Inorganic carbon dominates total dissolved carbon concentrations and fluxes in British rivers: Application of the THINCARB model - Thermodynamic modelling of inorganic carbon in freshwaters.

River water-quality studies rarely measure dissolved inorganic carbon (DIC) routinely, and there is a gap in our knowledge of the contributions of DIC to aquatic carbon fluxes and cycling processes. Here, we present the THINCARB model (THermodynamic modelling of INorganic CARBon), which uses widely-measured determinands (pH, alkalinity and temperature) to calculate DIC concentrations, speciation (bicarbonate, HCO; carbonate, CO; and dissolved carbon dioxide, HCO) and excess partial pressures of carbon dioxide (EpCO) in freshwaters. If calcium concentration measurements are available, THINCARB also calculates calcite saturation.

Phosphorus retention and remobilization along hydrological pathways in karst terrain.

Karst landscapes are often perceived as highly vulnerable to agricultural phosphorus (P) loss, via solution-enlarged conduits that bypass P retention processes. Although attenuation of P concentrations has been widely reported within karst drainage, the extent to which this results from hydrological dilution, rather than P retention, is poorly understood. This is of strategic importance for understanding the resilience of karst landscapes to P inputs, given increasing pressures for intensified agricultural production.

Universal fractal scaling in stream chemistry and its implications for solute transport and water quality trend detection.

The chemical dynamics of lakes and streams affect their suitability as aquatic habitats and as water supplies for human needs. Because water quality is typically monitored only weekly or monthly, however, the higher-frequency dynamics of stream chemistry have remained largely invisible. To illuminate a wider spectrum of water quality dynamics, rainfall and streamflow were sampled in two headwater catchments at Plynlimon, Wales, at 7-h intervals for 1-2 y and weekly for over two decades, and were analyzed for 45 solutes spanning the periodic table from H(+) to U.

Phosphorus mitigation to control river eutrophication: murky waters, inconvenient truths, and "postnormal" science.

This commentary examines an "inconvenient truth" that phosphorus (P)-based nutrient mitigation, long regarded as the key tool in eutrophication management, in many cases has not yet yielded the desired reductions in water quality and nuisance algal growth in rivers and their associated downstream ecosystems. We examine why the water quality and aquatic ecology have not recovered, in some case after two decades or more of reduced P inputs, including (i) legacies of past land-use management, (ii) decoupling of algal growth responses to river P loading in eutrophically impaired rivers; and (iii) recovery trajectories, which may be nonlinear and characterized by thresholds and alternative stable states. It is possible that baselines have shifted and that some disturbed river environments may never return to predisturbance conditions or may require P reductions below those that originally triggered ecological degradation.

High-frequency water quality time series in precipitation and streamflow: from fragmentary signals to scientific challenge.

Eighteen months of 7-hourly analyses of rainfall and stream water chemistry are presented, spanning a wide range of chemical determinands and building on over 20 years of weekly records for the moorland headwaters of the river Severn. The high-frequency time series data show that hydrochemical responses to major hydrological and biological drivers of short-term variability in rainfall and rivers are not captured by conventional low-frequency monitoring programmes. A wealth of flow related, flow independent, diurnal, seasonal and annual fluctuations indicate a cacophony of interactions within the catchment and stream.

An analysis of long-term trends, seasonality and short-term dynamics in water quality data from Plynlimon, Wales.

This paper examines two hydrochemical time-series derived from stream samples taken in the Upper Hafren catchment, Plynlimon, Wales. One time-series comprises data collected at 7-hour intervals over 22 months (Neal et al., 2012-this issue), while the other is based on weekly sampling over 20 years.

Linking groundwaters of high CO2 to aluminium levels in rivers: the case for the upper Severn in mid-Wales.

Al is a critical ecotoxicant in surface waters impacted by acidic deposition. Apart from the most acidic surface waters, Al concentrations are often considered to be controlled by Al(OH)(3) or aluminosilicate (clay) solubility for modelling studies. For many UK rivers there is no clear evidence for such solubility controls even though there is the potential under moderately acidic/alkaline conditions.

Aluminium in UK rivers: a need for integrated research related to kinetic factors, colloidal transport, carbon and habitat.

Dissolved aluminium concentrations ([Al]) in the <0.45 μm filtered fraction are described for 54 UK river sites covering rural, acidic/acid sensitive, agricultural and urban typologies, and wide pH range (4 to 11). High [Al] occurred under acidic conditions and for acid runoff neutralised by bicarbonate rich groundwater.

Quantifying phosphorus retention and release in rivers and watersheds using extended end-member mixing analysis (E-EMMA).

Extended end-member mixing analysis (E-EMMA) is presented as a novel empirical method for exploring phosphorus (P) retention and release in rivers and watersheds, as an aid to water-quality management. E-EMMA offers a simple and versatile tool that relies solely on routinely measured P concentration and flow data. E-EMMA was applied to two river systems: the Thames (U.

Titanium in UK rural, agricultural and urban/industrial rivers: geogenic and anthropogenic colloidal/sub-colloidal sources and the significance of within-river retention.

Operationally defined dissolved Titanium [Ti] (the <0.45μm filtered fraction) in rivers draining rural, agricultural, urban and industrial land-use types in the UK averaged 2.1μg/l with a range in average of 0.

The Ribble/Wyre observatory: major, minor and trace elements in rivers draining from rural headwaters to the heartlands of the NW England historic industrial base.

Information on a new observatory study of the water quality of two major river basins in northwestern England (the Ribble and Wyre) is presented. It covers upland, intermediate and lowland environments of contrasting pollution history with sufficient detail to examine transitional gradients. The upland rivers drain acidic soils subjected to long-term acidic deposition.

Sewage effluent clean-up reduces phosphorus but not phytoplankton in lowland chalk stream (River Kennet, UK) impacted by water mixing from adjacent canal.

Information is provided on phosphorus in the River Kennet and the adjacent Kennet and Avon Canal in southern England to assess their interactions and the changes following phosphorus reductions in sewage treatment work (STW) effluent inputs. A step reduction in soluble reactive phosphorus (SRP) concentration within the effluent (5 to 13 fold) was observed from several STWs discharging to the river in the mid-2000s. This translated to over halving of SRP concentrations within the lower Kennet.

Hydrology and water quality of the headwaters of the River Severn: Stream acidity recovery and interactions with plantation forestry under an improving pollution climate.

This paper presents new information on the hydrology and water quality of the eroding peatland headwaters of the River Severn in mid-Wales and links it to the impact of plantation conifer forestry further down the catchment. The Upper Hafren is dominated by low-growing peatland vegetation, with an average annual precipitation of around 2650 mm with around 250 mm evaporation. With low catchment permeability, stream response to rainfall is "flashy" with the rising limb to peak stormflow typically under an hour.

Predicting phosphorus concentrations in British rivers resulting from the introduction of improved phosphorus removal from sewage effluent.

Phosphorus (P) concentration and flow data gathered during the 1990s for a range of British rivers were used to determine the relative contributions of point and diffuse inputs to the total P load, using the Load Apportionment Model (LAM). Heavily urbanised catchments were dominated by sewage inputs, but the majority of the study catchments received most of their annual phosphorus load from diffuse sources. Despite this, almost 80% of the study sites were dominated by point source inputs for the majority of the year, particularly during summer periods when eutrophication risk is greatest.

The strategic significance of wastewater sources to pollutant phosphorus levels in English rivers and to environmental management for rural, agricultural and urban catchments.

The relationship between soluble and particulate phosphorus was examined for 9 major UK rivers including 26 major tributaries and 68 monitoring points, covering wide-ranging rural and agricultural/urban impacted systems with catchment areas varying from 1 to 6000km(2) scales. Phosphorus concentrations in Soluble Reactive (SRP), Total Dissolved (TDP), Total (TP), Dissolved Hydrolysable (DHP) and Particulate (PP) forms correlated with effluent markers (sodium and boron) and SRP was generally dominant signifying the importance of sewage sources. Low flows were particularly enriched in SRP, TDP and TP for average SRP>100microg/l indicating low effluent dilution.

Decreasing boron concentrations in UK rivers: insights into reductions in detergent formulations since the 1990s and within-catchment storage issues.

The changing patterns of riverine boron concentration are examined for the Thames catchment in southern/southeastern England using data from 1997 to 2007. Boron concentrations are related to an independent marker for sewage effluent, sodium. The results show that boron concentrations in the main river channels have declined with time especially under baseflow conditions when sewage effluent dilution potential is at its lowest.

Declines in phosphorus concentration in the upper River Thames (UK): links to sewage effluent cleanup and extended end-member mixing analysis.

Phosphorus concentrations in the upper River Thames Basin (southeastern England) are described and linked to sewage effluent sources. Weekly surveys between 1997 and 2007 of the Thames and two of its major tributaries, the Thame and the Kennet indicated that phosphorus was mainly in soluble reactive (SRP) form. Baseflow concentrations in the Thames reduced from 1584microg/l in 1998 to 376microg/l in 2006 and from 2655 to 715microg/l for the Thame.

The British river of the future: how climate change and human activity might affect two contrasting river ecosystems in England.

The possible effects of changing climate on a southern and a north-eastern English river (the Thames and the Yorkshire Ouse, respectively) were examined in relation to water and ecological quality throughout the food web. The CLASSIC hydrological model, driven by output from the Hadley Centre climate model (HadCM3), based on IPCC low and high CO(2) emission scenarios for 2080 were used as the basis for the analysis. Compared to current conditions, the CLASSIC model predicted lower flows for both rivers, in all seasons except winter.

Water quality, nutrients and the European union's Water Framework Directive in a lowland agricultural region: Suffolk, south-east England.

The water quality of 13 rivers in the lowland, agricultural county of Suffolk is investigated using routine monitoring data for the period 1981 to 2006 collected by the Environment Agency of England and Wales (EA), and its predecessors, with particular emphasis on phosphorus (as total reactive phosphorus, TRP) and total (dissolved and particulate) oxidised nitrogen (TOxN--predominantly nitrate NO3). Major ion and flow data are used to outline fundamental hydrochemical characteristics related to the groundwater provenance of base-flow waters. Relative load contributions from point and diffuse sources are approximated using Load Apportionment Modelling for both TRP and TOxN where concurrent flow and concentration data are available.

Changes in point and diffuse source phosphorus inputs to the River Frome (Dorset, UK) from 1966 to 2006.

Changes in the relationship between soluble reactive phosphorus (SRP) concentration and river flow between 1966 and 2006 were assessed for the River Frome, UK using the recently developed Load Apportionment Model. The resulting source load estimates gave good agreement with known changes within the catchment. The model indicated an increase in point source contribution to the total river load from 46% to 62% between 1970 and 1985.

Modelling of phosphorus inputs to rivers from diffuse and point sources.

The difference in timing of point and diffuse phosphorus (P) delivery to a river produces clear differences in the P concentration-flow relationship. Point inputs decrease in concentration with increasing river flow, due to dilution of a relatively constant input, whereas diffuse (non-point) load usually increases with river flow. This study developed a simple model, based on this fundamental difference, which allowed point and diffuse inputs to be quantified by modelling their contribution to river P concentration as a power-law function of flow.

Chlorophyll-a in the rivers of eastern England.

Chlorophyll-a concentration variations are described for two major river basins in England, the Humber and the Thames and related to catchment characteristics and nutrient concentrations across a range of rural, agricultural and urban/industrial settings. For all the rivers there are strong seasonal variations, with concentrations peaking in the spring and summer time when biological activity is at its highest. However, there are large variations in the magnitude of the seasonal effects across the rivers.

Nitrate concentrations in river waters of the upper Thames and its tributaries.

The spatial and temporal patterns of in-stream nitrate concentrations for the upper Thames and selected tributaries are described in relation to point and diffuse sources for these rural catchments. The rivers associated with catchments dominated by permeable (Cretaceous Chalk) bedrock show a smaller range in nitrate concentrations than those associated with clay and mixed sedimentary bedrock of lower permeability. The differences reflect the contrasting nature of water storage within the catchments and the influence of point and diffuse sources of nitrate.

The water quality of the River Thame in the Thames Basin of south/south-eastern England.

The water quality of the River Thame, a tributary of the River Thames in the Thames basin, is described in relation to point and diffuse contaminant inputs and runoff from permeable and impermeable bedrock geology with their own characteristic water quality. The data is examined to see if the market town of Aylesbury in the upper part of the catchment influences water quality. Previous studies highlighted the influence of Aylesbury sewage treatment works (STW) on soluble reactive phosphorus (SRP) concentrations in the river before and after phosphorus (P) stripping at the STW.

River water quality of the River Cherwell: an agricultural clay-dominated catchment in the upper Thames Basin, southeastern England.

The water quality of the River Cherwell and a tributary of it, the Ray, are described in terms of point and diffuse sources of pollution, for this rural area of the upper Thames Basin. Point sources of pollution dominate at the critical ecological low flow periods of high biological activity. Although the surface geology is predominantly clay, base flow is partly supplied from springs in underlying carbonate-bearing strata, which influences the water quality particularly with regards to calcium and alkalinity.