土壤水入渗补给数值模拟——以河北栾城为例

Numerical Modeling of Groundwater Recharge Based on Soil Water Infiltrating: A Case Study of Luancheng Area in Hebei Province

由于通过短时间尺度的土壤水动态监测数据难以准确获得土壤水入渗补给的规律,因此在中国地质科学院栾城试验场开展了长时间尺度(5 a)的土壤水动态监测试验,监测深度为340 cm。利用Hydrus-1D软件的双渗透(基质流区和大孔隙流区)模型进行数值模拟,并采用最小函数法对模型进行参数反演。为克服地表复杂的气象条件可能给模拟结果带来较大误差,选取140 cm深度为模型上边界。研究结果表明,基质流区(m)和大孔隙流区(F)土壤水动力特征参数nm,nF,αm和αF,大孔隙流区饱和导水系数Ks F对模型入渗补给量的灵敏性最高,并被选取为模型反演参数。总体上,土壤体积含水量的模拟值能较好地拟合其实测值,其决定系数为0.78。地下水入渗补给速率具有年际变化特征,但在年内具有明显的季节性,即在雨季达到最大,然后缓慢减小。年均入渗补给速率为220 mm/a,其中由优先流引起的入渗补给量为211 mm/a,这表明地下水入渗补给以优先流为主。该研究成果可提高对地下水入渗补给规律的认识,同时可为地下水资源评价与农业节水管理等提供参考。

In order to investigate groundwater recharge in a long-term scale,soil water volume content of a soil profile of 340 cm depth was observed for five years in Luancheng test site of Chinese Academy of Sciences. The dualpermeability model（ e. g.,matrix region and marcopore region） of Hydrus-1D containing parameter optimization procedure was applied to simulate the soil water movement and groundwater recharge. The place at 140 cm depth rather than on the soil surface was chosen as the upper boundary,which could overcome the complexity and uncertainty of datum on the soil surface. The sensitivities of 17 parameters to groundwater recharge in the Hydrus-1D were analyzed,and the results showed the sensitivities of soil water hydraulic parameters nm,nF,αmand αF（ subscriptmandFrepresents soil matrix and fracture regions,respectively） and saturated soil hydraulic conductivity Ks F were the highest. These five parameters and other two parameters,i. e.,Ka（ effective hydraulic conductivity of fracture-matrix interface） and w（ ratio of the volumes of the fracture domain and the total soil system） were chosen for the inversion. The modeling results showed that the modeled soil water volume content matched well to the measured values,with the correlation coefficient of 0. 78. The groundwater recharge displayed similar character in each year of five years,e. g.,the recharge was the largest in wet season,and then reduced gradually. The annual groundwater recharge was 220 mm / a,211 mm / a of which attributed to the preferential flow,which indicated that the groundwater recharge was controlled by the preferential flow in this area. The results of this paper could be helpful to understand groundwater infiltration in a long-term scale,and could be useful to the management of groundwater resource and agricultural water saving.