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Characterisation of rural phosphorus sources and their eutrophication impact in headwater streams (Linked to PARIS) - WT0705CSF

This project examines the influence of different rural sources of phosphorus (P) on potential eutrophication impacts in streams draining three catchments of varying agricultural land uses and intensity of production established under a companion Defra Project (PE0116, PARIS). The enrichment of water with P derived from anthropogenic activities can cause a number of undesirable symptoms (nuisance algal blooms, algal toxins which maybe harmful to health, reduction in water clarity including taste and odour problems and reduction in plant and fish species diversity) that reduce the quality of water for drinking, amenity and recreational use. This enrichment is termed eutrophication and the intensification of agriculture, and accumulation of surplus P in the soil, contributes to eutrophication problems in some areas. Understanding the relative significance of agriculture in relation to other ‘point’ P sources in rural catchments, and their relative impacts on water chemistry and ecology is necessary in order to determine what control strategies are required to provide good water quality for a range of users and to maintain healthy ecological communities.
Research over the last 15 years has indicated those farming systems and land management practices which are most likely to lead to high P losses at the field and farm scale, and the form (soluble or particulate) in which that loss is likely to occur. However, the ecological impacts of dissolved and particulate P in agricultural runoff entering rivers remains unclear. In addition to agricultural runoff P sources, there are also a number of other sources of P in rural catchments, such as runoff from farmyards, farm tracks and roads and discharge from septic tanks, that may need to be controlled to reduce stream P concentrations to appropriate levels. The relative contribution of these different rural sources, including agriculture, will determine where control measures are most cost-effectively targeted.
Targeted monitoring of a number of rural P sources in the headwaters of catchments (Avon, Wye and Loddington) that are currently included in the Defra PARIS project (PE0116) will be undertaken to establish their relative importance for eutrophication. These catchments have a variety of agricultural land uses ranging from low intensity grassland to intensive arable and livestock farming. The selected P sources include drainflow from fields of low, medium and high soil P status, surface runoff from roads, farm tracks and farmyards at various catchment locations and discharge from rural sewage systems (septic tanks). In the first instance, the contribution of these sources to the concentrations and/or loads of P entering the headwaters will be assessed over one winter. The project will also include the establishment of an experimental stream facility that will enable manipulation of stream P concentrations and simulation of different agricultural runoff types and other rural sources. An assessment of how data generated in the project and PARIS can be incorporated into existing in-stream ecological models will also be undertaken. The work is anticipated to lead onto further assessment of the direct ecological impact of these rural sources in headwater streams using the methodology and research expertise developed under the PARIS project.
The project will involve the same multi-discipline research team working on the PARIS project and will make maximum use of existing sites, monitoring facilities and data in that project. The results from this project will be used to help quantify the extent to which P losses from agricultural land might need to be reduced in different areas to comply with the Water Framework Directive (WFD). It will help distinguish the relative importance and contribution of different farming practices to eutrophication problems for targeting of cost-effective control measures and assess the implications for development of policy options to control diffuse P inputs from agriculture.

Overall Objective

To assess the eutrophication impact of different rural phosphorus sources entering headwater streams in three catchments with varying agricultural land use.

Specific objectives

1.To quantify the concentrations and loads of phosphorus in field drainflow from fields with low, medium and high soil P status entering headwater ditches in the Wye Kivernoll sub-catchment.
2.To quantify the concentrations and loads of phosphorus in runoff from two large road drains entering the headwater stream in the Wye Lewstone Mill sub-catchment.
3.To investigate the range in concentrations of phosphorus in storm runoff from a number of potential rural phosphorus sources in the Wye, Avon and Loddington catchments, including farm tracks, farmyards, roads and septic tanks.
4.To establish an experimental stream facility at Loddington.
5.To review existing models and datasets for predicting the in-stream chemical and ecological impacts of phosphorus inputs.
Time-Scale and Cost
From: 2006

To: 2008

Cost: £238,457
Contractor / Funded Organisations
Environmental Protection              
Water Quality              
Fields of Study
Water Quality