| Abstract: | Statistically secured relations between nutrient concentrations in the water and characteristics of the catchment areas can be proved for the storage reservoirs of the GDR. The o–PO4 concentration during the full overturn in spring shows a close relation to the population density of the catchment area. Existing differences of concentration between drinking-water and industrial-water storage reservoirs can be attributed to different degrees of worthiness of protection of the catchment areas and to differences of the water morphology. The NO3 concentration is closely correlated with the proportion of agriculturally used area in the catchment area. The mass ratio NO3–N: o–PO4–P mostly lies above the limiting range of the limitation of nitrogen (> 12: 1), so that phosphorus becomes the central quantity of a possible control of the trophic level. Especially for drinking-water storage reservoirs in the weakly eutrophic range the reduction of the P-load is necessary and it has a high trophy-improving effect here. |
