With almost three quarters of the UK's land surface in agricultural production, diffuse pollution from farming activities has a major effect on the quality of water resources and associated ecosystems. However, the relationship between agriculture and the environment is extremely complex.
In line with the objectives of the European Water Framework Directive (WFD), a national £6.2million project is underway to identify sustainable agricultural practices that would limit or reduce detrimental effects on groundwater and river water quality while maintaining food production and the profitability of farm businesses.
Initiated by Defra and the Environment Agency, the project involves three Demonstration Test Catchments (DTCs) based in rivers in England. Each of the DTCs is collecting high-resolution 24/7 data from a network of water quality monitoring stations, most of which were designed and installed by the Environment Agency's National Water Quality Instrumentation Service (NWQIS).
The DTC project seeks to produce sound evidence to test the hypothesis that we can cost-effectively reduce the impact of agriculturally-derived diffuse pollution on water quality and the delivery of ecosystem services through the implementation of multiple on-farm measures.
It should be possible to determine the best possible agricultural practices to reduce diffuse pollution, but the implementation of such measures will only be effective with the cooperation of stakeholders. The DTC project, therefore, involves over 40 research institutions and other stakeholder groups such as the Environment Agency, river trusts as well as farmers and landowners.
The Demonstration Test Catchments
The three DTCs (Eden, Wensum, and Hampshire) were chosen for their variable natural features, agricultural land use, and the past research or level of monitoring and management – all three are enhanced monitoring catchments under the England Catchment Sensitive Farming Delivery Initiative (ECSFDI).
Each DTC has employed the ‘Before-After Control-Impact’ (BACI) approach to the monitoring of water quality, which compares a manipulated stream with a non-manipulated stream before and after implementation of a mitigation measure. Data recorded pre-mitigation provide a baseline against which post-mitigation monitoring can be compared. The control stream provides an additional spatial reference that can be used to factor out confounding effects of changes in land use, rainfall, flow, etc.
The Monitoring Program Has 4 Main Objectives
- Identifying the status quo (characterization or source identification)
- Understanding the system (flow pathways and biogeochemical transformations)
- Predicting the consequences of management options
- Verifying the success/failure of interventions to the system (source control or pathway modification) once an option is chosen and in place
The NWQIS designed and commissioned two high-specification walk-in monitoring stations at the catchment outlets for each of the three DTCs. These include automatic samplers, YSI multiparameter sondes, and analyzers for phosphate, nitrate, and ammonium. In addition, NWQIS has also designed and commissioned smaller stations (without the ammonium, nitrate, and phosphate analyzers) at each of the DTCs.
Water flow is being recorded by a combination of pressure transducer level monitors and SonTek Argonauts, which combine multi-beam Doppler technology with channel profile data to provide instantaneous discharge values.
Water quality and flow monitoring data are being supplemented by ecological measurements and laboratory analysis of soils and sediment.
Water Quality Monitoring at the River Eden DTC from Graham Meller on Vimeo.
The River Eden DTC is based near Penrith in Cumbria and provides an opportunity to study the effects of upland, predominantly livestock, farming on water resources and the local ecology. Prof. Phil Haygarth from the Centre for Sustainable Water Management at Lancaster University is the project leader.
"This is a tremendously exciting opportunity to find answers to the problem of diffuse pollution; an issue of global importance. We've got the best monitoring equipment available, but importantly we have brought together, for the first time, a wide group of individuals with an impressive array of skills in addition to representatives from the local communities – it's all about pooling our knowledge and resources to find new solutions," says Haygarth.
The Eden catchment includes forest areas, pasture, moorland, and bog, and features both extensive and intensive farming. The project has been split into three sub-catchments covering a combined area of around 10 km2; one area will be used as a control and the other two will be used to investigate the effects of mitigation – changes to agricultural practices.
Staff from the NWQIS have installed continuous (every 15 minutes) water quality monitors at each of the sites. These employ a YSI multiparameter sonde in a flow-through chamber to measure conductivity, temperature, pH, dissolved oxygen, turbidity, and Chlorophyll-a. Each site is also fitted with telemetry so that live data can be transmitted to the project's website.
Larger, more comprehensive monitoring stations have been installed at the outlets for the Morland and Pow sub-catchments, which, in addition to the autosampler and YSI multiparameter monitors, also include analyzers for phosphate, ammonium, and nitrate. Dr. Clare Benskin is responsible for the water quality monitoring work and says
"The continuous monitoring equipment is performing extremely well and is providing valuable baseline data, which is being complemented by monthly spot samples that are collected manually and transferred to the laboratory for analysis."
Laboratory analysis is undertaken for samples taken from autosamplers at each water quality monitoring site, and from boreholes, river sediment, and soils. Clare and her colleagues also study ecological indicator organisms such as algal diatoms.
High-Resolution Monitoring
Traditional environmental monitoring often involved the collection of either samples that represented a moment in time or samples that are a composite taken over a period of time. In contrast, the latest monitoring and telemetry technology can provide data that are almost 'live' – high-resolution data.
The DTC project specified high-resolution monitoring equipment because of the many advantages that it brings. For example, spot sampling is laborious and inherently expensive; however, its greatest drawback is the potential for missing water quality incidents.
"Both sensing and telemetry technology has advanced considerably in recent years, which means that we can now generate continuous reliable data from remote sites. For example, we have a network of water quality monitoring stations spread over the entire catchment of the river Thames, delivering continuous data to the Environment Agency's offices in Reading.
As a result, we are immediately aware of any water quality deterioration and this is a major help in protecting water quality as well as looking for long-term trends," Matt Loewenthal from the NWQIS explains.
The experience that the NWQIS has gained over many years in the development of real-time water monitoring networks was a significant factor in the success of the DTC installations. However, YSI's Ian Thompson believes that advances in monitoring technology have also been a major factor in enabling the creation of continuous or high-resolution field data:
"For decades our development teams have been focused on finding ways to increase maintenance intervals so that customers have to spend less time in the field and more time at their desks reviewing better quality data. Predominantly this has been achieved through lower power usage; better sensor technology to reduce the need for recalibration, and improved resistance to fouling."
All of the DTCs have been delighted with the high-resolution data that are being generated. For example, the Wensum DTC has been recording baseline data since March 2011 and Prof. Hiscock has already found that the data are providing greater insight into pollution sources and pathways:
"We have recorded conductivity peaks following road gritting activity during cold snaps and autumn application of salt to sugar beet fields and these have come through as separate 'events' – firstly, via land drains and then later via the soil, and this means that we will be able to develop better models and more quickly understand the effects of mitigation measures."
Mitigation
The DTCs all have different topography, geology, soil types, climate, and land use, so mitigation measures have been designed to suit each specific area. The main mitigation measures for the Eden DTC are:
- Livestock yard Infrastructure
- Integrated manure and fertilizer planning
- Farm track re-surfacing
- Rural sustainable drainage systems
- Tree planting watercourses
- Biobed to treat sprayer spill/wash
Looking Forward
The participants of the DTC project are confident that they will be able to deliver the project's objectives and YSI, a Xylem brand's Ian Thompson says "Experience in other countries has demonstrated that the provision of live, web-based, local water quality data encourage communities to take a greater interest in their environment and in the factors that affect it, so I am confident that the stakeholder engagement activities that the DTCs have undertaken will deliver sustainable benefits in the future."
Prof. Harris says "An overarching goal of the DTC project is for communities to develop solutions to diffuse pollution that meet their own specific circumstances and that they learn from each other and serve as examples to communities in other catchments. If we can achieve that," he says, "we will have gone a long way toward helping develop a way to achieving the goals of the Water Framework Directive."
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