Investigating natural variability within headwater catchments in North Yorkshire, with regards to Margaritifera margaritifera conservation

Abstract

Catchment management for water quality is an evolving process that requires social cohesion between a variety of stakeholders, effective management of land, coupled with a change in social behaviour, in order to effect a reduction in the flux of nutrients entering a river. Through creating a dynamic strategy which acknowledges the limitations of reducing nutrient concentrations entering a river, catchment managers are required to improve water quality according to the Water Framework Directive Legislation (2000/60/EC). Current catchment management processes have successfully reduced nutrient concentrations from point sources and are beginning to address nutrient concentrations associated with diffuse sources. In rural catchments, such as the one studied, diffuse pollution is influenced by land management practices, agricultural practices, and septic tank contributions. Highlighting the importance of adopting an integrated catchment management plan to address the headwaters within a catchment, this thesis has recognised the variations within water quality which can be overlooked by monthly spot sampling at a downstream location of a river catchment. Conservation efforts for the umbrella species M. margaritifera requires spatial and temporal investigations across a catchment to ensure successful relocation and recruitment. Hydrological connectivity plays an integral role within a catchment; new transportation routes can elevate nutrient concentrations, thus degrading water quality. Through investigating the different hydrological connections within a catchment, appropriate management practices can be identified. Spatial variations across the low-order tributaries of a catchment can have a significant influence on river water quality downstream. The catchment management practices, which go hand in hand with creating a healthy, self-regulating ecosystem, with minimal environmental degradation, must be aligned to these spatial variations in connectivity and pollution transport. This thesis investigates the spatial and temporal variability of water quality within three rural subcatchments of the River Esk in the North York Moors, in particular the influence of land use, differences in management practices and the importance of viewing the hydrological connectivity at different scales of a catchment. Fortnightly sampling using a YSI probe and anion and cation analysis was undertaken. The results of the research led to suggestions for addressing water quality variations across the headwater tributaries with the aim of improving the recruitment of the umbrella species M. margaritifera in the River Esk catchment.