Socio-economic and bio-physical modelling of diffuse pollution: closing the gaps

The EU Water Framework Directive (WFD) throws up many challenges to river basin management. Central to these is the task of integrating bio-physical and socio-economic models for sustainable river basin management planning. In the past the socio-economic and bio-physical modelling of water management have tended to run in parallel, each prescribing best practice management options for specific pollution problems in river basins. These management practices are at times conflicting and can be contradictory with those favoured for reduction of diffuse pollution not always cost effective and vice versa. Here we identify the practical challenges involved in the integration of socio-economic and bio-physical modelling, demonstrating the requirement for such an integration through a case study example. The case study area, the Ythan catchment, was designated a Nitrate Vulnerable Zone in 2000 on the evidence of increased nitrate concentrations in the surface waters and the estuary showing signs of eutrophication. Two models, cost effectiveness analysis (CEA) and the Soil and Water Assessment Tool (SWAT) have been selected using a set of criteria that accounts for the requirements of the water managers and modellers. These were applied to assess the socio-economic and bio-physical implications, respectively, of a series of scenarios for managing in-stream nitrate load. Results highlight potential conflicts between land management practices recommended on the basis of bio-physical modelling and socio-economic modelling. Drawing from this experience, a framework and set of ground rules have been established to enhance integration of socio-economic and biophysical modelling in a manner that hopes to achieve congruence in choice of management options in the implementation of the WFD.