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Phosphorus Inputs to Large River Systems: Quantifying the Diffuse Export Coefficients for the River Swale Catchments - NT1024

The River Swale in the north of England integrates a succession of land uses and offers opportunities for measuring phosphorus exports in wholly agricultural sub-catchments and minor tributaries associated with different distributions of land use. This study will aim to provide detailed information on the transport of soluble and particulate phosphorus from agricultural land in the Swale catchment (especially during storm events) and relate measured phosphorus loads to land use in the catchment by an export coefficient approach incorporating normalisation with respect to rainfall; the study will also aim to evaluate the pattern of phosphorus fractionation in drainage water, tributaries and the main river and will relate this to land use in the catchment. Work will be focused on the measurement of fluxes of 3 phosphorus fractions (soluble reactive phosphorus (SRP), total dissolved phosphorus (TDP) and total phosphorus (TP)) at gauged river sites and will build on results from the NERC LOIS (Land Ocean Interaction Study) programme. Measurements of SRP, TDP, TP and suspended solids at river sites will permit the calculation of particulate associated phosphorus (the concentration of phosphorus associated with particulates) and hydrolysable phosphorus. Stability trials will be used to check the effects of short and long term storage of samples prior to analysis; interlaboratory trials between IFE and ADAS will also be conducted. An intensive sampling programme will be carried out in the spring or early summer to cover a period of base flow when there is phytoplankton growth in the river. Samples for this programme will be taken by EPICS at the selected river sites; these will be filtered and analysed for SRP within 24 hours of collection. Samples for TDP (filtered at the LOIS York laboratory) and TP will be analysed at IFE Wareham as soon as possible (typically within a week of collection). Automatic monitoring of pH, dissolved oxygen, temperature and conductivity will be performed at the main River Swale sites, while suspended solids will be measured at the York laboratory. Phosphorus concentrations will be used in conjunction with river discharge and rainfall data to calculate riverine loads and exports normalised with respect to rainfall. Computer programs will then be applied to mass balance and flux calculations for SRP, TDP and TP for the catchments. This information will be linked to the development of a GIS model for the entire River Swale catchment and will permit a comparison of exports of phosphorus in different parts of the catchment as well as indicating how variations in phosphorus exports link with land use. Comparisons between the upper Swale catchment and lower catchment and results from a more intensive study of a sub-catchment in the lower Swale, will provide key information for the development of the export coefficient approach, with appropriate consideration to the influence of additional factors such as rainfall and soils. A report will be submitted to MAFF on the influence of land use and other factors on the magnitude of phosphorus loss to large river catchments and the pattern of phosphorus speciation; this report will provide considerable benefits in terms of formulating phosphorus loss reduction strategies and will provide essential data for future policy guidance models.
Project Documents
• Final Report : Phosphorus Inputs to Large River Systems: Quantifying the Diffuse Export Coefficients for the River Swale Catchments   (650k)
Time-Scale and Cost
From: 1998

To: 2001

Cost: £180,000
Contractor / Funded Organisations
Natural Environment Research Council, ADAS UK Ltd.
Fields of Study
Fertilisers and Nitrate Pollution