Evolution of Groundwater Systems: Effects of Long-Acting Natural and Superimposed Anthropogenic Stressors

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Groundwater levels vary in response to a wide range of natural and anthropogenic stresses (e.g. seasonal climate variability, groundwater pumping) that act over varying time frames. By measuring the response of the aquifer system to such stresses and then attempting to model the response (i.e. using an analytical or process-based numerical model), we can gain considerable insight into how quickly a given stress will manifest in a groundwater level change and how long the effects will last. At the site scale, sufficient data are often available to constrain and calibrate models over short time frames. However, observations of longer-term responses (decades to millennia) are more challenging to acquire, as there are few long-term instrumental records available for aquifers. This means that we need to be innovative and develop new approaches for modeling, in order to explore long-term responses of aquifer systems. My research program will focus on two critically important topics: drought and salinization. We will examine how aquifer systems have responded to drought in both the paleorecord and the instrumental record, by reconstructing groundwater levels from tree ring records and using a range of statistical techniques to characterize groundwater level responses, linkages with climate cycles, and drought occurrence. We will quantify drought propagation rates (e.g. lag time and rates of decline and recovery of groundwater levels) and compare the results to observed data. We will carry out scenario modeling to attribute the causes of drought, determine whether there are tipping points associated with drought where the system recovery is significantly impacted, quantify how rapidly the system recovered, and explore different water management options. Finally, we will carry out two long-term groundwater evolution modeling studies; the first focusing on the occurrence of saline paleowater in coastal deltas, and the second focusing on how submarine groundwater circulation and the salinity distribution change over time in response to changes in sea level and recharge. In Canada and around the world, water resources are increasingly impacted by drought and salinization, with consequent impacts on food and energy security, and biodiversity. Globally, groundwater is increasingly being used to offset freshwater demands, but the long-term impacts of groundwater withdrawal are difficult to quantity, because groundwater responds more slowly to stressors compared to surface waters. My research will advance approaches for using proxy data in groundwater drought studies, characterize aquifer responsiveness to drought and identify management options, and determine climate change-related impacts on the salinity distribution in coastal aquifers. The knowledge gained and the modeling approaches we develop will be important tools for enhancing groundwater resource sustainability studies and for establishing appropriate monitoring networks to detect change.