I have found over the years, especially the drought years, that there is no substitute for rainfall when it comes to watering plants. I don’t have a scientific explanation for it, but when plants receive rainfall, they grow better, than they do from the city water supply. And, when there is lightening during the rainstorm, the plants do even better. I suspect the lightening creates ozone which benefits plants. Rain of course doesn’t contain chlorine, which, most if not all, city water does. Plants don’t particularly care for chlorine and, neither do people. It’s just not healthy for the body. Sure, it kills bacteria, but at what other expense to our health. I do know that rainfall also can contain pollutants that plants don’t like, but, they still seem to handle those pollutants better than the ones that come from tap water. The bottom line is, rain is better for your green friends than tap water is, so instead of watering, mulch heavily, and wait for the next rainfall, if you can. And the best part; rain is free.