The curtain is built up for stability and anti-seepage of dam foundation. By long-term water pressure and erosion

the seepage and uplift pressure under dam foundation increase gradually

causing its efficiency decay. Although the statistical model based on the monitoring data of groundwater macroscopic regime is often used to analyze

it has a lot of influential factors to calculate a finite period of time. The interaction between groundwater and some mineral

which reflects the mechanism of curtain decay

is modeled by a FORTRAN program according to the chemic-thermodynamics theory. A model is built up to analyze the anti-seepage efficiency of dam curtain; and the result shows that the 10th dam section has its efficiency decayed. The Saturation Index (SI) of section 10 kept the tendency of decreasing with time from 2001 to 2010. Calculated calcite saturation index changed from 2.03 to 0.26

It revealed the durability of curtain of dam section 10 was weakened. The microcosmic of dam section 10 kept a certain relationship with reservoir water level from 2001 to 2004 and from 2006~2008. The microcosmic of dam section 10 kept close relationship with reservoir water level at 2005 and from 2009 to 2010. The curtain is to be weakened locally. It is proved that the method can reflect the changes of the effect of curtain and its durability.