本文论述了地下水年龄计算的逆统计模型(ISM)的原理与方法，并将该模型用于大巴山隧道地下水年龄估算。计算显示隧址区地下水平均年龄介于45~75年之间，南坡(55~75年)高于北坡((45~60年)说明后者的水力传导性优于前者。该模型既考虑了基岩裂隙介质中地下水流普遍存在的水动力弥散作用的影响，又能使地下水年龄计算较之传统的同位素数学物理模型更为简便，具有实用价值。

The paper deals with the principle and method of an Inverse Statistical Model (ISM) for groundwater age, which is used to estimate at groundwater age in Dabashan Tunnel area. The calculation shows that the mean age in the area varies from 45 to 75 year, the longer in the south slope than the North Slope, indicating the hydraulic conductivity of the latter over the former on average. The ISM not only involves hydrodynamic dispersion of groundwater occurred commonly in fractured bedrock medium, but also makes the calculation of groundwater age simple compared with the traditional isotope mathematic model, so that it is of practice value.