NSF Rapid Proposal: Flows of the future: Capitalizing on an extreme weather year to evaluate future summer streamflows in the Cascades

雪是太平洋西北部和美国西部森林、水生生态系统和社区的重要水分来源。2014-2015年冬季是有记录以来最温暖的冬季，随后是异常温暖干燥的春季，导致俄勒冈州西部的河流流量创历史新低，并提前宣布干旱。这种水文干旱代表了河流流量的总体减少，可以通过下游的仪表方便地监测。然而，流量减少对上游的影响很难从下游的测量来评估。因此，有必要评估水源对降水减少和气象干旱的反应。了解水源如何（以及通过什么机制）对气象干旱作出反应，将能够根据上游生态反应来解释流量测量记录。实地活动将为本科生提供宝贵的实地培训，进行科学刺激和社会相关的研究。这项研究也将为博士后研究人员提供指导和培训本科生的机会。调查人员将通过一系列协调的活动来利用这一机会，包括：1)与公共和私人供水和电力公司会面，为未来的流量预测提供框架；2)与联邦和州的土地和水资源管理者会面，分享调查结果，讨论低流量对水资源可用性和生态后果的影响；3)与记者合作，传播准确的实时发现（类似于每月的降雪报告）。这一建议认为，水源可以通过横向或纵向收缩来应对干旱。泉水供给的水流会从连续的泉水流出水平“跳跃”，而地表供给的水流会收缩。这些水的来源区域将有不同的化学特征，他们可以追踪。研究区包括：(a)以地表水流为主的西喀斯喀特流域，呈现出基流退缩迅速、夏季流量极低的浮华流态；(b)泉水补给的高瀑布流域，代表了一个缓慢响应的流态，具有长期和持续的基流衰退，通过深层地下水对大容量冷水泉的贡献来维持夏末的流态。研究人员将采用基于实地的方法，从大约6月到10月的整个旱季（或第一次降雨事件）收集和分析来自泉水和地表水流主导的流域的数据。夏季流量衰退将使用美国地质调查局的主仪表和为我们的小溪流开发的项目阶段高度/溪流流量关系来监测。纵向收缩假说将通过对每个流域的水道源头位置的重复测量和对源头泉的水温（有水/无水的指示）的连续监测来检验。将通过对每条河流的多个断面的重复测量来检验河流的侧向收缩假设。

Snow is a crucial moisture source for forests, aquatic ecosystems, and communities in the Pacific Northwest and across the western US. The winter of 2014-2015 was the warmest winter on record followed by an anomalously warm, dry spring resulting in historically low streamflows and early declarations of drought conditions across western Oregon. This hydrologic drought represents an overall decrease in streamflow that can be monitored conveniently by downstream gages. However the upstream impact of decreased streamflow is difficult to assess from downstream gages. It is therefore necessary to assess how headwater streams react to decreased rainfall and meteorologic drought. Understanding how headwater streams react (and by what mechanisms) to meteorologic drought will enable the interpretation of stream gage records in terms of upstream ecological response. The field campaign will provide undergraduates with valuable field training, conducting scientifically exciting and societally relevant research. This research effort will also provide the post-doctoral researcher with an opportunity to mentor and train undergraduates. The investigators will capitalize on this opportunity through a coordinated set of activities including: 1) meeting with public and private water supply and power utilities to provide a framework for future flow forecasting; 2) meeting with Federal and State land and water managers to share findings and discuss implications for water availability and ecological consequences of low flows; and 3) working with journalists to disseminate accurate real-time findings (similar to the monthly snow report). This proposal posits that headwater streams can respond to drought by contracting laterally or longitudinally. And that spring fed streams will respond with "jumps" from sequential spring outflow levels whereas surface flow fed stream will contract. These source regions for water will have chemically differing signatures which they can track. The study region includes (a) surface-flow dominated Western Cascades watersheds, representing a flashy streamflow regime with rapid baseflow recession and very low summer flows; and (b) the spring-fed High Cascades watersheds, representing a slow-responding streamflow regime with a long and sustained baseflow recession that maintains late summer streamflow through deep-groundwater contributions to high-volume coldwater springs. The investigators will use a field-based approach to collect and analyze data from both spring-fed and surface flow-dominated watersheds throughout the dry season, from approximately June through October (or first rainfall event of consequence). Summer streamflow recession will be monitored using USGS mainstem gages and project stage height/stream discharge relationships developed for our small streams. The longitudinal contraction hypotheses will be tested by repeat measurements of channel head locations in each watershed and continuous monitoring of water temperature (an indication of presence/absence of water) at headwater springs. The lateral contraction hypotheses of streams will be tested by repeat surveys of multiple transects per stream.