Some food for thought: When we water plants, the majority of the time we're watering them until the water is coming out the bottom of the flower pot. Thus, we're watering deep enough to saturate the root zone and usually 3 inches of soil or more. The excess water will drip out. We're not watering the blades of the plants, we're watering the soil. The same scenario must play out for a lawn and yes, it will require lots of water during the summer heat season/drought season. This will play a major role in your water bill if you have to pay for your water through a municipality or on your electric bill if you have to run a pump from a well. Either way, if you want a nice lawn you're going to have to water it well and to do so will could certainly cost you a lot of money.