Incorporating seasonal and extreme hydrologic events into groundwater recharge and vulnerability assessment

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The security and sustainability of groundwater resources at the regional scale depend on the development of realistic source protection strategies and accurate estimates of natural replenishment or recharge, a parameter that has proven to be extremely difficult to quantify at the regional scale. The influence of transient hydrologic conditions on groundwater vulnerability and recharge is rarely accounted for yet may represent one of the most critical controlling parameters. For example, seasonal climatic variability and extreme hydrologic conditions, such as major precipitation events and mid-winter snow melt periods, can significantly influence recharge distribution and magnitude over the course of an annual cycle. Extreme hydrologic variability can also represent a major factor in introducing surface sources of contamination into the subsurface. This is particularly evident and critical in agricultural landscapes where diverse non-point sources exist ranging from nutrient solutes to colloidal pathogens. Climatic evidence suggests that the frequency of occurrence of these types of extreme hydrologic events is increasing in Canada and worldwide, potentially due to the influence of climate change. The main objective of this proposed research program is to investigate and quantify the impact of seasonal hydrologic variability on estimates of regional groundwater recharge and source vulnerability assessment. The research work will involve field experimentation to collect dense, integrated data sets designed to permit the quantification of recharge and contaminant mass flux throughout the course of the annual climatic cycle and numerical analysis using emerging models that can incorporate transient hydrologic complexity including climatic variability, fully integrated groundwater-surface water interaction, and temperature and contaminant transport under conditions of variably saturation in a three dimensional framework. The results of the research program will be immediately useful to provincial and municipal authorities in developing long-term groundwater management and source protection plans and in establishing science-based policies governing land use management related to emerging groundwater protection legislation.