大沽河极端气候指数特征及其对地下水的影响

Characteristics of Extreme Climate Index and Its Influence on Groundwater in Dagu River

掌握极端气候变化特征是地下水资源管理的重要环节。为了探究极端气候对地下水资源的影响,以大沽河水源地为例,基于40余年的气象数据,选取14个代表性的极端气候指标,并采用线性趋势法、Mann-Kendall突变检验、小波分析等方法分析了研究区气候变化的趋势性、突变性和周期性;基于极端气候指数和水文频率分析筛选了研究区代表性的极端气候年份,运用水均衡分析方法估算了极端气候年份条件下地下水平衡;并通过相关性和周期性分析评估了极端气候指数对地下水水位埋深的影响。结果表明:(1)1979-2021年,研究区内表征高温与降水的极端气候指数呈上升趋势,表征低温的极端气候指数总体呈下降趋势;极端丰水年代表性年份为2007年和2020年,极端枯水年代表性年份为1981年和1986年。(2)极端气候指数在20世纪90年代与21世纪初期发生突变,之后高温趋势更加显著。(3)极端降水指数第一周期对应的平均周期为11~16 a,极端气温指数第一主周期对应的平均周期主要有3个变化范围分别为20~24 a、12~14 a、5~6 a。(4)极端降水指数抑制地下水水位埋深的增加,极端降水量(R95p)和普通日降水强度(SDII)是影响大沽河水源地地下水水位埋深的主要降水指数;水位埋深的第一主周期对应的周期分别为13~15 a,与极端降水指数周期特征基本一致,意味着水位埋深受极端降水指数的影响较显著。(5)在极端丰水年(2007年),地下水总补给量约为319.4mm,总排泄量约为204.8 mm,均衡差约为114.6 mm;在极端枯水年(1981年),地下水总补给量约为104.2 mm,总排泄量约为141.1 mm,均衡差约为-36.9 mm。

Understanding the characteristics of extreme climate change is an important part of groundwater resources management.To investigate the impact of extreme climate on groundwater resources,this paper takes the Dagu River groundwater resources area as an example and based on the meteorological data for over 40 years,14 extreme climate indices are selected to analyze the trend,mutation and periodicity of meteorological changes in the study area by using methods such as linear trend method,Mann-Kendall mutation test and wavelet analysis.And based on extreme climate index and hydrological frequency analysis,the representative extreme climate years of the research area are determined,and the groundwater balance under extreme climate year is estimated by using water balance analysis method.Meanwhile,the influence of extreme climate index on groundwater depth is evaluated by correlation coefficient and periodicity analysis.The results are listed as follows:①From 1979 to 2021,the extreme climate indexes representing high temperature and precipitation show an increasing trend,while the extreme climate indexes representing low temperature show a decreasing trend.The representative years of extreme wet years are 2007 and 2020,and the representative years of extreme dry years are 1981 and 1986.②The extreme climate indexes mutate in the 1990s and the early 21st century,and then the trend of high temperature becomes more significant.③The mean period corresponding to the first main period of the extreme temperature index have three main variation ranges:20~24,12~14 and 5~6 a.The average cycles of most ex⁃treme rainfall indices are 11~16 a.④Extreme precipitation index inhibits the increase in groundwater level depth.Extreme precipitation(R95p)and simple daily precipitation intensity index(SDII)are the main precipitation indexes affecting the groundwater level depth in Da⁃gu River water source area.The period corresponding to the first main cycle of the groundwater level depth is 13~15 a,which is basically con⁃sistent with the cycle characteristics of the extreme precipitation index.This means that the groundwater level depth is significantly affected by the extreme precipitation index.⑤In the extreme wet year(2007),the total groundwater recharge and discharge are about 319.4 mm and 204.8 mm,respectively,with an equilibrium difference of about 114.6 mm.In the extreme dry year(1981),the total groundwater recharge and discharge are about 104.2 mm and 141.1 mm,respectively,with an equilibrium difference of about-36.9 mm.