Modeling heterogeneity of gravel-sand, braided stream, alluvial aquifers at the facies scale

Zappa, Giuseppe; Bersezio, R.; Felletti, Fabrizio; Giudici, M.

doi:10.1016/j.jhydrol.2005.10.016

Cited by 81 publications

(66 citation statements)

References 31 publications

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“…This hydraulic feature corresponds to that of open framework gravel (OFG), which is usually observed in outcrops or trenches, and is considered to be the most remarkable hydro-face due to its high permeability. OFG has a distribution that is only centimeters or decimeters thick, but its K value is of the order of 1 × 10 -3 to 1 × 10 -2 m/s, considerably greater than the value for the surrounding layers (Jussel et al 1994;Heinz 2003;Lunt et al 2004;Zappa et al 2006;Ferreira et al 2010;dell'Arciprete et al 2012).…”

Section: Relation Between Slug Tests and Core Propertiesmentioning

confidence: 90%

Dépendance à la profondeur et modèles exponentiels de perméabilité dans des cônes de déjection graveleux

Sakata

Ikeda

2013

Hydrogeol J

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Abstract:To determine depth dependence of permeability in various geologic deposits, exponential models have often been proposed. However, spatial variability in hydraulic conductivity, K, rarely fits this trend in coarse alluvial aquifers, where complex stratigraphic sequences follow unique trends due to depositional and post-depositional processes. This paper analyzes K of alluvial-fan gravel deposits in several boreholes, and finds exponential decay in K with depth. Relatively undisturbed gravel cores obtained in the Toyohira River alluvial fan, Sapporo, Japan, are categorized by four levels of fine-sediment packing between gravel grains. Grain size is also analyzed in cores from two boreholes in the mid-fan and one in the fan-toe. Profiles of estimated conductivity, K , are constructed from profiles of core properties through a well-defined relation between slug-test results and core properties. Errors in K are eliminated by a moving-average method, and regression analysis provides the decay exponents of K with depth. Moving-average results show a similar decreasing trend in only the mid-fan above ~30-m depth, and the decay exponent is estimated as ≈0.11 m -1 , which is 10-to 1000-fold that in consolidated rocks. A longitudinal cross section is also generated by using the profiles to establish hydrogeologic boundaries in the fan.

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Section: Relation Between Slug Tests and Core Propertiesmentioning

confidence: 90%

Dépendance à la profondeur et modèles exponentiels de perméabilité dans des cônes de déjection graveleux

Sakata

Ikeda

2013

Hydrogeol J

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“…Gravel-sand deposits are a common phenomenon along most of the major alluvial rivers. In the European quaternary sedimentary basins, gravel-sand deposits of braided alluvial stream constitute the most extensive and productive aquifer units [9]. From a hydrogeology perspective, detailed understanding of the distribution and connectivity of the most hydraulic zones in an aquifer is critical.…”

Section: Gravel-sand Depositsmentioning

confidence: 99%

“…Coarse-grained alluvial aquifers are typically regarded as close to homogeneous porous media when estimating hydraulic and transport parameters. Groundwater and transport flow through these unconsolidated sediments is however greatly controlled by internal aquifer material architecture [9]. It is therefore important for practicing hydrogeologists to be able to understand and describe spatial variations of aquifer materials using conventional site characterization tools.…”

Section: Introductionmentioning

confidence: 99%

Development of a Preliminary Hydrogeology Conceptual Model for a Heterogeneous Alluvial Aquifer using Geological Characterization

Tonder¹

2013

J Geol Geosci

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Geological characterization of a heterogeneous alluvial channel aquifer was conducted using outcrop mapping and analysis of lithological logs from 15 boreholes drilled at the site. The study was aimed at developing a preliminary hydrogeology conceptual model. A total of 12 lithological samples were tested in the laboratory using falling head permeameter to determine the hydraulic conductivity of each unconsolidated lithology unit. Shale and calcrete outcrops were observed on the study site. Outcrop mapping on the site also indicated the presence of a contact plane between the overlying unconsolidated sediments and the shale of the underlying bedrock where a groundwater discharge zone has been created. Geology logs show that the alluvial channel aquifer comprises of three distinct layered unconsolidated sediment materials (calcrete, clay-silt, sand-gravel deposited formations) that overlie low permeable shale formation. Geological lithology revealed the spatial variation in the nature and type of unconsolidated sediments deposits between boreholes that can influence groundwater occurrence and flow in the aquifer system. The gravel-sand aquifer layer that consists of medium to large pebbles is conceptually the main hydraulically conductive unit with an average laboratory determined hydraulic conductivity of 8.5 m/day. Hydraulic gradient calculated using a combination of boreholes ranges from 0.013-0.022.

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“…Étant donné le type de simulation numérique considéré pour cette étude, chacun de ces hydrofaciès doit être représenté par une seule valeur de conductivite hydraulique, considérée comme la valeur représentative de cet hydrofaciès. À cet effet, plusieurs expressions de la tendance centrale de la distribution de valeurs de conductivite hydraulique peuvent être adoptée, telles que la moyenne harmonique, la moyenne arithmétique et la moyenne géométrique (Zappa et al 2006). La moyenne arithmétique a été adoptée considérant que les valeurs de conductivite hydraulique pour un Le modèle est subdivisé en "n" couches et en "n" 1 mailles.…”

Section: Valeurs Représentatives Des Hydrofacièsunclassified

Caractérisation hydrogéologique des hydrofaciès dans le paléodelta de la rivière Valin au Saguenay /

Boumaiza¹

2008

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Modeling heterogeneity of gravel-sand, braided stream, alluvial aquifers at the facies scale

Cited by 81 publications

References 31 publications

Dépendance à la profondeur et modèles exponentiels de perméabilité dans des cônes de déjection graveleux

Dépendance à la profondeur et modèles exponentiels de perméabilité dans des cônes de déjection graveleux

Development of a Preliminary Hydrogeology Conceptual Model for a Heterogeneous Alluvial Aquifer using Geological Characterization

Caractérisation hydrogéologique des hydrofaciès dans le paléodelta de la rivière Valin au Saguenay /

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