Developing Tree-Ring Based Streamflow Reconstructions for Large and Complex River Basins

该项目分析了使用树木年轮导出的径流信息作为替代技术，以开发温带复杂流域河流径流的长期记录。 更好和更长时间的河流流量记录将有助于改善正在经历和预计会发生干旱和供水短缺的大型复杂流域的水资源管理。 在测得的径流记录有限的地方，基于树木年轮的径流记录可用于了解可能的变化范围，从而改善水管理规划和建模。 这项技术主要用于地表水文相对简单的半干旱环境。 该项目实施和分析基于树木年轮的径流模拟技术在温带，水文复杂的流域，以评估其有效性，从而改善干旱缓解这些流域。 这项研究将与当地利益攸关方合作进行，并有可能为当地水管理计划，鱼类保护以及正在进行的水和资源权利谈判提供信息。技术讲习班将建设利益攸关方将这些新记录纳入自身决策框架的能力。 该项目为本科生提供实地和学术学习机会，并支持一名早期职业女性博士后研究科学家的继续研究计划。大的温带流域越来越容易受到干旱的影响，但其复杂的水文复杂的流量重建供水预测的应用。 为了完成有意义的树木年轮在这些流域，其中多个，转移的径流源跨几个子流域意味着水资源管理是依赖于季节性径流信息建模，该项目直接针对干旱季节径流和分解研究流域到独立的主干和子流域重建。 该项目将比较一个大型的树木年轮年表网络与气象、网格气候和来自流域主干和子流域测量仪的仪器流量数据。 利用这些关系作为有针对性的年表重建的指导，过去的夏季径流和干旱的古气候重建将开发跨越过去几个世纪的每个流域。 在夏季，融雪、气温和降雨量的组合决定了径流量，这些因素中的每一个也与径向树木的生长有关。 重建将与过去水文气候变化的独立估计，模型模拟和独立开发的气候场进行统计比较，以确定最近的干旱是否在过去几个世纪中异常，以及中长期内部水文气候变化是否包含强制的人为信号。 更新后的年表将有助于审查最近的极端干旱事件，并估计今后发生类似规模干旱的可能性。 该项目以世界上最复杂的河流流域之一弗雷泽河流域（FRB）为目标，为加强美国和地球仪的温带流域水管理提供了一个健全的框架。该奖项反映了NSF的法定使命，并通过使用基金会的知识价值和更广泛的影响审查标准进行评估，被认为值得支持。

This project analyses the use of tree-ring derived streamflow information as an alternative technique to develop long-term records of river streamflow in temperate, complex river-basins. Better and longer stream-flow records will help improve water resource management in large and complex watersheds experiencing and anticipating drought and water supply shortages. In places where measured runoff records are limited, tree-ring based streamflow records can be used to understand the range of possible variability and to therefore improve water management planning and modeling. This technique has mostly been used in semi-arid environments with relatively simple surface hydrology. This project implements and analyses tree-ring based streamflow modeling techniques in temperate, hydrologically complex watersheds, to assess its effectiveness, and thereby improving drought mitigation in those basins. This research will be conducted in collaboration with local stakeholders, and has the potential to inform local water management plans, fish conservation, and ongoing negotiations of water and resource rights. Technical workshops will build capacity for stakeholders to incorporate these new records into their own decision-making framework. The project provides field and academic learning opportunities for an undergraduate student and supports the continuing research program of an early career female Postdoctoral Research Scientist. Large temperate watersheds are increasingly susceptible to the impacts of drought, but their complex hydrology complicates the application of flow reconstruction to water supply forecasting. To accomplish meaningful tree-ring modeling in these basins, where multiple, shifting sources of runoff across several sub-basins mean that water management is reliant on seasonal streamflow information, this project directly targets drought-season runoff and decomposes the study watershed basin into independent main-stem and sub-basin reconstructions. This project will compare a large network of tree-ring chronologies with meteorological, gridded climate, and instrumental streamflow data from the basin main-stem and sub-basin gauges. Using these relationships as a guide for targeted chronology resampling, paleoclimate reconstructions of past summer runoff and drought will be developed for each basin spanning the last several centuries. During the summer season a combination of snowmelt, air temperatures, and rainfall determine streamflow and each of these factors is also linked to radial tree growth. The reconstructions will be statistically compared against independent estimates of past hydro-climate variability, model simulations, and independently developed climate fields to determine whether recent droughts have been exceptional in the last several centuries, and whether medium- and long-term internal hydro-climate variability contains a forced anthropogenic signal. Updated chronologies will permit examination of a recent extreme drought event and estimates of the probability of similar-magnitude droughts in the future. By targeting one of the most complex river basins in the world, the Fraser River Basin (FRB), this project provides a sound framework for enhancing water management in temperate watersheds in the United States and around the globe.This award reflects NSF's statutory mission and has been deemed worthy of support through evaluation using the Foundation's intellectual merit and broader impacts review criteria.