Rainwater harvesting is the gathering, or accumulating and storing, of rainwater. Traditionally it has been provided as drinking water, domestic water, water for livestock, water for small irrigation and a way to replenish ground water levels. For the household, harvested rainwater can be used for flushing toilets and washing laundry. Indeed in hard water areas it is superior to mains water for this. It can also be used for showering or bathing. It may require treatment prior to use for drinking. There are many types of systems to harvest rainwater. The type used depends greatly on the purpose (domestic or industrial use) and to some extent also on physical and human considerations.