The sensitivity of groundwater recharge estimates on the Waterloo Moraine to rain gauge network scale

Andrew J. Wiebe, Steven J. Murray, Paul J. Martin, David L. Rudolph

In the proceedings of: GeoOttawa 2017: 70th Canadian Geotechnical Conference; 12th joint with IAH-CNC

Session: Groundwater and Resources II

ABSTRACT: Groundwater recharge is a critical component of hydrologic models. Recharge estimates require precipitation data; however, their spatial distributions are often based on rain gauges far from a subwatershed. As a result, typical modelling approaches may have significant recharge distribution uncertainty. This study investigates the value of using a network of local rain gauges for recharge estimation in the Alder Creek Subwatershed (80 km2) in southern Ontario, which supplies up to 40% of local municipal groundwater supply. A coupled, fully-distributed model was used to estimate the sensitivity of recharge rates to interpolated rainfall distributions based on five national gauges outside and six local gauges within the watershed. Overall recharge estimates were found to increase by >70% per year when the local gauge network was used, and spatial variability also differed significantly. Results show that increased rain gauge density may impact recharge rate estimations in subwatersheds, with implications for integrated hydrologic modeling.

RÉSUMÉ: La recharge des aquifères est critique aux modèles hydrologiques. Son estimation est néanmoins souvent biaisée puisque la distribution spatiale des précipitations est basé sur des pluviomètres situés loin d'un bassin versant. La distribution de l™estimation de recharge peut ainsi se retrouver avec une incertitude élevée. Notre recherche évalue l™avantage que procure l™utilisation d™un réseaux de pluviomètres locales à l™estimation de la recharge du bassin versant Alder Creek (80 km2), approvisionnant 40% des eaux municipales locales. Notre modèle intégré utilise deux distributions des précipitations interpoler de cinq pluviomètres nationaux et de six pluviomètres locales pour recherche le sensitivité de recharge des aquifères. Nos résultats montrent un accroissement des taux de recharge de >70% quand les pluviomètres locales sont employée. Intensifier la présence de pluviomètres peut donc influencer l™estimation des taux de recharge des bassins versants, ce qui peut enrichir modèles hydrologiques intégrés.

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