| Summary: | Intensified agriculture, input of sewage and waste, as well as deforestation in the 20th century in Europe caused a decline of river water quality and an increase in its turbidity, and rapid terrestrialisation of lakes. The situation was improved by sewerages and water purification plants, which, however, cannot retain all pollutants and toxins. Among the problems are elevated nitrate concentrations, Hg, microplastics and waste heat from power plants. Generally, immissions from mines, industry, and urban areas have impaired hydrochemistry of rivers and lakes. Examples: Potassium mining salinised the river Werra; unconventional oil development at Athabasca impaired ambient catchments with toxic aerosols. Ecological and hydrological degradation of very large lakes occurred due to the introduction of xenospecies to foster industrial fish catch, input of acid mine drainage, poor sewage treatment, nearby overgrazing and deforestation, and excess water abstraction from affluents. Washout of agricultural nutrients and inappropriate disposal of sewage effected vertical shoaling of the world's largest anoxic, sulphidic water body in the Black Sea. The global trend of lakes towards CO2 supersaturation results from enhanced input of dissolved organic carbon (DOC), promoting microbial respiration. In remote glacial lakes, climate warming has caused reduction of ice coverage and of permafrost, and effected substantial alteration of lacustrine hydrochemistries. A generalisation of effects of anthropogenic activities to the flow variability of large rivers is not possible. However, engineering, freshwater withdrawal, and extraction of sand and gravel fostered river bed erosion and caused delta starvation, subsidence, and coastal erosion. Hydrochemical studies recognised severe pollution of parts of surface waters in China. Radioactive contamination of surface waters occurred near nuclear plants and repositories.
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