The water extraction area around drinking water extraction from groundwater is the smallest protection zone around an extraction of groundwater for drinking water. It is the border from which the inflowing groundwater has a travel time of 60 days to extraction. These 60 days travel time through the subsoil are the minimum travel time to make the water bacteriologically reliable. There are strict requirements for the activities that may take place in this area. The groundwater protection area is determined by the province and laid down in the Provincial Environmental Ordinance. The area is usually determined on the basis of a calculated residence time of a water particle of 25 years in the aquifer where drinking water is extracted. The 100-year zones and the catchment areas around drinking water abstractions indicate the area within which the groundwater has been on its way to extraction for 100 years or less. This zone can be determined by the province for very vulnerable groundwater abstractions. How this is handled differs per province. Depending on the province, rules may apply based on the Provincial Environmental Ordinance (Environmental Management Act) or spatial ordinances (Spatial Planning Act). Spatial stimulation policy almost always applies in order to take drinking water interests into account. The drilling-free zones are set to prevent sealing layers in the subsoil (e.g. clay or loam layers) from being penetrated. These layers offer extra protection against leaching of contaminants into the deeper groundwater intended for drinking water production at vulnerable extraction sites. In addition to these local drilling-free zones around extraction sites, a number of regional drilling-free zones are also shown on this map. An example of this is the Central Rift. This area of Horsten and Slenken is protected with a drilling-free zone because of its status as a geological monument.
