Water Framework Directive catchment planning: a case study apportioning loads and assessing environmental benefits of programme of measures.

Complying with proposed Water Framework Directive (WFD) water quality standards for ‘good ecological status’ in England and Wales potentially requires a range of Programmes of Measures (PoMs) to control point and diffuse sources of pollution. There is an urgent need to define the benefits and costs of a range of potential PoMs. Water quality modelling can be used to understand where the greatest impact in a catchment can be achieved through ‘end of pipe’ and diffuse source reductions. This information can be used to guide cost-effective investment by private water companies and those with responsibilities for agricultural, industrial and urban diffuse inputs. In the UK, river water quality modelling with the Environment Agency SIMCAT model is regarded as the best current approach to support decision making for river water quality management and planning. The paper describes how a SIMCAT model has been used to conduct a trial WFD integrated catchment planning study for the River Ribble catchment in the North West of England. The model has been used to assess over 80 catchment planning scenarios. The results are being used support a national assessment of the cost-effectiveness of proposed PoMs.