Agricultural Diffuse Pollution Research Articles

Methodology for collecting initial data to assess diffuse agricultural pollution of water bodies (the case of the Lake Onego catchment)

Methodology for collecting initial data to assess diffuse agricultural pollution of water bodies (the case of the Lake Onego catchment)

Monetization of Ecosystem Services from Nature-Based Solutions for Agricultural Diffuse Pollution Control: Simplified Value Transfer Method at European Scale

When nature-based solutions (NBS) are developed with a primary scope, they also provide simultaneous additional economic, social, and environmental benefits, i.e., Ecosystem Services. A monetary assessment that accounts for these additional benefits is provided by this work, with a focus on Europe. Specifically, this is intended to evaluate nine identified benefits of those wetlands and buffer strips designed to primarily address agricultural diffuse pollution, which must surely be listed among the negative externalities of economic activities that NBS can help resolve. The aim of developing a simplified value transfer methodology for a rapid evaluation of NBS benefits with the adjusted unit Value Transfer method is to create an accessible solution when time, funding, or other constraints prevent the use of highly technical primary monetization approaches. The developed exercise allows us to gather insights from several primary valuation studies and to appropriately transfer the monetary valuation outcomes to new policy sites. In order to reduce the distance from the expected and required concrete achievements of the economic valuations, the study has been integrated with an case study located in the Venice lagoon catchment in Northwestern Italy. The results obtained are to be considered sound, with existing evidence showing that the most valuable benefits of the considered NBS are both water quality and recreation and tourism, to which is added, in the case of wetlands, water supply.

Discharge dynamics of agricultural diffuse pollution under different rainfall patterns in the middle Yangtze river

Rainfall plays a crucial role in influencing the loss of agricultural diffuse pollution. The middle Yangtze River region is well-know for its humid climate and numerous agricultural activities. Thus, this study quantitatively analyzed the concentration and distribution of nitrogen (N) and phosphorus (P) load and loss in a major tributary of the middle Yangtze River under different rainfall patterns by using sampling analysis and SWAT model simulation. The total nitrogen (TN) and nitrate-nitrogen (NO3−) concentrations were 1.604–3.574 and 0.830–2.556 mg/L, respectively. The total phosphorous (TP) and Soluble Reactive Phosphorus (SRP) were 2–148 and 2–104 μg/L, respectively. The modeling results demonstrated that higher rainfall intensity led to greater load and loss flux of diffuse pollutant at the outlet. Organic nitrogen (ORGN) is the main nitrogen form transported from the subbasin to the reach, while organic phosphorus (ORGP) and inorganic phosphorus (INORGP) were transported at similar amounts. Under the condition of conventional rainfall, the outlet reaches mainly transported NO3−, and ORGN gradually increased when rainstorm events occurred. The ratio of INORGP to ORGP was relatively stable. During extreme rainfall event, rainfall is the dominant element of agricultural diffuse pollution. A strong positive correlation exists between rainfall intensity and pollution loss during rainstorms. Storm rain events were the main source of TN and TP losses. Few storm rain days generated pollutants that accounted for a large proportion of the total loss, and their impact on TP loss was significantly greater than that of TN. The influence of storm rain on TN is mainly the increase in runoff, while TP is sensitive to the runoff and sediment transport promoted by rainfall. By setting different precipitation scenarios, it was confirmed that under the same rainfall amount, short-term storm rain has the most significant impact on the TN load, whereas TP load may be influenced more by the combined effects of rainfall duration and intensity. Therefore, to reduce the impact of agricultural diffuse pollution, it is important to take targeted measures for the rainstorm days.

A framework for applying interceptive mitigations for diffuse agricultural pollution

ABSTRACT Interceptive mitigation options implemented at the edge of agricultural fields and along run-off and drainage flow-paths can complement preventive in-field management actions to reduce diffuse contaminant losses to surface waters. However, it is often unclear to users which interceptive mitigation option is appropriate for their situation, where it should be located, what contaminant reductions and other benefits can be achieved, and what it would cost to implement, maintain, and operate these practices. We outline a framework for selecting and applying eight interceptive diffuse pollution mitigation practices potentially applicable on New Zealand farms: riparian grass filter, planted and multifunction buffers; constructed wetlands; woodchip bioreactors; filamentous algal nutrient scrubbers; sediment traps; and detainment bunds. The framework provides users with a semi-quantitative evaluation of the relative benefits and costs of the best suited mitigations across a range of farmed landscapes. It highlights where each mitigation has its niche in terms of the landscape fit, flow-path(s) intercepted, contaminant(s) targeted, efficacy, associated co-benefits, relative cost, operation and maintenance requirements, longevity, and consenting requirements. Testing and refinement of this framework is encouraged, using data from field-scale implementation, to better quantify efficacy in practice, and inform empirical models and decision making across farm and catchment scales.

A Connectivity Approach to Agricultural Diffuse Pollution in Tropical Montane Catchments Dominated by Swidden Landscapes

Shifting cultivation is widely practiced in many tropical mountainous watersheds. Agricultural practices are changing with the intensification of activities and the development of industrial monocultures associated with increasing land use and the use of pesticides and fertilisers. These changes have consequences for the evolution of sediment transfers in watersheds, resulting in new vulnerabilities for the inhabitants. This article shows the evolution of structural connectivity over 5 years in the village of Houaylack-Vangven, located in northern Laos, and its potential links with agricultural diffuse pollution. To develop a structural source-to-sink model to understand sediment transfers, our method was based on open-access data and various geographical tools. Field surveys were conducted to identify areas vulnerable to erosion and sediment transfers. The sources and sinks were then located using remote sensing techniques and image interpretation to then characterise connectivity rates. Finally, the relationship between the sources and sinks was analysed by graph theory to explore the potentialities for assessing the connectivity and exposure of sediment sinks. The main results are twofold: sinks coincide with areas at risk of contamination by pesticides and fertilisers, and the structural connectivity increases with the increasing of the source surfaces (swidden plots) due to the ongoing agricultural transition.

Diffuse agricultural pollution of groundwater: addressing impacts in Denmark and Eastern England

Abstract Diffuse groundwater pollution by agricultural land-use practices is a major international problem. The evolution of the problem in two similar areas of Northern Europe, highly dependent on groundwater for public water supply and arable agriculture for economic production, is reviewed over decades through reference to some exceptionally long-term monitoring data. In Denmark, the greatest concern has been with excessive concentrations of pesticides and their metabolites but significant nitrate problems have also been experienced in some areas. In Eastern England, rising groundwater nitrate concentrations constituted the greater problem but pesticide issues also had to be confronted. An in-depth assessment of the approaches available to water utilities for addressing the problem is provided, contrasting treatment solutions, which have major implications for carbon footprint, with land-use controls, to eliminate or reduce nitrate and pesticide leaching, in groundwater source catchment areas.

Land Cover and Human Disturbance Impact on Water Chemistry and Ecological Health in an Asian Temperate Lotic System

The ecological integrity of lotic ecosystems is influenced by land cover type and human activity throughout the watershed. This study evaluated Nakdong River conditions in 2016 using two multi-metric models, the index of biotic integrity (IBI) and the water pollution index (WPI), and compared model outputs for four land cover types: predominantly urban, forest, barren land, and agricultural. The primary objective of this study was to determine whether the land cover type and human disturbance metrics effectively regulate water quality, fish communities, and ecological integrity in the Nakdong River basin. Predominantly forest sites had low nutrient, organic matter, suspended solids, ion, and algal chlorophyll concentrations. In contrast, these concentrations were higher in predominantly agricultural, urban, and barren land areas. Concentrations of nutrients, organic matter, ions, suspended particle loadings, and algal growth regulated by the intensity of the Asian summer monsoon. Model outputs indicated that total phosphorus (TP) was the most important factor in algal growth in agricultural (R2 = 0.25) and barren land (R2 = 0.35) sites, and evidence of P limitation was found, with TN:TP ratios >17 in ambient water. Fish community analysis indicated that tolerant species dominated the fish community in the agricultural (52%), barren land (85%), and urban sites (53%), and sensitive species were dominant in the forest sites (56%). Fish composition analysis indicated that two exotic species (Lepomis macrochirus (3.99%) and Micropterus salmoides (3.92%)) were identified as the fifth and seventh most abundant fish species in the watershed and labeled as “ecologically disturbing species” in Korea. Nutrient enrichment, organic pollution, and algal blooms enhanced the mean relative abundance of omnivorous and tolerant fish species. Mean WPI and IBI scores indicated fair or poor conditions in the agricultural (WPI: 22, IBI: 16), barren land (WPI: 21, IBI: 14), and urban (WPI: 21, IBI: 17) sites and good or fair conditions in forest (WPI: 28, IBI: 21) sites. The chemical (r = −0.34) and biological (r = −0.21) health of the river basin were negatively related to human disturbance metrics. The findings suggested that regional land cover, summer monsoon intensity, and human disturbance are important drivers of water quality, fish community, and ecological health. The resulting information suggested that agricultural diffuse pollution control, cutting-edge wastewater treatment technologies, and reducing the degrees of human disturbance could improve the Nakdong River’s ecological integrity.

Spatio-temporal characterization of nutrient and organic pollution along with nutrient-chlorophyll-a dynamics in the Geum River

River water pollution is one of the biggest environmental challenges in the world. Therefore, it is imperative to assess the spatial and temporal variability of surface water quality to manage water resources from pollution. This study aimed to identify spatio-temporal variations of Geum River surface water quality and the factors that influence it. Summer monsoon, land-use land-cover (LULC), and weirs are dominant factors determining the dynamics of river water quality. Empirical analysis showed that total phosphorus (TP), total nitrogen (TN), biological oxygen demand (BOD), and chemical oxygen demand (COD) had positive linear functional relations with the agricultural and built-up cover but negative linear relations with forest cover. The results showed that the total suspended solids (TSS), chlorophyll-a (CHL-a), TP, and COD levels were higher in the summer than in any other season. On the other hand, total nitrogen (TN) and electrical conductivity (EC) levels were lower during summer in the river due to the dilution effect. Pollutant-transport theory shows that TSS acts as a TP carrier (R2 = 0.83, p < 0.001). The empirical model suggested that TP (R2 = 0.76, p < 0.001) was the better predictor for CHL-a compared to TN (R2 = 0.13, p < 0.001) as well as showed strong P-limitation based on TN:TP ratios. The high average WQI values of the Geum River (except for S01 and S02) show a higher pollution level, indicating its unsuitability for drinking, irrigation, and industrial usage. Our results suggest that industrial and domestic sewage treatment and agricultural diffuse pollution control could improve the Geum river water quality.

Modeling the Water and Nitrogen Management Practices in Paddy Fields with HYDRUS-1D

Rice production involves abundant water and fertilizer inputs and is prone to nitrogen (N) loss via surface runoff and leaching, resulting in agricultural diffuse pollution. Based on a two-season paddy field experiment in Jiangsu Province, China, field water and N dynamics and their balances were determined with the well-calibrated HYDRUS-1D model. Then, scenarios of different controlled drainage and N fertilizer applications were simulated using the HYDRUS-1D model to analyze the features and factors of N loss from paddy fields. Evapotranspiration and deep percolation were the two dominant losses of total water input over the two seasons, with an average loss of 50.9% and 38.8%, respectively. Additionally, gaseous loss of N from the whole soil column accounted for more than half of total N input on average, i.e., ammonia volatilization (17.5% on average for two seasons) and denitrification (39.7%), while the N uptake by rice accounted for 37.1% on average. The ratio of N loss via surface runoff to total N input exceeded 20% when the N fertilizer rate reached 300 kg ha−1. More and longer rainwater storage in rice fields under controlled drainage reduced surface runoff losses but increased the risk of groundwater contamination by N leaching. Therefore, compared with raising the maximum ponding rainwater depth for controlled drainage, optimizing N fertilizer inputs may be more beneficial for controlling agricultural diffuse pollution by reducing N loss via surface runoff and leaching. The HYDRUS-1D model provides an approach for the quantitative decision-making process of sustainable agricultural water and N management.

δ18O as a tracer of PO43− losses from agricultural landscapes

Accurately tracing the sources and fate of excess PO43− in waterways is necessary for sustainable catchment management. The natural abundance isotopic composition of O in PO43− (δ18OP) is a promising tracer of point source pollution, but its ability to track diffuse agricultural pollution is unclear. We tested the hypothesis that δ18OP could distinguish between agricultural PO43− sources by measuring the integrated δ18OP composition and P speciation of contrasting inorganic fertilisers (compound vs rock) and soil textures (sand, loam, clay) in southwestern Australia. δ18OP composition differed between the three soil textures sampled across six livestock farms: sandy soils had lower overall δ18OP values (21 ± 1‰) than the loams (23 ± 1‰), which corresponded with a smaller, but more readily leachable, PO43− pool. Fertilisers had greater δ18OP variability (∼8‰), with fluctuations due to type and manufacturing year. Consequently, catchment ‘agricultural soil leaching’ δ18OP signatures could span from 18 to 25‰ depending on both fertiliser type and timing (lag between application and leaching). These findings emphasise the potential of δ18OP to untangle soil-fertiliser P dynamics under controlled conditions, but that its use to trace catchment-scale agricultural PO43− losses is limited by uncertainties in soil biological P cycling and its associated isotopic fractionation.

Co-producing better land management? An ethnographic study of partnership working in the context of agricultural diffuse pollution

Partnership working has become a normative principle within agri-environmental governance. With more and more benefits becoming attributed to closer multi-stakeholder collaboration, more public monies are being directed towards this cause. These benefits have been studied widely and are usually presented in terms of their contributions to environmental, economic and/or social objectives. However, in contrast to these reported outcomes of partnership working, the practical ways towards them have received little attention. What does it mean to work together on a day-to-day basis? More specifically, how do stakeholders become trusted partners, bridge interests and coordinate their actions? What collaborative working culture becomes established within partnerships and how does this in turn affect wider governance outcomes, expectations and aspirations? Answers to these questions are not only important to better understand the factors that contribute to successful ways of partnership working, but also to account for its limitations. This paper responds to this research need by drawing on the example of Farm Herefordshire. This cross-organizational partnership promotes profitable farming, healthy soils and clean water to address the problem of diffuse pollution from agricultural practices within the Wye catchment in the UK. The insights from this case study contribute to the literature in two major ways: firstly, the paper follows prompts to study such modes of collective action holistically and bottom-up to capture all their contributions and implications. It does so by employing an ethnographic research approach to investigate the social interactions and struggles that characterize joint working. This commands attention to the backstories, the actual work meetings, the discussions, the processes of consensus building, and the joint actions undertaken; secondly, the paper connects with wider social science concerns around the underlying processes and practices of governmentality that are essential for establishing social and ecological orders. Thus, the paper explores how everyday practices of partnership working contribute to the co-production of institutions, discourses, identities, and representations—which in this case become strategically deployed to nudge—rather than revolutionise—better land management practices.

Effects of Water and Nitrogen Management on Water Productivity, Nitrogen Use Efficiency and Leaching Loss in Rice Paddies

Effective water and nitrogen (N) management strategies are critical for sustainable agricultural development. Lysimeter experiments with two deep percolation rates (low percolation and high percolation, i.e., LP and HP: 3 mm d−1 and 5 mm d−1) and five N application levels (N0~N4: 0, 60, 135, 210 and 285 kg N ha−1) were conducted to investigate the effects of controlled drainage on water productivity (WP) and N use efficiency (NUE) in water-saving irrigated paddy fields. The results demonstrated that NH4+-N and NO3−-N were the major components of total nitrogen (TN) in ponded water and leachate, accounting for more than 77.1% and 83.6% of TN, respectively. The risk of N leaching loss increased significantly under treatment of high percolation rates or high N application levels. High percolation loss required greater irrigation input, thus reducing WP. In addition, N uptake increased with increasing N application, but fertilization applied in excess of crop demand had a negative effect on grain yield. NUE was affected by the amount of N applied and increased with decreasing N levels. Water and N application levels had a significant effect on N uptake of rice, but their interaction on N uptake or NUE was not significant. For the LP and HP regimes, the highest N uptake and WP were obtained with N application levels of 285 kg ha−1 and 210 kg ha−1, respectively. Our overall results suggested that the combination of controlled drainage and water-saving irrigation was a feasible mitigation strategy to reduce N losses through subdrainage percolation and to provide more nutrients available for rice to improve NUE, thus reducing diffuse agricultural pollution. Long-term field trials are necessary to validate the lysimeter results.

Identification of multilevel priority management areas for diffuse pollutants based on streamflow continuity in a water-deficient watershed

Agricultural diffuse pollution is, on the global scale, one of the most important causes of surface water quality deterioration and eutrophication. However, the identification of agricultural priority management areas (APMAs) for diffuse pollutants is still an ongoing challenge in water-deficient watersheds. To enhance the accuracy of identification of APMA, a modified framework for APMA identification is proposed by combining the streamflow continuity index constructed by Reliability-Resilience-Vulnerability (R-R-V) indices and the SWAT model in this paper. This novel framework was tested in Zhang River Watershed and the main results are as follows. First, the SWAT model is calibrated and validated with a good performance of the Nash-Sutcliffe efficiency (NSE) and coefficient of determination (R2)greater than 0.75 and 0.80 for both the calibration and validation periods, respectively. Second, the wet year is found to be the critical period for diffuse TN and TP output at an annual scale. Specifically, the critical loss period of TN is identified as from April to October on the monthly scale, especially in July and August. However, the critical period of TP loss is mainly concentrated in the range from July to September in Zhang River Watershed. Third, the reaches with a high streamflow continuity index(SCI) are primarily located in mid-downstream part of the watershed. The reaches are mostly characterized by relatively low SCI values due to the lack of streamflow volume in the upper reaches. Fourth, the APMAs for TN and TP for the watershed final outlet connected to the Yuecheng Reservoir are approximately distributed in two areas by considering the SCI estimation, namely the Qingzhang River sub-watershed and the mid-downstream part of the Zhuozhang River sub-watershed. Compared with the results obtained from the modified APMA framework, the main areas of TN and TP APMAs may be overestimated by 27.17 and 10.02 percentage points, respectively, using the original APMAs framework without the SCI evaluation. This revised APMA framework can be easily extended to other water-deficient watersheds for improving the efficacy of the identification and the control of agricultural diffuse pollution.

Ardières‐Morcille in the Beaujolais, France: A research catchment dedicated to study of the transport and impacts of diffuse agricultural pollution in rivers

AbstractThe 8‐km2 Morcille catchment, which is a sub‐catchment of the 150‐km2 Ardières catchment in the Beaujolais region of France, is one of the first sites in Europe where research has been conducted on surface water contamination by pesticides. A consolidated hydrological and chemical dataset has been set up with data collected since 2002 on the Morcille River and since 2011 on the Ardières River. Additional data on the ecotoxicological and ecological impacts of pesticides on aquatic microbial communities and macroinvertebrates has also been recorded in both rivers since 2005. The ‘Site Atelier Ardières‐Morcille Dataset’ described here combines rainfall and stream water height measurements at gauged stations with concentrations of two trace elements and nine pesticides (mainly herbicides, fungicides and some of their metabolites) in both the Ardières and Morcille rivers. All contaminant concentration data showed spatial and temporal variability in water quality associated with pesticide use and rainfall patterns. This long‐term monitoring framework made it possible to estimate the persistence of two herbicides (diuron and norflurazon) after legislation banning them. It took 4 years for diuron and more than 10 years for norflurazon concentrations to fall below 0.1 μg/L. Concurrent biological data showed a gradient of impacts consistent with chemical anthropogenic pressure, and rapid recovery of phototrophic microbial communities after the diuron ban. Finally, monitoring data on pesticide transport in a grassed strip set on a slope of the Morcille catchment confirmed that vegetative filter strips can effectively reduce diuron fluxes in surface runoff (&gt;80% abatement) and infiltration water (&gt;70% abatement). The full dataset offers a valuable resource for the validation of hydrological models and the development of global approaches to better understand the pressure–transport–exposure–impact chain and aquatic community resilience at the small catchment scale.

Mapping the potential for Payments for Ecosystem Services schemes to improve water quality in agricultural catchments: A multi-criteria approach based on the supply and demand concept

Payments for Ecosystem Services (PES) schemes are an increasingly popular form of catchment management for improving surface water and groundwater quality. In these schemes, downstream water users who are impacted by agricultural diffuse pollution incentivise upstream farmers to adopt better practices. However, this type of scheme will not be successful in all situations, in part, due to a lack of potential for agriculture to improve the suuply of good water quality and/or a lack in demand from downstream users for good water quality. As such, this study aims to present a flexible approach to mapping the potential for PES schemes to improve water quality in agricultural catchments. The approach is based on multi-criteria analysis, with supply and demand as key criteria. It uses expert judgement or current guidance on PES to select supply and demand sub-criteria, expert judgement to weight all criteria through pairwise comparisons and readily available, national datasets to indicate criteria. Once indicator data are normalized, it combines them in a weighted sums analysis and presents results spatially at the national scale, all within a geographical information system. The approach can easily be applied to the country or region of interest by using locally relevant criteria, expert judgement and data. For example, when applied to the situation for river waterbodies in England, supply sub-criteria were the contribution of agriculture to loads of the major pollutants (nitrogen, phosphorus and sediments) and demand sub-criteria were the different downstream water users present (water companies and, tourist and local recreational users). Experts assigned equal weight to supply and demand criteria and the highest weights to sediments and water companies for sub-criteria, respectively. When national scale datasets to indicate these criteria were combined in a weighted sums analysis, it was possible to identify areas of high potential for PES. This would hopefully motivate more detailed research at the individual catchment level into the constraints in linking supply and demand. Three case-study schemes were also examined to show how some of these constraints are being identified and overcome. As such, the approach forms the first tier in a two-tier framework for establishing PES schemes to improve water quality in agricultural catchments.

Assessment of social demand heterogeneity to inform agricultural diffuse pollution mitigation policies

Agroecosystems provide several agroecosystem disservices, among which diffuse nutrient pollution is one of the most significant, mainly due to its negative impacts on surrounding ecosystems, such as coastal ecosystems. Therefore, the implementation of agricultural measures to mitigate nutrient pollution might become a way to overcome this environmental challenge. However, proper implementation requires both a cost-effectiveness assessment and social support. This paper aims to value the social demand for agricultural measures to mitigate nutrient pollution and the benefits gained in the surrounding ecosystems from their implementation. Additionally, the demand preference heterogeneity is assessed. Measures proposed by a law intended to mitigate diffuse nitrate pollution in the Campo de Cartagena catchment area (south-eastern Spain) and thereby restore one of the main coastal lagoons in the European Mediterranean Sea, the Mar Menor, are used as a case study. A choice experiment and latent class mixed logit were employed to disentangle heterogeneous social preferences. Despite the fact that preference heterogeneity was revealed regarding the proposed agricultural measures, strong preferences linked to the restoration of the Mar Menor were shown by all the distinct classes. The socioeconomic benefits derived from the measures along with the expected environmental benefits from the restoration of the surrounding ecosystems exceed the farmers' costs for their implementation. Consequently, the results provide guidance to policy makers in the establishment of socially supported strategies for agricultural nitrate pollution mitigation.

Understanding collective action for the achievement of EU water policy objectives in agricultural landscapes: Insights from the Institutional Design Principles and Integrated Landscape Management approaches

This paper aims to identify drivers and barriers to the achievement of EU water policy objectives in the agricultural sector by adopting an institutional perspective on water quality management at the landscape level. We apply a conceptual framework combining Integrated Landscape Management (ILM) and Institutional Design Principles (IDP) perspectives to analyze cooperation initiatives involving water suppliers and agricultural stakeholders to protect drinking water catchments from agricultural diffuse pollution. Three cases representing different forms of cooperation in rural landscapes in France were investigated on the basis of primary data collected at the local, water-basin and national levels. The results show that the success of multi-stakeholder collective action depends on both local factors such as characteristics of the water resource and stakeholders (knowledge, resources, trust and social capital) and on factors linked to the EU and national water and agricultural policy frameworks. In addition to the identification of drivers of and constraints on the implementation of EU water policy in agricultural landscapes, the analysis highlights the conceptual added value in combining the IDP and ILM approaches to understand policy implementation processes at the landscape level.

The changing face of science communication, technology, extension and improved decision-making at the farm-water quality interface

In recent decades, significant advances have been made in understanding the generation, fates and consequences of water quality pollutants in the Great Barrier Reef ecosystem. However, skepticism and lack of trust in water quality science by farming stakeholders has emerged as a significant challenge. The ongoing failures of both compulsory and particularly voluntary practices to improve land management and reduce diffuse agricultural pollution from the Great Barrier Reef catchment underlines the need for more effective communication of water quality issues at appropriate decision-making scales to landholders. Using recent Great Barrier Reef catchment experiences as examples, we highlight several emerging themes and opportunities in using technology to better communicate land use-water quality impacts and delivery of actionable knowledge to farmers, specifically supporting decision-making, behavior change, and the spatial identification of nutrient generation ‘hotspots’ in intensive agriculture catchments. We also make recommendations for co-designed monitoring-extension platforms involving farmers, governments, researchers, and related agencies, to cut across stakeholder skepticism, and achieve desired water quality and ecosystem outcomes.

Sediment and Nutrient Retention in Ponds on an Agricultural Stream: Evaluating Effectiveness for Diffuse Pollution Mitigation

The creation of ponds and wetlands has the potential to alleviate stream water quality impairment in catchments affected by diffuse agricultural pollution. Understanding the hydrological and biogeochemical functioning of these features is important in determining their effectiveness at mitigating pollution. This study investigated sediment and nutrient retention in three connected (on-line) ponds on a lowland headwater stream by sampling inflowing and outflowing concentrations during base and storm flows. Sediment trapping devices were used to quantify sediment and phosphorus accumulations within ponds over approximately monthly periods. The organic matter content and particle size composition of accumulated sediment were also measured. The ponds retained dissolved nitrate, soluble reactive phosphorus and suspended solids during baseflows. During small to moderate storm events, some ponds were able to reduce peak concentrations and loads of suspended solids and phosphorus; however, during large magnitude events, resuspension of deposited sediment resulted in net loss. Ponds filtered out larger particles most effectively. Between August 2019 and March 2020, the ponds accumulated 0.306 t ha−1 sediment from the 30 ha contributing area. During this period, total sediment accumulations in ponds were estimated to equal 7.6% of the suspended flux leaving the 340 ha catchment downstream. This study demonstrates the complexity of pollutant retention dynamics in on-line ponds and highlights how their effectiveness can be influenced by the timing and magnitude of events.

What is the deal with the Green Deal: Will the new strategy help to improve European freshwater quality beyond the Water Framework Directive?

Agricultural land use covers almost half of the EU territory and reducing nutrient and pesticide losses to freshwaters is central to existing EU policy. However, the progress of improving freshwater quality and reducing eutrophication is slow and lags behind targets. The Green Deal is a key element of the EU plans to implement the United Nation's Sustainable Development Goals. Here, we discuss the opportunities that the Green Deal and associated strategies may provide for the achievement of the water quality goals of the Water Framework Directive in agricultural landscapes. We welcome Green Deal's aspirational stated goals. However, the reliance of mitigation of diffuse agricultural pollution on the reform of the Common Agricultural Policy represents grave risks for practical implementation and the achievement of the Green Deal objectives. We also argue that the new strategies should be targeted at tackling and understanding the sources of water quality problems along the full pollution continuum. To maximise the opportunities for tackling diffuse pollution from agricultural land use and achieving the delayed water quality targets, we stress that a range of targeted new instruments will be needed to close the gaps in the pollution continuum ‘from source to impact’. These gaps include: (I) smart and standardised monitoring of the impacts of proposed eco-schemes and agri-environment-climate measures, (ii) active restoration of agricultural streams and ditches and their floodplains to reduce secondary pollution sources, (iii) options to draw down nutrient levels to or below the agronomic optimum that reduce legacy sources, (iv) integrating farm-scale and catchment-scale analysis of trade-offs in reducing different pollutants and their combined effects, and finally (v) accounting for emerging pressures to freshwater quality due to climate change. Incorporation of the pollution continuum framework into tackling diffuse agricultural pollution will ensure that the European water-related policy goals are achieved.