海河平原地下水储量变化的重力卫星反演和流域水量平衡

GRACE satellite-based estimation of groundwater storage changesand water balance analysis for the Haihe River Basin

南水北调工程向华北输水与地下水压采的实施,一定程度改变了海河平原供用水格局,影响了海河平原的地下水储量。准确监测地下水储量变化是水安全保障和地下水战略储备的基础。本研究以水资源公报数据为基准,比较了重力卫星(GRACE)不同的信号处理方法和相关产品,反演了2003—2020年海河流域总水储量及其平原区地下水储量变化,分析了海河流域2000—2019年供用水结构变化和水量平衡关系,量化了总水储量变化对流域蒸散发估算的影响。结果表明:GRACE JPL Mascons数据反演的海河平原地下水储量变化与水资源公报数据的决定系数最高;2003—2020年海河平原地下水储量总体分3阶段呈下降趋势,2003—2011年、2012—2015年和2016—2020年的下降速率分别约为-23.9±1.3亿m^(3)a、-75.5±5.3亿m^(3)a、-37.3±2.6亿m^(3)a;在不考虑海河流域年总水储量变化条件下估算的2003—2019年多年平均蒸散量(521 mm a),与考虑年总水储量变化的多年平均蒸散量(530 mm a)相差约10 mm a,但年蒸散量差异最高可达约80 mm a(2014年)。研究结果为认识近二十年海河平原地下水储量的变化提供了最新参考。

The South-to-North Water Diversion and reductions in groundwater withdrawals have changed water supply and use structure and profoundly influenced groundwater storage(GWS)in the Haihe Plain(HP).Reliable monitoring of regional GWS changes serves as a basis for water security and strategic groundwater reserves.Here,we compare different methods of processing GRACE signals and use four GRACE products to estimate changes in total water storage(TWS)in the Haihe River Basin and GWS in the HP from 2003 to 2020.Impact of changes in TWS on evapotranspiration(ET)estimates across the basin is quantified.Results show that the coefficient of determination of GWS changes in the HP retrieved from GRACE JPL Mascons data is highest relative to ground monitoring data.GWS in the HP generally shows a downward trend at three distinct stages,and declining rates from 2003 to 2011,2012 to 2015 and 2016 to 2020 are estimated to be-2.39±0.13 km^(3)yr,-7.55±0.53 km^(3)yr,-3.73±0.26 km^(3)yr by GRACE JPL Mascons data.The multi-year average ET(521 mm yr)without considering changes in TWS differs by up to 10 mm(3.2 km^(3)yr)from the multi-year average ET(530 mm yr)considering changes in TWS.The maximum difference in annual ET with and without considering changes in TWS is about 80 mm yr(25 km^(3)yr,2014).The findings from this study provide the latest understanding of changes in GWS in the HP over the past two decades.