Water, Drought and Snowpack Monitoring in the United States Using the EarthScope Plate Boundary Observatory GPS Network

含水层、土壤、湖泊和冰川中储水量的变化导致地球弹性变形，这种变形可以用全球定位系统（GPS）探测到。我们建议在地球范围内的GPS站点研究这种与水有关的变形。美国的板块边界观测站（PBO），并利用这些观测结果来估计美国大陆上水负荷的变化。考虑到水和干旱在西部的长期重要性，以及气候变化对整个美国水安全的威胁，改善对水循环的直接监测具有重大的社会和经济意义。通过提供关于水储存和水循环的新数据，这项工作除了改善基础科学外，还有可能对美国的水管理产生重大而积极的影响。这项工作的目标是将GPS负载估计与美国宇航局GRACE卫星任务的质量变化估计以及水文系统及其边界的独立信息相结合，以开发改进的水再分配模型。这项研究特别强调了内华达山脉和落基山脉所有重要的积雪估计，以及加州干旱对地下水变化的影响。美国的中央山谷和其他主要含水层。具体而言，在未来三年内，我们将：1)重新处理所有每日GPS位置数据，以生成可靠的季节性和非季节性位移序列；2)校正所有时间序列的偏移量、瞬态位移和已知的大气/海洋载荷；3)美国大陆水负荷时空反演；4)利用GRACE任务的低分辨率数据约束GPS质量变化，以更好地估算水通量；5)研究当前美国西部干旱对脆弱山地积雪和地下水含水层系统的影响；5)将这项工作的结果作为一组数据产品和随附的方法发布，供科学家使用，并供水管理人员可能的操作使用。

Changes in water storage in aquifers, soils, lakes and glaciers cause the Earth to deform elastically in ways that can be detected using the Global Positioning System (GPS). We propose to study this water- related deformation at GPS stations in EarthScope?s Plate Boundary Observatory (PBO) and use these observations to estimate the variation of water loads over the continental United States. Given the longstanding importance of water and drought in the West, and the threat of climate change to water security across the entire USA, improvements in direct monitoring of the water cycle are of great social and economic relevance. By providing new data on water storage and the water cycle, this work has the potential to make a significant and positive impact on water management in the United States, in addition to improving the underlying science.The goal of this work is to combine GPS load estimates with mass change estimates from NASA's GRACE satellite mission and independent information about hydrological systems and their boundaries to develop improved models for water redistribution. This study puts special emphasis on the all- important snowpack estimates for the Sierra Nevada and Rocky Mountains, and drought impacts on groundwater changes in California?s Central Valley and other principal aquifers in the USA. Specifically, over the next three years, we will: 1) reprocess all daily GPS position data to generate reliable series of seasonal and nonseasonal displacements; 2) correct all time series for offsets, transient displacements, and known atmospheric/oceanic loads; 3) invert for the spatiotemporal water loading across the continental USA; 4) constrain GPS mass changes with lower-resolution data from the GRACE mission to develop better estimates of water fluxes; 5) investigate mass changes of vulnerable mountain snowpack and groundwater aquifer systems in response to the current western USA drought; and 5) publish the results of this work as a set of data products and accompanying methodology for use by scientists and for possible operational use by water managers.