Electrical Resistivity Tomography Investigation of Buried Valley Aquifer Systems in the Edmonton Area, Alberta
Notice bibliographique
Résumé
Buried valley aquifers underlying the Edmonton region are a potential source of potable groundwater. The location of the valleys has been mapped previously via borehole investigations, however valley fill heterogeneities and geometry are less known and are important for assessing the buried valley groundwater flow systems. This study focusses on the use, and implementation of electrical resistivity tomography (ERT) for aquifer investigations of buried valleys within the greater Edmonton area. ERT is a geophysical tool used in many applications, including hydrogeological. In this thesis, an overview is provided on ERT use, and factors to consider when carrying out investigations. These factors include array setup and choice, inversion techniques and parameters, error negation, and interpretation based on site knowledge. This study builds upon previous work by more closely examining Edmonton buried valley geometry and heterogeneity through ERT resistivity measurements at a reconnaissance scale. Areas of hydrogeological interest, considerable sediment thickness and proximity to mapped features were a priority. Using reference lithologies, resistivity forward models were developed as a reference point. ERT resistivity values produced two categories of results. Low to moderate resistivity profiles (<50 Ω m) were present in areas with poor drainage, and more likely to exist in areas with high water tables. Moderate to high resistivity profiles (~50 – >500 Ω m) were present in areas with greater drainage. Within each type, up to three resistivity units were identified. Glaciolacustrine silt and surficial clays: 9-12 Ω m; coarse valley fill: 20 – 100 Ω m; and bedrock shale and sandstone: 18 – 30 Ω m. Local tills could not be differentiated through resistivity values, as this was a transitionary unit between valley fill sediments and surface sediments. \n ERT data was found to be most valuable in combination with ground truthing field data, as changes in resistivity may be confidently assigned to geologic units. We experienced variable success in buried valley geometry interpretations. Clear bedrock topography is visible at several sites, while valley sidewalls were not confidently identified. We suggest to supplement ERT data with other data such as borehole lithology, mapping, AEM data, forward modelling, and sediment exposures. In sites of interest, ERT is useful as a reconnaissance-scale tool to determine buried valley presence, and identify areas with thicker coarse basal sediment. The ERT data in this study has provided better characterization of buried valleys in the Edmonton area, and these results can be used to make informed decisions regarding the water security in central Alberta.
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Comment cette classification a été obtenuedéplier
Prédiction machine sur la base complète
Imitation des enseignantsNi prévalence calibrée, ni vérité terrain. Validation humaine à venir. Le volet Gemma est une étiquette directe du modèle pour chaque travail de la base, lue sur la notice réduite au titre. Le volet Codex est un classifieur appris des 10 348 étiquettes directes de Codex et calibré sur les taux pondérés de l'échantillon; les champs sans appui suffisant ne portent aucun appel Codex. Le mode candidate est l'union des deux volets; le consensus est leur intersection. Ces sorties portent le statut machine_predicted_unvalidated et ne sont pas des étiquettes humaines.
Scores du classifieur distillé par catégorie (deux têtes)
| Catégorie | Codex | Gemma |
|---|---|---|
| Métarecherche | 0,000 | 0,000 |
| Méta-épidémiologie (sens strict) | 0,000 | 0,000 |
| Méta-épidémiologie (sens large) | 0,000 | 0,000 |
| Bibliométrie | 0,001 | 0,001 |
| Études des sciences et des technologies | 0,001 | 0,000 |
| Communication savante | 0,001 | 0,000 |
| Science ouverte | 0,000 | 0,000 |
| Intégrité de la recherche | 0,000 | 0,000 |
| Charge utile insuffisante (le modèle a refusé de juger) | 0,001 | 0,000 |
Scores machine (provisoires)
Les deux têtes enseignantes du modèle étudiant, lues sur ce travail. Un score ordonne la base pour la relecture; il n'affirme jamais une catégorie, et le statut de validation accompagne chaque rangée tel quel.
Scores de référence d'un modèle non mature (critères de maturité non atteints, 7 itérations). Un score ordonne; il n'affirme jamais une catégorie.
score_only:v0-immature-baseline · tel quel depuis la passe de notation : score_only signifie que le nombre peut ordonner les travaux, et qu'aucune étiquette de catégorie n'en découleClassification
machine, non validéePrédiction automatique; un appel candidat d’une seule source (Gemma direct ou Codex distillé), pas un consensus.
Le détail, modèle par modèle et score par score, se trouve en fin de page sous « Comment cette classification a été obtenue ».