Sources of Nitrogen_SEPARATE

# SEPARATE Dataset Summary This dataset presents modelled annual loads of nitrogen, phosphorus (total and dissolved), and fine sediment delivered to rivers across England and Wales at the Water Framework Directive (WFD) waterbody scale. It was produced using SEPARATE v2 and supports environmental policy development, particularly for the WFD. ## Pollution Sources ───────────────────────────────┬────────────────────────────────────────── Source │Description ───────────────────────────────┼────────────────────────────────────────── Diffuse Agricultural │From grassland, arable land, and woodland ───────────────────────────────┼────────────────────────────────────────── Diffuse Urban │Highways, residential and industrial areas ───────────────────────────────┼────────────────────────────────────────── River Channel Banks │Erosion from riverbanks ───────────────────────────────┼────────────────────────────────────────── Atmospheric Deposition │Direct deposition to water surfaces ───────────────────────────────┼────────────────────────────────────────── Sewage Treatment Works (STWs) │Discharges > 3 m³/day ───────────────────────────────┼────────────────────────────────────────── Septic Tanks │Unsewered household/industrial units ───────────────────────────────┼────────────────────────────────────────── Combined Sewer Overflows (CSOs)│Overflow during runoff events ───────────────────────────────┼────────────────────────────────────────── Storm Tanks │Overflow storage at STWs ───────────────────────────────┼────────────────────────────────────────── Groundwater │Baseflow pollutant delivery ───────────────────────────────┴────────────────────────────────────────── ## Pollutants by Source ──────────────────────┬───────┬───────┬───────────┬──────── Source │Total N│Total P│Dissolved P│Sediment ──────────────────────┼───────┼───────┼───────────┼──────── Diffuse Agricultural │X │X │X │X ──────────────────────┼───────┼───────┼───────────┼──────── Diffuse Urban │X │X │X │X ──────────────────────┼───────┼───────┼───────────┼──────── River Channel Banks │X │X │ │X ──────────────────────┼───────┼───────┼───────────┼──────── Atmospheric Deposition│X │X │ │- ──────────────────────┼───────┼───────┼───────────┼──────── STWs │X │X │X │X ──────────────────────┼───────┼───────┼───────────┼──────── Septic Tanks │X │X │X │- ──────────────────────┼───────┼───────┼───────────┼──────── CSOs │X │X │X │- ──────────────────────┼───────┼───────┼───────────┼──────── Storm Tanks │X │X │X │- ──────────────────────┼───────┼───────┼───────────┼──────── Groundwater │X │ │X │ ──────────────────────┴───────┴───────┴───────────┴──────── ## Modelling Methods * Agriculture: ADAS APT framework using PSYCHIC (P, sediment) and NIPPER (N) with inputs like soil, slope, rainfall, and farming practices. * Urban Runoff: Wallingford Modified Rational Method combined with event mean concentrations. * River Banks: Bank erosion index considering channel shape and flow stress. * Atmospheric: NEAP-N model (N) and ECN rainfall data (P). * STWs: Monitored 2010–2012 EA discharge data for >3m³/day. * Septic Tanks: Environment Agency data. * CSOs and Storm Tanks: SAGIS model; overflow assumptions based on sewer capacity and rainfall. * Groundwater: N contributions via baseflow. ## Uncertainties & Limitations * High uncertainty for small waterbodies (<25 km²). * STW and agriculture data reflect 2010–2012 period; mitigation uptake included for agriculture. * STW data does not include estuarine or coastal discharges. * Riverbank estimates exclude areas with protective works. ## Data Fields (Table Extract) ────────┬─────────────────────────────────────┬───────── Column │Description │Unit ────────┼─────────────────────────────────────┼───────── region │River Basin District │n/a ────────┼─────────────────────────────────────┼───────── wb_ID │WFD Waterbody ID │n/a ────────┼─────────────────────────────────────┼───────── loc_area│Local catchment area │km² ────────┼─────────────────────────────────────┼───────── X_au_L_t│Agricultural unmitigated load │tons/year ────────┼─────────────────────────────────────┼───────── X_am_L_p│Agricultural mitigated load (percent)│% ────────┼─────────────────────────────────────┼───────── X_to_L_t│Total load to waterbody │tons/year ────────┴─────────────────────────────────────┴───────── X = Nitrogen (N), Phosphorus (P), Dissolved Phosphorus (D), or Sediment (S) ### References For full methodology, refer to: Zhang et al. (2014), Environmental Science & Policy, 42, pp. 16–32. [DOI:10.1016/j.envsci.2014.04.010] Source data includes PSYCHIC, NIPPER, APT, NEAP-N, and SAGIS frameworks.