Management of Rain and Waste Water 2017
02.09.1 Type of Drainage
In Berlin, four fifths of the sewerage-equipped urban area is drained by separate sewerage; about one fifth has combined sewerage. Thus, a total of 52.8 % of Berlin’s overall area is connected to a sewerage system. Urban areas connected to a separate sewerage system fall into the following 4 categories: separate sewerage systems with waste water and rainwater sewers account for the largest share (66.1 % of the type of drainage), followed by separate sewerage systems with waste water sewers without rainwater sewers, e.g. in areas where all rainwater seeps into the ground. A minute share of separate sewerage systems is made up of areas with rainwater sewers without waste water sewers, which are mainly traffic areas. Areas where rainwater sewers discharge into the overflows of combined sewerage systems constitute a unique case (2.2 % of the type of drainage).
The number of block and block segment areas that are drained via combined sewerage systems has increased by just under 5 %. Much like in 2012, they account for almost 18 % of the total municipal area.
Inhabited areas without any type of drainage are blocks and block segment areas that are not connected to a sewerage system, which, however, presumably produce waste water based on their type of use. Here, sewage is mainly collected in septic tanks. The sewage is then taken to sewage treatment plants by transport companies. Since the early nineties, when 12 % of the inhabited area (7 % of West Berlin and 19 % of East Berlin) was still not connected to the public sewerage system, this figure has dropped steadily and amounts to about1.3 % according to the current analysis. The population-referenced overall connection rate to waste water sewers is thus almost 100 %.
In recent years, increased construction activity and the associated increase in both impervious areas and the efforts of the Berlin Waterworks to expand the sewerage network into previously unconnected residential areas have resulted in new areas being connected to a sewerage system. This has been confirmed, too, by the most recent analysis, even though the methods used differ between the years 2012 and 2017. Overall, the share of areas connected to a sewerage system has risen by 2 % in the total built-up area.
Local rainwater management is becoming increasingly more important, which entails rainwater remaining directly on site and not being discharged. Only in case of difficult conditions (e.g. poor percolation properties), does this type of rainwater management require an additional, controlled discharge via drains. The distribution of this new type of rainwater management is not yet recorded in the current map “Type of Drainage”. It will be considered, however, going forward.
When analyzing how the different systems are distributed across the municipal area, the following key areas emerge.
In the inner-city areas of Wedding, Tiergarten, Mitte, Prenzlauer Berg, Friedrichshain, Kreuzberg Schöneberg, parts of Neukölln and Wilmersdorf, Westend and in the old town of Spandau, waste water and rainwater is drained together via the combined sewerage system.
Outer areas, including Reinickendorf, Pankow, Weißensee, Hohenschönhause, Marzahn, Hellersdorf, Lichtenberg, Köpenick, Neukölln, Tempelhof, Steglitz, Zehlendorf, Spandau, and parts of Wilmersdorf and Charlottenburg are connected to the separate sewerage system.
In Berlin, the prevalent type of separate sewerage system is that of rainwater drainage plus a sewerage system. Areas with this type of system are mainly found in outer areas, in the new boroughs of Spandau, Reinickendorf, Pankow, Lichtenberg, Marzahn-Hellersdorf, Treptow-Köpenick, Neukölln, Tempelhof-Schöneberg and Steglitz-Zehlendorf, as well as some south-western parts of Wilmersdorf-Charlottenburg, a small area in the north-eastern part of Mitte, and the Stralau peninsula in the south-eastern part of Friedrichshain.
To reduce the load on the combined sewerage system in some parts of Wilmersdorf, Weißensee and Spandau, as well as some areas of Charlottenburg, along Schloßstraße, rainwater sewers were built which discharge into the rain overflow drains of the combined sewerage system. There, sewage continues to pass through these combined sewers.
In areas with sewerage systems without rainwater sewers, rainwater percolation may be controlled or uncontrolled. These areas can be found at the outskirts predmoninantly in parts of Gatow, Kladow, Spandau, Staaken, Konradshöhe, Heiligensee, Frohnau, Karow, Adlershof, Biesdorf, Kaulsdorf and Köpenick.
The development of Category I old settlement areas (main areas to be connected to a sewerage system) has been completed (House of Representatives of Berlin 2009). The development of the Wartenberg settlement area was also completed in 2018 but is not part of the map. There are still further old settlement areas without sewerage systems. It was decided that the sewerage development of five of these areas (Biesenhorst, Buchholz Nord I, Schönholz, Karow Süd, Karow Ost) would be completed by 2030. The strategy for the remaining eight old settlement areas (Schmöckwitz-Werder, Schmöckwitz Schwarzer Weg, Neu-Venedig, Rahnsdorf-Süd, Siedlung Schönhorst, Siedlung Spreewiesen, Gatow Siedlung Habichtswald, Blankenfelde Altsiedlung) will be decided at a later stage.
What is more, there is still a variety of individual roads, that has not yet been connected to the central waste water treatment system either (gap closure areas). These will be developed successively. According to available documentation, there are also isolated plots of varied use (e.g. restaurants or sports facilities) outside settlement areas not yet connected to sewerage systems.
02.09.2 Catchment Areas of Rainwater Drainage
Depending on the main receiving water body, the catchment areas of rainwater sewers are found in the catchment areas of the Spree and Dahme rivers in the eastern and southeastern areas of Berlin, of the Havel river in the northern, northwestern and southwestern parts of Berlin, and of the catchment area of the Teltowkanal in the south of the city.
Lakes, park lakes, ponds and other blind drainage water bodies are spread over the entire area of the city.
Since within the inner S-Bahn Circle Line, the combined system prevails, and rainwater only rarely enters the water system, it has not been assigned to any rainwater drainage catchment area. The only exceptions are Tempelhofer Feld and parts of Wilmersdorf to the north of the urban motorway, which drain into the canals south of the Spree (the Neuköllner Schifffahrtskanal and the Landwehrkanal).
Table 2 shows the total catchment areas for individual water body sections. Based on the 2016, most recent, mapping of the impervious soil coverage degree of block and block segment areas (cf. Environmental Atlas 01.02, SenStadtWohn 2017), impervious areas that lie within catchment areas may be identified for each individual catchment area. As already described, however, not all impervious areas within blocks and block segments that are considered to be equipped with drains are completely connected to the rainwater sewer system. Table 1 of the text accompanying Map 02.13.1 “Surface Runoff from Precipitation” (cf. Environmental Atlas 02.13.1, SenStadtUm 2013) was used to establish the actual proportion of the impervious area connected. This table contains generalized actual connection rates for the Urban Structure Types (Area Types), divided into buildings, roads and other impervious areas. In the Area Types in the outskirts, the connection rate amounts to only 30 % of the impervious area in part. The actual connection rates may vary considerably on site, but the figures provide some insight into the characteristic properties of the catchment areas.
Table 5 of the text accompanying Map 02.13.1 “Surface Runoff from Precipitation” shows the amounts of introduction into the Berlin waters, summarized by segments. Except for those quantities which at heavy rainfall flow through the emergency outlets of the pumping stations and through the rain overflows of the wastewater network, and then also flow directly into the bodies of water, the surface runoff in the area of the mixed system is passed to the sewage treatment plants, from where they are fed into the bodies of waters after appropriate sewage-treatment, together with the treated sewage.
The Teltowkanal has the largest catchment area of the rainwater drainage, with more than 95 km² (including the Rudower Arm). Its long-term average intake is 14 million m³ of rainwater from the separate sewerage system. It is followed by the Wuhle, with a catchment area of 23 km² and 3 million m³ of intake, and the Panke (downstream from the Verteilerbauwerk) with approx. 18 km² and also about 3 million m³ of intake. The area of combined sewerage accounts for some 84 km² and about 21 million m³ of rainwater are mostly discharged to the sewage treatment plants (cf. Environmental Atlas 02.13.1, SenStadtUm 2019).