According to the World Health Organization (WHO) and SPHERE Standards, each person needs 45 liters of water per day. This includes water for drinking, washing, cooking, and also includes some for livestock. In addition, a portion of wastage is included in this rate.
This rate is quite high and in many areas it is not possible to plan a water supply system to match this amount. Practically speaking, it makes sense to build wells or water supply systems geared toward 20 liters and more.