Wuhlebecken

The Wuhlebecken is a lake in Berlin's Marzahn- Heller village. It is also called Wuhlesee. It is located in the southern course of the Wuhle and is almost 6 hectares one of the largest lakes, which forms the Wuhle. It measures at the widest point of 110 meters and is over 520 meters long, but he is quite deep with 5 meters and thus covers a large volume of fresh water.

Description

The lake is as jammed at its beginning at its end by two locks and the Wuhle is passed into a branch to the west around the lake. Is thus formed between the basin and the creek a inaccessible, protected shoreline, which is 5 to 10 meters wide.

Landscape provides the Wuhlebecken and its surroundings is a diverse area that invites the visitor to go for walks. On the eastern shore of the basin, the only unobstructed waters edge of Wuhle, there are large reeds and reed areas and some trees. On the banks of the tributary to the west, there is a newly planted row of weeping willows. In large areas of the Wuhle is marked on its slope through dense bushes and shrubs and thus offers, in addition to its great plant diversity protection for numerous species of animals and thus forms a distinct habitat. The diversity of vegetation, especially near the shore stands out clearly from other stretches of water. Water birds found on the blocked off the dam needed rest for hatching and the fish stock of the Wuhlebeckens is consistent with the Spree in conjunction.

Genesis and headwaters

The Wuhle, as a tributary of the River Spree, emerged at the end of the last ice age, the Weichsel ice age, around 18,000 years ago as an outlet for the melting water from the glaciers, and is on the edge of the Berlin glacial valley. It rises near Ahrensfelde.

Since the melting of glaciers icebergs the Wuhle of groundwater and seepage water is fed. Your visible beginning is a narrow trench near the railway station " Ahrensfelde Cemetery ". From here up to its confluence with the River Spree, the Wuhle travels 16.4 km and overcomes a difference in altitude of about 30 meters. The Wuhle and thus the Wuhlebecken are oversized Jungmoränenlandschaften which lime and mineral rich soil layers spawned when they are incurred, which are coveted farmland.

First, was located at the present site of the Wuhlebeckens an elongated sand ridge, which the Wuhle flew around on the Western side. In the 1950s, the Wuhle and Wuhlebecken were created. The lake newly created served to lower the ground water and also to objects carried by the Wuhle sludge should settle it flows through the lake.

End of the 80s the Wuhle had to be expanded again. The Falkenberg treatment plant had been taken over the function of the sewage, and the Wuhle the clarified water was derived. As increasing amounts were to dispose of dirty water, also took to the outflow of clear water. The passage capacity of Wuhle should therefore be increased from 9 to 15 m³ / s. At the same time Wuhlesee was dredged to a depth of 5 m and bordered on the west side of a dam, so that the Wuhle now flows around the lake. The aim was to regulate over a dam, the water supply and the ground water level and improve the water quality of the lake.

Climate

The climate is probably one of the most important density-independent abiotic factors. It likewise has an effect on all species in a biotope, as it acts over a large area. The various climate elements, such as rainfall, temperature means, maxima and minima, influence the ability to thrive and spread a kind; on the other hand can be as bioindicators for specific climatic conditions certain species.

Due to the homogeneity of the climate in larger areas fell back on Climate averages of Berlin region, so as to also meet general, longer valid statements.

Berlin and thus also the habitat Wuhlebecken is, with an annual mean temperature of 8.4 ° C and an average rainfall of 587 mm, in the temperate zone which contains distinct seasons assignments, in the spring, summer, autumn and winter, to proceed. The typical Berlin and Central Europe are mild and rainy climate values ​​, as well as the slight difference (19 ° C) between temperature minimum (-1 ° C) and maximum ( 18 ° C), due to the influence of the Gulf Stream. At the climate diagram of Berlin is seen that the average rainfall values ​​are in each month over the average temperature. This is a basic condition for growth to take place. Thus prevails in the area Wuhlebecken all year round growing season, with the preferred time of development of the plants from species to species is different.

The climate makes a statement about the distribution of species. Looking at the Mandarin duck, it can be seen that the average climate data of China, one of the regions of origin of the Mandarin Duck, with a mean temperature of 11.9 ° C and the average precipitation of 593 mm, only slightly different from those of Berlin. This is one reason that the Mandarin Duck is also common in us as the local climate values ​​cover their tolerance range.

Water

The water of the Wuhle recruited after the decommissioning of the sewage treatment plant Falkenberg almost exclusively from groundwater and seepage water of 21.3 km ² catchment area. From this catchment area of approximately 6.4 square kilometers are sealed, with the Versieglungsgrad of 31% is well below the Berlin average of 40%. The water has pH 7 with 8.4 ° dH and reflects the characteristic of the Berlin Water Hardness resist. In a today's celebration of the Wuhlebeckens a strong green color of the water is clear, indicating a large algae concentration. This eutrophication can have several reasons, such as too high a concentration of nutrients in the water or standing or slowly flowing waters.

With the decommissioning of the sewage treatment plant in February 2003, the annual runoff decreased from 2.6 million cubic meters in 2001 to around 0.9 million cubic meters in 2005. Since the Wuhle was then upgraded to a discharge rate of 15 m / s, decreases now the flow rate in the wide trench and the drain comes in particularly hot and dry weather even a complete standstill. Therefore, the water circulation and thus the oxygen concentration has fallen dramatically, which reduces fish populations and even can die individual fish species, but also other aquatic animals harms. On the other hand, the pollution levels of water have continued to improve since the closure, which particularly affects the sodium and phosphorus levels.

Although the low oxygen concentration and low flow rate make the waters and the aquatic animals difficult to create, the water values ​​are generally described as good. So all pollutant concentrations are below the allowable limits for lowland rivers, but they are not approached the quality of drinking water. In the course of a water analysis of Wuhlebeckens the nitrate concentration of the water was measured, which plays a strong role in eutrophication, since nitrate is an important nutrient for the algae. The value was 6 mg / l, which is below the limit of 50 mg / l significantly. Also, the nitrite level of 0.1 mg / l is still within the tolerance range. The ammonium concentration was so low that it could no longer be detected, but is given in the report of the Senate with 0.002 mg / l at a permissible limit of 0.5 mg / l.

Furthermore, the burden fell sharply in recent years by heavy metals. A large part of this was the construction of the largest filter plant in Biesdorfer quarry, in which the rainwater catchment area of the federal highway collects fifth and commercial area märkische Avenue and the sludge settles. In this mud most of the heavy metals are adsorbed. Thus, the concentration of the strongly responsible for the eutrophication nutrient phosphorus decreased by 79%.

The low nutrient load of the water is not the trigger for the eutrophication of Wuhlewassers, but the criteria described above, as too little oxygen and low flow velocity. Thus, a better water quality can only be achieved through increased flow rates. At this point some problem projects on the restoration of Wuhle aim.

Projects for the restoration of Wuhlebeckens

Requirements

Inbound one must mention that one can not fully consider separately the projects at the Wuhle and on Wuhlebecken, as these are directly related. Since 1994, it was announced that Falkenberg treatment plant should be closed, there are many plans and studies on the restoration of Wuhle. Here we divided the river in accordance with the requirements for a comprehensive restoration in two sections: in the north part of the national road 1/5, which offers numerous opportunities for reclamation measures, and in the southern section, which also includes the Wuhlebecken. So there is in the northern area a lot of free surface with a very urban use pressure, so you could remäandrieren the Wuhle without major problems here, ie the running straightening undo and thus not only recreate a natural floodplain, but also reduce the contrary, the flow rate of Wuhle and thus the reduce nutrient inputs to the consequence waters, which simultaneously prevents eutrophication. Another important condition is the relatively good water quality with respect to the pollutants. South of the highway fifth approach was built up to the continuously straightened the river Spree Wuhle, but this has no great measures to increase retention.

Previous projects / current projects

In addition to the various " entertainment activities " of the water body such as desilting and external filtering of the water, a first step to further improve the water quality was made in 2004 with the construction of the filter system in Biesdorfer Stretch. In mid-April this year also began a program lasting until 2008 to clean up the Wuhle valley. Content of these projects are in addition to the raising of the water level by heaping up of the river bed and floor exchanges even more strongly with soil pollutants (heavy metals) contaminated sites, a deconstruction of some weirs to create a continuous habitat for aquatic animals such as fish.

Critique / reflection

The potential, which provides the Wuhle in terms of restoration, however, is not fully exploited. Thus, the measures are aimed almost exclusively on improving the water quality in order to relieve the relatively highly contaminated waters as a result Spree and Havel as to revive rather the Wuhle with their adjacent habitats. The area of ​​the Wuhle valley is not a really obvious and practiced in other cases Remäandrierung ( barrel extension ) exploited and for the areas south of the B1 / 5, there are no concepts. On the contrary, bordering on the Wuhle area Biesdorf -South was even provided in the zoning plan for a development with apartments, which increases the sealing of the left Wuhle and retention efforts is disturbing ( Going for a lower flow rate ). Furthermore, the Wuhle from Wuhlebecken is still attached with gravel rather than rely on natural measures such as willow planting. In summary it must be said that there is still a rethinking of short-term maintenance measures to sustainable restoration necessary.