RAPID: Quantifying timescales of groundwater recharge and discharge in seasonally snow-covered headwater catchments

在美国西部，有效和公平的水资源管理面临的最大挑战之一是河流流量的高时空变异性。尽管冬季总降雪量是河流流量的主要驱动因素，但随着气温变暖和降水模式的变化，冬季降雪量与河流流量之间的关系正变得越来越多变。这种变化在2020年和2021年科罗拉多河上游流域的春季径流中得到了突出体现，那里的年降雪量接近平均水平，但年流量远低于预期。最近的研究表明，这种变化的一个主要原因是地下水储存对多年来的气候作出反应。该项目将提供基线数据，以确定区域地下水储存量变化的方式和原因，最终使资源管理者和用水用户能够提前数月至数年预测和规划年度供水，消除因水资源过多或往往太少而无法满足需求的意外情况。该项目将直接解决每年时间尺度上水平衡关闭的隐含假设。这项工作建立在几十年的水化学研究的基础上，该研究表明融雪产生的水流主要由“老”水组成，而这种老水的变化与径流效率的变化有很大关系。在本项目中，使用最先进的示踪剂（如3H、3H/3He、SF6）、水同位素和主要离子化学进行样本收集和分析，将开始阐明这些关系的机制，以及它们如何随着景观结构、底层地质和气候而变化。这项工作的重点是广泛研究犹他州的集水区，以及整个美国西部的研究集水区（CZCN， CZO， USFS, USDA ARS， USGS）。与犹他州、亚利桑那州、科罗拉多州和新墨西哥州的资源管理人员的持续合作将促进将获得的知识转化为应用。该奖项由水文科学和关键地带项目共同资助。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。

One of the largest challenges in efficient and equitable water resource management in the western US is the high spatial and temporal variability in streamflow. Although total winter snowfall is the primary driver of streamflow, the relationship between winter snow and river discharge is becoming ever more variable as temperatures warm and precipitation patterns change. This variability is highlighted by Spring runoff in the upper Colorado River Basin during 2020 and 2021, where annual snowfall was close to average, but annual streamflow was much lower than expected. Recent work has demonstrated that a major cause of this variability is groundwater storage that responds to climate over multiple years. This project will provide baseline data to determine how and why regional groundwater storage varies, ultimately allowing resource managers and water users to anticipate and plan for annual water supply months to years in advance, eliminating surprises due to having either too much, or more often too little water to meet demands.This project will directly address the implicit assumptions of water balance closure on an annual time scale. The work builds on decades of hydrochemical research that demonstrates snowmelt-derived streamflow consists primarily of “old” water and that variability in this old water is significantly related to variability in runoff efficiency. Sample collection and analyses using state of the art age tracers (e.g. 3H, 3H/3He, SF6), water isotopes, and major ion chemistry during this project will begin to elucidate the mechanisms underlying these relationships and how they vary with landscape structure, underlying geology, and climate. The work focuses on extensively studied catchments in Utah as well as research catchments (CZCN, CZO, USFS, USDA ARS, USGS) throughout the western US. Ongoing partnerships with resources managers in Utah, Arizona, Colorado, and New Mexico will facilitate translation of knowledge gained into application.This award is co-funded by the Hydrologic Sciences and Critical Zone programs.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.