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Hourly chemical data from four southern England rivers are subsampled for WFD parameters (dissolved phosphorus, dissolved oxygen, pH, temperature) and used for site classification. Monthly sampling is less precise than weekly; uncertainty depends on proximity to class boundaries.",{"@graph":14,"@context":73},[15,34,56],{"@type":16,"itemListElement":17},"BreadcrumbList",[18,23,27,31],{"item":19,"name":20,"@type":21,"position":22},"https://docshare.wps.com","Home","ListItem",1,{"item":24,"name":25,"@type":21,"position":26},"https://docshare.wps.com/document/","Document",2,{"item":28,"name":29,"@type":21,"position":30},"https://docshare.wps.com/document/research-report/","Research & Report",3,{"item":32,"name":10,"@type":21,"position":33},"https://docshare.wps.com/document/using-high-frequency-water-quality-data-to-assess-sampling-strategies-for-the-eu-water-framework-directive/292432/",4,{"url":32,"name":10,"@type":35,"image":36,"author":41,"headline":10,"publisher":44,"fileFormat":47,"inLanguage":8,"description":12,"dateModified":48,"datePublished":49,"encodingFormat":47,"isAccessibleForFree":50,"interactionStatistic":51},"DigitalDocument",{"url":37,"@type":38,"width":39,"height":40},"https://docshare.wps.com/thumbnails/using-high-frequency-water-quality-data-to-assess-sampling-strategies-for-the-eu-water-framework-directive/292432.png","ImageObject",300,407,{"name":42,"@type":43},"River Wang","Person",{"url":19,"name":45,"@type":46},"DocShare","Organization","application/pdf","2026-11-08","2026-09-17",true,{"@type":52,"interactionType":53,"userInteractionCount":55},"InteractionCounter",{"@type":54},"ViewAction",13,{"@type":57,"mainEntity":58},"FAQPage",[59,65,69],{"name":60,"@type":61,"acceptedAnswer":62},"What sampling strategies are compared in the paper?","Question",{"text":63,"@type":64},"The study compares monthly and weekly sampling approaches using subsampled high-frequency (hourly) chemical data to simulate different WFD-oriented sampling regimes.","Answer",{"name":66,"@type":61,"acceptedAnswer":67},"How does weekly sampling affect uncertainty compared with monthly sampling?",{"text":68,"@type":64},"Weekly sampling considerably reduces uncertainties relative to monthly sampling, with confidence interval widths reduced to about one-third to two-thirds depending on the parameter.",{"name":70,"@type":61,"acceptedAnswer":71},"Why can low-frequency measurements be problematic for some WFD assessment targets?",{"text":72,"@type":64},"Low-frequency measurements are often unsuitable for standards expressed as high percentiles; the paper reports that monthly sampling can bias the assessed mean downward for water temperature due to limited data for high-percentile estimation.","https://schema.org",{"og:url":32,"og:type":75,"og:title":10,"og:site_name":45,"og:description":12},"article",{"robots":77,"canonical":32},"index,follow",{"doc_id":79,"site_id":7},292432,1789651249,{"code":4,"msg":82,"data":83},"success",[84,88,92,96,101,106,111,115,120,123,127],{"id":22,"doc_module":4,"doc_module_name":25,"category_name":85,"show_sort_weight":86,"slug":87},"Story & Novel",90,"story-novel",{"id":26,"doc_module":4,"doc_module_name":25,"category_name":89,"show_sort_weight":90,"slug":91},"Literature",80,"literature",{"id":33,"doc_module":4,"doc_module_name":25,"category_name":93,"show_sort_weight":94,"slug":95},"Exam",70,"exam",{"id":97,"doc_module":4,"doc_module_name":25,"category_name":98,"show_sort_weight":99,"slug":100},5,"Comic",60,"comic",{"id":102,"doc_module":4,"doc_module_name":25,"category_name":103,"show_sort_weight":104,"slug":105},6,"Technology",50,"technology",{"id":107,"doc_module":4,"doc_module_name":25,"category_name":108,"show_sort_weight":109,"slug":110},7,"Healthcare",40,"healthcare",{"id":112,"doc_module":4,"doc_module_name":25,"category_name":29,"show_sort_weight":113,"slug":114},8,30,"research-report",{"id":116,"doc_module":4,"doc_module_name":25,"category_name":117,"show_sort_weight":118,"slug":119},9,"Religion & Spirituality",20,"religion-spirituality",{"id":118,"doc_module":4,"doc_module_name":25,"category_name":121,"show_sort_weight":118,"slug":122},"World Cup","world-cup",{"id":124,"doc_module":4,"doc_module_name":25,"category_name":125,"show_sort_weight":124,"slug":126},10,"Lifestyle","lifestyle",{"id":128,"doc_module":4,"doc_module_name":25,"category_name":129,"show_sort_weight":97,"slug":130},19,"General","general",{"code":4,"msg":82,"data":132},{"doc_id":79,"user_id":133,"nickname":42,"user_avatar":134,"doc_module":4,"category_id":112,"category_name":29,"doc_title":10,"doc_description":12,"doc_content":135,"file_id":136,"file_url":137,"file_type":138,"file_size":139,"view_count":55,"is_deleted":4,"is_public":22,"is_downloadable":22,"audit_status":22,"page_count":140,"language":141,"language_code":8,"site_id":7,"html_lang":8,"table_of_contents":142,"faqs":143,"seo_title":144,"seo_description":12,"update_tm":80,"read_time":145,"preview_page_count":4},1099514067438,"https://ap-avatar.wpscdn.com/avatar/100002539ee87300030?x-image-process=image/resize,m_fixed,w_180,h_180&k=1780474512215547542","Hydrol. Earth Syst. Sci., 19, 2491–2504, 2015 [www.hydrol-earth-syst-sci.net/19/2491/2015/](www.hydrol-earth-syst-sci.net/19/2491/2015/)[ ](www.hydrol-earth-syst-sci.net/19/2491/2015/)[doi:10.5194/hess-19-2491-2015](doi:10.5194/hess-19-2491-2015)  \n© Author(s) 2015 . CC Attribution 3.0 License.  \nUsing high-frequency water quality data to assess sampling strategies for the EU Water Framework Directive  \nR. A. Skeffington 1 , S. J. Halliday 1 , A. J. Wade 1 , M. J. Bowes2 , and M. Loewenthal3  \n1Dept. of Geography and Environmental Sciences, University of Reading, Reading, RG6 6DW, UK  \n2 Centre for Ecology and Hydrology, Wallingford, Oxon., OX10 8BB, UK  \n3Environment Agency, Fobney Mead, Reading, RG2 0SF, UK Correspondence to: R. A. Skeffington (r.a.skeffi[ngton@reading.ac.uk](ngton@reading.ac.uk))  \nReceived: 17 December 2014 – Published in Hydrol. Earth Syst. Sci. Discuss.: 28 January 2015  \nAccepted: 8 May 2015 – Published: 26 May 2015  \nAbstract. The EU Water Framework Directive (WFD) requires that the ecological and chemical status of water bodies in Europe should be assessed, and action taken where possible to ensure that at least “good” quality is attained in each case by 2015 . This paper is concerned with the accuracy and precision with which chemical status in rivers can be measured given certain sampling strategies, and how this can be improved. High-frequency (hourly) chemical data from four rivers in southern England were subsampled to simulate different sampling strategies for four parameters used for WFD classification: dissolved phosphorus, dissolved oxygen, pH and water temperature. These data sub-sets were then used to calculate the WFD classification for each site. Monthly sampling was less precise than weekly sampling, but the effect on WFD classification depended on the closeness of the range of concentrations to the class boundaries. In some cases, monthly sampling for a year could result in the same water body being assigned to three or four of the WFD classes with 95 % confidence, due to random sampling effects, whereas with weekly sampling this was one or two classes for the same cases. In the most extreme case, the same water body could have been assigned to any of the five WFD quality classes. Weekly sampling considerably reduces the uncertainties compared to monthly sampling. The width of the weekly sampled confidence intervals was about 33 % that of the monthly for P species and pH, about 50 % for dissolved oxygen, and about 67 % for water temperature. For water temperature, which is assessed as the 98th percentile in the UK, monthly sampling biases the mean downwards by about 1 􀀎 C compared to the true value, due to problems of assessing high percentiles with limited data. Low-frequency measure-  \nments will generally be unsuitable for assessing standards expressed as high percentiles. Confining sampling to the working week compared to all 7 days made little difference, but a modest improvement in precision could be obtained by sampling at the same time of day within a 3 h time window, and this is recommended. For parameters with a strong diel variation, such as dissolved oxygen, the value obtained, and thus possibly the WFD classification, can depend markedly on when in the cycle the sample was taken. Specifying this in the sampling regime would be a straightforward way to improve precision, but there needs to be agreement about how best to characterise risk in different types of river. These results suggest that in some cases it will be difficult to assign accurate WFD chemical classes or to detect likely trends using current sampling regimes, even for these largely groundwaterfed rivers. A more critical approach to sampling is needed to ensure that management actions are appropriate and supported by data.  \n1 Introduction  \nThe principal aim of the EU Water Framework Directive (WFD: EU, 2000) is to protect and enhance the status of aquatic ecosystems in the European Union and to prevent their further dete","cbCaivNkwkGfw76v","https://ap.wps.com/l/cbCaivNkwkGfw76v","pdf",1157755,14,"English","# Abstract\n# 1 Introduction","[{\"question\":\"What sampling strategies are compared in the paper?\",\"answer\":\"The study compares monthly and weekly sampling approaches using subsampled high-frequency (hourly) chemical data to simulate different WFD-oriented sampling regimes.\"},{\"question\":\"How does weekly sampling affect uncertainty compared with monthly sampling?\",\"answer\":\"Weekly sampling considerably reduces uncertainties relative to monthly sampling, with confidence interval widths reduced to about one-third to two-thirds depending on the parameter.\"},{\"question\":\"Why can low-frequency measurements be problematic for some WFD assessment targets?\",\"answer\":\"Low-frequency measurements are often unsuitable for standards expressed as high percentiles; the paper reports that monthly sampling can bias the assessed mean downward for water temperature due to limited data for high-percentile estimation.\"}]","Using high-frequency water quality data to assess sampling strategies for the EU Water Framework Directive | PDF",35]