Examination of flow, sediment and phosphorus relationships using monitored storm event data from a multiscale research platform

Examination of flow, sediment and phosphorus relationships using monitored storm event data from a multiscale research platform Yusheng Zhang, Steve Granger, Tegan Darch, Louise Olde and Adie Collins Agriculture and the Environment Aarhus, Denmark, 3-6 June 2025 The challenge Environmental Improvement Plan: 40% reduction in sediment and nutrient loss from agricultural land by 2038 compared with a baseline in 2018 Source: https://doi.org/10.1007/s13593-025-01015-4 BBSRC national capability •North Wyke Farm Platform (NWFP): 15 hydrologically-isolated field scale catchments; 4 catchments were targeted. •Upper River Taw Observatory (URTO): 3 nested catchments (Upper Ratcombe, Lower Ratcombe and Pecketsford) with contrasting land uses •High resolution and continuous monitoring and recording of rainfall, flow rates, sediment and nutrients (nitrogen and phosphorus), etc. •Focus on selected storm events where lab data for sediment and phosphorus are available for physical water samples Storm sampling and laboratory analyses •Sampling period: Nov 2018 to Feb 2021. •Number of events per catchment:7 - 10 •NWFP: Flow-based sampling; 7 – 8 samples per event; cover both falling and rising limbs. •URTO: Time-based sampling; 24 – 48 samples per event; cover whole hydrograph. •All samples were analysed for suspend solids (SS) and total phosphorus (TP) concentrations (sodium hydroxide fusion) Smith, B.F.L., Bain, D.C. (1982). A sodium hydroxide fusion method for the determination of total phosphate in soils. Communications in Soil Science and Plant Analysis 13(3), 185190. https://doi.org/10.1080/00103628209367257 Sites experience designed arable conversion and extreme weather conditions. Maximum concentrations in the storm events Catchment area (km2) Land uses Sediment conc. mg/l TP conc. µg/l NWFP Catchment 2 0.0673 grass and then converted to arable in Sep 2019 981 1413 Catchment 3 0.0684 grass and then converted to arable in Sep 2019 1423 2905 Catchment 5 0.0673 improved grass 206 699 Catchment 8 0.0733 permanent grass 317 1073 UTRO Upper 1.7 grass 172 282 Lower 4.4 major area of arable 765 852 Pecketsford 41.4 mixed 424 546 Data processing and analysis •Phosphorus content of sediment: total P concentration divided by sediment concentration. Mean values for each event were estimated •Sediment and phosphorus relationship: simple linear regression to estimate slopes; correlation analysis to assess the strength of the relationship. •Statistical tests to compare different land uses. •Load estimates at UTRO: multiplication of flow rates and concentrations. Example event data from Pecketsford - URTO Flow rates and SS concentrations on NWFP: land use change Source: https://doi.org/10.1016/ j.agee.2025.109713 SS and TP concentrations on UTRO: dry year vs wet year SS and TP concentrations on NWFP TP content of topsoil (down to 10 cm) was estimated to be around 0.09 to 0.14% based on soil survey undertaken in 2016.