Abstract. Human activities have resulted in increased nutrient levels in many rivers all over Europe. Sustainable management of river basins demands an assessment of the causes and consequences of human alteration of nutrient flows, together with an evaluation of management options. In the context of an integrated and interdisciplinary environmental assessment (IEA) of nutrient flows, we present and discuss the application of the nutrient emission model MONERIS (MOdelling Nutrient Emissions into River Systems) to the Catalan river basin, La Tordera (north-east Spain), for the period 1996-2002. After a successful calibration and verification process (Nash-Sutcliffe efficiencies E = 0.85 for phosphorus and E = 0.86 for nitrogen), the application of the model MONERIS proved to be useful in estimating nutrient loads. Crucial for model calibration, in-stream retention was estimated to be about 50 % of nutrient emissions on an annual basis. Through this process, we identified the importance of point sources for phosphorus emissions (about 94 % for 1996-2002), and diffuse sources, especially inputs via groundwater, for nitrogen emissions (about 31 % for 1996-2002). Despite hurdles related to model structure, observed loads, and input data encountered during the modelling process, MONERIS provided a good representation of the major interannual and spatial patterns in nutrient emissions. An analysis of the model uncertainty and sensitivity to input data indicates that the model MONERIS, even in datastarved Mediterranean catchments, may be profitably used by water managers for evaluating quantitative nutrient emission scenarios for the purpose of managing river basins. As an example of scenario modelling, an analysis of the changes in nutrient emissions through two different future scenarios allowed the identification of a set of relevant measures to reduce nutrient loads.

Abstract. Rivers in developed regions are under significant stress due to nutrient enrichment generated mainly by human activities. Excess nitrogen and phosphorus emissions are the product of complex dynamic systems influenced by various factors such as demographic, socio-economic and technological development. Using a Catalan river catchment, La Tordera (North-East of Spain), as a case study of an integrated and interdisciplinary environmental assessment of nutrient flows, we present and discuss the development of narrative socio-economic scenarios through a participatory process for the sustainable management of the anthropogenic sources of nutrients, nitrogen and phosphorus.

Human activities have resulted in increased nutrient levels in many rivers all over Europe. Sustainable management of river basins demands an assessment of the causes and consequences of human alteration of nutrient flows, together with an evaluation of management options. In the context of an integrated and interdisciplinary environmental assessment (IEA) of nutrient flows, we present and discuss the application of the nutrient emission model MONERIS (MOdelling Nutrient Emissions into River Systems) to the Catalan river basin, La Tordera (North-East of Spain), for the period 1996-2002. After a successful calibration and verification process (Nash-Sutcliffe efficiencies <i>E</i> = 0.85 for phosphorus, and <i>E</i> = 0.86 for nitrogen), the application of the model MONERIS proved to be useful to estimate nutrient loads. Crucial for model calibration, in-stream retention (mainly affected by variability in precipitation) was estimated to be about 50 % of nutrient emissions on an annual basis. Through this process, we identified the importance of point sources for phosphorus emissions (about 94 % for 1996–2002), and diffuse sources, especially inputs via groundwater, for nitrogen emissions (about 31 % for 1996–2002). Despite potential hurdles related to model structure, observed loads, and input data encountered during the modelling process, MONERIS provided a good representation of the major interannual and spatial patterns in nutrient emissions. An analysis of the model uncertainty and sensitivity to input data indicates that the model MONERIS, even in data-starved Mediterranean catchments, may be profitably used for evaluating quantitative nutrient emission scenarios that may help catchment managers and planners to develop effective policy and management measures to reduce nutrient loads

Abstract. Rivers in developed regions are under significant stress due to nutrient enrichment generated mainly by human activities. Excess nitrogen and phosphorus emissions are the product of complex dynamic systems influenced by various factors such as demographic, socio-economic and technological development. Using a Catalan river catchment, La Tordera (North-East of Spain), as a case study of an integrated and interdisciplinary environmental assessment of nutrient flows, we present and discuss the development of socio-economic scenarios through a participatory process for the sustainable management of the anthropogenic sources of nutrients, nitrogen and phosphorus. In this context, scenarios are an appropriate tool to assist nutrient emissions modelling, and to assess impacts, possible pathways for socio-economic development and associated uncertainties. Evaluated against the 1993–2003 baseline period, scenarios target the 2030 horizon, i.e., through the implementation process of the Water Framework Directive (Directive 2000/60/EC). After a critical examination of the methodology used in the participatory development of socio-economic scenarios, we present four possible futures (or perspectives) for the Catalan river catchment conceived by stakeholders invited to a workshop. Keys to the success of such a participatory process were trust, which enhanced openness, and disagreements, which fostered the group's creativity for scenario development. The translation of narrative socio-economic scenarios into meaningful nutrient emission scenarios is also presented. By integrating findings of natural sciences and socio-economic analysis, we aim to assist decision makers and stakeholders in evaluating optimal management strategies for the anthropogenic sources of nitrogen and phosphorus.

Global change driven by human activity is overimposed on the hierarchical structure of fluvial ecosystems, causing a myriad of effects on their physical template and hydrology as well as on the quantity and quality of the resources for stream biota. Global change operates at all scales within this hierarchy, but its effects on the ecology of fluvial ecosystems at any particular scale may be exacerbated or overridden by concomitant effects occurring at other scales. The resulting effects can have major ecological implications on both ecosystem services (namely, biogeochemical processes associated to energy and matter flow) and biodiversity (namely, community structure), which currently are issues of central concern in environmental management. In this paper we focus on a particular ecological attribute of fluvial ecosystems, the capacity to process and retain nutrients, and examine how physical and chemical alterations caused by human activities, occurring at different scales, may interact to affect this capacity. We illustrate these effects based on existing knowledge and highlight the key changes at different scales which can be susceptible of major effects.