A new approach to deriving ‘best-estimate’ chemical fluxes for rivers draining the LOIS study area

Webb, B.; Phillips, John; Walling, D. E.

doi:10.1016/s0048-9697(00)00413-7

Cited by 48 publications

(38 citation statements)

References 14 publications

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“…Detailed analysis, however, is limited by the fortnightly or monthly frequency of sampling, which means that very few samples were taken during storm hydrographs and thus storm-event pollution levels and associated chemograph hysteresis patterns cannot be explored. Although methods for computing 'best estimate' chemical fluxes from HMS data have been developed (Webb et al, 2000), the absence of strong or consistent relationships between metal concentrations and river discharge in the archived data set of the Nant-y-Fendrod suggests analysis of historical data alone in this complex catchment does not provide an adequate basis upon which to model aqueous contaminant fluxes or even to assess reliably the current pollution problem in the study area (Walsh et al, 2000).…”

Section: A Historical Perspective On Nant-y-fendrod Water Qualitymentioning

confidence: 99%

Heavy metal concentrations during storm events in a rehabilitated industrialized catchment

Blake

Walsh

Barnsley

et al. 2003

Hydrological Processes

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Abstract:Water quality data collected on a fortnightly or monthly basis are inadequate for assessment and modelling of many water quality problems as storm event samples are underrepresented or missed. This paper examines the stormflow dynamics of heavy metals (Pb, Cu, Cd and Zn) in the Nant-y-Fendrod stream, South Wales, which has been affected by 250 years of metal smelting, followed by 35 years of landscape rehabilitation measures. For storm events of contrasting (very dry and very wet) antecedent conditions in May 2000 and February 2001, respectively, temporal changes in streamwater heavy metal concentrations above and below an in-line flood detention lake are analysed. At the upstream site, peaks in total metal concentration were recorded on the rising limb for Pb (0Ð150 mg l 1 ) and Cu (0Ð038 mg l 1 ) but on the falling limb for Zn (1Ð660 mg l 1 ) and Cd (0Ð006 mg l 1 ) in the summer 2000 storm event, yielding clockwise and anticlockwise hysteretic loops respectively. In contrast, metal concentrations, although high throughout the winter storm event, were diluted somewhat during the storm peak itself. The Pb and Cu appear to be supplied by quickflow processes and transported in close association with fine sediment, whereas Zn and Cd are delivered to the channel and lake by slower subsurface seepage in dissolved form. In the winter 2001 event, antecedent soil moisture and shallow groundwater levels were anomalously high and seepage sources of dissolved metals dominated. Downstream of the lake, Pb and Cu levels and suspended sediment were high in the summer storm, but low in the winter storm, suggesting retention with deposition of fine sediment in the lake during the latter. In the winter storm, Zn and Cd levels were higher downstream than upstream of the lake, perhaps because of additional seepage inputs from the surrounding slopes, which failed to have an impact during summer. An understanding of the complex interplay of antecedent soil moisture and the dynamics of subsurface seepage pathways in relation to the three-dimensional distribution of sources is important in modelling heavy metal fluxes and levels in contaminated urban catchments.

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Section: A Historical Perspective On Nant-y-fendrod Water Qualitymentioning

confidence: 99%

Heavy metal concentrations during storm events in a rehabilitated industrialized catchment

Blake

Walsh

Barnsley

et al. 2003

Hydrological Processes

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“…Dealing with these points requires specialist treatment using long-term and highly detailed monitoring data, the use of "synthetic"/modelled time series data and detailed statistical approaches (Littlewood, 1992;Littlewood et al, 1998;Webb et al, 2000;Cooper and Evans, 2002;Cooper and Watts, 2002). The reader nonetheless needs to be aware of the issues.…”

Section: Cumulative Flux and Flux-change Time-series Patterns: Represmentioning

confidence: 99%

Assessing environmental impacts on stream water quality: the use of cumulative flux and cumulative flux difference approaches to deforestation of the Hafren Forest, mid-Wales

Neal

2002

Hydrol. Earth Syst. Sci.

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A method for examining the impacts of disturbance on stream water quality based on paired catchment "control" and "response" water quality time series is described in relation to diagrams of cumulative flux and cumulative flux difference. The paper describes the equations used and illustrates the patterns expected for idealised flux changes followed by an application to stream water quality data for a spruce forested catchment, the Hore, subjected to clear fell. The water quality determinands examined are sodium, chloride, nitrate, calcium and acid neutralisation capacity. The anticipated effects of felling are shown in relation to reduction in mist capture and nitrate release with felling as well as to the influence of weathering and cation exchange mechanisms, but in a much clearer way than observed previously using other approaches.

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“…This novel approach is essentially an extrapolation technique (e.g. Verhoff et al, 1982;Webb et al, 2000) designed to extract new information from long term monthly monitoring data.…”

Section: Theorymentioning

confidence: 99%

“…This is the consequence of several related factors (Meyer and Likens, 1979;Rigler, 1979;Jordan-Meille et al, 1998b). It could have been implemented in the model (see Webb et al, 2000) but its impact on monthly T P mass balance is deemed to be negligible. The hydrological conditions preceding the storm events may actually be more important than the magnitude of the storm event itself for T P flux (Dorioz et al, 1989(Dorioz et al, , 1998Svendsen and Kronvang, 1993;Jordan-Meille et al, 1998a).…”

Section: Model: Assumptions and Uncertaintiesmentioning

confidence: 99%

“…Government agencies typically collect regular water samples over the long term, but cannot afford to routinely monitor storm events. There are therefore, large uncertainties associated with the calculation of loads (Rigler, 1979;Webb et al, 1997Webb et al, , 2000Phillips et al, 1999a), unless models are constructed to simulate continuous data (e.g. Verhoff et al, 1982;Webb et al, 2000).…”

Section: Introductionmentioning

confidence: 99%

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Impact of phosphorus control measures on in-river phosphorus retention associated with point source pollution

Demars¹,

Harper

Pitt

et al. 2005

Hydrol. Earth Syst. Sci.

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Abstract. In-river phosphorus retention alters the quantity and timings of phosphorus delivery to downstream aquatic systems. Many intensive studies of in-river phosphorus retention have been carried out but generally on a short time scale (2-4 years). In this paper, monthly water quality data, collected by the Environment Agency of England and Wales over 12 years (1990)(1991)(1992)(1993)(1994)(1995)(1996)(1997)(1998)(1999)(2000)(2001), were used to model daily phosphorus fluxes and monthly in-river phosphorus retention in the lowland calcareous River Wensum, Norfolk, UK. The calibrated model explained 79% and 89% of the observed variance before and after phosphorus control, respectively. A split test revealed that predicted T P loads were in good agreement with observed T P loads (r 2 =0.85), although T P loads were underestimated under high flow conditions. During relatively dry years, there was no net export of phosphorus from the catchment. High retention of phosphorus occurred, particularly during the summer months, which was not compensated for, by subsequent higher flow events. This was despite a relatively modest critical discharge (Q) above which net remobilisation occur. Phosphorus removal from the effluent at two major STWs (Sewage Treatment Works) reduced phosphorus retention but not the remobilisation. This may indicate that the presence of impoundments and weirs, or overbank flows may have more control on the phosphorus dynamics under high flow conditions. Further phosphorus remedial strategies will be necessary to prevent downstream risks of eutrophication occurring independently of the unpredictable variability in weather conditions. More research is also needed to quantify the impact of the weir and overbank flows on phosphorus dynamics.

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A new approach to deriving ‘best-estimate’ chemical fluxes for rivers draining the LOIS study area

Cited by 48 publications

References 14 publications

Heavy metal concentrations during storm events in a rehabilitated industrialized catchment

Heavy metal concentrations during storm events in a rehabilitated industrialized catchment

Assessing environmental impacts on stream water quality: the use of cumulative flux and cumulative flux difference approaches to deforestation of the Hafren Forest, mid-Wales

Impact of phosphorus control measures on in-river phosphorus retention associated with point source pollution

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