Sentence:  The facade of the Peggy Notebaert Nature Museum building includes a “<WSD>waterwall</WSD>” made of natural limestone veneer over a CMU block wall that allows surplus rainwater from the green roof to cascade down to provide water to small planting pockets; overflow water is stored in a cistern and recirculated with solar energy to irrigate the wall and provide makeup water for the created wetland in an outdoor classroom space. 
Meaning of the word marked with <WSD> tags:  An architectural feature consisting of a wall down which water flows.