If you are fortunate enough to have a backyard pool, make sure the water stays in it instead of evaporating. Cover your pool when you're not using it, even in the summer.
Instead of taking the hose out for play time this summer season, why not have kids use smaller squirt bottles instead? Small squirt bottles can be filled with a little amount of water each time and only release water when used, limiting the amount of waste.
Use a sprinkler over dry patches of grass or near plants that need to be watered AND give the kids a daily time to run through the sprinkler. Win Win!