Fine-scale spatiotemporal variation in subsidence across California’s San Joaquin Valley explained by groundwater demand
Fine-scale spatiotemporal variation in subsidence across California’s San Joaquin Valley explained by groundwater demand
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DOI：
10.1088/1748-9326/abb55c
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发表时间：
2020-10
影响因子：
6.7
通讯作者：
M. Levy;W. Neely;A. Borsa;J. Burney
中科院分区：
文献类型：
--
作者：
M. Levy;W. Neely;A. Borsa;J. Burney
实现农业地下水的可持续利用仍然是全世界面临的一项重大挑战，部分原因是关于地下水抽取量的数据有限。新一代干涉合成孔径雷达（干涉合成孔径雷达）数据提供了对地表沉降和抬升的高空间和时间分辨率测量，已知这反映了地下水储存的变化。在这里，我们建立了第一次在当地灌溉用水需求和InSAR派生的垂直地面位移在加州的圣华金河谷，以提高利用遥感位移的理解和管理地下水在精细尺度的目标之间的定量联系。我们涉及100米，次月位移估计产生的土地覆盖和天气数据的灌溉用水需求，通过执行一套物理过程驱动的统计分析，利用（一）气候造成的地表水供应的时间变化，和（二）空间变化的水需求不同的土地利用。2015年至2017年，耕地的总沉降量是未耕地的7倍，干旱年沉降率是未耕地的9倍。在未开垦的地区，在干旱和潮湿的年份，沉降率差别很小。相反，在耕地内，干旱年的沉降率是湿润年沉降率的两倍以上，这表明在降水和地表水供应减少的情况下，农业地下水抽水量增加。平均沉降和沉降对水需求的边际响应对于耕地、特别是农田和牧场作物来说是最大的，并且与距地表水供应基础设施的距离成比例。这些研究结果表明，陆面观测有可能用于量化连接的地表水和地下水过程在政策相关的规模。
Achieving sustainable agricultural groundwater use remains a significant challenge worldwide in part because data on groundwater withdrawals are limited. A new generation of interferometric synthetic aperture radar (InSAR) data provide high spatial- and temporal- resolution measurements of subsidence and uplift of the earth’s surface, which are known to reflect change in groundwater storage below. Here, we establish for the first time a quantitative link between local irrigation water demand and InSAR-derived vertical land surface displacements in California’s San Joaquin Valley, with the goal of increasing the utility of remotely sensed displacements for understanding and managing groundwater at fine scales. We relate 100 m, sub-monthly displacements to estimates of irrigation water demand generated from land cover and weather data by performing a suite of physical process-motivated statistical analyses that leverage (i) temporal variations in surface water supplies created by climate, and (ii) spatial variations in water demand created by different land uses. Between 2015 and 2017, cultivated land experienced up to seven times the total subsidence, and up to nine times the dry year subsidence rate, of uncultivated land. In uncultivated areas, subsidence rates differed minimally across dry and wet years. In contrast, within cultivated areas, dry year subsidence rates were more than double wet year rates, indicating increased agricultural groundwater pumping under diminished precipitation and surface water supplies. Mean subsidence, and the marginal response of subsidence to water demand, were greatest for cultivated lands and for field and pasture crops in particular, and were also proportional to distance from surface water supply infrastructure. These findings demonstrate that land surface observations have the potential for use in the quantification of connected surface water and groundwater processes at policy-relevant scales.