Identifying priorities for nutrient mitigation using river concentration–flow relationships: The Thames basin, UK

Abstract

Collins, Adrian L. 2014. Identifying priorities for nutrient mitigation using river concentration-flow relationships: the Thames basin, UK.Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. 1Identifying priorities for nutrient mitigation using river AbstractThe introduction of tertiary treatment to many of the sewage treatment works (STW) across the Thames basin in southern England has resulted in major reductions in river phosphorus (P)concentrations. Despite this, excessive phytoplankton growth is still a problem in the River Thames and many of its tributaries. There is an urgent need to determine if future resources should focus on P removal from the remaining STW, or on reducing agricultural inputs, to improve ecological status.Nutrient concentration-flow relationships for monitoring sites along the River Thames and 15 of its major tributaries were used to estimate the relative inputs of phosphorus and nitrogen from continuous (sewage point sources) and rain-related (diffuse and within-channel) sources, using the Load Apportionment Model (LAM). The model showed that diffuse sources and remobilisation of within-2 channel phosphorus contributed the majority of the annual P load at all monitoring sites. However, the majority of rivers in the Thames basin are still dominated by STW P inputs during the ecologically-sensitive spring-autumn growing season. Therefore, further STW improvements would be the most effective way of improving water quality and ecological status along the length of the River Thames, and 12 of the 15 tributaries. The LAM outputs were in agreement with other indicators of sewage input, such as sewered population density, phosphorus speciation and boron concentration. The majority of N inputs were from diffuse sources, and LAM suggests that introducing mitigation measures to reduce inputs from agriculture and groundwater would be most appropriate for all but one monitoring site in this study. The utilisation of nutrient concentration-flow data and LAM provide a simple, rapid and effective screening tool for determining nutrient sources and most effective mitigation options.

Reconstructing historical changes in phosphorus inputs to rivers from point and nonpoint sources in a rapidly developing watershed in eastern China, 1980–2010

“…4). These results are comparable with previous LAM applications (Bowes et al, 2008(Bowes et al, , 2009a(Bowes et al, , 2009b(Bowes et al, , 2010(Bowes et al, , 2014Greene et al, 2011;Chen et al, 2013), as well as SWAT, AGNPS, HSPF and INCA-P applications [reviewed by Moriasi et al (2007) and Jackson-Blake et al (2015)], where NS N 0.20 and R 2 N 0.20 for daily TP concentration simulation results were considered acceptable for NPS pollution dominated watersheds. Monthly and annual riverine TP loads estimated by the LAM were further compared to those obtained with the LOADEST model (Supplementary material: Fig.…”

“…Enrichment of phosphorus (P) is a major cause of waterbody eutrophication and associated impairments to water quality and aquatic ecosystems (Bowes et al, 2014;Sharpley et al, 2015). To reduce the negative impacts of excess P, watershed managers develop strategies to attain a target P level that can satisfy the designated use of a water body through control of anthropogenic sources (Freedman et al, 2008;Chen et al, 2012;Bowes et al, 2015).…”

“…Based on the fundamental hydrological differences between nutrient inputs from PS and NPS to rivers, a load apportionment model (LAM) may be developed for statistically quantifying point and nonpoint source nutrient inputs as a power-law function of river discharge (Bowes et al, 2008(Bowes et al, , 2009a(Bowes et al, , 2009b(Bowes et al, , 2010(Bowes et al, , 2014Greene et al, 2011;Chen et al, 2013). The LAM does not require detailed watershed attribute information and can potentially be applied to any dataset comprised of paired P concentrations and river discharge measurements.…”

“…The LAM does not require detailed watershed attribute information and can potentially be applied to any dataset comprised of paired P concentrations and river discharge measurements. This approach has been successfully applied to a wide range of watersheds in England, Ireland, U.S.A. and China (Bowes et al, 2008(Bowes et al, , 2009a(Bowes et al, , 2009b(Bowes et al, , 2010(Bowes et al, , 2014Greene et al, 2011;Jarvie et al, 2012;Chen et al, 2013). In terms of long-term riverine P source apportionment, however, existing LAM applications encounter some important limitations.…”

Identifying multiple stressor controls on phytoplankton dynamics in the River Thames (UK) using high-frequency water quality data

“…Water samples were taken at weekly intervals from six points along the length of the River Thames (Bowes et al, 2012a;Bowes et al, 2014). Sub-samples were immediately filtered through a 0.45 µm cellulose nitrate membrane (WCN grade: Whatman, Maidstone, UK) for subsequent soluble reactive phosphorus (SRP), nitrate and dissolved reactive silicon analysis.…”