Characterising phosphorus and nitrate inputs to a rural river using high-frequency concentration–flow relationships

Abstract

Characterising phosphorus and nitrate inputs to a rural river using highfrequency concentration-flow relationships.Contact CEH NORA team at noraceh@ceh.ac.ukThe NERC and CEH trademarks and logos ('the Trademarks') are registered trademarks of NERC in the UK and other countries, and may not be used without the prior written consent of the Trademark owner. AbstractThe total reactive phosphorus (TRP) and nitrate concentrations of the River Enborne, southern England, were monitored at hourly interval between January 2010 and December 2011. The relationships between these high-frequency nutrient concentration signals and flow were used to infer changes in nutrient source and dynamics through the annual cycle and each individual storm event, by studying hysteresis patterns. TRP concentrations exhibited strong dilution patterns with increasing flow, and predominantly clockwise hysteresis through storm events. Despite the Enborne catchment being relatively rural for southern England, TRP inputs were dominated by constant, non-rain-related inputs from sewage treatment works (STW) for the majority of the year, producing the highest phosphorus concentrations through the spring-summer growing season. At higher river flows, the majority of the TRP load was derived from within-channel remobilisation of phosphorus from the bed sediment, much of which was also derived from STW inputs. Therefore, future phosphorus 2 mitigation measures should focus on STW improvements. Agricultural diffuse TRP inputs were only evident during storms in the May of each year, probably relating to manure application to land. The nitrate concentration-flow relationship produced a series of dilution curves, indicating major inputs from groundwater and to a lesser extent STW. Significant diffuse agricultural inputs with anticlockwise hysteresis trajectories were observed during the first major storms of the winter period.The simultaneous investigation of high-frequency time series data, concentration-flow relationships and hysteresis behaviour through multiple storms for both phosphorus and nitrate offers a simple and innovative approach for providing new insights into nutrient sources and dynamics.

Impacts of climate change, land-use change and phosphorus reduction on phytoplankton in the River Thames (UK)

“…Figure 3 shows the combined effects of climatic alterations (uniform changes in precipitation and temperature) and land use and phosphorus removal strategies on the average phosphorus concentrations of the River Thames at Runnymede, approximately 12 km upstream of the tidal limit. Under current land-use and phosphorus removal mitigation strategies, average phosphorus concentrations range from 0.11 to 0.16 mg L -1 , being inversely proportional to precipitation due to the dominance of sewage effluent inputs at this site (Bowes et al, 2015). When an increase in agricultural land use is applied, the average phosphorus concentration increases up to between 0.15 and 0.18 mg L -1 .…”

Changing climate and nutrient transfers: Evidence from high temporal resolution concentration-flow dynamics in headwater catchments

“…There is, therefore, increasing interest in the use of in-stream high resolution water quality monitoring to assemble higher resolution catchment-scale datasets (e.g. Bowes et al, 2015;Halliday et al, 2012;Jordan et al, 2012;Mellander et al, 2012;Mellander et al, 2014;Outram et al, 2014;Skeffington et al, 2015;Wade et al, 2012), which can be used to understand key catchment processes in terms of hydrology, diffuse pollution transfer and trophic impacts and how these may alter under a changing climate.…”

Quantifying watershed‐scale groundwater loading and in‐stream fate of nitrate using high‐frequency water quality data

“…Recent studies have demonstrated that the collection and interpretation of high-frequency nitrate data collected using water quality sensors can be used to better quantify nitrate loads to sensitive stream and coastal environments [Ferrant et al, 2013;Bieroza et al, 2014;Pellerin et al, 2014], and provide insights into temporal nitrate dynamics that would otherwise be difficult to obtain using traditional field-based mass balance, solute injection, and/or isotopic tracer studies [Pellerin et al, 2009[Pellerin et al, , 2012Heffernan and Cohen, 2010;Sandford et al, 2013;Carey et al, 2014;Hensley et al, 2014Hensley et al, , 2015Outram et al, 2014;Crawford et al, 2015]. Coupling these measurements with techniques for quantifying water sources and/or flow paths [Gilbert et al, 2013;Bowes et al, 2015;Duncan et al, 2015] provides further opportunity for understanding and managing the drivers of coastal eutrophication.…”