Drainage basin morphology: a starting point for balancing water needs, land use and fishery protection

The drainage basin, including the coastal zone, may be seen as a large-scal e system of interlinked natural resources and ecosystem services which supp ort human activities on land and in the sea. Social and economic activities in the drainage basin have to be consistent with the hydrological and ecol ogical needs for human well-being. Proper attention must also be paid to th e impacts of these factors on ecosystems further downstream. A macro-scale ecosystem approach to a basin has to consider: (1) direct uses of water bot h instream and after extraction when pollutants may be added to the return flow; and (2) indirect use of water for agriculture and forestry where the river may be depleted as a result of evapotranspiration from land surface, crops and trees. Both uses have repercussions on the quantitative flow and quality of water, which may damage water-based instream ecosystem services. The present paper addresses relationships between different types of human intervention in a drainage basin and their consequences. Two analytical mo dels are introduced: (1) a conceptual model which distinguishes between urb an and rural water uses, and their respective tools; and (2) a conceptual m odel for handling spatially ordered land/water use segments subject to diff erent types of interference. Finally, the present paper comments on the nee d to develop methodologies for cross-disciplinary dialogue, and for balanci ng water needs, land use and fishery protection.