Our Trip to Yibin City
When
On Friday.
How
We will go there 1.
What
But you will need to bring 2 .
Where
Then in the afternoon we will go to 3.
What time
⑴Now please remember that the bus will leave right at 4 .
⑵Tell your parents we'll be back at school 5.
雨水花园是一种模仿自然界雨水汇集、渗漏而建设的浅凹绿地，主要用于汇聚并吸收来自屋顶或地面的雨水，并通过植物及各填充层的综合作用使渗漏的雨水得到净化。净化后的雨水不仅可以补给地下水，也可以作为城市景观用水、厕所用水等。下图示意雨水花园结构。据此完成
雨水花园的核心功能是
