Hydrogeological parameterization is a key step in modeling well head protection zones in alluvial heterogeneous deposits, often exploited for drinking water needs. We performed field and laboratory scale experiments for subsurface investigation at the “Lauswiesen” site in southern Germany, targeted to set up a numerical model for probabilistic wellhead protection zones assessment. The neighbouring Neckar river is the main boundary condition and strongly impacts the groundwater flow regime. Spatial variations of hydraulic conductivity, K, over several orders of magnitude, mainly dominate flow and transport processes. Sieve analyses performed on undisturbed core samples emphasized a very heterogeneous , highly conductive aquifer. By means of a multivariate cluster analysis, three different types of aquifer materials (clusters / facies) were identified to characterize the heterogeneity of the aquifer lithology. Spatial variability of each material type was separately analysed by a geostatistical procedure based on indicator variography. As a result, 3D recombined spatial distributions of the identified clusters were used to reconstruct the internal aquifer architecture. Since each cluster is completely characterized in terms of its hydraulic and transport parameters, internal variability as well as structural properties, the methodology yields three-dimensional pictures of aquifer parameter distributions, avoiding the usual difficulties of upscaling. The assessment of well head protection zones and their associated uncertainty are then obtained by a Monte Carlo procedure, based on equiprobable realizations of hydraulic conductivity fields. These are embedded within the numerical aquifer model to render the probabilistic well-capture zones distribution, subject to the initial and transient boundary conditions observed at the field site.

Multivariate geostatistical parameterization approach for 3D transient stochastic modeling of wellhead protection zones in a highly heterogeneous aquifer

GUADAGNINI, LAURA;RIVA, MONICA;
2003

Abstract

Hydrogeological parameterization is a key step in modeling well head protection zones in alluvial heterogeneous deposits, often exploited for drinking water needs. We performed field and laboratory scale experiments for subsurface investigation at the “Lauswiesen” site in southern Germany, targeted to set up a numerical model for probabilistic wellhead protection zones assessment. The neighbouring Neckar river is the main boundary condition and strongly impacts the groundwater flow regime. Spatial variations of hydraulic conductivity, K, over several orders of magnitude, mainly dominate flow and transport processes. Sieve analyses performed on undisturbed core samples emphasized a very heterogeneous , highly conductive aquifer. By means of a multivariate cluster analysis, three different types of aquifer materials (clusters / facies) were identified to characterize the heterogeneity of the aquifer lithology. Spatial variability of each material type was separately analysed by a geostatistical procedure based on indicator variography. As a result, 3D recombined spatial distributions of the identified clusters were used to reconstruct the internal aquifer architecture. Since each cluster is completely characterized in terms of its hydraulic and transport parameters, internal variability as well as structural properties, the methodology yields three-dimensional pictures of aquifer parameter distributions, avoiding the usual difficulties of upscaling. The assessment of well head protection zones and their associated uncertainty are then obtained by a Monte Carlo procedure, based on equiprobable realizations of hydraulic conductivity fields. These are embedded within the numerical aquifer model to render the probabilistic well-capture zones distribution, subject to the initial and transient boundary conditions observed at the field site.
Understanding through Modelling
cluster analysis; multivariate; facies
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Utilizza questo identificativo per citare o creare un link a questo documento: https://hdl.handle.net/11311/562281
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