title: Dominant mechanisms for the delivery of fine sediment and phosphorus to fluvial networks draining grassland dominated headwater catchments.
abstract: Recent advances in monitoring technology have enabled high frequency, in-situ measurements of total phosphorus and total reactive phosphorus to be undertaken with high precision, whilst turbidity can provide an excellent surrogate for suspended sediment. Despite these measurements being fundamental to understanding the mechanisms and flow paths that deliver these constituents to river networks, there is a paucity of such data for headwater agricultural catchments. The aim of this paper is to deduce the dominant mechanisms for the delivery of fine sediment and phosphorus to an upland river network in the UK through characterisation of the temporal variability of hydrological fluxes, and associated soluble and particulate concentrations for the period spanning March 2012-February 2013. An assessment of the factors producing constituent hysteresis is undertaken following factor analysis (FA) on a suite of measured environmental variables representing the fluvial and wider catchment conditions prior to, and during catchment-wide hydrological events. Analysis indicates that suspended sediment is delivered to the fluvial system predominantly via rapidly responding pathways driven by event hydrology. However, evidence of complex, figure-of-eight hysteresis is observed following periods of hydrological quiescence, highlighting the importance of preparatory processes. Sediment delivery via a slow moving, probably sub-surface pathway does occur, albeit infrequently and during low magnitude events at the catchment outlet. Phosphorus is revealed to have a distinct hysteretic response to that of suspended sediment, with sub-surface pathways dominating. However, high magnitude events were observed to exhibit threshold-like behaviour, whereby activation and connection of usually disconnected depositional zones to the fluvial networks results in the movement of vast phosphorus fluxes. Multiple pathways are observed for particulate and soluble constituents, highlighting the challenges faced in mitigating the delivery of contaminant fluxes to headwater river systems.
authors: School of Geography Politics and Sociology, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom. Electronic address: matthew.perks@ncl.ac.uk.
authors: M T
authors: MT
authors: Perks
authors: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom.
authors: G J
authors: GJ
authors: Owen
authors: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
authors: C McW H
authors: CM
authors: Benskin
authors: School of Civil Engineering and Geosciences, Newcastle University, Newcastle upon Tyne NE1 7RU, United Kingdom.
authors: J
authors: J
authors: Jonczyk
authors: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom; Department of Geography, Durham University, Durham DH1 3LE, United Kingdom; Northumbrian Water Ltd., Boldon House, Wheatlands Way, Pity Me, Durham DH1 5FA, United Kingdom.
authors: C
authors: C
authors: Deasy
authors: British Geological Survey, Environmental Science Centre, Nicker Hill, Keyworth, Nottingham NG12 5GG, United Kingdom.
authors: S
authors: S
authors: Burke
authors: Department of Geography, Durham University, Durham DH1 3LE, United Kingdom.
authors: S M
authors: SM
authors: Reaney
authors: Lancaster Environment Centre, Lancaster University, Lancaster LA1 4YQ, United Kingdom.
authors: P M
authors: PM
authors: Haygarth
mesh_terms: D000383:Agriculture; D004784:Environmental Monitoring; D019015:Geologic Sediments / Q000032:analysis*; D065948:Grassland; D010758:Phosphorus / Q000032:analysis*; D045483:Rivers; D014873:Water Pollutants / Q000032:analysis*
chemical_list: D014873:Water Pollutants; D010758:Phosphorus
keywords: Connectivity; Diffuse pollution; Fluvial; Grassland; Headwater; Phosphorus; Suspended sediment; Water quality