Precipitation is the most significant source of the water supply in the State of Brandenburg. Around two thirds of the available water comes from precipitation and only one third from the inflows from the bordering regions.
Most of the precipitation that falls on built-up areas is gathered in the sewage system, drained off and fed into the surface waters. The water is removed from the area and the recharging of the ground water is thereby significantly impeded. There are also additional sources of water pollution and the intensified surface drainage leads to an enhanced risk of flooding. Finally, the construction, running and maintenance of the drainage systems carries its own costs.
For these reasons, an up-to-date city and drainage system requires a shift of perspective in dealing with rainwater. In recent years, alternatives to traditional rainwater drainage have been developed which offer a decentralized management of rainwater runoff. Decentralized systems have now been tested, are available on the market and are equivalent to the traditional solutions in regard to their operation.
Given the desire for an environmentally friendly and cost-saving solution in urban drainage, the State of Brandenburg is now oriented toward local leaching of rainwater runoff. Thus § 54, Para. 4 of the Brandenburg Water Act (BbgWG) provides for the leaching of rainwater runoff as long as the contamination of the ground water or other concerns are not an issue.
The removal of rainwater runoff is a fundamental, communal obligation according to § 66 of the Brandenburg Water Act. One exception to this is the rainwater runoff from public transportation facilities outside the city in connection with built-up districts. The municipalities can also utilize a communal statute to require that rainwater runoff must be leached into the property where it falls. That is, the obligation to remove rainwater runoff can be transferred to the property owner. The brochure "Nature-oriented Rainwater Management" is aimed at property owners and builders, and provides them with practical information about the various options for decentralized rainwater management.
In addition, the municipalities have the ability to inspect the current options for decentralized rainwater management at an early stage and codify the corresponding statutes in development plans. The municipalities were informed of this in a joint circular of the Ministry for Infrastructure and Agriculture (MIL) and the Ministry for Environment, Health and Consumer Protection (MUGV) from October 11, 2011. The circular includes elucidations and suggestions for the implementation of the required inspections and provides advice regarding the statutes in development plans. The brochure "Rainwater Management in New Development Areas - Expert Information" provides further information and installation examples. It is aimed at municipalities, planning authorities and engineering offices as well as at the representative of municipalities and technical committees.