title: Changing climate and nutrient transfers: Evidence from high temporal resolution concentration-flow dynamics in headwater catchments.
abstract: We hypothesise that climate change, together with intensive agricultural systems, will increase the transfer of pollutants from land to water and impact on stream health. This study builds, for the first time, an integrated assessment of nutrient transfers, bringing together a) high-frequency data from the outlets of two surface water-dominated, headwater (~10km(2)) agricultural catchments, b) event-by-event analysis of nutrient transfers, c) concentration duration curves for comparison with EU Water Framework Directive water quality targets, d) event analysis of location-specific, sub-daily rainfall projections (UKCP, 2009), and e) a linear model relating storm rainfall to phosphorus load. These components, in combination, bring innovation and new insight into the estimation of future phosphorus transfers, which was not available from individual components. The data demonstrated two features of particular concern for climate change impacts. Firstly, the bulk of the suspended sediment and total phosphorus (TP) load (greater than 90% and 80% respectively) was transferred during the highest discharge events. The linear model of rainfall-driven TP transfers estimated that, with the projected increase in winter rainfall (+8% to +17% in the catchments by 2050s), annual event loads might increase by around 9% on average, if agricultural practices remain unchanged. Secondly, events following dry periods of several weeks, particularly in summer, were responsible for high concentrations of phosphorus, but relatively low loads. The high concentrations, associated with low flow, could become more frequent or last longer in the future, with a corresponding increase in the length of time that threshold concentrations (e.g. for water quality status) are exceeded. The results suggest that in order to build resilience in stream health and help mitigate potential increases in diffuse agricultural water pollution due to climate change, land management practices should target controllable risk factors, such as soil nutrient status, soil condition and crop cover.
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK. Electronic address: m.ockenden@lancaster.ac.uk.
authors.forename: M C
authors.initials: MC
authors.lastname: Ockenden
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK; Department of Geography, Lower Mountjoy, South Road, Durham University, Durham DH1 3LE, England, UK; Northumbrian Water, Boldon House, Wheatlands Way, Pity Me, Durham, DH1 5FA, England, UK.
authors.forename: C E
authors.initials: CE
authors.lastname: Deasy
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK.
authors.forename: C McW H
authors.initials: CMH
authors.lastname: Benskin
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK.
authors.forename: K J
authors.initials: KJ
authors.lastname: Beven
authors.affiliation: British Geological Survey, Keyworth, Nottingham, England, UK.
authors.forename: S
authors.initials: S
authors.lastname: Burke
authors.affiliation: Rothamsted Research, North Wyke, Okehampton, Devon EX20 2SB, England, UK.
authors.forename: A L
authors.initials: AL
authors.lastname: Collins
authors.affiliation: Global Sustainability Institute, Anglia Ruskin University, Cambridge CB1 1PT, England, UK.
authors.forename: R
authors.initials: R
authors.lastname: Evans
authors.affiliation: Met Office Hadley Centre, Exeter, Devon EX1 3PB, England, UK.
authors.forename: P D
authors.initials: PD
authors.lastname: Falloon
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK.
authors.forename: K J
authors.initials: KJ
authors.lastname: Forber
authors.affiliation: School of Environmental Sciences, University of East Anglia, Norwich Research Park, Norwich NR4 7TJ, England, UK.
authors.forename: K M
authors.initials: KM
authors.lastname: Hiscock
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK.
authors.forename: M J
authors.initials: MJ
authors.lastname: Hollaway
authors.affiliation: Met Office Hadley Centre, Exeter, Devon EX1 3PB, England, UK.
authors.forename: R
authors.initials: R
authors.lastname: Kahana
authors.affiliation: James Hutton Institute, Aberdeen AB15 8QH, Scotland, UK.
authors.forename: C J A
authors.initials: CJA
authors.lastname: Macleod
authors.affiliation: Department of Geography, Lower Mountjoy, South Road, Durham University, Durham DH1 3LE, England, UK.
authors.forename: S M
authors.initials: SM
authors.lastname: Reaney
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK.
authors.forename: M A
authors.initials: MA
authors.lastname: Snell
authors.affiliation: School of Engineering, Liverpool University, L69 3GQ, England, UK.
authors.forename: M L
authors.initials: ML
authors.lastname: Villamizar
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK.
authors.forename: C
authors.initials: C
authors.lastname: Wearing
authors.affiliation: Bangor University, Bangor, Gwynedd, LL58 8RF, Wales, UK.
authors.forename: P J A
authors.initials: PJA
authors.lastname: Withers
authors.affiliation: School of Engineering, Liverpool University, L69 3GQ, England, UK.
authors.forename: J G
authors.initials: JG
authors.lastname: Zhou
authors.affiliation: Lancaster Environment Centre, Lancaster University, Bailrigg, Lancaster LA1 4YQ, England, UK.
authors.forename: P M
authors.initials: PM
authors.lastname: Haygarth
mesh_terms: D000383:Agriculture; D057231:Climate Change; D004784:Environmental Monitoring; D009584:Nitrogen / Q000032:analysis*; D010758:Phosphorus / Q000032:analysis*; D045483:Rivers / Q000737:chemistry; D012621:Seasons; D014874:Water Pollutants, Chemical / Q000032:analysis*
chemical_list: D014874:Water Pollutants, Chemical; D010758:Phosphorus; D009584:Nitrogen
keywords: Diffuse pollution; Eden; High resolution data; Phosphorus; Rainfall; Water quality