Groundwater is a primary hydrological reservoir of the Great Lakes Water Basin (GLB), which is an important region to both Canada and US in terms of culture, society and economy. Due to insufficient observations, there is a knowledge gap about groundwater storage variation and its interaction with the Great Lakes. The objective of this study is to examine the detectability of the groundwater storage change within the GLB using the monthly models from the Gravity Recovery And Climate Experiment (GRACE) satellite mission, auxiliary soil moisture, snow and lake (SMSL) data, and predictions from glacial isostatic adjustment (GIA) models. A two-step filtering method is developed to optimize the extraction of GRACE signal. A two dimensional basin window weight function is also introduced to reduce ringing artifacts caused by the band-limited GRACE models in estimating the water storage change within the GLB. The groundwater storage (GWS) as deviation from a reference mean storage is estimated for the period of 2002 to 2009. The average GWS of the GLB clearly show an annual cycle with an amplitude range from 27 to 91 mm in water thickness equivalent (WTE), and a phase range of about two months. The estimated phases of GWS variations have a half year shift with respect to the phase of SMSL water storage variations which show peaks in March and April. The least squares estimation gives a GWS loss trend of from 2.3 to 9.3 km3/yr within the GLB for the period of study. This wide range of the GRACE GWS results is caused largely by the differences of soil moisture and snow storage from different land surface models (LSMs), and to a lesser extent by the GRACE commission and omission errors, and the GIA model error.
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机译：地下水是大湖流域（GLB）的主要水文蓄水池，从文化，社会和经济方面看，这是加拿大和美国的重要地区。由于观测不足，关于地下水储量变化及其与五大湖之间的相互作用存在知识鸿沟。这项研究的目的是使用重力恢复和气候实验（GRACE）卫星任务的月度模型，辅助土壤湿度，雪和湖泊（SMSL）数据以及来自预测的预测来检验GLB中地下水储量变化的可检测性。冰川等静压调整（GIA）模型。开发了一种两步滤波方法来优化GRACE信号的提取。还引入了二维盆地窗口权重函数，以减少由带限制的GRACE模型引起的振铃伪影，以估计GLB中的储水量变化。估计2002年至2009年期间地下水储量（GWS）与参考平均储量之间的偏差。GLB的平均GWS清楚地显示了一个年循环，其水厚当量（WTE）的幅度范围为27至91 mm ，阶段范围约为两个月。相对于SMSL储水量变化的阶段，GWS变化的估计阶段有半年的偏移，后者在3月和4月达到峰值。最小二乘估计得出在研究期间内，GLB中的GWS损失趋势为2.3至9.3 km3 / yr。 GRACE GWS结果的广泛范围主要是由于不同陆地表面模型（LSM）的土壤水分和积雪的差异所致，较小程度上是由GRACE委托和遗漏误差以及GIA模型误差引起的。
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