On the one hand, rainwater is extremely beneficial for irrigation, and plants and grass respond well to it (especially in comparison to say, municipal water, which is chlorinated, or well water, which is generally iron-heavy and hard). And, on the surface, it looks as if rainwater harvesting for lawn irrigation would be the "green" thing to do. 

However, if we peel back the layers a bit, I believe we are asking the wrong questions when we're talking about "green" ways of watering lawn. I would offer that the first question should be, "Can I install a lawn that doesn't need to be watered?" 

Lawn irrigation uses a lot of water. If you irrigate to recommended amounts, then you want to add at least 1" of precipitation to your lawn per week. 1" of water on an acre of grass equates to 27,000 gallons! PER WEEK! Even the largest of residential roofs cannot collect that much water, which means that a rainwater harvesting cistern will only be able to supplement irrigation water usage. For this reason, we encourage our customers to explore low-maintenance grass seed -- Pearl's Premium being one example -- that require little to no irrigation. Even if you have to re-seed your lawn, doing so is a lot less expensive than putting in a large underground cistern to meet watering needs. With a lower maintenance lawn in place, rainwater harvesting then becomes much more feasible for lawn irrigation, allowing the customer to downsize their harvesting capacity while quickening their Return On Investment by potentially eliminating the need for municipal water back-up. 

Should we, then, use rainwater harvesting systems to irrigate our lawns? I believe we should, but only after re-examining the lawn itself.

As always, thanks for reading!