The landscape architect provides LEED documentation for submittal to LEED Online.

Provide landscape drawings.
Provide the total water applied (both for the baseline and design case) and non-potable water supply.
If using non-potable water, provide information on source, and other documents that support proof of non-potable water use.
Write a narrative describing the landscape and irrigation installed, provide detail on the calculations used, and detail about the supply and availability of non-potable water used.