Integrated climate-chemical indicators of diffuse pollution from land to water

Abstract

Management of agricultural diffuse pollution to water remains a challenge and is influenced by the complex interactions of rainfall-runoff pathways, soil and nutrient management, agricultural landscape heterogeneity and biogeochemical cycling in receiving water bodies. Amplified cycles of weather can also influence nutrient loss to water although they are less considered in policy reviews. Here, we present the development of climate-chemical indicators of diffuse pollution in highly monitored catchments in Western Europe. Specifically, we investigated the influences and relationships between weather processes amplified by the North Atlantic Oscillation during a sharp upward trend (2010–2016) and the patterns of diffuse nitrate and phosphorus pollution in rivers. On an annual scale, we found correlations between local catchment-scale nutrient concentrations in rivers and the influence of larger, oceanic-scale climate patterns defined by the intensity of the North Atlantic Oscillation. These influences were catchment-specific showing positive, negative or no correlation according to a typology. Upward trends in these decadal oscillations may override positive benefits of local management in some years or indicate greater benefits in other years. Developing integrated climate-chemical indicators into catchment monitoring indicators will provide a new and important contribution to water quality management objectives.

Multidecadal Trajectory of Riverine Nitrogen and Phosphorus Dynamics in Rural Catchments

“…Sharp shifts in phosphate and nitrate concentrations in the late 1990s to early 2000s have been interpreted by Romero et al () as the result of the upgrading of a large wastewater treatment plant in the Seine basin, France. Responses to diffuse emissions resulting from evolving land management systems are usually more gradual due to the potentially long transit time of nutrients in catchments (Fovet et al, ; Hrachowitz et al, ; Vero et al, ) and to interaction of nutrient cycling with interannual climate variations (Gascuel‐Odoux et al, ; Mellander et al, ). Disentangling the influence of interannual climate variations from long‐term changes in land use and management on water quality is a challenge in many areas (Burt et al, ).…”

Hydrologic Extremes and Legacy Sources Can Override Efforts to Mitigate Nutrient and Sediment Losses at the Catchment Scale

“…Several factors have been shown to determine the success or failure of BMPs, including insufficient landowner participation, challenging weather, improper selection of BMPs, misunderstanding of pollution sources, inadequate level or distribution of BMPs, and time lags due to long delivery pathways both in space and time (Meals et al, 2010; Mellander et al, 2018; Withers et al, 2014). The landowner participation in E23 was very good throughout (9 out of 10 landowners participated), and the selected measures were appropriate for reaching the required reductions in P and SS losses (Malgeryd et al, 2015; Schoumans et al, 2014).…”

“…The influence of changing weather on the effectiveness of water quality management was recently highlighted because of an increasing intensity of the North Atlantic Oscillation (NAO) during the last decade that coincided with implementation of mitigation measures in many countries (Mellander et al, 2018; Ulén et al, 2019). These studies showed significant correlations between the NAO index and water quality parameters that were not evident in our study (Supplemental Fig.…”

“…Mitigation measures are often built in headwater catchments, which control the water quality signature of the stream network (Abbott et al, 2018; Alexander et al, 2007) and are hot spots of agricultural water pollution (Bieroza et al, 2018). Recent studies indicate that extreme weather can exacerbate nutrient and sediment export from agricultural headwater catchments (Mellander et al, 2018), requiring large‐scale mitigation solutions to offset the increased hydrologic flashiness of the changing climate (Ockenden et al, 2017). …”

A Global Perspective on Phosphorus Management Decision Support in Agriculture: Lessons Learned and Future Directions

“…Both agronomic and environmental P management decisions are highly site specific, which makes them variably cost effective and, in the case of environmental decisions, liable to failure, such as during extreme rainfall events (Howden et al, 2007; Nelson et al, 2009; Ockenden et al, 2017). For this reason, Mellander et al (2018) recommends the development of integrated climate–chemical watershed response indicators for water quality objectives. As high‐frequency sensors become more common, the promise exists to update DSTs and/or DSSs on a near real‐time basis.…”