The underground rock mass condition is very complex. Therefore

the deficiency of seepage monitoring data exists. To comprehensively analyze the underground seepage field in time and space

it is necessary to replenish the missing data. Three types of supplement methods of missing data are proposed: missing data in time sequence can be replenished by creating monitoring statistic model; missing data on spatial sections can be supplemented by regression analysis modified by physical factors; missing data in the whole area can be replenished by back analysis calculation. All these can reflect the regulation of missing data and the influence of chronological and spatial factors on measuring data. Integrated and comprehensive seepage field is obtained

by which seepage stability can be determined

providing reference to project evaluation. These methods are used in Tianhuangping power station. The results show that the complementary piezometric heads and flow rates are in good agreement with the measured data

the back-analyzed seepage field conforms to the engineering practice

and the locations where seepage failure may happen are effectively determined by the back-calculated field. Engineering suggestions are proposed based on the seepage stability

which has instructive meaning to project reinforcement.