Complementarity of multiple in-situ techniques for spatiotemporal assessment of groundwater/surface-water exchanges
Evaluación espaciotemporal de los intercambios entre aguas subterráneas y superficiales mediante la complementariedad de múltiples técnicas in situ
Complémentarité de plusieurs techniques in situ pour l’évaluation spatio-temporelle des échanges entre eaux souterraines et eaux de surface
Complementaridade de múltiplas técnicas in-situ para a avaliação espaço-temporal das trocas entre águas subterrâneas e águas superficiais
Abstract
Site-specific heterogeneity in geological materials plays a crucial role in groundwater (GW) and surface water (SW) interaction, especially in ecosystems sensitive to groundwater influx; for example, salmonid habitats are influenced by localized GW input to streams. While numerous methods have emerged to better understand mechanisms governing GW-SW interaction, few studies compare these methods directly. Therefore, the objective of this study is to evaluate the strengths and limitations of an innovative active heat tracing method to quantify the role of riverbed heterogeneity on GW-SW exchanges. This method was compared with several established techniques such as seepage meters, piezometers, and passive heat tracing at a field site on the Sainte-Marguerite River in Quebec, Canada. The measured spatial variation of the exchange rates due to the presence of a sandbar with coarse materials was shown to be statistically significant. Additionally, temporal analysis helped to identify variations of GW flux even during the cold season when GW flux was expected to be limited due to frozen ground and low infiltration from the snow-covered ground surface. Seepage meters and active heat tracing allowed for spatial analysis of GW-SW interaction, while piezometers with water level loggers and passive heat tracing with installed temperature sensors in the riverbed were convenient for identifying temporal variation of GW-SW exchange rates. The combination of temperature sensors and a heating cable was used for the first time as a tool for active heat tracing and showed good potential to evaluate riverbed thermal properties and GW seepage rates in the river.