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

该项目分析了使用树轮衍生的径流信息作为一种替代技术来开发温带复杂河流流域的河流径流的长期记录。更好和更长的河流流量记录将有助于改善正在经历和预测干旱和供水短缺的大型和复杂流域的水资源管理。在测量径流记录有限的地方，可以使用基于树轮的径流记录来了解可能的变化范围，从而改进水管理规划和建模。这项技术主要用于地表水文相对简单的半干旱环境。该项目在温带、水文复杂的流域实施和分析基于树轮的径流模拟技术，以评估其有效性，从而改善这些流域的抗旱工作。这项研究将与当地利益攸关方合作进行，有可能为当地的水管理计划、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其自己的决策框架的能力。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，但其复杂的水文学使水流重建在供水预测中的应用变得复杂。为了在这些流域中完成有意义的树木年轮模拟，这些流域的多个径流来源不断变化，意味着水资源管理依赖于季节性径流信息，该项目直接针对干旱季节径流，并将研究流域分解为独立的主干和子流域重建。该项目将把一个大型树轮年表网络与气象、网格化气候和来自盆地主干和次流域量规的仪器径流数据进行比较。利用这些关系作为有针对性的年表重新采样的指南，将为过去几个世纪的每个盆地重建过去夏季径流和干旱的古气候。在夏季，积雪融化、气温和降雨量共同决定了径流，这些因素中的每一个也都与树木的径向生长有关。重建结果将与过去水文气候可变性的独立估计、模型模拟和独立开发的气候场进行统计比较，以确定最近的干旱在过去几个世纪是否异常，以及中长期内部水文气候可变性是否包含强迫的人为信号。更新的年表将使人们能够审查最近的极端干旱事件，并估计未来发生类似规模干旱的可能性。该项目以世界上最复杂的流域之一弗雷泽河流域(FRB)为目标，为加强美国和全球温带流域的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智力优势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.