Abstract The Central Valley in California is characterized by a semi-arid climate prone to droughts, a variable surface water supply, and immense agricultural areas dependent on groundwater irrigation. The groundwater is stored in a complex aquifer system composed of alternating layers of coarse sediments and fine-grained sediments acting as confining materials. Groundwater fluctuations are coupled with both the elastic and inelastic land surface deformation historically observed in the Central Valley. Surface deformation poses a hazard to the California Aqueduct, which supports Central Valley agriculture and large urban populations in Southern California. The risk of reduced aqueduct efficacy and expensive repairs compels water resource managers to carefully monitor land deformation in the Valley. A persistent drought in the region began in 2012, intensified in 2014, and was abruptly alleviated by a wet period from Dec-2016 to Feb-2018. NASA's UAVSAR L-band synthetic aperture radar acquired 31 high resolution radar images between May-2013 and Nov-2018. The interferometric phase difference between acquisitions is used to develop a time series of vertical displacement and identify and track a rapidly forming subsidence feature adjacent to the California Aqueduct. The surface area of the feature that subsided 10 cm or more by the end of the time series reaches 4452 ha and a 10.5+ km segment of the aqueduct. This study also incorporates extensometer measurements, precise leveling surveys, Sentinel-1A displacement, concurrent water elevation data, well construction reports, nearby extensometer measurements, aquifer material characterization, and environmental conditions. Spatiotemporal data availability limits the appropriateness of calculations and models able to be performed for different sites along the aqueduct. We aim to offer insight into heterogeneous subsurface properties and mechanics, estimate the permanent loss of aquifer storage volume, and identify additional data that would aid water management.

中文翻译：

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干旱引起的快速地面沉降及其对加利福尼亚渡槽的影响

摘要 加利福尼亚州中央山谷的特点是半干旱气候容易发生干旱，地表水供应多变，以及依赖地下水灌溉的广阔农业区。地下水储存在一个复杂的含水层系统中，该系统由作为限制材料的粗沉积物和细粒沉积物的交替层组成。地下水波动与历史上在中央谷地观察到的弹性和非弹性地表变形有关。表面变形对支持中央山谷农业和南加州大量城市人口的加利福尼亚渡槽构成危害。渡槽效率降低和维修费用昂贵的风险迫使水资源管理者仔细监测山谷的土地变形。该地区的持续干旱始于 2012 年，2014 年加剧，并在 2016 年 12 月至 2018 年 2 月的潮湿期突然缓解。NASA 的 UAVSAR L 波段合成孔径雷达在 2013 年 5 月至 2018 年 11 月期间获取了 31 张高分辨率雷达图像。采集之间的干涉相位差用于开发垂直位移的时间序列，并识别和跟踪与加利福尼亚渡槽相邻的快速形成的沉降特征。在时间序列结束时下降 10 厘米或更多的特征的表面积达到 4452 公顷和 10.5 公里以上的渡槽段。这项研究还包括引伸计测量、精确水准测量、Sentinel-1A 位移、并发水位高程数据、井施工报告、附近引伸计测量、含水层材料特性和环境条件。时空数据的可用性限制了能够为沿渡槽不同地点执行的计算和模型的适当性。我们的目标是提供对异质地下特性和力学的洞察，估计含水层存储量的永久损失，并确定有助于水管理的其他数据。