Using a Nested Watershed Approach to Assess Cumulative Effects of Forest Disturbance on Hydrology in a Sub-Boreal Forested Watershed

森林干扰对水文的影响一直是一个重要的研究课题，但大多数研究都是在小流域（1000 km2）上进行的。在我的NSERC发现基金（2005-2012;2013/2015）的支持下，我们成功地开发了一种分离森林干扰和气候变率对水文的相对贡献的方法，并将该方法的应用发表在高影响力期刊上（如Water Resources Research， Journal of hydrology）。我们的进步引出了一个重要的研究问题，这个问题将在本提案中讨论。由于我们以前的研究通常将大流域视为“黑盒子”，因此无法理解大流域森林扰动累积水文响应的潜在机制和过程。因此，一个关键的研究需要是评估森林干扰如何在不同的时空尺度上累积影响水文。要解决这个问题，需要一个嵌套分水岭方法。***在这项拟议的研究中，我将以位于不列颠哥伦比亚省南部内陆的Similkameen河流域（包含9个巢状和测量的子流域）为例，研究森林干扰对水文的累积效应。研究目标（2015-2020年）包括：(1)评估森林干扰和气候变率对各小流域水文的累积影响；(2)应用VIC（变入渗能力）模型模拟未来森林扰动、气候变率和流域性质对各子流域水文的累积效应；3)探索尺度特性，可以用来理解可能的控制机制，并推断不同空间尺度下水文对流域扰动的敏感性。我的长期目标是应用地球化学和景观方法来研究这个大流域的更多机制（例如地表水和地下水的相互作用），以进一步推进流域科学。该研究将为不列颠哥伦比亚省管理森林干扰以保护水生功能提供重要和及时的信息。它将允许制定森林干扰阈值，并确定可能出现的尺度和分水岭特性，以推断不同流域对森林干扰的累积水文反应。最后，该项目将培养2名hqp和4-5名本科生

The impact of forest disturbance on hydrology has long been an important research topic, but the majority of this research has been conducted on small watersheds (1000 km2). With the support from my NSERC Discovery Grants (2005-2012; 2013/2015), we have successfully developed a method for separating relative contributions of forest disturbance and climate variability to hydrology, and the applications of the method have been published on the high-impact journals (e.g., Water Resources Research, Journal of Hydrology). Our progress has led an important research question, which will be addressed in this proposal. As our previous studies normally treated large watersheds as "black boxes", they would not lead to understanding of underlying mechanisms and processes which govern the cumulative hydrological responses to forest disturbance in large watersheds. Thus, a critical research need is to assess how forest disturbance cumulatively influences hydrology over different spatial and temporal scales. To address this question, a nested watershed approach is required.***In this proposed study, I will use the Similkameen River watershed (containing 9 nested and gauged sub-watersheds) located in the Southern Interior of British Columbia as an example to study the cumulative effects of forest disturbance on hydrology. The objectives (2015-2020) include: (1) assessing the cumulative effects of forest disturbance and climatic variability on hydrology for each sub-watershed; (2) applying the VIC (Variable Infiltration Capacity) model to simulate the cumulative effects of future forest disturbance, climatic variability and watershed property on hydrology for each sub-watershed; and 3) exploring scaling properties which can be used to understand possible governing mechanisms and infer hydrological sensitivity to watershed disturbance at various spatial scales. My longer-term goal is to apply geochemistry and landscape approaches to examine more mechanisms (e.g. surface water and groundwater interactions) in this large watershed to further advance watershed science. The proposed research will provide important and timely information for British Columbia to manage forest disturbance to protect aquatic functions. It will allow development of forest disturbance thresholds as well as identification of possible emerging scaling and watershed properties for inferring the cumulative hydrological responses to forest disturbance among different watersheds. Finally, this project will train 2 HQPs and 4-5 undergraduate students.**