基于GRACE的京津冀地下水储量变化时空演变格局

Spatiotemporal evolution pattern of groundwater storage changes in Beijing-Tianjin-Hebei region based on GRACE

基于2003—2019年GRACE陆地水储量变化数据和全球陆地水文模型(global land data assimilation system,GLDAS)数据反演京津冀地下水储量变化,运用时空分析方法对地下水等效水高变化进行时空演变特征分析。在空间变化上,整个京津冀地下水等效水高变化速率约为-51.77 mm/a,其中:北京市变化速率最低,约为-38.15 mm/a;天津市变化速率最高,约为-62.85 mm/a;河北省变化速率与区域平均变化水平相当,约为-52.42 mm/a。基于Sen Slope和Mann-Kendall非参数检验法分析得出西部、西南部和中部地区地下水等效水高下降趋势最明显,东北部下降趋势最小。在时间变化上,地下水等效水高变化具有一定的季节性规律:夏季变化速率最大,约为-75.99 mm/a;冬季变化速率最小,约为-37.24 mm/a;春秋两季的变化速率大致相同,分别为-52.34 mm/a和-48.21 mm/a。在影响因素分析中,人类活动是引起京津冀地区地下水等效水高变化的主要因素。研究结果可为科学掌握京津冀地下水储量时空变化规律提供数据支撑。

Groundwater is significant for an important political, economic and cultural center(Beijing-Tianjin-Hebei) in China.Therefore, scientifically analyzing the spatiotemporal pattern of groundwater storage is fundamental research in the Beijing-Tianjin-Hebei region.However, there are some shortcomings in previous research, such as the limited locations of groundwater wells and the representation of in-situ data in a single geological condition.In the 21 st century, the emerging GRACE satellite data, which is subject to little geological conditions, is applied in measuring water storage spatial continuity.Herein, the GRACE-based terrestrial water storage anomalies and global land data assimilation system(GLDAS) are used to retrieve the groundwater storage in the Beijing-Tianjin-Hebei region, and Sen′s slope and Mann-Kendall time series test are applied to analyze the spatiotemporal variations of groundwater.It is foand that the changing rate of groundwater is about-51.77 mm/a equivalent height of water in the Beijing-Tianjin-Hebei region from 2003 to 2019.Zonal statistics analysis with provincial administrative units showed that the depletion of groundwater in Beijing city has a minimum rate of-38.15 mm/a.Tianjin city has a maximum rate of-62.85 mm/a, and in Hebei Province, the rate of change is equivalent to the regional average rate of change with about-52.42 mm/a.The annual average groundwater storage of the National Bureau of Statistics was used to evaluate the GRACE-based retrieval result.It is also find that the groundwater storage has decreased about 375 million cubic meters from 2003 to 2019 in the entire region.Furthermore, the depletion of groundwater is significant in the western, southwestern, and central regions, but the depletion of groundwater is slight.In addition, the change of groundwater storage has some seasonal trend based on time-series analysis, the reduction of groundwater storage in summer is more than that in other seasons, with a mean rate of-75.99 mm/a, while the rate is the smallest in winter with about-37.24 mm/a equivalent height of water.The rate of change is similar in spring and autumn with a value of about-52.34 mm/a and-48.21 mm/a equivalent height of the water, respectively.According to the analysis of the change of groundwater storage in the same month of each year, it is found that the change value of groundwater storage fluctuated within a relatively stable range in the 12 months of the years, and the change value was generally low in June and July.The minimum in August, while December, January, and February are generally higher than that in other months, and the fluctuation range of the change is also smaller than that in other months.There are six months(March, April, May, September, October, November) when the distribution range and fluctuation range of the changes in groundwater storage are similar.When analyzing the impact factors, the groundwater storage is negatively correlated with the area changes of forest land, construction land, and agricultural land, with the highest correlation coefficient of-0.65.While groundwater storage and grassland shrubs are positively correlated(correlation coefficient is 0.68,significant 0.004).Based on the analysis combining with precipitation data, it is found that anthropogenic factor has a greater impact on the groundwater storage than natural meteorological factor.The results are roughly the same as the statistical data of the Water Resources Bulletin, which both show that groundwater storage has decreased.Combining groundwater retrieval results with land use data, population data, precipitation data, and other auxiliary data, the spatiotemporal analysis methods are applied to analyze the spatiotemporal evolution pattern of groundwater, and it is concluded that the changing rate of groundwater storage of Beijing-Tianjin-Hebei is about-51.77 mm/a equivalent height of water, and the lowest rate of change about-38.15 mm/a in Beijing city and the highest rate of change about-62.85 mm/a in Tianjin city.The rate of change in Hebei Province is about-52.42 mm/a, which is equivalent to that of regional average change.Based on the Sen′s slope and Mann-Kendall analysis, groundwater storage has a significant, negative trend in the western, southwestern, and central regions, and the minimum trend of depletion is present in the northeast.Time-series analysis showed that the changes in groundwater storage are seasonal and the impact factor analysis shown that the changes in groundwater storage in Beijing-Tianjin-Hebei are negatively correlated with area changes of forest land, construction land, and agricultural land, with the highest correlation coefficient value of-0.65.While the groundwater storage and grassland shrubs are positively correlated(the correlation coefficient is 0.68,the significance is 0.004).Based on the analysis combining with precipitation data, it is found that anthropogenic factor has a significant impact on the groundwater storage of Beijing-Tianjin-Hebei than natural meteorological factor.The research has a significance for protecting water safety and the ecological environment of the Beijing-Tianjin-Hebei region.