Rainwater Collected for Irrigation

Hi Andrea,

LEED Guide says ''All runoff from the chosen percentile of precipitation events must be managed such that there is no surface
discharge from the site. Techniques include, but are not limited to, infiltration, storage and re-use, bioretention,
open-grid pavement, and the reduction of impervious area.'' So, I guess it is to use all those techniques that best mimic the natural hydrological conditions before any development occurred. And I read it in this forum that only storing and reusing the runoff volume does not comply with the requirements. However, if it is solely used for irrigation and not for toilet flushing etc. then you can prepare a narrative how the water reused for irrigation will mimic the natural hydrology e.g through transpiration, infiltration, evaporation etc. Let's see what others have to say about this.

Hi Andrea, 

we are in the same situation, more than 1 year after your post do you have already more information if it is an applicable solution or not? Thank You in advance!

Using rainwater for irrigation is considered reuse and is acceptable to support pursuit of the rainwater management credit.

Hi Andrea, it seems like you are following option 1. I've always found easier Option 2 and it gives you more points. I would give it a try!

per GBCI:

There is more than one way to do this, and the process is iterative in nature. Pipes and tanks may be acceptable if they are paired with an LID strategy and it can be demonstrated that all of the captured water is evapotranspirated, infiltrated, and/or reused on site.

Hi Gustavo, thank you for your help. Option 2 says "Manage on site the annual increase in runoff volume from the natural land cover condition to the postdeveloped
condition." I wonder which condition is the postdeveloped condition in our case. I am not sure if the postdeveloped condition means the actual condition or before any human development. We have an existing building and we will also build a new building on the same project boundary. Now there is only impervious  outdoor area (for parking in the courtyard) while in the future we will have underground parking garage and greenroofs etc. 

Please clarify it if you have experience in it. 

Thank You in advance!

Hi Claudia, postdevelopment condition is the scenario after your project has been completed.

Hi David, this response is very helpful. However, I wonder if you have any insight regarding the timeframe for reusing collected rainwater for irrigation: our project is collecting all the rainwater and storing it for irrigation purposes. However, the collected rainwater is much more than the daily irrigation needs, which means that it will need to remain stored for several days, more than the average days between storms. Does the project need to demonstrate that all collected rainwater will be used before the following storm, or is it enough to show that it will all be stored on-site for future reuse? Thanks for any guidance!

We have the same question - can the collected rainwater be stored for a temporary period before being reused? Any help is appreciated!

apologies, just seeing the post from CT G this morning. 

LEED does not specify timeframes for evapotranspiration, infiltration, and/or reuse on site. 

If stored for extended periods of time I would guess that GBCI would require the project team to demonstrate that storage capacity is sized to account for multiple storms and has a plan to evapotranspirate / infiltrate / reuse all the water in the rainwater collection tank. Or in other words "prove that the rainwater tank(s) will not be emptied (sent offsite) in efforts to prepare for the rainwater collection from the next storm"

Hope this helps!

Helps a lot, thanks!