GDR 9 07/09/2016 A�set�of�analytical solutions > Analytical�solutions�of�advective�dispersive�solute�transport� equation�(ADE)�are�useful�in�predicting�the�fate�of�solutes�in� groundwater > Actual available methods : • 1D,�2D,�radial�converging/diverging flow; • Instantaneous (Dirac),�continuous,�step�injection; • Delay�factor�(in�development); • Degradation constant�(exponential form); • Variable�direction�of�the�groundwater flow. EAU\GDR 10 07/09/2016
Applications > Hypothesis of�uniform flow�is valid : • In�laboratory,�for�soil�column experiments (Q�constant,�u�constant) • On�the�field,�for�tracer�tests�under natural conditions�in�an�homogenous and� isotrope�aquifer Observation point Injection point > Forced flow�:�radial�convergent Injection point Observation point EAU\GDR 11 07/09/2016 TRAC�– Session�sample > Two modes�:�« simulate and�design »�/�« interpret tracer�test » EAU\GDR 12 07/09/2016
Tracer�test�configuration EAU\GDR 13 07/09/2016 Parameterization International System of Units are used in TRAC, you can still add units from other systems : feet, inch, gallon … EAU\GDR 14 07/09/2016
Theorical breakthrough EAU\GDR 15 07/09/2016 Optimal�mass�to�inject EAU\GDR 16 07/09/2016
Sampling frequency EAU\GDR 17 07/09/2016 Interpretation mode > Fill the�description�of�tracer�test�and�the�technical informations > Import�your field/lab data�:�concentration,�time,�flow > Select�an�adequate solution > Adjust the�parameters by�trial�and�errors EAU\GDR 18 07/09/2016
Soil column tracer�test > Filled with differents materials (glass�ball,�small gravel) sampling & analyse > Fixed flow > Injection�of�fluoresceine in�the�middle�with a�needle > Measure of�concentration�with fluorimeter d > Tracer�tests�with : x • Variable�height of�column • Variable�diameter of�column • Differents flows • Differents concentrations�of�tracer Injection (M 0 ) Q EAU\GDR 19 07/09/2016 Context informations > Description�of�the�tracer�test > Technical informations > Opening an�existing project EAU\GDR 20 07/09/2016
Import�data EAU\GDR 21 07/09/2016 Selection of�an�adequate solution EAU\GDR 22 07/09/2016
Parameterization EAU\GDR 23 07/09/2016 Optimization process EAU\GDR 24 07/09/2016
Estimation�of�transport�parameters EAU\GDR 25 07/09/2016 Estimation�of�transport�parameters Relation dispersivité/diamètre moyen 1.00 Diamètre moyen du matériau (cm) 0.80 0.60 0.40 Ø=f(�) 0.20 Linéaire (Ø=f(�)) 0.00 0.00 0.50 1.00 1.50 2.00 2.50 small gravel Dispersivité (cm) medium gravel mix of small and medium gravel glass ball EAU\GDR 26 07/09/2016
Field�scale > Pollution�of�drinkable water�supply by�two industrials sites� (chloronitobenzen) EAU\GDR 27 07/09/2016 Features – Radial�converging/diverging flow > Tracer�experiments�on�groundwater�radial�flow�provide�an� economical�method�of�determining�transport�parameters > The�interpretation�of�the�breakthrough�curves�gives�rise�to�some� difficulties�since�there�is�no�exact�analytical�solution�that�can�easily� be�used�for�transport�in�radial�flow > Development�of�an�accurate�semi�analytical�solution�(D.�Thiéry,�to� be�published) • Maximize�the�recovery�of�tracer; • Accelerate�the�experimental�procedure�(higher�velocity); EAU\GDR 28 07/09/2016
Features – Step�injection > The�hypothesis�of an instantaneous�injection is valid when�the� injection�period is negligible�compared�with�that of�the average� transit�time. > Use�of�superposition�principle�for�continuous�injection � � � � � C t C t For t < T i : c � � � � � � � � � For t � T i : C t C t C t T c c i C in j C 0 time 0 T i -C 0 EAU\GDR 29 07/09/2016 Features – Step�injection > Example to�take into account of�injection�length C inj C 1 C 3 C 2 C 4 time 0 t 1 t 2 t 3 t 4 For t < t 1 : C ( t ) = C c ( C 1 , t ) For t 1 � t < t 2 : C ( t ) = C c ( C 1 , t ) � C c ( C 1 , t-t 1 ) + C c ( C 2 , t-t 1 ) For t 2 � t < t 3 : C ( t ) = C c ( C 1 , t ) � C c ( C 1 , t-t 1 ) + C c ( C 2 , t-t 1 ) � C c ( C 2 , t-t 2 ) + C c ( C 3 , t-t 2 ) And so on … EAU\GDR 30 07/09/2016
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