Demonstration Test Catchments Research Articles

Conservation tillage and soil health: Lessons from a 5-year UK farm trial (2013–2018)

In 2010, the UK government launched the Demonstration Test Catchments (DTC) platform to evaluate the extent to which on-farm mitigation measures can cost-effectively reduce the impacts of agricultural water pollution on river ecology whilst maintaining food production capacity. In this paper, we compare the impacts on soil health of two types of conservation tillage (direct drill and shallow non-inversion) against conventional mouldboard ploughing after five years (2013–2018) of adoption within the River Wensum DTC. Across the 143 ha conservation tillage trial area, temporal changes in the physical, chemical and biological condition of the soils were examined through the analysis of 324 soil samples, whilst the impacts on soil water chemistry were assessed through the analysis of 1176 samples of subsurface field drainage. Riverine water pollution was also explored through high-resolution (30 min) hydrochemistry measurements generated by an automated, in-situ bankside monitoring station located 650 m downstream of the trial area. Results revealed that conservation tillage did not significantly alter the soil physical, chemical or biological condition relative to conventional ploughing during the first five years. In addition, conservation tillage did not reduce nutrient leaching losses into field drainage and did not significantly impact upon river water quality, despite the trial area covering 20% of the catchment. Economically, however, conservation tillage yielded net profit margins 13% higher than conventional ploughing after five years of practice due to a combination of operational efficiency savings and improved yields. Overall, the results of this study demonstrate that conservation tillage alone is ineffective at improving the short-term environmental sustainability of farming practices in this lowland intensive arable setting and indicates that a broader, integrated approach to conservation agriculture is required incorporating aspects of cover cropping, crop rotations and precision farming techniques. The improvements in farm business performance do, however, demonstrate land managers can make important financial gains by converting to a conservation tillage system.

Identifying Flow Pathways for Phosphorus Transport Using Observed Event Forensics and the CRAFT (Catchment Runoff Attenuation Flux Tool)

Identifying key flow pathways is critical in order to understand the transport of Phosphorus (P) from agricultural headwater catchments. High frequency/resolution datasets from two such catchments in Northwest England enabled individual events to be examined to identify the flow (Q) and Total P (TP) and Total Reactive P (TRP) dynamics (forensics). Detailed analysis of multiple flow and water quality parameters is referred to here as the event forensics. Are there more flow pathways than just surface runoff (dominated by overland flow) and baseflow (mainly groundwater) contributing at the outlet of these catchments? If so, hydrograph separation alone will not be sufficient. This forensic analysis gives a classification of four storm event response types. Three classes are based on the balance of old and new water giving enrichment and dilution of TRP pattern in the subsurface flow. A fourth type was observed where a plume of nutrient is lost to the channel when there is no observed flow. Modelling is also essential when used in combination with the event forensics as this additional tool can identify distinct flow pathways in a robust form. A case study will apply the Catchment Runoff Attenuation Flux Tool (CRAFT) to two contrasting small headwater catchments in Northwest England, which formed part of the Demonstration Test Catchments (DTC) Programme. The model will use data collected during a series of events observed in the two catchments between the period 2012 and 2014. It has the ability to simulate fast near surface (that can represent flow in the upper soil horizons and field drains) and event subsurface soil flow, plus slower groundwater discharge. The model can capture P enrichment, dilution and the role that displacement of “old” P rich water has during events by mixing these flows. CRAFT captures the dominant flow and P fluxes as seen in the forensic analysis and can create outputs including smart export coefficients (based on flow pathways) that can be conveyed to policy makers to better underpin decision making.

Temporal hydrochemical dynamics of the River Wensum, UK: Observations from long-term high-resolution monitoring (2011–2018)

In 2010, the UK government established the Demonstration Test Catchment (DTC) initiative to evaluate the extent to which on-farm mitigation measures can cost-effectively reduce the impacts of agricultural water pollution on river ecology whilst maintaining food production capacity. A central component of the DTC platform was the establishment of a comprehensive network of automated, web-based sensor technologies to generate high-temporal resolution (30 min) empirical datasets of surface water, groundwater and meteorological parameters over a long period (2011–2018). Utilising 8.9 million water quality measurements generated for the River Wensum, this paper demonstrates how long-term, high-resolution monitoring of hydrochemistry can improve our understanding of the complex temporal dynamics of riverine processes from 30 min to annual timescales. This paper explores the impact of groundwater-surface water interactions on instream pollutant concentrations (principally nitrogen, phosphorus and turbidity) and reveals how varying hydrochemical associations under contrasting flow regimes can elicit important information on the dominant pollution pathways. Furthermore, this paper examines the relationships between agricultural pollutants and precipitation events of varying magnitude, whilst demonstrating how high-resolution data can be utilised to develop conceptual models of hydrochemical processes for contrasting winter and summer seasons. Finally, this paper considers how high-resolution hydrochemical data can be used to increase land manager awareness of environmentally damaging farming operations and encourage the adoption of more water sensitive land management practices.

Application of high-resolution telemetered sensor technology to develop conceptual models of catchment hydrogeological processes

Mitigating agricultural water pollution requires changes in land management practices and the implementation of on-farm measures to tackle the principal reasons for water quality failure. However, a paucity of robust empirical evidence on the hydrological functioning of river catchments can be a major constraint on the design of effective pollution mitigation strategies at the catchment-scale. In this regard, in 2010 the UK government established the Demonstration Test Catchment (DTC) initiative to evaluate the extent to which on-farm mitigation measures can cost-effectively reduce the impacts of agricultural water pollution on river ecology while maintaining food production capacity. A central component of the DTC platform has been the establishment of a comprehensive network of automated, web-based sensor technologies to generate high-temporal resolution empirical datasets of surface water, soil water, groundwater and meteorological parameters. In this paper, we demonstrate how this high-resolution telemetry can be used to improve our understanding of hydrological functioning and the dynamics of pollutant mobilisation and transport under a range of hydrometerological and hydrogeological conditions. Furthermore, we demonstrate how these data can be used to develop conceptual models of catchment hydrogeological processes and consider the implications of variable hydrological functioning on the performance of land management changes aimed at reducing agricultural water pollution.

The Role of Attenuation and Land Management in Small Catchments to Remove Sediment and Phosphorus: A Modelling Study of Mitigation Options and Impacts

It is well known that soil, hillslopes, and watercourses in small catchments possess a degree of natural attenuation that affects both the shape of the outlet hydrograph and the transport of nutrients and sediments. The widespread adoption of Natural Based Solutions (NBS) practices in the headwaters of these catchments is expected to add additional attenuation primarily through increasing the amount of new storage available to accommodate flood flows. The actual type of NBS features used to add storage could include swales, ditches, and small ponds (acting as sediment traps). Here, recent data collected from monitored features (from the Demonstration Test Catchments project in the Newby Beck catchment (Eden) in northwest England) were used to provide first estimates of the percentages of the suspended sediment (SS) and total phosphorus (TP) loads that could be trapped by additional features. The Catchment Runoff Attenuation Flux Tool (CRAFT) was then used to model this catchment (Newby Beck) to investigate whether adding additional attenuation, along with the ability to trap and retain SS (and attached P), will have any effect on the flood peak and associated peak concentrations of SS and TP. The modelling tested the hypothesis that increasing the amount of new storage (thus adding attenuation capacity) in the catchment will have a beneficial effect. The model results implied that a small decrease of the order of 5–10% in the peak concentrations of SS and TP was observable after adding 2000 m3 to 8000 m3 of additional storage to the catchment.

Determining the sources of nutrient flux to water in headwater catchments: Examining the speciation balance to inform the targeting of mitigation measures

Diffuse water pollution from agriculture (DWPA) is a major environmental concern, with significant adverse impacts on both human and ecosystem health. However, without an appropriate understanding of the multiple factors impacting on water, mitigation measures cannot be targeted. Therefore, this paper addresses this gap in understanding, reporting the hydrochemical monitoring evidence collected from the UK Government's Demonstration Test Catchments (DTC) programme including contrasting chalk and clay/mudstone catchments. We use data collected at daily and sub-daily frequency over multiple sites to address: (1) How does the behaviour of the full range of nitrogen (N) species and phosphorus (P) fractions vary? (2) How do N species and P fractions vary inter- and intra-annually? (3) What do these data indicate about the primary pollution sources? And (4) which diffuse pollution mitigation measures are appropriate in our study landscapes?Key differences in the rates of flux of nutrients were identified, dependent on catchment characteristics. Full N speciation and P fractionation, together with dissolved organic carbon (DOC) enabled identification of the most likely contributing sources in each catchment. Nitrate (NO3-N) was the dominant N fraction in the chalk whereas organic and particulate N comprised the majority of the load in the clay/mudstone catchments. Despite current legislation, orthophosphate (PO4-P) was not found to be the dominant form of P in any of the catchments monitored. The chalk sub-catchments had the largest proportion of inorganic/dissolved organic P (DOP), accompanied by episodic delivery of particulate P (PP). Contrastingly, the clay/mudstone sub-catchments loads were dominated by PP and DOP. Thus, our results show that by monitoring both the inorganic and organic fractions a more complete picture of catchment nutrient fluxes can be determined, and sources of pollution pin-pointed. Ultimately, policy and management to bring nutrient impacts under control will only be successful if a multi-stressor approach is adopted.

Assessing the potential impacts of a revised set of on-farm nutrient and sediment ‘basic’ control measures for reducing agricultural diffuse pollution across England

The need for improved abatement of agricultural diffuse water pollution represents cause for concern throughout the world. A critical aspect in the design of on-farm intervention programmes concerns the potential technical cost-effectiveness of packages of control measures. The European Union (EU) Water Framework Directive (WFD) calls for Programmes of Measures (PoMs) to protect freshwater environments and these comprise ‘basic’ (mandatory) and ‘supplementary’ (incentivised) options. Recent work has used measure review, elicitation of stakeholder attitudes and a process-based modelling framework to identify a new alternative set of ‘basic’ agricultural sector control measures for nutrient and sediment abatement across England. Following an initial scientific review of 708 measures, 90 were identified for further consideration at an industry workshop and 63 had industry support. Optimisation modelling was undertaken to identify a shortlist of measures using the Demonstration Test Catchments as sentinel agricultural landscapes. Optimisation selected 12 measures relevant to livestock or arable systems. Model simulations of 95% implementation of these 12 candidate ‘basic’ measures, in addition to business-as-usual, suggested reductions in the national agricultural nitrate load of 2.5%, whilst corresponding reductions in phosphorus and sediment were 11.9% and 5.6%, respectively. The total cost of applying the candidate ‘basic’ measures across the whole of England was estimated to be £450 million per annum, which is equivalent to £52 per hectare of agricultural land. This work contributed to a public consultation in 2016.

The scale problem in tackling diffuse water pollution from agriculture: Insights from the Avon Demonstration Test Catchment programme in England

AbstractMitigation of diffuse water pollution from agriculture is of concern in the United Kingdom, so that freshwater quality can be improved in line with environmental objectives. Targeted on‐farm mitigation is necessary for controlling sources of pollution to rivers; a positive impact must also be delivered at the subcatchment and catchment scales before good ecological status can be achieved. A farm on the River Sem in the Hampshire Avon Demonstration Test Catchment was selected for monitoring due to its degraded farmyard, track, and drainage ditch, which was targeted by the Demonstration Test Catchment programme for improvement using a treatment train of interventions. The river was monitored before and after, upstream and downstream, of the potential sources of pollution and subsequent mitigation, both locally at farm scale, and downstream at the subcatchment scale. Sediment was obtained from the riverbed using a conventional disturbance technique, and source samples were collected from across the subcatchment. Samples were analysed for geochemistry, mineral magnetism, and environmental radionuclide activity using the <63‐μm fraction, before sediment source fingerprinting was conducted to apportion sources. Source tracing revealed that, although the degraded farm track was experiencing channelized flow and erosion in the pre‐mitigation period, it was not a major sediment source even at farm scale. Repeat source apportionment during the pre‐ and post‐mitigation periods showed that the targeted treatment train did not result in statistically significant decreases in predicted contributions from the farm track sources at either scale. Sediment sources must be determined at a range of spatial scales to support effective mitigation.

Use of farm survey returns from the Demonstration Test Catchments to update modelled predictions of sediment and total phosphorus loadings from subsurface drains across England and Wales

AbstractBoth experimental and monitoring studies have underscored the importance of the agricultural subsurface drain delivery pathway for sediment and phosphorus in England and Wales. Modelling studies to date using the Phosphorus and Sediment Yield CHaracterisation In Catchments (PSYCHIC) model have included a default drain connectivity coefficient of 0.9. Recent telephone and field‐based surveys in three Demonstration Test Catchments of farmer attitudes towards field drains and their maintenance have provided new data on the presence of permeable backfill, the frequency of subsoiling, mole draining and maintenance of the freeboard at drain outfalls. These survey returns have therefore been used to revise the default drain connectivity coefficient in PSYCHIC. Revised subsurface drain connectivity at the Water Management Catchment scale ranges from 0.52 to 0.89 with a median of 0.75. Relative to modelled baseline (2010) data using the default drain connectivity of 0.9, the revised estimates of connectivity resulted in a reduction in the prediction of relative contributions from the subsurface drain pathway at national scale of 8.1% for sediment and 6.8% for total phosphorus.

Simulating high frequency water quality monitoring data using a catchment runoff attenuation flux tool (CRAFT)

High resolution water quality data has recently become widely available from numerous catchment based monitoring schemes. However, the models that can reproduce time series of concentrations or fluxes have not kept pace with the advances in monitoring data. Model performance at predicting phosphorus (P) and sediment concentrations has frequently been poor with models not fit for purpose except for predicting annual losses. Here, the data from the Eden Demonstration Test Catchments (DTC) project have been used to calibrate the Catchment Runoff Attenuation Flux Tool (CRAFT), a new, parsimonious model developed with the aim of modelling both the generation and attenuation of nutrients and sediments in small to medium sized catchments. The CRAFT has the ability to run on an hourly timestep and can calculate the mass of sediments and nutrients transported by three flow pathways representing rapid surface runoff, fast subsurface drainage and slow groundwater flow (baseflow). The attenuation feature of the model is introduced here; this enables surface runoff and contaminants transported via this pathway to be delayed in reaching the catchment outlet. It was used to investigate some hypotheses of nutrient and sediment transport in the Newby Beck Catchment (NBC) Model performance was assessed using a suite of metrics including visual best fit and the Nash-Sutcliffe efficiency. It was found that this approach for water quality models may be the best assessment method as opposed to using a single metric. Furthermore, it was found that, when the aim of the simulations was to reproduce the time series of total P (TP) or total reactive P (TRP) to get the best visual fit, that attenuation was required. The model will be used in the future to explore the impacts on water quality of different mitigation options in the catchment; these will include attenuation of surface runoff.

Tackling agricultural diffuse pollution: What might uptake of farmer-preferred measures deliver for emissions to water and air?

Mitigation of agricultural diffuse pollution poses a significant policy challenge across Europe and particularly in the UK. Existing combined regulatory and voluntary approaches applied in the UK continue to fail to deliver the necessary environmental outcomes for a variety of reasons including failure to achieve high adoption rates. It is therefore logical to identify specific on-farm mitigation measures towards which farmers express positive attitudes for higher future uptake rates. Accordingly, a farmer attitudinal survey was undertaken during phase one of the Demonstration Test Catchment programme in England to understand those measures towards which surveyed farmers are most receptive to increasing implementation in the future. A total of 29 on-farm measures were shortlisted by this baseline farm survey. This shortlist comprised many low cost or cost-neutral measures suggesting that costs continue to represent a principal selection criterion for many farmers. The 29 measures were mapped onto relevant major farm types and input, assuming 95% uptake, to a national scale multi-pollutant modelling framework to predict the technically feasible impact on annual agricultural emissions to water and air, relative to business as usual. Simulated median emission reductions, relative to current practise, for water management catchments across England and Wales, were estimated to be in the order sediment (20%)>ammonia (16%)>total phosphorus (15%)≫nitrate/methane (11%)>nitrous oxide (7%). The corresponding median annual total cost of the modelled scenario to farmers was £3ha−1yr−1, with a corresponding range of -£84ha−1yr−1 (i.e. a net saving) to £33ha−1yr−1. The results suggest that those mitigation measures which surveyed farmers are most inclined to implement in the future would improve the environmental performance of agriculture in England and Wales at minimum to low cost per hectare.

Discharge and nutrient uncertainty: implications for nutrient flux estimation in small streams

The measurement of discharge is fundamental in nutrient load estimation. Because of our ability to monitor discharge routinely, it is generally assumed that the associated uncertainty is low. This paper challenges this preconception, arguing that discharge uncertainty should be explicitly taken into account to produce robust statistical analyses. In many studies, paired discharge and chemical datasets are used to calculate ‘true’ loads and used as the benchmark to compare with other load estimates. This paper uses two years of high frequency (daily and sub-hourly) discharge and nutrient concentration data (nitrate-N and total phosphorus (TP)) collected at four field sites as part of the Hampshire Avon Demonstration Test Catchment (DTC) programme. A framework for estimating observational nutrient load uncertainty was used which combined a flexible non-parametric approach to characterising discharge uncertainty, with error modelling that allowed the incorporation of errors which were heteroscedastic and temporally correlated. The results showed that the stage–discharge relationships were non-stationary, and observational uncertainties from ±2 to 25% were recorded when the velocity–area method was used. The variability in nutrient load estimates ranged from 1.1 to 9.9% for nitrate-N and from 3.3 to 10% for TP when daily laboratory data were used, rising to a maximum of 9% for nitrate-N and 83% for TP when the sensor data were used. However, the sensor data provided a better representation of the ‘true’ load as storm events are better represented temporally, posing the question: is it more beneficial to have high frequency, lower precision data or lower frequency but higher precision data streams to estimate nutrient flux responses in headwater catchments?

High-frequency monitoring of nitrogen and phosphorus response in three rural catchments to the end of the 2011–2012 drought in England

Abstract. This paper uses high-frequency bankside measurements from three catchments selected as part of the UK government-funded Demonstration Test Catchments (DTC) project. We compare the hydrological and hydrochemical patterns during the water year 2011–2012 from the Wylye tributary of the River Avon with mixed land use, the Blackwater tributary of the River Wensum with arable land use and the Newby Beck tributary of the River Eden with grassland land use. The beginning of the hydrological year was unusually dry and all three catchments were in states of drought. A sudden change to a wet summer occurred in April 2012 when a heavy rainfall event affected all three catchments. The year-long time series and the individual storm responses captured by in situ nutrient measurements of nitrate and phosphorus (total phosphorus and total reactive phosphorus) concentrations at each site reveal different pollutant sources and pathways operating in each catchment. Large storm-induced nutrient transfers of nitrogen and or phosphorus to each stream were recorded at all three sites during the late April rainfall event. Hysteresis loops suggested transport-limited delivery of nitrate in the Blackwater and of total phosphorus in the Wylye and Newby Beck, which was thought to be exacerbated by the dry antecedent conditions prior to the storm. The high rate of nutrient transport in each system highlights the scale of the challenges faced by environmental managers when designing mitigation measures to reduce the flux of nutrients to rivers from diffuse agricultural sources. It also highlights the scale of the challenge in adapting to future extreme weather events under a changing climate.

Methods for detecting change in hydrochemical time series in response to targeted pollutant mitigation in river catchments

Detecting changes in catchment hydrochemistry driven by targeted pollutant mitigation is high on the scientific agenda, following the introduction of the European Union Water Framework Directive. Previous research has shown that understanding natural variability in hydrochemistry time series is vital if changes due to mitigation are to be detected. In order for change to be detected in a statistically robust manner, the data analysis methods need careful consideration. Previous work has shown that erroneous results have often been obtained when statistical analyses have been carried out despite the associated test assumptions not being met. This paper discusses the principal data issues which must be considered when analysing hydrochemical datasets, including non-normality and non-stationarity. A range of statistical techniques is discussed which could be used to detect gradual or abrupt changes in hydrochemistry, including parametric, non-parametric and signal decomposition methods. The statistical power of these techniques as well as their suitability for identifying change is discussed. Using the uniquely detailed hydrochemical datasets generated under the Demonstration Test Catchments programme in England, the efficacy and robustness of change detection methods for hydrochemical data series is assessed. A conceptual framework for choosing a change detection method is proposed, based on this analysis, in order to raise awareness of the types of questions a researcher should consider in order to perform robust statistical analyses, for informing river catchment management and policy support decisions.

Groundwater conceptual models: implications for evaluating diffuse pollution mitigation measures

The EU Water Framework Directive (WFD) identifies diffuse pollution as a long-term threat to water quality. Farming contributes significantly to this pollution. There is a clear need for mitigation measures and assessment of their efficacy. Accordingly, Demonstration Test Catchments (DTCs) have been established in England to test the effect of changes in agricultural practice on river water quality and ecology. However, the presence of groundwater in these hydrological systems implies a wide range of travel times for pollutants from source to receptor. Unless flow routes are better characterized, it will be difficult to gauge the success of control measures in the short term. Using 3D modelling and supplementary hydrochemical information, this study considers the hydrogeology of several sub-catchments in the Avon DTC, southern England. Data suggest that groundwater ages >25 years exist in parts of the catchments; clearly, observations like these must be used to judge the likely effectiveness of targeted control measures. The revealed hydrogeological complexity of the Avon catchment is unlikely to be unique, so the techniques described here should be applicable to other lowland river systems with moderate to high baseflow indices (>0.5). To support the WFD, groundwater conceptual models should inform the design of effective measures for diffuse pollution mitigation.

Developing Demonstration Test Catchments as a platform for transdisciplinary land management research in England and Wales

Whilst a large body of plot and field-scale research exists on the sources, behaviour and mitigation of diffuse water pollution from agriculture, putting this evidence into a practical, context at large spatial scales to inform policy remains challenging. Understanding the behaviour of pollutants (nutrients, sediment, microbes and pesticides) and the effectiveness of mitigation strategies over whole catchments and long timeframes requires new, interdisciplinary approaches to organise and undertake research. This paper provides an introduction to the demonstration test catchments (DTC) programme, which was established in 2009 to gather empirical evidence on the cost-effectiveness of combinations of diffuse pollution mitigation measures at catchment scales. DTC firstly provides a physical platform of instrumented study catchments in which approaches for the mitigation of diffuse agricultural water pollution can be experimentally tested and iteratively improved. Secondly, it has established national and local knowledge exchange networks between researchers and stakeholders through which research has been co-designed. These have provided a vehicle to disseminate emerging findings to inform policy and land management practice. The role of DTC is that of an outdoor laboratory to develop knowledge and approaches that can be applied in less well studied locations. The research platform approach developed through DTC has brought together disparate research groups from different disciplines and institutions through nationally coordinated activities. It offers a model that can be adopted to organise research on other complex, interdisciplinary problems to inform policy and operational decision-making.

Contemporary fine‐grained bed sediment sources across the River Wensum Demonstration Test Catchment, UK

AbstractBecause the sources of fine‐grained sediment problems in river systems are diffuse, it is essential to assemble catchment scale information for informing management strategies. Sediment source‐tracing procedures have increasingly been adopted in this respect. Accordingly, a recently refined composite tracing procedure was used to investigate contemporary sources of fine‐grained channel bed sediment in 11 sub‐catchments (364 km2) of the River Wensum Demonstration Test Catchment, in the eastern UK. The procedure incorporated a combination of statistical tests for discriminating source end members, plus numerical mass balance modelling incorporating weightings for within‐source tracer variations and tracer‐specific discriminatory power, as well as a combination of local and genetic algorithm optimisation coupled with Monte Carlo uncertainty analysis. Replicate Monte Carlo runs demonstrated the convergence of the modelling outputs within ±1% of the average medians. Relative frequency‐weighted average median source type contributions were estimated to range between 27%–69% (agricultural topsoils; predicted deviate median inputs 0%–98% and 9%–100%), 0%–38% (damaged road verges; predicted deviate median inputs 0%–58% and 0%–100%) and 21%–48% (channel banks/subsurface sources; predicted deviate median inputs 0%–50% and 4%–50%). The study provides further evidence of the importance of channel banks and damaged road verges as sediment sources and the need to include such areas in catchment sediment management strategies. Copyright © 2012 John Wiley & Sons, Ltd.

Application of the FARMSCOPER tool for assessing agricultural diffuse pollution mitigation methods across the Hampshire Avon Demonstration Test Catchment, UK

Abstract Agricultural diffuse pollution is a significant contributor to water and air quality in many catchments and the need to control harmful emissions remains paramount for government policy. In England, the Demonstration Test Catchments (DTCs) have been established to provide a basis for testing on-farm mitigation measures using collaborative multi-partner research and some of this work is targeting the Hampshire Avon (∼1700 km2) catchment. To help provide integrated farm advice across England and Wales, a new Excel-based tool, FARM Scale Optimisation of Pollutant Emission Reductions (FARMSCOPER), has recently been developed for characterising diffuse agricultural pollutant emissions from representative farm types and quantifying the expected impacts of control options on those losses to the environment. Against this background, this paper describes the application of FARMSCOPER in the Hampshire Avon DTC in order to assess its utility at catchment scale and the potential benefits of relevant and practical mitigation options. Spatial datasets and the Agricultural Census returns for 2009 specific to the River Avon catchment were integrated to produce a collection of representative farm types which capture the characteristics of the local physical environment, land use patterns and farm management practices. FARMSCOPER was used to estimate the annual emissions of nitrate, phosphorus, sediment, nitrous oxide, methane and ammonia for each representative farm type. The scenarios investigated comprised baseline losses with no mitigation measures implemented, current emissions using information on the present implementation of options under existing schemes and initiatives and, the maximum potential reduction possible on the basis of implementing all available and relevant options. Model outputs suggested that reductions in pollutant loads in response to the existing uptake of mitigation methods are small (e.g. 10% for phosphorus, 7% for sediment, 4% for nitrate and 5% for nitrous oxide). FARMSCOPER suggested that technically feasible pollutant reductions on the basis of the implementation of more mitigation options could be of the order of 47% for phosphorus, 66% for sediment, 22% for nitrate and 16% for nitrous oxide. This work represents the first catchment scale application of the FARMSCOPER tool.

Monitoring agricultural diffuse pollution through a dense monitoring network in the River Eden Demonstration Test Catchment, Cumbria, UK

The water quality of our rivers and lakes is a reflection of the landscape over and through which it travels. The UK government, along with all European Union member states, are obliged under the Water Framework Directive (WFD) to aim for good ecological status of fresh water bodies by 2015. In order to evaluate the effectiveness of potential mitigation measures in reducing diffuse water pollution from agriculture at the catchment scale, the Demonstration Test Catchment (DTC) project was developed. The project is jointly funded by Defra, the Environment Agency (EA) and the Welsh Assembly Government (WAG). There are three DTCs across the country: the Eden catchment, Cumbria; the Wensum catchment, Norfolk and the Hampshire Avon catchment. The Eden DTC has established three ∼10 km2 focus catchments, chosen to reflect different farming practices, geologies, elevations and hydrological characteristics. Within each focus catchment, two sub‐catchments have been selected, one control and one mitigated, in which numerous existing and novel mitigation measures will be tested. It is hoped that the mitigation features will be multi‐purpose, having positive effects on pollutant retention, flooding, carbon sequestration, habitat creation and biodiversity. The effectiveness of these measures is assessed through networks of hydro‐meteorological and water‐quality instrumentation, most of which will provide data in near real time, with sub‐hourly time steps.