Hydrogeologische Gesichtspunkte bei der Festsetzung von Wasser- und Heilquellenschutzgebieten
[Required dimensions of protective zones for groundwater gathering]
published: Jan 1, 1972
Experiences within the Federal Republic of Germany. The "Deutscher Verein von Gas- und Wasserfachmännern" as German Water Works Association published in January 1953 "Richtlinien für die Einrichtung von Schutzgebieten für Trinkwassergewinnungsanlagen (Trinkwasserschutzgebiete), I. Teil, Schutzgebiete für Grund- und Quellwassergewinnungsanlagen". These directions for the arrangement of protection areas of drinking water supplies obtained from groundwater wells or springs found application to thousands of public water supplies in the states of Western Germany and in Western Berlin. The arrangement of protective areas is demanded by laws since 1957. The above-mentioned directions served as guide without important difficulties. In September 1959 the second pari, concerning reservoirs used for municipal water supply, was published, in November 1961 the improved second edition of the first pari. Since 1969 the directions are in revision. An international comparison of underlying principles of arrangement and delimitation not only of the whole area but also of its subdivisions or zones promises new Stimulation and knowledge. Principles of demarcation of zones. Outer boundary. Inert inorganic solutions pass readily through soil and travel in aquifers without amelioration or decomposition from the outer boundary of a catchment area until they discharge from a well or a spring. As example sodium Chloride may be mentioned, accumulated in great dumps in connection with potash-mines. Therefore, the outer boundary of a catchment or drainage area should also be the outer demarcation of a protection area. But immediately several questions arise. Which of all substances are inert or resistant? What is about radioactive contaminants or about chlorinated organic pesticides or about newly invented chemical compounds? - Another difficulty is not surmountable when the groundwater replenishment area is unknown, a frequent case by deep lieing aquifers. The difficulty has political character when the replenishment area is situated in another non-cooperating state. The outer distal peripheral zone may reach more than 10 kilometers from the discharging construction. The zone is called "Zone III". In such cases of great distance the zone is subdivided in two subzones, "Zone III B" in external Position and "Zone III A" in internal position of a circle drawn with 2 km radius. This subdivision is based on an expertise concluding that domestical and industrial tanks of petrol (gasoline, fuel) under a certain volume are not hazardous beyond this distance. 50-days-line. Bacteriological investigations (KNORR) have demonstrated that pathogenic bacterias do not survive a time of 50 days within the subsurface (non-saturated plus saturated zone). By this reason the 50-days-line represents the limit between "Zone III" or "Zone III A" and Zone II. The inner zone. The inner zone, called "Zone I" surrounds the catchment construction, that is the well or the spring or a group of such objects. This zone is fenced in and shall protect against direct contamination, pollution or impairment. The outer boundary is determined by the distance beyond which normal natural manuring (without local concentration, but immediate distribution) is harmless. Dimensions of zones. The distances necessary to satisfy the above-mentioned conditions are calculated or estimated by experts. They depend on natural conditions such as geological and hydrological and operating conditions. In most cases the distance of the outer boundary of zone I is less than 100 m, that of zone II less than 500 m, that of zone III less than 2000 m. Subjection of all sources of deterioration to the System The determination of all limits of protective zones is based on the commented view-points, proceeding from distinct sources of deterioration. All other sources of deterioration, such as human activities, buildings, recreation, agriculture, mining, traffic, road construction, sewage-treatment, removal and deposition of refuse, establishment of cementeries, excavation of gravel, stones and other minerals, construction of pipelines, construction of industrial plants, deep well disposal, disposal of cooling water, use of radioactive materials are subjected to the system of 3 or 4 zones. The method seems rigorous, the practical application, however, has produced no severe difficulties and justified a certain simplification.