Grace Groundwater Subsetting Tool (GGST)

This app produces basic maps and timeseries using data from the GRACE mission.
NASA’s GRACE mission provides the first opportunity to directly measure groundwater changes from space. By observing changes in the Earth’s gravity field, scientists can estimate changes in the amount of water stored in a region, which cause changes in gravity. GRACE provides a more than 10 year-long data record for scientific analysis. This makes a huge difference for scientists and water managers who want to understand trends in how our resources are being consumed over the long term. GRACE has returned data on some of the world’s biggest aquifers and how their water storage is changing [e.g. Rodell and Famiglietti, 2001; Yeh et al., 2006; Rodell et al., 2007]. Using estimates of changes in snow and surface soil moisture, scientists can calculate an exact change in groundwater in volume over a given time period.
A study by Rodell et al. [2009] in northwest India used terrestrial water storage-change observations from GRACE and simulated soil-water variations from a data-integrating hydrological modeling system to show that groundwater is being depleted at a mean rate of 4.0 +/- 1.0 cm yr-1 equivalent height of water (17.7 +/- 4.5 km3 yr-1) over the Indian states of Rajasthan, Punjab and Haryana (including Delhi). During the study period of August 2002 to October 2008, groundwater depletion was equivalent to a net loss of 109 km3 of water, which is double the capacity of India's largest surface-water reservoir.

本应用借助GRACE（Gravity Recovery and Climate Experiment，重力恢复与气候实验）任务的数据集，生成基础地图与时间序列成果。美国国家航空航天局（National Aeronautics and Space Administration，NASA）的GRACE任务首次实现了从太空直接监测地下水变化的可能。通过观测地球重力场的变化，科学家能够估算区域内储水量的增减——而储水量的变化正是重力场扰动的诱因。GRACE拥有超过10年的长时序观测记录，可用于科学分析，这对希望长期掌握水资源消耗趋势的科研人员与水资源管理者而言具有重要意义。GRACE已获取全球多个大型含水层的相关数据，以及其储水量的动态变化[例如Rodell与Famiglietti，2001；Yeh等，2006；Rodell等，2007]。结合积雪与表层土壤湿度的变化估算值，科学家可计算出特定时段内地下水体积的精确变化量。
Rodell等人2009年开展的印度西北部地区研究，依托GRACE获取的陆地水储量变化观测数据，以及多源数据融合水文模型系统模拟的土壤水变化结果，证实印度拉贾斯坦邦、旁遮普邦与哈里亚纳邦（含德里）的地下水正以平均4.0±1.0厘米/年的等效水层高度（折合17.7±4.5立方千米/年）的速率被损耗。在2002年8月至2008年10月的研究周期内，该区域地下水亏损总量达109立方千米，相当于印度最大地表水库总库容的两倍。