Collaborative Research: P2C2--Where Has the water Gone? Results from a Watershed Model with Dendroclimatic Inputs

本项目旨在通过应用多种树木年轮变量和水平衡模型的组合来确定河流流量、蒸散发和雪水当量的过去行为。这项研究是一项努力的一部分，旨在提高对200条最大河流中约三分之一的径流的理解，这些河流自20世纪50年代以来发生了重大变化，但缺乏关于单个流域季节性径流变化的更长时间（世纪尺度）信息的背景，而这些信息可能有助于限制未来的气候模型预测。具体来说，研究人员的目标是通过应用多个树木年轮变量和水平衡模型的组合来确定河流流量、蒸散和雪水当量的过去行为。季节性输入，即降水和气温，将来自美国西部的多代理树木年轮年表（早期和晚期木材宽度，蓝色强度和木材解剖测量）。实地研究设计将更新ITRDB（国际树木年轮数据库）的树木年表，并将经典采样方法与现代标准化工具相结合。与仅使用统计数据的重建相比，使用流域模型可以提供一种进行敏感性研究的方法，从而改进对扩展记录中不确定性的估计，特别是关于影响入渗和径流效率（径流与降水的比率）的景观和植被因素。该项目包括一项概念验证研究，以阐明我们的月度水平衡模型如何使用季节性气候仪器和代理记录进行校准和运行。用水平衡法重建的流量精度将与传统的基于树木年轮数据的定量流量回归方法重建的流量精度进行比较。研究区域是特拉基/卡森河流域（内华达州和加利福尼亚州），它体现了美国西部管理者和规划者目前面临的许多水资源问题。该流域的干旱特征将被研究，以将最近的干旱置于长期背景下。通过将新的重建结果与其他西部河流的现有重建结果进行比较，将评估与大尺度气候驱动因素相关的干旱变异的空间方面。该项目还包括开发一个互动式在线地图工具，供资源管理者、规划者和公众用于探索当地和区域水文气候的历史。潜在的更广泛影响（bi）包括有助于改善特拉基/卡森盆地以及内华达山脉（美国西部淡水资源的重要山脉）的水资源和森林资源管理的数据。该项目将支持两名直接参与该项目的研究生和几名本科生。该项目还将开发一个在线地图工具，供参加UA树轮实验室外展项目的K-12学生使用。该奖项反映了美国国家科学基金会的法定使命，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 aims to determine the past behavior of river discharge, evapotranspiration, and snow-water equivalent by applying a combination of multiple tree-ring variables and water balance modeling. This research is part of an effort to improve the understanding of runoff from about one-third of the 200 largest rivers which has changed significantly since the 1950s yet lacks context for much longer (century-scale) information on seasonal runoff variability for individual watersheds that could help constrain future climate model projections.Specifically, the researchers aim to determine the past behavior of river discharge, evapotranspiration, and snow-water equivalent by applying a combination of multiple tree-ring variables and water balance modeling. Seasonal inputs, i.e. precipitation and air temperature, will be derived from multi-proxy tree-ring chronologies (early- and late-wood width, blue intensity, and wood anatomy measurements) in the western U.S. The field study design will update tree-ring chronologies that are part of the ITRDB (International Tree-Ring Data Bank) and will combine classic sampling methods with modern standardization tools. Compared with statistics-only reconstructions, the use of a watershed model may provide a way to perform sensitivity studies that improve the estimation of uncertainty in the extended records, in particular with regard to landscape and vegetation factors influencing infiltration and runoff efficiency (ratio of runoff to precipitation). A proof-of-concept study is included in the project to clarify how our monthly water balance model can be calibrated and run using seasonal instrumental and proxy records of climate. Accuracy of discharge reconstructions by the water-balance approach will be compared with that of reconstructions by the conventional approach of regression of gaged discharge on tree-ring data. The study area is the combined Truckee/Carson River Basin (Nevada and California), which embodies many of the water resources issues currently confronting managers and planners in the western U.S. Drought characteristics of this basin will be examined to place recent droughts in a long-term context. Spatial aspects of drought variability related to large-scale climatological drivers will be evaluated by comparing the new reconstructions with existing ones for other western rivers. The project also includes development of an interactive online mapping tool for use by resource managers, planners, and the general public in exploring the history of local and regional hydroclimate.The potential Broader Impacts (B.I.) include data useful for improved management of water and forest resources in the Truckee/Carson Basin and by extension in the Sierra Nevada, a critical mountain range for freshwater resources in the western United States. The project will support two graduate students directly engaged in the project as well as several undergraduate students. The project will also develop an online mapping tool that K-12 students who participate in UA Tree-Ring Lab's outreach program would be able to use.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.