[Drinking water data collection and information system in North Rhine-Westphalia. Integration of water supply zones].

To comply with the drinking water regulation act of 2001 and as basis for reports to the European Community, North Rhine-Westphalia has defined water supply zones and collected the necessary data from local health authorities. The software used for drinking water surveillance by the local health authorities and on state level has been adapted to the new requirements. In principle, a supply zone in NRW means a region where the water comes from one water-works. Under certain conditions exceptions are possible. 53 out of 54 local health authorities supplied data about water supply zones up to summer 2006. There are 410 water supply zones which get their water from around 550 water-works. The number of people per supply zone varies between a few hundred and nearly 900,000. Most of the supply zones fall within the responsibility of one health authority. Only 37 supply zones out of 410 contain regions of more than one local health authority. 27 % of the supply zones get water from three or more water-works, 73% get water from one or two water-works. Looking at the other side of the medal, the structure is also relatively simple. More than 80% of the water-works deliver water into only one supply zone. The definition of water supply zones as chosen in NRW has proved to be a good basis for a clear description of the drinking water supply. Besides, the definition enables the state to produce reports which can link water quality, regions and the supplied persons.