ModBack – Simplified contaminant source zone delineation using backtracking

K. Thielsch, M. Herold, T. PtakApplied Geology, Geoscience Centre, University of Göttingen, 37077 Göttingen, Germany, kthielsch@gwdg.de

1 Geographical data view / input

define the max./min. plume length using analytical equations or use plume length statistics (Schiedek et al., 1997) cut pathlines to specific length

Estimation of the required pumping duration of an integral pumping test (IPT, Teutsch et al., 2000) using Excelfollowing Rothschink, 2002: enter RC (red box) define model parameters (blue box) pumping time is calculatedautomatically (green box)

Maximum radius of contribution (RC) is defined as half distance between two neighboring wells within ModBack by measuring tool

2a Analytical approach

Creation of pathlines using PMPath:

two pathlines (red lines), one at eachend of the control plane for one well backtracking, simulation time is entireduration transient flow simulation export data

2b Numerical groundwater model

Groundwater model set up using PMWin (example data):

hor. hydraulic conductivity: 0.032 [ms -1 ] specific storage: 0.01 [m-1] eff. porosity: 0.15 [-], aquifer thickness:2m mesh size: 5x5m, around wells: 1x1m layer type: transmissivity varies period length equal to pumping time (RC)

ModBack enables a simplified delineation of contaminant source zones and zones free of contamination sources in saturated aquifers following the approach by Jarsjö et al. (2005).

It uses a GIS-based interface comprising four steps: geographical data view / input, analytical and numerical groundwater modeling, ana-lytical and numerical backtracking, result illustration / output.

Combination of directly controlled modeling tools: PMWin© (WebTech 360, Inc., Processing Modflow Pro), ArcGIS® (ESRI®, ArcMap, ArcCatalog), CSTREAM (Bayer-Raich et al., 2003), Surfer® (Golden Software), Excel© (Microsoft ®)

based on results of numerical groundwater model (PMWin)

needs concentration-time series of a pumping well, IPT

export of results as shapefile or DXF (Surfer)

analytical IPT evaluation possible as well

3 IPT evaluation

CSTREAM

ModBack convert the pathlines (results num. model) matrix to x,y data add theses pathlines as points

convert the points to polylines, change color add .dxf files (results backtracking CSTREAM)

4 Result illustration / output

create possible zones containing contamination sources and zones free of contamination sources from the pathlines directly within ModBack reactive and inert compounds

Acknowledgements: The authors greatly acknowledge the support by the Slovenian INCOME project partners and by Fugro GmbH, Braunschweig, Germany as well as the financial contribution by the EU, LIFE+ program.

ModBackInput data required:

referenced data sets with coordinate information in x,y format

Inert compoundsSource zone absence

Inert compoundsSource zone

no pathline cutting

Jarsjö et al. (2005)

Reactive compoundsSource zone absence

consideration of plume length statisticsmax:4500m, min: 20m

Reactive compoundsSource zone

Jarsjö et al. (2005)

References: Jarsjö, J., Bayer-Raich, M., Ptak, T. (2005), Monitoring groundwater contamination and delineation source zones at industrial sites: Uncertainties using integral pumping test, J. Contam. Hydrol., 79, 107-134; Rothschink, P. (2007): IPV-TOOL. http://www.lubw.baden-wuerttemberg.de/servlet/is/47957/; Schiedek, T., Teutsch, G. and Gratwohl, P. (1997), Literaturstudie zum natürlichen Rückhalt / Abbau von Schadstoffen im Grundwasser. Landesamt für Umweltschutz, Baden-Württemberg, Germany (in German); Teutsch, G., Ptak, T., Schwarz, R., Holder, T. (2000), Ein neues integrales Verfahren zur Quantifizierung der Grundwasserimmission: I. Beschreibung der Grundlagen, Grundwasser 4 (5), 170–175 (in German).

Data frame

Coordinates

Main menu & Toolbar

TOC

3a

Standalone anlaytical approach, Rothschink, P. (2002)

Co

py

R

es

ults

Co

py

Re

su

ltsCreate, run

CSTREAM projects

3b Edit results in Golden Software Surfer

Analytical Numerical

Backtracking model

Result illustration / output4

Plume length statistics

Source zone / Source zone absence

Cut pathlines

Convert pathlines matrix to x,y data, add as Points

Convert points to polylines

Save results as shapefile

Ed

itable in

side

of D

ata

frame

2a

Investigation of max. radius of contribution (Control Plane)

Creation of conceptional IPT pumping duration

Paste results from 2a

Open, create, run PMWin projects

Create pathlines in PMPath

2b

Create new ArcGIS projects (ESRI .mxd format)

Add geographical data, vector data (Esri .shp format)

Open ArcGIS projects (ESRI .mxd format) 1

Geographical data view/ input

Analytical Numerical

Groundwater model