References and Validation

The diffuse component of the RAPS methodology is based on the empirical Export Coefficient Model (ECM) approach, which was originally developed by Vollenweider (1968) in the late 1960’s and in this work has ? been optimised to estimate present day diffuse pollutant loads. The ECM relies on the use of export coefficients that describe the amount of pollutant loss per unit area and per unit time for a variety of land uses and practices. An extensive database of export coefficients was compiled for the diffuse component of RAPS. The majority of the data provided in this database are derived from field measurements of contaminant concentrations in runoff which have been extracted from peer reviewed literature. If further information is required on the details of the data and methodology see the 'contacts' page for information on who to approach.

The purpose of the Rapid Assessment of diffuse Pollution Sources is to provide a basic analysis of diffuse pollution. It is not intended to provide thoroughly accurate or highly detailed results. If the results are to be applied in a practical scenario they should be used as starting point to focus further detailed analysis, or alongside additional data. A few key references are listed below to provide examples of how this approach is best used.

The approach is currently been updated and a new tool for assessing diffuse pollution loads is envisaged to be released in November 2004. Further details of this new tool can be obtained from jocelyn.delacruz@plymouth.ac.uk

Key references:

Frink C. R. (1991). Estimating nutrient exports to estuaries. J. Environ. Qual., 20, 717-724.

Hilton J., Buckland P. and Irons G. P. (2002). As assessment of a simple method for estimating the relative contributions of point and diffuse source phosphorus to in-river phosphorus loads. Hydrobiologia, 472, 77-83.

Johnes P. J. (1996). Evaluation and management of the impact of land use change to the nitrogen and phosphorus load delivered to surface waters: the export coefficient modelling approach. Journal of Hydrology, 183, 323-349.

Johnes P. J. and O’Sullivan P. E. (1989). The natural history of Slapton Ley Nature Reserve XVIII. Nitrogen and phosphorus losses from the catchment – an export coefficient approach. Field Studies, 7, 285-309.

Lepisto A., Kenttamies K. and Rekolainen S. (2001). Modeling combined effects of forestry, agriculture and deposition on nitrogen export in a northern river basin in Finland. Ambio, 30(6), 338-348.

Vollenweider R. A. (1968). Scientific fundamentals of stream and lake eutrophication, with particular reference to nitrogen and phosphorus. OECD Technical Report No. DAS/DST/88.

Worral F. and Burt T. P. (1999). The impact of land-use change on water quality at the catchment scale: the use of export coefficient and structural models. Journal of Hydrology, 221, 75-90.