drainage map

例句：

1. 1. The drainage map shows the areas with high water levels.
   排水地图显示了高水位区域。
2. 2. The hydrographic survey was crucial for understanding the geography of the region.
   水文调查对于理解该地区的地理至关重要。
3. 3. The watershed map helped us to identify the potential sources of pollution in the area.
   水文图帮助我们识别了该地区潜在的污染源。