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Excessive phytoplankton concentrations in rivers can result in the loss of plant and invertebrate communities, and threaten drinking water supplies. Whilst the physicochemical controls on algal blooms have been identified previously, how these factors combine to control the initiation, size, and cessation of blooms in rivers is not well understood. We applied flow cytometry to quantify diatom, chlorophyte, and cyanobacterial group abundances in the River Thames (UK) at weekly intervals from 2011 to 2022, alongside physicochemical data. A niche modeling approach was used to identify thresholds in water temperature, flow, solar radiation, and soluble reactive phosphorus (SRP) concentrations required to produce periods of phytoplankton growth, with blooms only occurring when all thresholds were met. The thresholds derived from the 2011 to 2018 dataset were applied to a test data set (2019–2022), which predicted the timing and duration of blooms at accuracies of > 80%. Diatoms and nano-chlorophyte blooms were initiated by flow and water temperature, and usually terminated due to temperature and flow going out of the threshold range, or SRP and Si becoming limiting. Cyanobacterial bloom dynamics were primarily controlled by water temperature and solar radiation. This simple methodology provides a key understanding of phytoplankton community succession and inter-annual variation and can be applied to any river with similar water quality and phytoplankton data. It provides early warnings of algal and cyanobacterial bloom timings, which support future catchment management decisions to safeguard water resources, and provides a basis for modeling changing phytoplankton bloom risk due to future climate change.

This review is a summary of the most up-to-date knowledge regarding assessment of atmospheric deposition of reactive nitrogen (Nr) pollutants across complex terrain in the UK. Progress in the understanding of the mechanisms and quantification of Nr deposition in areas of complex topography is slow, as no concerted attempts to measure the components of Nr in complex terrain have been made in the last decade. This is likely due to the inherent complexity of the atmospheric processes and chemical interactions which contribute to deposition in these areas. More than 300 studies have been reviewed, and we have consulted with a panel of international experts which we assembled for that purpose. We report here on key findings and knowledge gaps identified regarding measurement and modelling techniques used to quantify deposition of Nr across complex terrain in the UK, which depending on definition, may represent up to 60% of land coverage across Great Britain. The large body of peer reviewed papers, reports and other items reviewed in this study has highlighted both the strengths and weaknesses in the tools available to scientists, regulators and policy makers. This review highlights that there is no coherent global research effort to constrain the uncertainties in Nr deposition over complex terrain, despite the clearly identified risk of N deposition to ecosystems and water quality. All evidence identified that enhanced Nr deposition across complex terrain occurs, and magnitude of the enhancement is not known; however, there are major uncertainties particularly in the differences between modelled and measured wet deposition in complex terrain and representing accurate surface interactions in models. Using simplified estimates for Nr deposition, based on current understanding of current measurement and model approaches, an enhancement across UK complex terrain in the range of a factor of 1.4–2.5 (i.e. 40–150% larger than current estimates) is likely over complex upland ter

This project was commissioned by the Environment Agency (EA) Ecology & Ecosystems team, part of the Agriculture Fisheries and Natural Resources department (Environment & Business Directorate, Head Office), with support from the EA Water Resources. The Ecology & Ecosystems team is in charge of EA standard invertebrate methods for assessing rivers, including river status classification, and of developing the River Invertebrate Classification Tool (RICT). RICT has at its core the River Invertebrate Prediction and Classification System (RIVPACS) model. This model has been upgraded and refined through years, with Model 44 being the latest experimental working version. Model 44 has been designed to provide more accurate predictions of invertebrate communities in rivers impacted by hydro-morphological alterations. In particular, the new input variables exclude width, depth and substrate, and are hydro-morphologically independent. In 2017, UKCEH created a UK-wide database for these new Model 44 variables (Kral et al., 2017). The aim of this project is to generate a testing dataset including a sufficient number of sites across England, and their Model 1 and Model 44 input variables so the original and new models can be compared, and should they yield different results, to assess if Model 44 is better suited for water resource assessments, and can better capture impact of flow and fine sediment pressures.

Climate change is expected to alter water quality in rivers, but where and when this may happen is uncertain. This report describes a study of projected response in the amount of algal plant growth (phytoplankton biomass). Increasing algal growth is one of the ecological manifestations of eutrophication in slow flowing rivers, where the water starts to resemble a green soup. Eutrophication is a process in which too much nutrient in water causes algae and higher plants to grow excessively. Eutrophication alters the quality of the water and how it can be used. Phytoplankton (suspended algae) is considered to be a useful indicator of eutrophication in standing freshwaters and can also be useful as one measure of impacts in rivers, particularly slow flowing rivers. Excess algal growth can result in blooms that eventually die off. The disruption of dissolved oxygen dynamics in the water column may, in turn, have adverse impacts on fish and macroinvertebrates. The onset and decline of algal blooms is measured by the concentration of chlorophyll (a green pigment in algae) in the water. In this context, algal bloom risk – and the risk of negative eutrophication impacts in the lower reaches of rivers – is identified through observations of threshold chlorophyll concentrations. Exceedence of a chlorophyll concentration threshold is not by itself used in the diagnosis of river eutrophication but can be used as a proxy for algal blooms for understanding and modelling risk. The future risk of eutrophication impact, including algal blooms, is affected by changes in the concentration of nutrients from altered river flow and changes in phosphorus inputs from a range of sources. An earlier study (Phase 1 of this project) demonstrated that climate change impacts on river flow would increase phosphorus concentrations by 2050 and beyond. However, climate-driven changes in river temperature regime and light, and plant responses to these, are also important in altering the future risk of

Interest in urban agriculture has increased rapidly in recent decades, but little is known about the effect of potential contaminants, such as groundwater pollution, in urban areas. Furthermore, local and timely science necessary for developing place-based solutions and management plans are lacking. We present a citizen-science-driven case study of water quality in a large urban community garden in southwestern London that was initiated in response to the concerns of members about the effect of inorganic compounds in the water supply on organic produce. The 5.6-ha community garden has been cultivated for fruit and vegetables since 1921 and hand-pumped boreholes drawing water from an underlying shallow aquifer provide the only source of irrigation. We assessed the spatial and temporal distributions of specific conductance and tryptophan-like fluorescence to explore the dynamics of inorganic and organic pollution based on water drawn from the boreholes. A trained citizen scientist made measurements with a calibrated Manta II probe over a 28-mo period from 2014 to 2016. We also surveyed >80 members of the community garden to gain insight into cultivation practices. Results indicate that the concerns about external sources of pollution were unfounded. We found little evidence of the effect of potential adjacent sources of contamination or of changes in water quality in time. Distinct trends were absent, and evidence of poorer water quality close to possible sources of urban contamination was not apparent. However, significant interborehole variations in water quality were directly associated with the storage and use of manure on the site and local geological conditions. The study demonstrates the potential of citizen science to respond to community concerns and generate new and novel information when participants are engaged, trained, and equipped over longer periods of time.

The River Thames and 15 of its major tributaries have been monitored at weekly intervals since March 2009. Monitored determinands include major nutrient fractions, anions, cations, metals, pH, alkalinity, and chlorophyll a and are linked to mean daily river flows at each site. This catchment-wide biogeochemical monitoring platform captures changes in the water quality of the Thames basin during a period of rapid change, related to increasing pressures (due to a rapidly growing human population, increasing water demand and climate change) and improvements in sewage treatment processes and agricultural practices. The platform provides the research community with a valuable data and modelling resource for furthering our understanding of pollution sources and dynamics, as well as interactions between water quality and aquatic ecology. Combining Thames Initiative data with previous (non-continuous) monitoring data sets from many common study sites, dating back to 1997, has shown that there have been major reductions in phosphorus concentrations at most sites, occurring at low river flow, and these are principally due to reduced loadings from sewage treatment works (STWs). This ongoing monitoring programme will provide the vital underpinning environmental data required to best manage this vital drinking water resource, which is key for the sustainability of the city of London and the wider UK economy. The Thames Initiative data set is freely available from the Centre for Ecology and Hydrology’s (CEH)Environmental Information Data Centre at https://doi.org/10.5285/e4c300b1-8bc3-4df2-b23a-e72e67eef2fd.

This study provides a first national-scale assessment of the nutrient status of British headwater streams within the wider river network, by joint analysis of the national Countryside Survey Headwater Stream and Harmonised River Monitoring Scheme datasets. We apply a novel Nutrient Limitation Assessment methodology to explore the extent to which nutrients may potentially limit primary production in headwater streams and rivers, by coupling ternary assessment of nitrogen (N), phosphorus (P), and carbon (C) depletion, with N:P stoichiometry, and threshold P and N concentrations. P limitation was more commonly seen in the rivers, with greater prevalence of N limitation in the headwater streams. High levels of potential P and N co-limitation were found in the headwater streams, especially the Upland-Low-Alkalinity streams. This suggests that managing both P and N inputs may be needed to minimise risks of degradation of these sensitive headwater stream environments. Although localised nutrient impairment of headwater streams can occur, there were markedly lower rates of P and N impairment of headwater streams relative to downstream rivers at the national scale. Nutrient source contributions, relative to hydrological dilution, increased with catchment scale, corresponding with increases in the extent of agricultural and urban land-use. The estimated nutrient reductions needed to achieve compliance with Water Framework Directive standards, and to reach limiting concentrations, were greatest for the Lowland-High-Alkalinity rivers and streams. Preliminary assessments suggest that reducing P concentrations in the Lowland-High-Alkalinity headwater streams, and N concentrations in the Upland-Low-Alkalinity rivers, might offer greater overall benefits for water-quality remediation at the national scale, relative to the magnitude of nutrient reductions required. This approach could help inform the prioritisation of nutrient remediation, as part of a directional approach to water

This paper describes the development of the first operational seasonal hydrological forecasting service for the UK, the Hydrological Outlook UK (HOUK). Since June 2013, this service has delivered monthly forecasts of streamflow and groundwater levels, with an emphasis on forecasting hydrological conditions over the next three months, accompanied by outlooks over longer time horizons. This system is based on three complementary approaches combined to produce the outlooks: (i) national-scale modelling of streamflow and groundwater levels based on dynamic seasonal rainfall forecasts, (ii) catchment-scale modelling where streamflow and groundwater level models are driven by historical meteorological forcings (i.e. the Ensemble Streamflow Prediction, ESP, approach), and (iii) a catchment-scale statistical method based on persistence and historical analogues. This paper provides the background to the Hydrological Outlook, describes the various component methods in detail and then considers the impact and usefulness of the product. As an example of a multi-method, operational seasonal hydrological forecasting system, it is hoped that this overview provides useful information and context for other forecasting initiatives around the world.

Discrete data for trace elements for both the dissolved and acid available fractions for thirteen core sites in the Humber catchment over the period 1993 to 1997 and for three sites from the Tweed catchment over the period 1994 to 1997. Part of the Land Ocean Interaction Study project (LOIS). Trace elements measured were: Aluminium (Al), Antimony (Sb), Arsenic (As), Barium (Ba), Beryllium (Be), Boron (B), Cadmium (Cd), Cerium (Ce), Chromium (Cr), Cobalt (Co), Copper (Cu), Gadolinium (Gd), Iron (Fe), Lanthanum (La), Lead (Pb), Lithium (Li), Manganese (Mn), Molybdenum (Mo), Neodymium (Nd), Nickel (Ni), Rubidium (Rb), Samarium (Sm), Scandium (Sc), Strontium (Sr), Tin (Sn), Uranium (U), Yttrium (Y), Zinc (Zn). The Core sites were sampled at regular weekly intervals and more intermittently during high flows (on average an extra sampling once a month per site). The Swale sites were sampled during hydrological events and the Aire sites were sampled both weekly and during hydrological events. The majority of samples were obtained using a wide neck grab sampler. Those samples collected from the Aire during hydrological events were obtained using EPIC automatic samplers. Both dissolved and acid available trace element fractions were determined for all samples. The dissolved fraction was measured by filtering samples and acidifying the filtrates with concentrated aristar grade nitric acid (1%vv) on the same day of sampling. The acid available fraction was determined by acidifying an unfiltered sample as above and agitating for 24 hours, at room temperature, prior to filtration. Samples were then analysed by inductively coupled plasma optical emission spectrometry (ICP-OES: B, Ba, Fe, Mn, Sr) and mass spectrometry (ICP-MS: Al, As, Be, Cd, Ce, Co, Cr, Cu, Gd, La, Li, Mo, Nd, Ni, Pb, Rb, Sb, Sc, Sm, Sn, U, Y, Zn).

Discrete data for major ions and nutrients in river water for 13 sites in the Humber catchment over the periods 1993 to 1997 and 1996 to 1997 and for 3 sites from the Tweed catchment over the period 1994 to 1997. Ions and nutrients measured were: Ammonia, Calcium (dissolved), Magnesium (dissolved), Potassium (dissolved), Sodium (dissolved), Bromide-ion, Carbon (organic dissolved), Chloride-ion, Nitrate, Nitrite, Phosphorus (soluble reactive), Phosphorus (total dissolved), Silicate (reactive dissolved), Sulphate, Carbon (organic particulate), Nitrogen (particulate), Phosphorus (total). Sites were sampled at regular weekly intervals and more intermittently during high flows (on average an extra sampling once a month per site). Samples were obtained using a wide neck PTFE bottle in a plastic covered bottle carrier (lowered from bridges where possible otherwise collected by immersing sample bottle by hand in the water as near the main flow as possible). Samples were filtered through Whatman 0.45um sterile membrane filters immediately on return to laboratory. Samples stored in sterilin tubes in the dark at 40C and analysed by Dionex DX100 ion chromatography system. Silicate reactive dissolved and Chloride-ion concentrations were determined by automated colourimetry and dissolved organic carbon concentrations were determined using a TOCsin II aqueous carbon analyser. Some samples on the River Aire were collected using EPIC automatic samplers. The analysis was carried out by members of the analytical chemistry section at York University (from April 1994 until November 1996) and at Wallingford Institute of Hydrology (September 1993 to April 1994 and December 1996 to April 1997), as part of the Land Ocean Interaction Study (LOIS).

Continuous measurements of temperature, pH, conductivity and dissolved oxygen from river water at ten sites located within the rivers Swale, Derwent, Aire, Calder, Trent, Ouse and Nidd. Part of the Land Ocean Interaction Study (LOIS) project. Hydrolab H20 water quality monitors were installed at ten sites and used to log water temperature, pH, conductivity and dissolved oxygen between 1994 and 1997. Data were collected continuously at 30 minute intervals (for periods of variable lengths depending on site) between 1994 and 1997. Data were collected using Hydrolab DataSonde 3 continuous monitoring units. Hydrolabs at River Nidd (Hunsingore) and the River Swale (Crakehill) were suspended from trees. The other hydrolabs were located in large steel pipes running from the bank into the rivers which allowed the flow of water over the probes but offered a high degree of safety from damage by vandals and large water borne objects. The units on the Trent and the Ouse at Skelton were fitted with stirrers, as the probes were prone to fouling by the high levels of suspended solids often encountered in these rivers during spate conditions. The deployment of the units and the collection of data were carried out by members of the field sampling team at York University, as part of the Land Ocean Interaction Study (LOIS).

River water alkalinity, chloride-ion, conductivity, pH and nutrients data from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2003 and 2006. River water samples were collected fortnightly at twenty three sites within these catchments and analysed for Alkalinity pH 4.5, Ammonia, Chloride-ion, Conductivity 20 deg C, Nitrate, pH, Phosphorus soluble reactive (SRP), Silicate reactive dissolved (SRD) and Sulphate. The samples were collected as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline river water chemistry data across the LOCAR catchments.

Micro-organic herbicide levels in river water for various sites within the Humber and Tweed catchments collected as part of the Land Ocean Interaction Study project (LOIS). The dataset contains data for Phenyl urea and Phenoxy acid herbicides, measured as 2,4-Dichlorophenoxyacetic acid, 4-(4-Chloro-O-tolyloxy) butyric acid, 4-Chloro-O-tolyloxyacetic acid, Chlorotoluron dissolved, Diuron dissolved, Isoproturon dissolved, Linuron dissolved, Mecoprop dissolved. Phenyl urea herbicide data is available for twelve sites in the Humber catchment within 1994 to 1995 and 1994 to 1997 and for three sites on the Tweed catchment within 1995. Phenoxy acid herbicide data is available for six sites (S1, U3, N4, W5 and O6) over the period December 1994 to September 1995, for 7 sites (S2, D7, A8, C9, D10, T11 and O12) over the period December 1994 to February 1997 and 3 sites (TW13, TW14 and TW15) over the period January 1995 to September 1995. Attempts were made to sample the sites at weekly intervals. However sampling was halted for short periods when it was not possible to process the samples quickly. Linuron dissolved was only measured from April 1994 - October 1994. Samples were collected in chromic acid-washed 1 litre glass bottles. Herbicide levels were concentrated before being measured using High Performance Liquid Chromatography for Phenyl urea herbicides and Gas Chromatography for Phenoxy acid herbicides. Until November 1994, analysis was completed by the York University and the Institute for Freshwater Ecology, Wareham, laboratories. From December 1994 onwards the samples were dispatched to the Institute for Hydrology, Wallingford, for extraction and analyses

Polychlorinated biphenyls (PCB), chlorobenzenes (CB) and organochlorine pesticides (OC) data from river water collected at various sites within the Humber catchment area as part of the Land Ocean Interaction Study project (LOIS). Data were collected at regular weekly intervals and intermittently during periods of high flows. All sites were samples from early 1994 to the end of 1996 except for O12, which was sampled from November 1994 till November 1996. The sampling was carried out by the LOIS team at York University. The unfiltered samples were transported to the Institute of Terrestrial Ecology, Monks Wood, UK, where they were extracted with hexane, cleaned up by alumina column chromatography, concentrated and then analysed for CBs by Gas Chromatography-Mass Spectrometry (GC-MS) and PCBs and OCs by Gas Chromatography with Electron Capture Detection (GC-ECD).

Rainwater alkalinity, chloride-ion, conductivity, pH and nutrients data from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2004 and 2006. Rainwater samples were collected fortnightly at seven sites in these catchments and analysed for Alkalinity pH 4.5, Ammonia, Chloride-ion, Conductivity 20 °C, Nitrate, pH, Phosphorus soluble reactive (SRP), Silicate reactive dissolved (SRD) and Sulphate. The samples were collected as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline rainwater chemistry data across the LOCAR catchments.

Continuous measurements of conductivity, dissolved oxygen, pH, temperature and water level from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2002 and 2007. YSI sondes were installed at 16 sites in these catchments to record continuous measurements of conductivity, dissolved oxygen, pH and temperature. Druck pressure transducers were installed at the same sites to measure continuous water level values. The instruments were installed as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline river water chemistry data across the LOCAR catchments. Data were collected continuously at 15-minutes intervals for periods of variable length, depending on site.

On site measurements of pH, conductivity and temperature for thirteen sites in the Humber catchment and three sites in the Tweed catchment within the period 1994 to 1997 as part of the Land Ocean Interaction Study project (LOIS). Sites were sampled at regular weekly intervals and more intermittently during high flows (on average an extra sampling once a month per site). Samples were obtained using a wide neck PTFE bottle in a plastic covered bottle carrier (lowered from bridges where possible otherwise collected by immersing sample bottle by hand in the water as near the main flow as possible). pH and conductivity reading were taken using Mettler Toledo Check Mate meters and probes. Temperature readings were obtained using a PT 100 probe with a Digitron 3204 Pt meter (RS components). The measurements were carried out by members of the field sampling team at York University, as part of the Land Ocean Interaction Study (LOIS).

Continuous measurements of rainfall from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2002 and 2007. Continuous recording rain gauges were installed at 6 sites in these catchments to record 15 minute rainfall data for differing periods at the varying sites. The instruments were installed as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline rainfall data across the LOCAR catchments.

Continuous measurements of meteorological parameters from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2002 and 2006. Automatic weather stations were installed at 7 sites in these catchments to record hourly values of soil heat flux, relative humidity, atmospheric pressure, solar and net radiation (upward and downward short and long wave), rainfall, soil temperature at 10 and 30 cm, air temperature and wind direction and speed for differing periods at the varying sites. The instruments were installed as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline metrological data across the LOCAR catchments.

Discrete total alkalinity data for 13 sites in the Humber catchment sampled within the period 1993 to 1997 and 1996 to 1997 and for 3 sites from the Tweed catchment over the period 1994 to 1997, as part of the Land Ocean Interaction Study project (LOIS). Sites were sampled at regular weekly intervals and more intermittently during high flows (on average an extra sampling once a month per site). Samples were analysed on day of collection or on arrival at the laboratory using a Metrohm 702 Titrino autosampler.

Triazine, organophosphate and pyrethroid (TOP) pesticide data from river water collected at various sites within the Humber catchment area as part of the Land Ocean Interaction Study project (LOIS).. Water samples were collected weekly and during storm periods between 1994 and 1996. The unfiltered samples were extracted on the day of collection using solid-phase-extraction (SPE), the SPE cartridges stored overnight at 4 degreesC and then transported to the Institute of Freshwater Ecology (IFE), Wareham for elution, drying and Gas Chromatography (GC) analysis. Pesticides measured were Atrazine, Cyanazin, Desmetryn, Fenitrothion, HCH gamma, Malathion, Parathion, Permethrin, Prometryn, Simazine, Terbutryn. The sampling and extraction of the pesticides was carried out by the LOIS team at York University and the elution and sample preparation for GC analysis was done at IFE.

Continuous measurements of meteorological parameters from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2002 and 2006. Automatic weather stations were installed at 7 sites in these catchments to record hourly values of soil heat flux, relative humidity, atmospheric pressure, solar and net radiation (upward and downward short and long wave), rainfall, soil temperature at 10 and 30 cm, air temperature and wind direction and speed for differing periods at the varying sites. The instruments were installed as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline metrological data across the LOCAR catchments.

Rainwater alkalinity, chloride-ion, conductivity, pH and nutrients data from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2004 and 2006. Rainwater samples were collected fortnightly at seven sites in these catchments and analysed for Alkalinity pH 4.5, Ammonia, Chloride-ion, Conductivity 20 °C, Nitrate, pH, Phosphorus soluble reactive (SRP), Silicate reactive dissolved (SRD) and Sulphate. The samples were collected as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline rainwater chemistry data across the LOCAR catchments.

On site measurements of pH, conductivity and temperature for thirteen sites in the Humber catchment and three sites in the Tweed catchment within the period 1994 to 1997 as part of the Land Ocean Interaction Study project (LOIS). Sites were sampled at regular weekly intervals and more intermittently during high flows (on average an extra sampling once a month per site). Samples were obtained using a wide neck PTFE bottle in a plastic covered bottle carrier (lowered from bridges where possible otherwise collected by immersing sample bottle by hand in the water as near the main flow as possible). pH and conductivity reading were taken using Mettler Toledo Check Mate meters and probes. Temperature readings were obtained using a PT 100 probe with a Digitron 3204 Pt meter (RS components). The measurements were carried out by members of the field sampling team at York University, as part of the Land Ocean Interaction Study (LOIS).

Continuous measurements of conductivity, dissolved oxygen, pH, temperature and water level from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2002 and 2007. YSI sondes were installed at 16 sites in these catchments to record continuous measurements of conductivity, dissolved oxygen, pH and temperature. Druck pressure transducers were installed at the same sites to measure continuous water level values. The instruments were installed as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline river water chemistry data across the LOCAR catchments. Data were collected continuously at 15-minutes intervals for periods of variable length, depending on site.

Micro-organic herbicide levels in river water for various sites within the Humber and Tweed catchments collected as part of the Land Ocean Interaction Study project (LOIS). The dataset contains data for Phenyl urea and Phenoxy acid herbicides, measured as 2,4-Dichlorophenoxyacetic acid, 4-(4-Chloro-O-tolyloxy) butyric acid, 4-Chloro-O-tolyloxyacetic acid, Chlorotoluron dissolved, Diuron dissolved, Isoproturon dissolved, Linuron dissolved, Mecoprop dissolved. Phenyl urea herbicide data is available for twelve sites in the Humber catchment within 1994 to 1995 and 1994 to 1997 and for three sites on the Tweed catchment within 1995. Phenoxy acid herbicide data is available for six sites (S1, U3, N4, W5 and O6) over the period December 1994 to September 1995, for 7 sites (S2, D7, A8, C9, D10, T11 and O12) over the period December 1994 to February 1997 and 3 sites (TW13, TW14 and TW15) over the period January 1995 to September 1995. Attempts were made to sample the sites at weekly intervals. However sampling was halted for short periods when it was not possible to process the samples quickly. Linuron dissolved was only measured from April 1994 - October 1994. Samples were collected in chromic acid-washed 1 litre glass bottles. Herbicide levels were concentrated before being measured using High Performance Liquid Chromatography for Phenyl urea herbicides and Gas Chromatography for Phenoxy acid herbicides. Until November 1994, analysis was completed by the York University and the Institute for Freshwater Ecology, Wareham, laboratories. From December 1994 onwards the samples were dispatched to the Institute for Hydrology, Wallingford, for extraction and analyses

River water alkalinity, chloride-ion, conductivity, pH and nutrients data from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2003 and 2006. River water samples were collected fortnightly at twenty three sites within these catchments and analysed for Alkalinity pH 4.5, Ammonia, Chloride-ion, Conductivity 20 deg C, Nitrate, pH, Phosphorus soluble reactive (SRP), Silicate reactive dissolved (SRD) and Sulphate. The samples were collected as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline river water chemistry data across the LOCAR catchments.

Discrete total alkalinity data for 13 sites in the Humber catchment sampled within the period 1993 to 1997 and 1996 to 1997 and for 3 sites from the Tweed catchment over the period 1994 to 1997, as part of the Land Ocean Interaction Study project (LOIS). Sites were sampled at regular weekly intervals and more intermittently during high flows (on average an extra sampling once a month per site). Samples were analysed on day of collection or on arrival at the laboratory using a Metrohm 702 Titrino autosampler.

Polychlorinated biphenyls (PCB), chlorobenzenes (CB) and organochlorine pesticides (OC) data from river water collected at various sites within the Humber catchment area as part of the Land Ocean Interaction Study project (LOIS). Data were collected at regular weekly intervals and intermittently during periods of high flows. All sites were samples from early 1994 to the end of 1996 except for O12, which was sampled from November 1994 till November 1996. The sampling was carried out by the LOIS team at York University. The unfiltered samples were transported to the Institute of Terrestrial Ecology, Monks Wood, UK, where they were extracted with hexane, cleaned up by alumina column chromatography, concentrated and then analysed for CBs by Gas Chromatography-Mass Spectrometry (GC-MS) and PCBs and OCs by Gas Chromatography with Electron Capture Detection (GC-ECD).

Continuous measurements of temperature, pH, conductivity and dissolved oxygen from river water at ten sites located within the rivers Swale, Derwent, Aire, Calder, Trent, Ouse and Nidd. Part of the Land Ocean Interaction Study (LOIS) project. Hydrolab H20 water quality monitors were installed at ten sites and used to log water temperature, pH, conductivity and dissolved oxygen between 1994 and 1997. Data were collected continuously at 30 minute intervals (for periods of variable lengths depending on site) between 1994 and 1997. Data were collected using Hydrolab DataSonde 3 continuous monitoring units. Hydrolabs at River Nidd (Hunsingore) and the River Swale (Crakehill) were suspended from trees. The other hydrolabs were located in large steel pipes running from the bank into the rivers which allowed the flow of water over the probes but offered a high degree of safety from damage by vandals and large water borne objects. The units on the Trent and the Ouse at Skelton were fitted with stirrers, as the probes were prone to fouling by the high levels of suspended solids often encountered in these rivers during spate conditions. The deployment of the units and the collection of data were carried out by members of the field sampling team at York University, as part of the Land Ocean Interaction Study (LOIS).

Continuous measurements of rainfall from the Frome Piddle; Pang Lambourn and Tern catchments, recorded between 2002 and 2007. Continuous recording rain gauges were installed at 6 sites in these catchments to record 15 minute rainfall data for differing periods at the varying sites. The instruments were installed as part of the NERC funded Lowland Catchment Research (LOCAR) Programme to provide comparable baseline rainfall data across the LOCAR catchments.

Triazine, organophosphate and pyrethroid (TOP) pesticide data from river water collected at various sites within the Humber catchment area as part of the Land Ocean Interaction Study project (LOIS).. Water samples were collected weekly and during storm periods between 1994 and 1996. The unfiltered samples were extracted on the day of collection using solid-phase-extraction (SPE), the SPE cartridges stored overnight at 4 degreesC and then transported to the Institute of Freshwater Ecology (IFE), Wareham for elution, drying and Gas Chromatography (GC) analysis. Pesticides measured were Atrazine, Cyanazin, Desmetryn, Fenitrothion, HCH gamma, Malathion, Parathion, Permethrin, Prometryn, Simazine, Terbutryn. The sampling and extraction of the pesticides was carried out by the LOIS team at York University and the elution and sample preparation for GC analysis was done at IFE.