Determining optimal space and depth of the subsurface plastic drainage tubes is a main task in planning and design of a drainage system. 农田塑料暗管埋深和间距的确定，是塑料暗管排水系统规划设计的主要任务，关系到排水效果和投资效益。
The classification of the community types mainly reflected the variations of soil salt content and ground water depth, which were decided by microtopography. 群落类型的划分主要反映了微地貌所决定的地下水埋深及土壤盐分含量的变化。
