Influence of Seasonal Hydrology on Watershed Dynamics and Groundwater Vulnerability

点击翻译按钮获取中文摘要

The sustainability of groundwater resources has become an issue of concern at a global scale particularly in light of increasing climatic extremes and the impact of legacy contaminants. Understanding and adapting to these changing realties is requiring consideration of hydrologic phenomena at the watershed scale. Conventional groundwater source protection strategies are challenged to incorporate the influences of transient hydrologic conditions and the influence of historical land use practices. Modern numerical models serve as primary tools to investigate regional groundwater sustainability and vulnerability at the watershed scale. Major challenges relate to the appropriate parameterization of these models and minimizing uncertainty in the results. Particularly challenging is the variability in groundwater recharge, which directly controls the replenishment of subsurface reservoirs and the loading of contaminants. Seasonal events including high intensity precipitation and snow melt can significantly influence recharge processes and their influence is poorly understood. The proposed research program will include three main components. The first involves field estimates of transient groundwater recharge throughout rural landscapes within southern Ontario. The information will provide insight into the transient nature of the groundwater recharge process and the variable loading patterns of contaminants under different hydrologic, geologic and topographic conditions. The second component will involve the incorporation of the recharge estimates into large scale, integrated groundwater-surface water models of the watersheds. Simulations will be conducted to compare the results of predictive estimations of regional contaminant mass loading from non-point agricultural sources, water balance calculations and capture zone dynamics based on conventional recharge estimation techniques and on an approach that incorporates measured recharge values. Overall, this work will illustrate the value of providing field measured estimates of recharge in the applicability and degree of uncertainty related to regional scale modeling. The third component involves detailed monitoring of near-surface hydrologic phenomena at locations within the watersheds where intense, short term recharge phenomena occur during seasonal climatic events. These types of local recharge phenomena are challenging to capture within a regional model and the results can provide information valuable to enhancing the regional modeling exercises and the quantification of public supply well vulnerability. Overall, the research will provide critical insight into the major processes controlling recharge phenomena and intrinsic uncertainty, and will help to inform policy makers who are in the process of re-examining groundwater source protection strategies across Canada.