The dammed Berlin stream segments in some cases showed significant differences in quality class over the course of time of the investigation:
Quality Class II: Tegel Lake, Müggel-Spree 1993 – 1995; since then only Tegel Lake
Quality Class II-III: Müggel-Spree, Great Müggel Lake, Seddin Lake, Teltow Canal
Quality Class III: Dahme, Stadtspree, Havel, Zeuthen Lake after 1997
Quality Class III-IV: Zeuthen Lake 1993 – 1997
The Zeuthen Lake shows a considerably higher P burden than other bodies of water in the southeastern Berlin area, such as Seddin Lake and Great Müggel Lake. This is primarily to be explained by the immissions from the Notte Canal (immissions from the former sewage-farm processes) and by high Pre-dissolution rates during the investigation periods.
The measured chlorophyll-a concentrations with view depths of in some cases less than 0.5 m can be explained largely by particular algae-physiological and morphological conditions. In terms of its trophics, Zeuthen Lake is the most strongly polluted river lake of the other Berlin stream segments.
The fact that under this classification proposal, which judges water quality exclusively on the basis of chlorophyll-a content, the Teltow Canal must be assigned to Quality Class II-III also shows that in some cases, supplemental water-quality descriptions depending of local conditions are required.
The Teltow Canal has a special position within the water system, since it is subjected to immissions from sewage-treatment plants (Wassmannsdorf, Marienfelde to 1998, resting life and Stahnsdorf) with a share of 30% of mean drainage. The high phosphorus concentrations (Quality Class III) (cf. Map 02.01) ascertained for the Teltow Canal, by contrast with the rather moderate chlorophyll-a concentrations (Quality Class II-III), indicate that in the Teltow Canal, the eutrophication potential is not nearly as well utilized as in the other parts of the Berlin water system. Investigations in the Teltow Canal indicate increased heterotrophic decomposition processes, because of the great heat and sewage load, so that saprobiological processes become more significant.
The oxygen curve in the Teltow Canal/Teltow Wharf Measurement Station shows considerably lower values in dry weather than the Spree/ Sophienwerder Measurement Station.
The temperature conditions in the Teltow Canal, which are relatively constant throughout the year due to the high specific heat immissions from the power stations, affect the algae composition. Moreover, phytotoxic effects of the sewage plant processes may impede algae growth.
Tegel Lake was the only bodies of water in the investigation time period to show Water-Quality Class II. The inflow to Tegel Lake from the northeast (Nordgraben, Tegel Creek) has since 1985 been passed through the Tegel Surface Water Treatment Facility (phosphate elimination), which has relieved the lake from high nutrient immissions.