a small drainage area的用法和样例：
- This small drainage area will not be influenced by the Siberian cold current.
- harnessing of small drainage area
- The flash flood index calculating model for small drainage areas of Jiangxi province, which does not require lots of data and analysis, and its calculating methods are introduced.
- There is a small drainage outlet for changing water under the vase, and we use the rubber buffer to block it.