Drinking water and water for domestic use often come from groundwater. In order to protect this water, local water authorities can apply to local administrative authorities to mark certain locations as water protection areas. The size of these areas is calculated in such a way that the quantity of groundwater taken from them corresponds to the actual rainfall going into them. In the water protection, areas certain uses of the land and activities on the land are banned or restricted. Water protection areas fall into three zones. Zone 3 is the outermost zone with a diameter of 4 kilometers around the groundwater well. Here no chemical works or the use of pesticides (杀虫剂) are allowed. Zone 2 is determined around the so-called 50-day line. It is assumed that after 50 days in the groundwater harmful bacteria will have died off. Here settlements and fertilizer storage are forbidden. Zone 1 marks the ten-meter boundary around the well. Here, any use of the land, as well as access by unauthorized persons, is forbidden.