The ENVIBASE-Project

Documentation / Online Handbook

Water

Description of the Problem

Berlin is situated in the Warsaw-Berlin glacial valley, a landscape formed in the Ice Age, with an abundance of natural lakes and running water. But in terms of feeder streams and precipitation, the metropolitan area of Berlin suffers from a water shortage. The lakes are shallow, the rivers are slow-running and, especially in summer, carry little water. This makes Berlin's bodies of water ecologically very sensitive systems. The water supply and wastewater disposal for the city of Berlin depends in large measure on influents from the brown coal open-cast mining areas of Brandenburg. The quantity of groundwater being pumped there into the Spree River is decreasing because of the decline in brown coal extraction, and it will decrease further.

For the purpose of regulating the rate of flow of the Spree, large reservoirs are planned or are already under construction. High levels of direct and indirect discharge from sewage works, use of the river for industrial and other purposes, the effects of shipping and leisure seekers are all impairing the water quality. On account of the high level of sealing of the city, when it rains, large amounts of polluted storm water flow through the separate drainage system into the water bodies.

The main water quality problems are eutrophication, the associated growth of algae, and damage to the oxygen balance caused by eight major sewage plants. Following technological improvements, phosphate and nitrogen effluents from the sewage works, and thus pollution, have been reduced substantially since the end of the eighties. In order to obtain the clean-up goal of water quality Class II – slightly eutrophic – further upgrading of the sewage works and storm water drainage measures are necessary and planned.

Unlike many other cities, drinking water is obtained in Berlin solely from groundwater extracted within the city. Drinking water wells are mostly in the immediate vicinity of the water bodies. Thus, two-thirds of the water extracted actually consist of bank filtrate or artificially recharged surface water. Therefore, the quality of both the surface and groundwater is very important for the drinking water supply. It is estimated that about 40% of groundwater reserves are threatened by contamination, mainly by some 5.500 old polluted sites and areas not yet connected to the sewage system. The main problems are heavy metals, phenoles, hydrocarbons, and ammonium. Unlike in many federal Länder, nitrate pollution is not a problem. While cleaning up the polluted sites will take a long time yet, the sewage system is scheduled to be completed by the end of the nineties. Ever more sealing of the city and rising water consumption had caused the groundwater table to sink sharply until the beginning of the eighties. Since then, the water table has risen significantly thanks to a 25 % decline of in water consumption and more widespread groundwater replenishment.

The regulations and instruments for the management and protection of surface and groundwater resources are based on federal laws governing water resource management and wast water disposal and passed at the end of the eighties, and on the 1989 Berlin Water Act. In the meantime, attempts are being made, with increasing success, to influence the use and consumption of water resources using economic instruments, such as fees and prices.

The shortage of surface and groundwater resources in Berlin and their vulnerability mean that there is a special need for sustainable water resource management. This must apply both to the quantity and quality of the water. In the future, water must be used only in such a way that it becomes available again, in a short cycle, for drinking and industrial purposes. In terms of water use, sustainability means:

• extraction of the water within the confines of the city;
• minimising the quantity of water used;
• groundwater withdrawal must be proportional to replenishment and recharge;
• there is a direct correlation between drinking water use and surface water quality; this requires particular efforts with respect to pollution control of the water bodies;
• consequently, the standard of wastewater treatment must be particularly high; treated wastewater must be used to boost the rate of flow of the bodies of water;
• a high degree of storm water retention in the area.

Data Sources

For water quality monitoring and as a basis for problem analysis and the elaboration of framework plans and concepts, a number of continuous and discontinuous quality measuring programmes are carried out by the responsible water resources agency in the Ministry Administration for Urban Development, Environmental Protection and Technology. For the block-related scale 1:50 000, these data were evaluated using the methods and instruments of the Environmental Information System (UIS Berlin) and the final results published as maps in the Environmental Atlas of Berlin.

Surface water quality is controlled at 170 representative measuring points. Measurements for more than thirty parameters monthly or every fourteen days and discontinuous sediment samples are taken. Multiple sampling is carried out at various places and the level of pollutants in fishes is also measured.

The routine measuring programme for groundwater quality produces data for more than 400 measuring points and street wells of two values per year. Data from other special surveys are evaluated: waste site monitoring programmes; measurements for the depth of the groundwater table; the type of strata over the groundwater; terrain levels and groundwater tables; the ecological state of river banks and lakesides, the fish and fauna; water conservation areas; public and private groundwater delivery; data of water companies and water authorities; about 2,000 groundwater monitoring pipes with six or twelve values per year, to determine the level of percolation of precipitation; full coverage data on evaporation, ground sealing, built-up and non-built-up areas, type of land use, groundwater tables, field capacity of soils, and degree of canalisation.

Methods

To depict data from measurement programmes or special surveys which are only representative for the area of the measurement point, data were evaluated using standard values or own classifications, showing the level of pollution on this point.

Measurement values which can be seen as representative for areas or special parts of areas were evaluated using mathematical or geo-statistical methods like interpolation or gridding. The decision of which method depends on the type of themes and data. Point measurements of heavy-metals, for example, cannot be presented as representative for more extensive areas.

Some themes, for example the vulnerability to pollution of the groundwater, were created by overlaying full coverage maps or by using, summarising, and composing information from other maps and other scales.

On the basis of the block-orientated environmental information system (UIS), the complex and summarising maps were computed using digital models like a groundwater table model, a terrain level model, or, for calculating the percolation of precipitation, a complex digital discharge model.

Results and Uses

In the Berlin Environmental Atlas, nine maps have so far been published in printed form for the water sector. Six of these are available on CD-ROM and on the internet.

All methods and results are documented in detailed texts; the digital methods and proceedings are available in a special databank.

With this information, the main pollutants of surface and groundwater are named and the most heavily polluted areas shown. The polluters are named and localised. Areas with high potential and quality for the use or protection of water and areas which are vulnerable to over-use are outlined and indicated. Cause and effect chains and threats for natural resources are presented. Sustainable use is necessary to secure groundwater resources in the long term. To that end, groundwater management concepts must be drawn up, for which the above-mentioned knowledge is a sine qua non.

All regional planning, urban, landscape, transport and commercial planning authorities must be involved in this task, as well, of course, as the authorities responsible for water resource management. To avoid damage to the environment, such fundamental data and knowledge are, however, also important for private companies, the public, and every individual citizen.