Biological Water Quality (Trophics) 2003
A quality measurement network is operated to monitor Berlin’s surface bodies of water. It concentrates as a matter of priority on ascertaining the effects of the numerous single-point and diffuse water pollution sources into the watercourse. The measurement network contains a total of 63 measurement points, of which 39 are on the Dahme, Spree, Havel and the canals, and 24 are on the streams and country lakes.
As a rule, physical chemical, bacteriological and biological parameters are ascertained from monthly sample tests. For the continuous supervision of oxygen conditions, water temperature, pH value and conductivity, nine water-quality measurement stations are in addition operated along the major streams.
As a rule, 11 to 17 measurements per year are carried out on the average at the test points in the sample measurement stations. Normally, the 90th percentile (minimum sample size n= 11) is taken for the determination of the quality classes in the assessment; for temperature, the maximum values are used, and for oxygen, the minimum values.
At the continuously measurement stations, fifteen-minute values are ascertained and compiled to statistical key values. The assessment of the temperature is based on the 95th percentile, and of the oxygen content on the 10th percentile of the day values. These values are naturally of greater significance than the sample tests.