substratum for waterproofing

例句：

1. 1. The substratum of the soil is crucial for plant growth.
   土壤的基底对植物生长至关重要。
2. 2.The geological survey revealed a new layer of sediment at the bottom of the ocean.
   地质调查发现，海洋底部有新的沉积层。
3. 3.The research team found that the substratum of the river had been altered by human activities.
   研究小组发现，河流的底层已经被人类活动改变。