Potential contribution of system‐specific knowledge (SSK) to stream‐management decisions: ecological and economic aspects

Abstract

SUMMARY Stream‐management decisions must produce an optimal cost‐effect ratio, as related to social, ecological and economic concerns. Therefore, decisions must be reached in a systematic approach by scrutinizing the system‐specific knowledge (SSK) provided by many disciplines. This paper is organized into five sections: following the introduction (Section 1), Section 2 sets a framework for the numerous elements of the SSK that can serve as a checklist to identify potentially important topics for a particular management decision; Section 3 illustrates errors in stream‐management policies that have been made because the SSK was not considered; Section 4 demonstrates how the SSK can be applied in formulating appropriate stream‐ and water‐management policies; finally Section 5 summarizes the major points in the context of alternative stream‐management strategies. Examples on limiting values in Europe, restrictions of NH4‐N emission, and the routine application of the Saprobian index demonstrate that current management practices often ignore the SSK. Combining trivial elements of the SSK we demonstrate how complex problems of stream management can be solved, focusing on the sources, sinks, and effects of water, organic carbon, nitrogen and phosphorus. On the basis of costs and effects, we rate various management options for a fictitious north German lowland catchment. If that catchment does not carry a dense human population, SSK‐based management is distinctly more efficient than traditional management, which focuses on a minor sink (sewer system plus sewage treatment plant). Stream management ignoring the SSK wastes financial, intellectual, and natural resources. If we project the estimated costs for water‐resource management in Germany over the forthcoming decade on to the standards of recent European Community (EC) guidelines concerning this subject, a large portion of a sum of around $US 1–2 trillion (1012) will be squandered in the EC unless practices change. The results of our analysis are rather disturbing and suggest that totally different practices are needed in legislation, administration and execution, monitoring, and research. Therefore, we propose that our paper be the starting point for a discussion involving representatives of all relevant disciplines about potential priorities for new management strategies.