Standard values for nutrients in surface-water bodies

Critical characteristics have been evaluated indication of the switch from the eutrophic status to the recovered clear-water status. Reduction of the nutrient load or nutrient concentration was assumed to be the only factor of any weight in making this switch. The choice made for the desirable ecological status of the water body in question was the authors'. To safeguard vulnerable downstream waters, values for some cases were calculated; this avoided a "roll on" of high concentrations of upstream waters. The observed critical characteristics were very low, but ascertained in the switch indicated the need to study additional measures to fix recovery. Recovery time is assumed to be long. Additional measures will be necessary in order to establish good ecological conditions.