You can greatly reduce the amount of watering required by containerized plants firstly by using a top quality potting mix, and secondly by mulching the surface of each pot with a 2cm layer of washed river sand. Heat bounces off this rather than being absorbed by the dark potting mix.
The effect is that less surface moisture is lost, there is less stress on surface roots because the soil temperature is lower, and less water is needed, all adding up to a saving of this precious commodity.
You can achieve the same effect for plants in garden beds, using a range of mulch materials.
Choose from light coloured gravels, sand, straw, shredded tree clippings or raked up dried & fallen leaves (do not use fresh grass, however), all of which will give excellent results when applied 10 to 15 cm thick ensuring you allow breathing space around the stem of the plant.
But what you do beneath the mulch is even more important.