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THE USE OF 3D GEOLOGICAL INFORMATION IN A LARGE MANAGED AQUIFER RECHARGE PROJECT

THE USE OF 3D GEOLOGICAL INFORMATION IN A LARGE MANAGED AQUIFER RECHARGE PROJECT. Aki Artimo and Sami Saraperä Turku Region Water Ltd., Finland aki.artimo@turku.fi. Three-Dimensional M apping Workshop, Oct . 8 th 2011, Minneapolis, MN. INTRODUCTION.

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THE USE OF 3D GEOLOGICAL INFORMATION IN A LARGE MANAGED AQUIFER RECHARGE PROJECT

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  1. THE USE OF 3D GEOLOGICAL INFORMATION IN A LARGE MANAGED AQUIFER RECHARGE PROJECT Aki Artimo and Sami Saraperä Turku RegionWater Ltd., Finland aki.artimo@turku.fi Three-DimensionalMapping Workshop, Oct. 8th 2011, Minneapolis, MN

  2. INTRODUCTION Artificiallyinfiltratedgroundwaterwillbeproduced for 300,000 inhabitantsliving in the Turku areaat the end of thisyear. The infiltrationwater is obtainedfrom the River Kokemäenjoki, 90 km north of Turku. Artificialinfiltrationtakesplace in the VirttaankangasQuaternaryeskeraquifer, 60 km north of Turku. The length of feederpipelines (DN=1200 mm) is about 100 km. The cost of the project is 176,000,000 euros.

  3. BACKGROUND • Precisecontrol of the infiltratedwater (i.e. flowpathsand residencetime in the aquifer) is important in the operation of the managedaquiferrecharge (MAR) plant. • The aquifer is not used merely to store the infiltrated river water, but also to enhance the quality of the water. • The natural purification of the infiltrated water during the flow within the saturated zone of the aquifer is a crucial process for those artificial recharge plants operating in the Nordic countries. • After its completion, the Virttaankangas managed aquifer recharge project will significantly increase the number of consumers using artificially recharged groundwater in Finland.

  4. BACKGROUND • The main factorsaffecting the qualitychange of the artificiallyinfiltratedgroundwaterare the composition of the soilmaterial, hydraulicconductivitydistributionwithin the eskeraquiferand residencetime of the infiltratedwater. • Eventhough the waterqualitychangeoccursbeyond the MAR plant’sfacilities, the operationcanbecontrolled with the help of: • - Measurements of hydraulicheadchanges • - Waterqualitymonitoring data • - 3D hydrogeologicalmodel • - Groundwaterflowmodel • - Tracers (naturalisotopes,organiccarbonand artificialtracers)

  5. TOOLS FOR THE PROJECT EXECUTION The 3D geologicalinformationdatabasehasbeenavailableduring the construction of the MAR plant. Automatedupdating of the 3D hydrogeological and groundwaterflowmodelshasenabled the immediateuse of the newestresearchinformation in the construction of the plant. In addition to basicsedimentological and hydrogeologicalinformation, the Virttaankangas 3D hydrogeologicalmodelhasseen the introduction of geochemical, isotopic, and geophysical data into the 3D modelingworkflow. Furthermore, the 3D hydrogeologicalmodelworks as a structuralbasis for the 60-layer groundwaterflowmodel.

  6. TOOLS FOR THE PROJECT EXECUTION Quantitative understanding GW flowmodels Hydrostratigraphicalmodels Geologicalmodels Databasedevelopment Simplifiedbasinanalysisapproach. ModifiedfromSharpe et al. 2002

  7. TOOLS FOR THE PROJECT EXECUTION Quantitativeunderstanding (Aquifer management) Hydrogeochemical data Geophysical data Isotope data Tracertests Drillhole data Infiltrations and pumpings 3D Groundwater FlowModel GW level measurements Sedimentological interpretations 3D Geologicalinformationsystem (includingtimerelated data) Integratedapproach with constantlyevolving and updating 3D modelsprovidesversatiletools for managedaquiferrecharge.

  8. THE USE OF 3D GEOLOGICAL INFORMATION Geologicalinformation and 3D modelshavebeenused to solve, for example, legislative, constructional, and land-userelatedissuesduring the execution of the MAR project. Modelingtoolswereused to design the optimal layout and configuration of the infiltrationpond and productionwellareas of the MAR plant. For example, locations of fivepreviouslyplannedinfiltrationareaswererejecteddue to discovery of morphologicallyundetectablekettleholesystemunderlying the infiltrationareasrestricting the flow of infiltratedwater. Exactlocations of the productionwellsweredecidedafter a thoroughexamination of availablesedimentological and hydrogeological data, whichresulted in extremelyhighyields of the new productionwells. As compared with the pre-3D plans for pumpingwelllocations, the amount of wellsneeded for fullscaleproductionwasalmostreducedin half.

  9. Avg. pumpingrate per well 6,700 m3/d Previouslybuiltwells5,000 m3/d New wells8,500 m3/d (Maximum yields of the new wells arehigherthan the usedpumpingrates.) Coarsestpart of the esker

  10. THE USE OF 3D GEOLOGICAL INFORMATION Geologicalinformationsystem with the modelingtoolsprovided the means to design and control the infiltrations and pumpingsrelated to the one-yeartestingphaserequiredin the environmentalpermits. Accordingto thosepermits, the fullscaleproduction is onlyallowed to startafter the results of the testingphaseprovideenoughinformation of the controlledexecution of fullscaleinfiltrationand pumping. During the oneyeartestingphasethe observedflowpaths and residencetimes of the infiltratedwatercoincidedextremelywell with the groundwaterflowsimulationsconductedprior to the testingphase. Thiswasnot the case when the earlier pre-3D plans for infiltration and pumpingweresimulated with the sameflowmodel. Thoseplanswouldhaveresulted in a failure in the operation of the MAR plant.

  11. THE USE OF 3D GEOLOGICAL INFORMATION The groundwaterflowmodel is the onlytoolthatcanbeused to decide the exactinfiltration and pumpingrates for all the 19 infiltrationponds and 12 productionwellssothat the residencetime of the infiltratedwater in the aquifer is sufficientthroughout the flowfield. The groundwaterflowsimulations for fullscaleproductionwillbeconductedlaterthismonth. Modelingtools, tracertests and the testingphasehaveshownthat the influence of the artificialinfiltrationcanonlybeobserved in the coarsestpart of the esker (glaciofluvialcoarseunit).

  12. The ”glaciofluvialcoarse” unitfrom the 3D hydrogeologicalmodel(left) and the correspondinggwflowmodelcellsdepicting the detailedvariationof hydraulicconductivitywithinthatunit(right).

  13. Flow of infiltratedwater (5 days)

  14. Flow of infiltratedwater (10 days)

  15. Flow of infiltratedwater (5 weeks)

  16. Flow of infiltratedwater (10 weeks)

  17. Flow of infiltratedwater (15 weeks)

  18. Flow of infiltratedwater (26 weeks)

  19. CONCLUSIONS Allthe investments in researchhavebeenlessthan 5 M€ (lessthan 3% of the totalbudget). The cost of oneproductionwell is about 100,000 €. Averagepumpingrateof the MAR plant’sproductionwell is 6,700 m3/d, whereas the avg. yield of otherwaterproducers’ wellswithin the sameeskerarea is 500 m3/d. The requiredone-yeartestingphasewassuccessfullycompletedbefore the entireconstructionwork of the projectwascompleted. The cost of eachday of delay in waterproductionafter the construction is completed is about 20,000 € due to the loan interests. The requiredproductionrates of the artificiallyinfiltratedgroundwater in this 176 M€ projectwouldnothavebeenachievedwithout the 3D geologicalinformationsystem and models.

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