Influence of Seasonal Hydrology on Watershed Dynamics and Groundwater Vulnerability

地下水资源的可持续性已成为全球范围内的一个令人关切的问题，特别是考虑到气候极端情况的增加和遗留污染物的影响。理解和适应这些不断变化的现实需要考虑分水岭尺度上的水文现象。传统的地下水水源保护战略面临挑战，以纳入瞬变水文条件的影响和历史土地利用做法的影响。现代数值模型是在流域尺度上研究区域地下水可持续性和脆弱性的主要工具。主要挑战涉及这些模型的适当参数化和将结果的不确定性降至最低。特别具有挑战性的是地下水补给的可变性，它直接控制地下水库的补给和污染物的装载。季节性事件，包括高强度降水和积雪融化，会对补给过程产生重大影响，但人们对它们的影响知之甚少。拟议的研究计划将包括三个主要组成部分。第一个涉及对安大略省南部农村地区瞬时地下水补给的现场估计。这些信息将使人们深入了解地下水补给过程的瞬变性质，以及不同水文、地质和地形条件下污染物的不同负荷模式。第二个组成部分将涉及将补给估计纳入流域的大型综合地下水-地表水模型。将进行模拟，以比较基于传统补给估计技术和结合测量补给值的方法对来自非点源农业的区域污染物质量负荷的预测估计、水平衡计算和捕获区动态的结果。总体而言，这项工作将说明提供现场测量的补给量估计在与区域尺度建模相关的适用性和不确定性程度方面的价值。第三部分涉及对流域内在季节性气候事件期间出现强烈短期补给现象的地点的近地表水文现象进行详细监测。这些类型的局部补给现象很难在区域模型中捕捉到，其结果可以为加强区域建模工作和量化公共供应井脆弱性提供有价值的信息。总体而言，这项研究将为控制补给现象和内在不确定性的主要过程提供关键的见解，并将有助于为正在重新审查加拿大各地地下水水源保护战略的政策制定者提供信息。

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.