这里是while doing sth的用法，其实是状语从句的省略，由于状语从句的主语和主句主语一致，同时状语从句又有be动词，从句主语和be动词就可以省略掉。还原这部分句子就可以写成: Climate change is expected to intensify droughts and floods while climate change (it) is shifting where water will be and when. 

这样的例子有很多，比如：
She met Andy while working on a production of ‘Carmen’.

=She met Andy while she was working on a production of ‘Carmen’.

The truck driver dozed off while driving. 

=The truck driver dozed off while he was driving.