Plate 7.6 Changes in Selected Chemical Parameters in Rivers and Lakes, 1976–2000

In recent years, the state of rivers and lakes in Switzerland has continued to improve, thanks to the expansion of sewage treatment and the ban on phosphates in washing powders. Water quality can be described as good to excellent in rivers and streams whose catchments are mainly in Alpine regions and larger rivers where the pollutants are considerably diluted by the pure volume of water. In contrast, a significant level of pollution can still be observed in smaller rivers and streams in the densely populated Central Lowlands. This development is illustrated in the present plate, which presents a time series for the period 1976 to 2000. The results of water analyses carried out by cantonal and federal authorities have been used to illustrate selected chemical parameters in rivers and lakes.