Novel approaches to investigating spatial variability in channel bank total phosphorus at the catchment scale

• Published in: Catena (Giessen) 2021-07, Vol.202, p.105223, Article 105223
• Main Authors: Granger, S.J., Harris, P., Upadhayay, H.R, Sint, H., Pulley, S., Stone, M., Krishnappan, B.G., Collins, A.L.
• Format: Article
• Language: English
• Subjects: Geographically weighted; Land use; Riverbank sediment; Sample design; Spatial; Stream order
• ISSN: 0341-8162; 1872-6887
• DOI: 10.1016/j.catena.2021.105223

[Display omitted] •Total phosphorus (TP) content in channel banks ranged between 129.6 and 1206.9 mg P kg−1.•Water extractable P comprised between 0.01 and 0.12% of TP.•Marginal evidence indicated TP to vary as a function of land use or catchment scale.•Stronger evidence indicated TP to vary as a function of stream order.•A novel spatial analysis shows TP averages & variances vary along the stream network. Phosphorus (P) is often a limiting nutrient that leads to the eutrophication of aquatic systems. While dissolved P forms are the most bioavailable, the form, mobility, transport and fate of P are directly related to its association with fine-grained riverine sediment. Therefore, to implement successful P catchment management strategies it is important to understand the relative contribution of different sediment sources to P loads across the river continuum. While agricultural topsoil and, to a lesser extent, riverbed sediment are important sources of sediment-associated P, channel banks have been shown to be an important sediment source in some catchments. However, comparatively little is known about the P concentration and corresponding spatial variability in channel bank sediment and the associated implications for catchment management. The present study examines the spatial variability of P associated with channel bank profiles within a series of three nested catchments using both non-spatial and spatial statistical methods, where for the latter, a novel spatial approach was used to estimate the spatial averages and variances of P in channel bank sediment along the stream network. Channel bank P concentrations were compared to factors such as catchment scale, stream order, land use, bank exposure and location along the stream network. Concentrations of TP ranged between 129.6 and 1206.9 mg P kg−1 of which the water extractable P (WEP) content ranged from 0.01 to 0.12%. Stream order was found to influence TP concentrations, while land use and catchment scale provided only a moderate influence. This suggested that focussing channel bank sampling strategies at the largest catchment scale would capture key drivers of TP variability provided stream order is sufficiently represented. Whether the bank was had limited vegetation and was exposed and potentially eroding had a slight influence on TP variability in second-order stream banks in the larger of the two nested catchments. However, the slightly lower TP concentrations measured at these sites indicated