Rain Water Harvesting
Depending on your landscape design and the amount of plants or grass you have, one can use a majority of their water usage for landscape irrigation. Landscape irrigation is the most common use for rainwater harvesting because it can be used without pumps and without expensive treatment.
Passive rainwater harvesting uses that natural landscape to not only contain water but also direct it where it needs to go. The goal is to design the landscape so one can slow down the flow of the water and let it soak into the ground where you need it. This is done with the use of swales, basins and berms along with many other techniques.
Active rainwater harvesting stores the water for future use in containers or cisterns. With active systems, the options are based on how much you want to store, the duration you want to keep the water, if you want to use it for more than irrigation (if you want to make it drinkable) and how you want to disperse it when you call for it. Obviously, cost is always a contributing factor.