Abstract: There was a lot of plain reservoirs in northwest of arid and semi-arid area for agricultural irrigation , needless to say, the plain reservoir played an irreplaceable role in the national production and daily life, but there were also many urgent ecological environment problems need to solve. Leakage problem of the plain reservoir uplifted the underground water level behind the dam, a large area of land was salinization, which led to the output reduction and abandoned cultivation severely. This paper focus on the perspective seepage of reservoir using the finite element model to calculate the relationship between dam foundation seepage discharge and impervious body size of the permeable dam foundation with vertical anti-seepage wall and horizontal bedding. The critical groundwater level was controlled comprehensively with the combination of the drainage body and the impervious body size calculation formula was derived for controlling the critical groundwater level of reservoir. Combined with the engineering example of calculation shows that, as long as the choice of reasonable impervious body type and water seepage drainage body, leakage can be completely controlled from the foundation head, the dam underground water level could be controlled at the critical level, secondary salinization prevention of soil dam could be conducted gradually.

Key words: plain reservoir, land salinization, seepage proofing body, seepage drainage body, critical underground water level