This book gathers the extended abstracts of the presentations given

at the international symposium "Man and River Systems II; Interactions

among Rivers, their Watersheds and the Sociosystem", Paris, December

4-6, 2006. The symposium was organised by the PIREN-Seine

programme, a major long lasting scientific project enabling long term

ecological research at the river basin scale. At this scale, the ecosystem

to consider is based on complex interactions between the natural system

and the sociosystem.

Unlike the previous Man and River Systems symposium which major

subject was the interaction between biological, chemical and physical

processes at various scales within the watershed, our present objective

is to promote interdisciplinarity between natural and social sciences.

Historians, sociologists, economists thus provided key inputs to the

symposium.

The symposium addressed physical, geochemical and microbial processes

that are studied within river ecosystems and their catchments. These

elementary processes are involved in the transformations, circulations

and cycling of natural elements and contaminants along their transfers

across all compartments of the hydrosystems. A strong focus is given

on the interactions between aquatic and terrestrial systems, such as

diffuse sources and sinks. This includes historical descriptions of the

pressures as well as present time analysis of the fluxes and impacts of

nitrogen, phosphorus, total solids, metals, pesticides at the river basin

scale. An important final outcome of this complex set of processes and

pressures is the ecological status of the hydrosystem. A series of presentations

illustrate a panel of approaches which have been developed

to assess the ecological status of river systems at the basin scale in

relations to applied stresses. Last but not least, because of the major

importance of human activities in river basin ecosystems, evaluating

public policies and technical tools for river basin management. The efficiency

for various economic tools is discussed, and compared to more

politic incentives, including the strongly demanded public participation.

Numerous case studies illustrate this topic.