GEOSCAN, résultats de la recherche


TitreA numerical study of barometric loading
TéléchargerTéléchargement (publication entière)
AuteurWalsh, R; Milloy, C
SourceRegional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario geoscientists open house; par Russell, H A J; Ford, D; Priebe, E H; Holysh, S; Commission géologique du Canada, Dossier public 8363, 2018 p. 41,
ÉditeurRessources naturelles Canada
RéunionRegional-Scale Groundwater Geoscience in Southern Ontario: Open House; Guelph; CA; février 28 - mars 1, 2018
Documentdossier public
Mediaen ligne; numérique
Référence reliéeCette publication est contenue dans Russell, H A J; Ford, D; Priebe, E H; Holysh, S; (2018). Regional-scale groundwater geoscience in southern Ontario: an Ontario Geological Survey, Geological Survey of Canada, and Conservation Ontario geoscientists open house, Commission géologique du Canada, Dossier public 8363
Sujetseau souterraine; aquifères; ressources en eau souterraine; gestion des ressources; régimes des eaux souterraines; niveaux des eaux souterraines; puits d'eau; fluctuations de niveaux des puits; établissement de modèles; simulations par ordinateur; logiciel; eau de gisement; fluides des pores; écoulement de la nappe d'eau souterraine; puits d'observation; eaux de surface; hydrogéologie; géologie de l'environnement; géomathématique
Bibliothèque de Ressources naturelles Canada - Ottawa (Sciences de la Terre)
ProgrammeAquifer Assessment & support to mapping, Géoscience des eaux souterraines
Diffusé2018 02 16
Résumé(disponible en anglais seulement)
This work was inspired by a presentation by RVCA at last year's Groundwater Open House, which was a literature review of barometric pressure responses in groundwater level time series data. Barometric pressure changes are known to produce water level fluctuations in monitoring wells while the water level in the aquifer does not change. Last year's review identified barometric loading signals in some PGMN wells, and recommended further research. As it happened, Geofirma had developed modelling tools for other purposes which were well suited to modelling barometric loading phenomena. In particular, we have added a one-dimensional hydromechanical coupling algorithm to TOUGH2, a general-purpose numerical simulation program for multi-phase fluid and heat flow. Unlike many geotechnical and hydrogeological codes, this model explicitly accounts for compressibility of the pore fluid (gas, water, or both). Out of interest, we undertook a small modeling project using this code to simulate barometric loading. This work demonstrates several different possible barometric loading scenarios using an idealized model of a well and aquifer system.
There are two mechanisms responsible for transmission of barometric pressure changes to an aquifer: (1) air flow through the unsaturated zone, and (2) mechanical transmission of pressure changes to subsurface formations. Both mechanisms are present in all hydrogeological settings, but the dominant mechanism is a function of aquifer confinement, compressibility, and the presence or absence of gas. Since observation wells are generally open to the atmosphere, changes in barometric pressure reach the well water almost instantly, but vertical flow due to barometric pressure fluctuations may be delayed in reaching the aquifer or may never reach the aquifer at all. The difference in atmospheric communication between the well water and formation water cause well water levels to fluctuate in order to stay in hydraulic equilibrium with the aquifer.
This project was limited in scope, but the tools and understanding that have been developed could be used to examine a number of questions related to barometric loading, including: the influence of observation well construction on barometric loading, including the effects of wellbore storage, well skin, sealed wells, and buried vibrating wire piezometers; the testing of barometric efficiency, barometric response functions, and other deconvolution algorithms; modelling of the barometric response of specific observation wells, improving understanding of site specific properties and processes governing the barometric response; development of templates or algorithms for assessment of barometric efficiency or barometric response functions; and, the influence of loading by precipitation events or changes in river and lake stage.