华南滨海小流域降雨入渗对地下水的补给分析

Observation and analyses of groundwater recharge from rainfall infiltration in a coastal watershed,south China

以华南滨海小流域——中山大学滨海水循环试验基地(试验基地)作为研究区,在对该流域地下水和雨水分别进行采样、实验分析的基础上,利用氯量平衡法(CMB)与地下水动态法计算了该流域的降雨入渗补给系数与给水度。研究发现,试验基地地下水主要受降雨补给,地下水埋深在雨季(4—9月)、旱季(10—3月)的变动范围大致为0～1.5 m与0～0.5 m。根据CMB计算结果,补给区、中间区雨季降雨入渗补给系数分别为旱季的1.3～1.6倍和1.3～2.0倍,且补给区大于中间区(M5井除外)。利用地下水动态法计算次降雨入渗补给系数,所得雨季、旱季的均值(7.6%和4.6%)与CMB计算结果(7.7%和5.3%)较为接近。给水度、雨强与入渗补给系数均存在一定的线性关系。将地下水埋深分别与降雨入渗补给量及潜水蒸发量进行多项式拟合对比,发现降雨入渗对地下水的最大入渗补给埋深约为2.3 m,当埋深为3.1 m时,地下水可获得最大净补给量。

Infiltration coefficients from rainfall and specific yield of unsaturated aquifer are two important parameters to define groundwater recharge,which is a key issue in the relevant research on surface water and groundwater interaction.Rainfall and change of groundwater level have been monitored at Zhuhai Campus of Sun Yat-sen University since 2006 at an interval of 30 minutes,and groundwater and rainwater samples been collected monthly and analyzed for major ions.Infiltration coefficients from rainfall of event and monthly average bases and specific yield are calculated using methods of chloride mass balance（CMB） and the change in groundwater level as well.Precipitation was found to be the main source of groundwater recharge in the study area,and the variation of groundwater table is about 0～1.5 m in the wet season（from April to September） higher than that in the dry season（0～ 0.5 m,from October to March）.The infiltration coefficients in the wet season is about 1.3～1.6 and 1.3～2.0 times than that in the dry season for the recharge and intermediate zones of the watershed respectively.Linear relationships between variation of groundwater table and rainfall amount were found at three sites,yielding relevant site specific linearity between the infiltration coefficient and specific yield.The averaged infiltration coefficient from rainfall events is calculated to be 4.6% and 7.6% in the dry and wet seasons,close to 5.3% and 7.7% respectively by CMB which is monthly based.Rainfall intensity is another factor affecting the infiltration coefficient,and a positive relationship was obtained with relatively low linear correlation coefficient.The empirical relationships among groundwater depth,recharge and evaporation from the groundwater table（E（h）） were developed in the study area,giving a peak recharge at a groundwater table of approximately 2.3 m depth.Net recharge,defined as the difference between recharge/infiltration and Eh,was estimated to be the highest at a depth of 3.1 m.