ABSTRACT
The Ouse and Nene Washes are designated as important washland habitat and will be Protected Areas under the Water Framework Directive. An investigation was carried out to assess the risk posed by the significant level of water supply abstractions and wastewater discharges in the upstream catchment. Ecohydrological prescriptions were developed to describe the conditions that would allow the conservation objectives to be met. Integrated catchment modelling was then used to test whether these prescriptions could be met for a range of current and future scenarios. Diffuse inputs from agricultural sources were included within the modelling framework so that the relative importance of diffuse and point contamination could be judged. The assessment demonstrated that the water supply abstractions are not likely to have a significant impact on the conservation features. In addition, the wastewater discharges were shown to have little impact upon nitrogen levels, which are predominantly impacted by agricultural inputs. It was found that the wastewater discharges in the Ouse catchment do cause phosphorus levels to exceed the ecohydrological prescription levels set for the ditch flora and fauna.
