The Impact of Destocking on the Microbiological Quality of Rivers in the Caldew Catchment - Volumes 1 & 2
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w w w.environment-agency.gov.uk The Impact of Destocking on the Microbiological Quality of Rivers in the Caldew Catchment - Volumes 1 & 2 Science Report SC020045/SR The Environment Agency is the leading public body protecting and improving the environment in England and Wales. It’s our job to make sure that air, land and water are looked after by everyone in today’s society, so that tomorrow’s generations inherit a cleaner, healthier world. Our work includes tackling flooding and pollution incidents, reducing industry’s impacts on the environment, cleaning up rivers, coastal waters and contaminated land, and improving wildlife habitats. This report is the result of research commissioned and funded by the Environment Agency’s Science Programme. Author(s): Published by: B. Sanders, S.G. Anthony, C. M. Stapleton, D. Kay, J. Crowther Environment Agency, Rio House, Waterside Drive, Aztec West, and J. G. Wilson Almondsbury, Bristol, BS32 4UD Tel: 01454 624400 Fax: 01454 624409 Dissemination Status: www.environment-agency.gov.uk Publicly available ISBN: 1 84432 382 X Keywords: Bathing waters, faecal indicator organisms, foot and mouth © Environment Agency March 2005 disease, destocking, rivers, manure management, storm events, diffuse pollution All rights reserved. This document may be reproduced with prior permission of the Environment Agency. Research Contractors: ADAS Consulting Ltd., Woodthorne, Wergs Road, The views expressed in this document are not necessarily Wolverhampton, WV6 8 TQ. those of the Environment Agency. Tel. 01902 69322. Fax. 01902 693166 This report is printed on Cyclus Print, a 100% recycled stock, Centre for Research into Environment and Health, IGES, which is 100% post consumer waste and is totally chlorine free. University of Wales, Aberystwyth, Ceredigion, SY23 3DB Water used is treated and in most cases returned to source in Tel. & Fax 01570 423565 better condition than removed. Environment Agency’s Project Manager: Further copies of this report are available from: Dr Jon Greaves, Science Group, Richard Fairclough House, The Environment Agency’s National Customer Contact Centre by Warrington. emailing [email protected] or by telephoning 08708 506506. Statement of Use: This technical report contains the results of a study to describe the impact of changes in stocking density on the microbiological water quality of the Caldew Catchment in Cumbria, which was heavily affected by foot and mouth disease (FMD). The information in this document is for use by Environment Agency staff and others involved in the regulation of diffuse microbial pollution. Science Project Number: SC020045 (P2-293) Product Code: SCHO0305BIRO-E-P Science at the Environment Agency Science underpins the work of the Environment Agency, by providing an up to date understanding of the world about us, and helping us to develop monitoring tools and techniques to manage our environment as efficiently as possible. The work of the Science Group is a key ingredient in the partnership between research, policy and operations that enables the Agency to protect and restore our environment. The Environment Agency’s Science Group focuses on five main areas of activity: • Setting the agenda: To identify the strategic science needs of the Agency to inform its advisory and regulatory roles. • Sponsoring science: To fund people and projects in response to the needs identified by the agenda setting. • Managing science: To ensure that each project we fund is fit for purpose and that it is executed according to international scientific standards. • Carrying out science: To undertake the research itself, by those best placed to do it - either by in-house Agency scientists, or by contracting it out to universities, research institutes or consultancies. • Providing advice: To ensure that the knowledge, tools and techniques generated by the science programme are taken up by relevant decision-makers, policy makers and operational staff. Professor Mike Depledge Head of Science Executive Summary Objectives and design This project monitored and described the impact of changes in stocking density on the microbiological water quality of the Caldew Catchment in Cumbria, which was heavily affected by foot and mouth disease (FMD). To characterize the catchment in agricultural terms, manure production and farm management practices were monitored through the integration of Department of Environment, Food and Rural Affairs (Defra) agricultural census data and livestock movement statistics, by a field survey of representative farms and by the seasonal modelling of manure management using the results of national and regional stratified surveys of farm practices. Twenty-five farms, selected as typical of the catchment, were recruited for detailed survey. The farms represented 23% of the total farmed area in the catchment and accounted for 26% of the total cattle population and 14% of the total sheep population. At the start of the project, they were surveyed using a questionnaire and farm map for livestock and land-use practices both prior to and following the FMD outbreak. The farm locations were distributed evenly across the subcatchments. Monthly log sheets, which provided information on farming activities during the project, were completed by each of the 25 farmers from December 2002 to December 2003. The timing of animal grazing is of special importance in assessing the risk of faecal indicator delivery to watercourses, as fresh excreta voided directly onto fields is not subject to die-off in storage. For the water-quality data analysis the study was divided into ‘summer’ periods, when virtually all cattle are out in the fields, and ‘winter’ periods, when the majority of the cattle are indoors, defined as follows: • October 2001-April 2002: restocking winter; • May-September 2002: mostly stocked summer; • October 2002-April 2003: restocked post-FMD winter; • May-September 2003: restocked post-FMD summer. Fifteen sites, selected for their particular catchment characteristics of topography, potential land-use, stocking densities and management practices, were sampled for total coliforms, faecal coliforms and enterococci between December 2001 and January 2004. Discharge (m3 s-1) was estimated for each site based on data from Environment Agency flow-monitoring stations, flow modelling and/or hydrometric survey. The impact of foot and mouth disease on stock levels and manure management The catchment is predominantly a productive grass-growing area with mainly dairy and stock-rearing farms. Most are family farms of medium size, although there are a substantial number of fairly large livestock holdings. 330 individual holdings were located within the Caldew Catchment, of which half accounted for 90% of grazed livestock. i Science Report The Impact of Destocking on the Microbiological Quality of Rivers in the Caldew Catchment–- Volume 1 The catchment was heavily affected by FMD, with a total of 175 infected premises (IPs) and dangerous contacts (DCs) where stock was culled, the majority between April and May 2001. Approximately 80% of cattle and 90% of sheep in the catchment were culled. The majority of stock was culled during April and May 2001. By mid-2002 stock numbers increased rapidly (i.e. to 75% of cattle and 52% of sheep numbers prior to FMD), but this rate of increase has not been sustained and the most recent available census statistics for June 2003 show only 79% and 59% of pre-FMD numbers, respectively (Figure S1). Stock densities may never reach pre-FMD levels because of Common Agricultural Policy (CAP) reforms and de-coupling of farm subsidies. Monthly stock records from the surveyed farms and records of restocking during 2002 were used to identify stock numbers within the catchment from September 2001 to June 2003. It was assumed that no farm began restocking until September 2001. The restocking of cattle, many of which were in calf, occurred between January and March 2002 at a time when animals were normally housed. Therefore, by the time the newly introduced animals were out grazing and presented the greatest risk of faecal indicator organism pollution of streams, the estimated excreta load was already at 70% of pre- FMD levels. Sheep were restocked in two phases over the winters of 2001/02 and 2002/03, although some evidence suggests that some farms abandoned sheep rearing. Faecal indicator organism concentrations and flux Generally, there was an increase in microbial concentrations downstream under both base-flow and high-flow conditions. Geometric mean (GM) concentrations were lowest in the headwater, fell and areas of the upper Caldew Catchment during all four study periods. In contrast, the concentrations in the predominantly improved pasture headwaters of the Roe Beck Catchment were greater. Overall, concentrations within the Roe Beck and River Ive Catchment upstream of its confluence with the River Caldew were greater than those within the upper and middle Caldew Catchment. These differences in water quality may be explained by the variation in land use within each subcatchment, with a greater proportion of improved pasture and lower proportion of rough grazing in the Roe Beck and River Ive Catchment compared to the Caldew Catchment. The subcatchment delivery of faecal indicators exhibits strong seasonality – summer concentrations exceeded winter concentrations at all sites (Figure S2). This seasonality is significant to the design of future studies of diffuse pollution remediation strategies. High-flow periods exhibited the highest