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Neil Stuart - One of the best experts on this subject based on the ideXlab platform.
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assessing the effect of broadleaf woodland expansion on acidic dry deposition and Streamwater acidification
Forest Ecology and Management, 2011Co-Authors: Z Gagkas, Kate Heal, T R Nisbet, Massimo Vieno, Neil StuartAbstract:The study aim was to determine whether enhanced dry deposition of acidic atmospheric pollutants by broadleaf woodland expansion could increase the potential for acidification of surface waters in acid-sensitive areas. Dry sulphur (S) and nitrogen (N) deposition was modelled with the Fine Resolution Atmospheric Multi-pollutant Exchange (FRAME) model using a roughness length value calculated specifically for birchwoods. Two scenarios were investigated for an acid-sensitive area in Scotland where broadleaf woodland expansion, mainly as birchwood, is occurring: (1) 2002 emissions and broadleaf woodland cover of 5.6%; (2) 2020 projected emissions and broadleaf cover of 29%. The roughness length calculated for birch with Raupach's simplified drag-partition model was 0.73 m, lower than the value of 1.0 m for conifers which is the default for forest land cover in FRAME. Modelled dry S and N deposition increased between 2002 and 2020 from 8.7 to 29 x 10(-3) keq ha(-1) year(-1) of H(+). However, modelled total dry and wet non-marine S and N deposition decreased during the same period from 1070 to 682 x 10(-3) keq ha(-1) year(-1) of H(+) due to the lower projected emissions in 2020 and the dominance of wet deposition in the remote and upland study area (mean annual rainfall 2275 mm). The modelled total non-marine S and N deposition was used to calculate Streamwater critical loads exceedance with the First-order Acidity Balance (FAB) model for five catchments in the study area. The modelled deposition for both the 2002 and 2020 scenarios was less than the calculated Streamwater critical loads so the catchments were not considered at risk of Streamwater acidification under the projected future emissions and increased broadleaf woodland cover. Nevertheless, broadleaf expansion could pose a greater risk of acidification in acid-sensitive areas with lower rainfall, closer to pollutant sources, where dry deposition accounts for a higher proportion of total S and N deposition. (C) 2011 Elsevier B.V. All rights reserved.
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comparison of different critical load approaches for assessing Streamwater acid sensitivity to broadleaf woodland expansion
Science of The Total Environment, 2010Co-Authors: Z Gagkas, Kate Heal, T R Nisbet, Neil StuartAbstract:Abstract Due to its potential adverse effects on freshwater acidification, risk assessments of the impacts of forest expansion on surface waters are required. The critical load methodology is the standard way of assessing these risks and the two most widely used models are the Steady-State Water Chemistry (SSWC) and First-order Acidity Balance (FAB) models. In the UK the recommended risk assessment procedure for assessing the impact of forest expansion on freshwater acidification uses the SSWC model, whilst the FAB model is used for guiding emission policy. This study compared the two models for assessing the sensitivity of Streamwater to acidification in 14 catchments with different proportions of broadleaf woodland cover in acid-sensitive areas in the UK. Both models predicted the exceedance of Streamwater critical loads in the same catchments, but the magnitudes of exceedance varied due to the different treatment of nitrogen processes. The FAB model failed to account for high nitrogen leaching to Streamwater, attributed to nitrogen deposition and/or fixation of nitrogen by alder trees in some study catchments, while both models underestimated the influence of high seasalt deposition. Critical load exceedance in most catchments was not sensitive to the use of different acid neutralising capacity thresholds or runoff estimates, probably due to the large difference between critical load values and acidic deposition loadings. However, the assessments were more sensitive to differences in calculation procedure in catchments where nitrogen deposition was similar to the availability of base cations from weathering and/or where critical load exceedance values were + ha − 1 yr − 1 . Critical load exceedance values from both models agreed with assessments of acid-sensitivity based on indicator macroinvertebrates sampled from the study catchments. Thus the methodology currently used in the UK appears to be robust for assessing the risk of broadleaf woodland expansion on surface water acidification and ecological status.
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effects of broadleaf woodland cover on Streamwater chemistry and risk assessments of Streamwater acidification in acid sensitive catchments in the uk
Environmental Pollution, 2008Co-Authors: Z Gagkas, Kate Heal, Neil Stuart, T R NisbetAbstract:Abstract Streamwater was sampled at high flows from 14 catchments with different (0–78%) percentages of broadleaf woodland cover in acid-sensitive areas in the UK to investigate whether woodland cover affects Streamwater acidification. Significant positive correlations were found between broadleaf woodland cover and Streamwater NO 3 and Al concentrations. Streamwater NO 3 concentrations exceeded non-marine SO 4 in three catchments with broadleaf woodland cover ≥50% indicating that NO 3 was the principal excess acidifying ion in the catchments dominated by woodland. Comparison of calculated Streamwater critical loads with acid deposition totals showed that 11 of the study catchments were not subject to acidification by acidic deposition. Critical loads were exceeded in three catchments, two of which were due to high NO 3 concentrations in drainage from areas with large proportions of broadleaved woodland. The results suggest that the current risk assessment methodology should protect acid-sensitive catchments from potential acidification associated with broadleaf woodland expansion.
B Reynolds - One of the best experts on this subject based on the ideXlab platform.
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upland Streamwater nitrate dynamics across decadal to sub daily timescales a case study of plynlimon wales
Biogeosciences, 2013Co-Authors: S J Halliday, B Reynolds, A J Wade, Colin Neal, R A Skeffington, D A Norris, James W KirchnerAbstract:Streamwater nitrate dynamics in the River Hafren, Plynlimon, mid-Wales were investigated over decadal to sub-daily timescales using a range of statistical techniques. Long-term data were derived from weekly grab samples (1984–2010) and high-frequency data from 7-hourly samples (2007–2009) both measured at two sites: a headwater stream draining moorland and a downstream site below plantation forest. This study is one of the first to analyse upland Streamwater nitrate dynamics across such a wide range of timescales and report on the principal mechanisms identified. The data analysis provided no clear evidence that the long-term decline in Streamwater nitrate concentrations was related to a decline in atmospheric deposition alone, because nitrogen deposition first increased and then decreased during the study period. Increased Streamwater temperature and denitrification may also have contributed to the decline in stream nitrate concentrations, the former through increased N uptake rates and the latter resultant from increased dissolved organic carbon concentrations. Strong seasonal cycles, with concentration minimums in the summer, were driven by seasonal flow minimums and seasonal biological activity enhancing nitrate uptake. Complex diurnal dynamics were observed, with seasonal changes in phase and amplitude of the cycling, and the diurnal dynamics were variable along the river. At the moorland site, a regular daily cycle, with minimum concentrations in the early afternoon, corresponding with peak air temperatures, indicated the importance of instream biological processing. At the downstream site, the diurnal dynamics were a composite signal, resultant from advection, dispersion and nitrate processing in the soils of the lower catchment. The diurnal Streamwater nitrate dynamics were also affected by drought conditions. Enhanced diurnal cycling in Spring 2007 was attributed to increased nitrate availability in the post-drought period as well as low flow rates and high temperatures over this period. The combination of high-frequency short-term measurements and long-term monitoring provides a powerful tool for increasing understanding of the controls of element fluxes and concentrations in surface waters.
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Upland Streamwater nitrate dynamics across decadal to sub-daily timescales: a case study of Plynlimon, Wales
Biogeosciences Discussions, 2013Co-Authors: S J Halliday, B Reynolds, A J Wade, R A Skeffington, C. Neal, D. Norris, James W KirchnerAbstract:Abstract. Streamwater nitrate dynamics in the River Hafren, Plynlimon, mid-Wales were investigated over decadal to sub-daily timescales using a range of statistical techniques. Long-term data were derived from weekly grab samples (1984–2010) and high-frequency data from 7 hourly samples (2007–2009) both measured at two sites: a headwater stream draining moorland and a downstream site below plantation forest. This study is one of the first to analyse upland Streamwater nitrate dynamics across such a wide range of timescales and report on the principal mechanisms identified. The data analysis provided no clear evidence that the long term decline in Streamwater nitrate concentrations was related to a decline in atmospheric deposition only; nitrogen deposition first increased and then decreased during the study period. Increased Streamwater temperature and denitrification may also have contributed to the decline in stream nitrate concentrations, the former through increased N uptake rates and the latter resultant from increased dissolved organic carbon concentrations. Strong seasonal cycles, with concentration minimums in the summer, were driven by seasonal flow minimums and seasonal biological activity enhancing nitrate uptake. Complex diurnal dynamics were observed, with seasonal changes in phase and amplitude of the cycling, and the diurnal dynamics were variable along the river. At the moorland site, a regular daily cycle, with minimum concentrations in the early afternoon, corresponding with peak air temperatures, indicated the importance of instream biological processing. At the downstream site, the diurnal dynamics were a composite signal, resultant from advection and nitrate processing in the soils of the lower catchment. The diurnal Streamwater nitrate dynamics were also affected by drought conditions. Enhanced diurnal cycling in spring 2007 was attributed to increased nitrate availability in the post-drought period as well as low flow rates and high temperatures over this period. The combination of high-frequency short-term measurements and long-term monitoring provides a powerful tool for increasing understanding of the controls of element fluxes and concentrations in surface waters.
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the impact of a riparian wetland on Streamwater quality in a recently afforested upland catchment
Journal of Hydrology, 1994Co-Authors: Bridget A Emmett, J A Hudson, P A Coward, B ReynoldsAbstract:The influence of a small remnant wetland on Streamwater chemistry at the outflow of an afforested catchment has been investigated. The wetland reduced the volume weighted mean concentrations of a number of solutes. Stream solute loadings were calculated from chemical and flow data from two flumes situated above and below the wetland at the catchment outlet. The flow contribution from the wetland itself was estimated on an areal basis and combined with sampled chemistry to estimate solute fluxes. Streamwater dissolved nitrogen loading, equivalent to an input of 55 kg N ha−1 year−1, was reduced by 38% after flowing through the wetland. Reductions in Streamwater loadings were also observed for phosphate (94%), total dissolved-P (42%), total monomeric aluminium (39%), total filtrable aluminium (21%), iron (54%), DOC (34%) and silica (21%). All other retention rates were within the original Streamwater loading estimate errors. Retention of nitrogen was lower than expected, perhaps due to exhaustion of the wetland's immobilisation capacity by the large nitrogen loading in the Streamwater entering the wetland from the surrounding land in combination with atmospheric loadings. Retention of nitrogen and other solutes was also reduced due to a prolonged period of low rainfall during the summer of 1989 which resulted in high concentration events of various elements from the wetland relative to concentrations at the wetland inflow.
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variations in Streamwater nitrate concentrations and nitrogen budgets over 10 years in a headwater catchment in mid wales
Journal of Hydrology, 1992Co-Authors: B Reynolds, Bridget A Emmett, C WoodsAbstract:Between 1980 and 1989, samples of bulk precipitation, soil water and stream water have been collected regularly from a small catchment within the headwaters of the River Wye at Plynlimon. Subsequent analysis for nitrate-N and ammonium-N revealed that ammonium-N was present in bulk precipitation but concentrations were below detection limit (< 0.1 mg 1−1N) in soil waters and Streamwaters. Over the 10 year period, no consistent trends were observed in the concentration or wet deposition of inorganic nitrogen compounds. Between 1980 and 1983, soil water nitrate-N concentrations varied irregularly over time, in contrast to the regular pattern of summer minima and winter maxima observed in the stream. Following the dry summer of 1984, large increases in soil water nitrate-N concentrations were observed in the stream such that during 1985, winter maximum concentrations increased by a factor of two and summer minima by a factor of ten as compared with previous years. Winter maxima declined gradually over the following 3 years to values similar to those prior to 1984. The variations in Streamwater nitrate concentration are discussed in relation to the processes controlling nitrate supply from the catchment and nitrogen depletion within the stream channel. The significance of inorganic nitrogen deposition at Plynlimon is discussed on the basis of Streamwater nitrate-N data from an adjacent headwater catchment and a simple mass balance comparing wet deposition of inorganic nitrogen compounds with nitrate exports in the stream. Although nitrate leaching losses vary between 4 and 5 kg ha−1 year−1, there is a net retention of inorganic nitrogen within the catchment. The mass balance also indicates that nitrogen transformations within the catchment may generate an average of 0.34 kEq H+ ha−1 year−1.
Z Gagkas - One of the best experts on this subject based on the ideXlab platform.
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assessing the effect of broadleaf woodland expansion on acidic dry deposition and Streamwater acidification
Forest Ecology and Management, 2011Co-Authors: Z Gagkas, Kate Heal, T R Nisbet, Massimo Vieno, Neil StuartAbstract:The study aim was to determine whether enhanced dry deposition of acidic atmospheric pollutants by broadleaf woodland expansion could increase the potential for acidification of surface waters in acid-sensitive areas. Dry sulphur (S) and nitrogen (N) deposition was modelled with the Fine Resolution Atmospheric Multi-pollutant Exchange (FRAME) model using a roughness length value calculated specifically for birchwoods. Two scenarios were investigated for an acid-sensitive area in Scotland where broadleaf woodland expansion, mainly as birchwood, is occurring: (1) 2002 emissions and broadleaf woodland cover of 5.6%; (2) 2020 projected emissions and broadleaf cover of 29%. The roughness length calculated for birch with Raupach's simplified drag-partition model was 0.73 m, lower than the value of 1.0 m for conifers which is the default for forest land cover in FRAME. Modelled dry S and N deposition increased between 2002 and 2020 from 8.7 to 29 x 10(-3) keq ha(-1) year(-1) of H(+). However, modelled total dry and wet non-marine S and N deposition decreased during the same period from 1070 to 682 x 10(-3) keq ha(-1) year(-1) of H(+) due to the lower projected emissions in 2020 and the dominance of wet deposition in the remote and upland study area (mean annual rainfall 2275 mm). The modelled total non-marine S and N deposition was used to calculate Streamwater critical loads exceedance with the First-order Acidity Balance (FAB) model for five catchments in the study area. The modelled deposition for both the 2002 and 2020 scenarios was less than the calculated Streamwater critical loads so the catchments were not considered at risk of Streamwater acidification under the projected future emissions and increased broadleaf woodland cover. Nevertheless, broadleaf expansion could pose a greater risk of acidification in acid-sensitive areas with lower rainfall, closer to pollutant sources, where dry deposition accounts for a higher proportion of total S and N deposition. (C) 2011 Elsevier B.V. All rights reserved.
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comparison of different critical load approaches for assessing Streamwater acid sensitivity to broadleaf woodland expansion
Science of The Total Environment, 2010Co-Authors: Z Gagkas, Kate Heal, T R Nisbet, Neil StuartAbstract:Abstract Due to its potential adverse effects on freshwater acidification, risk assessments of the impacts of forest expansion on surface waters are required. The critical load methodology is the standard way of assessing these risks and the two most widely used models are the Steady-State Water Chemistry (SSWC) and First-order Acidity Balance (FAB) models. In the UK the recommended risk assessment procedure for assessing the impact of forest expansion on freshwater acidification uses the SSWC model, whilst the FAB model is used for guiding emission policy. This study compared the two models for assessing the sensitivity of Streamwater to acidification in 14 catchments with different proportions of broadleaf woodland cover in acid-sensitive areas in the UK. Both models predicted the exceedance of Streamwater critical loads in the same catchments, but the magnitudes of exceedance varied due to the different treatment of nitrogen processes. The FAB model failed to account for high nitrogen leaching to Streamwater, attributed to nitrogen deposition and/or fixation of nitrogen by alder trees in some study catchments, while both models underestimated the influence of high seasalt deposition. Critical load exceedance in most catchments was not sensitive to the use of different acid neutralising capacity thresholds or runoff estimates, probably due to the large difference between critical load values and acidic deposition loadings. However, the assessments were more sensitive to differences in calculation procedure in catchments where nitrogen deposition was similar to the availability of base cations from weathering and/or where critical load exceedance values were + ha − 1 yr − 1 . Critical load exceedance values from both models agreed with assessments of acid-sensitivity based on indicator macroinvertebrates sampled from the study catchments. Thus the methodology currently used in the UK appears to be robust for assessing the risk of broadleaf woodland expansion on surface water acidification and ecological status.
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effects of broadleaf woodland cover on Streamwater chemistry and risk assessments of Streamwater acidification in acid sensitive catchments in the uk
Environmental Pollution, 2008Co-Authors: Z Gagkas, Kate Heal, Neil Stuart, T R NisbetAbstract:Abstract Streamwater was sampled at high flows from 14 catchments with different (0–78%) percentages of broadleaf woodland cover in acid-sensitive areas in the UK to investigate whether woodland cover affects Streamwater acidification. Significant positive correlations were found between broadleaf woodland cover and Streamwater NO 3 and Al concentrations. Streamwater NO 3 concentrations exceeded non-marine SO 4 in three catchments with broadleaf woodland cover ≥50% indicating that NO 3 was the principal excess acidifying ion in the catchments dominated by woodland. Comparison of calculated Streamwater critical loads with acid deposition totals showed that 11 of the study catchments were not subject to acidification by acidic deposition. Critical loads were exceeded in three catchments, two of which were due to high NO 3 concentrations in drainage from areas with large proportions of broadleaved woodland. The results suggest that the current risk assessment methodology should protect acid-sensitive catchments from potential acidification associated with broadleaf woodland expansion.
T R Nisbet - One of the best experts on this subject based on the ideXlab platform.
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assessing the effect of broadleaf woodland expansion on acidic dry deposition and Streamwater acidification
Forest Ecology and Management, 2011Co-Authors: Z Gagkas, Kate Heal, T R Nisbet, Massimo Vieno, Neil StuartAbstract:The study aim was to determine whether enhanced dry deposition of acidic atmospheric pollutants by broadleaf woodland expansion could increase the potential for acidification of surface waters in acid-sensitive areas. Dry sulphur (S) and nitrogen (N) deposition was modelled with the Fine Resolution Atmospheric Multi-pollutant Exchange (FRAME) model using a roughness length value calculated specifically for birchwoods. Two scenarios were investigated for an acid-sensitive area in Scotland where broadleaf woodland expansion, mainly as birchwood, is occurring: (1) 2002 emissions and broadleaf woodland cover of 5.6%; (2) 2020 projected emissions and broadleaf cover of 29%. The roughness length calculated for birch with Raupach's simplified drag-partition model was 0.73 m, lower than the value of 1.0 m for conifers which is the default for forest land cover in FRAME. Modelled dry S and N deposition increased between 2002 and 2020 from 8.7 to 29 x 10(-3) keq ha(-1) year(-1) of H(+). However, modelled total dry and wet non-marine S and N deposition decreased during the same period from 1070 to 682 x 10(-3) keq ha(-1) year(-1) of H(+) due to the lower projected emissions in 2020 and the dominance of wet deposition in the remote and upland study area (mean annual rainfall 2275 mm). The modelled total non-marine S and N deposition was used to calculate Streamwater critical loads exceedance with the First-order Acidity Balance (FAB) model for five catchments in the study area. The modelled deposition for both the 2002 and 2020 scenarios was less than the calculated Streamwater critical loads so the catchments were not considered at risk of Streamwater acidification under the projected future emissions and increased broadleaf woodland cover. Nevertheless, broadleaf expansion could pose a greater risk of acidification in acid-sensitive areas with lower rainfall, closer to pollutant sources, where dry deposition accounts for a higher proportion of total S and N deposition. (C) 2011 Elsevier B.V. All rights reserved.
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comparison of different critical load approaches for assessing Streamwater acid sensitivity to broadleaf woodland expansion
Science of The Total Environment, 2010Co-Authors: Z Gagkas, Kate Heal, T R Nisbet, Neil StuartAbstract:Abstract Due to its potential adverse effects on freshwater acidification, risk assessments of the impacts of forest expansion on surface waters are required. The critical load methodology is the standard way of assessing these risks and the two most widely used models are the Steady-State Water Chemistry (SSWC) and First-order Acidity Balance (FAB) models. In the UK the recommended risk assessment procedure for assessing the impact of forest expansion on freshwater acidification uses the SSWC model, whilst the FAB model is used for guiding emission policy. This study compared the two models for assessing the sensitivity of Streamwater to acidification in 14 catchments with different proportions of broadleaf woodland cover in acid-sensitive areas in the UK. Both models predicted the exceedance of Streamwater critical loads in the same catchments, but the magnitudes of exceedance varied due to the different treatment of nitrogen processes. The FAB model failed to account for high nitrogen leaching to Streamwater, attributed to nitrogen deposition and/or fixation of nitrogen by alder trees in some study catchments, while both models underestimated the influence of high seasalt deposition. Critical load exceedance in most catchments was not sensitive to the use of different acid neutralising capacity thresholds or runoff estimates, probably due to the large difference between critical load values and acidic deposition loadings. However, the assessments were more sensitive to differences in calculation procedure in catchments where nitrogen deposition was similar to the availability of base cations from weathering and/or where critical load exceedance values were + ha − 1 yr − 1 . Critical load exceedance values from both models agreed with assessments of acid-sensitivity based on indicator macroinvertebrates sampled from the study catchments. Thus the methodology currently used in the UK appears to be robust for assessing the risk of broadleaf woodland expansion on surface water acidification and ecological status.
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effects of broadleaf woodland cover on Streamwater chemistry and risk assessments of Streamwater acidification in acid sensitive catchments in the uk
Environmental Pollution, 2008Co-Authors: Z Gagkas, Kate Heal, Neil Stuart, T R NisbetAbstract:Abstract Streamwater was sampled at high flows from 14 catchments with different (0–78%) percentages of broadleaf woodland cover in acid-sensitive areas in the UK to investigate whether woodland cover affects Streamwater acidification. Significant positive correlations were found between broadleaf woodland cover and Streamwater NO 3 and Al concentrations. Streamwater NO 3 concentrations exceeded non-marine SO 4 in three catchments with broadleaf woodland cover ≥50% indicating that NO 3 was the principal excess acidifying ion in the catchments dominated by woodland. Comparison of calculated Streamwater critical loads with acid deposition totals showed that 11 of the study catchments were not subject to acidification by acidic deposition. Critical loads were exceeded in three catchments, two of which were due to high NO 3 concentrations in drainage from areas with large proportions of broadleaved woodland. The results suggest that the current risk assessment methodology should protect acid-sensitive catchments from potential acidification associated with broadleaf woodland expansion.
Jeffrey J Mcdonnell - One of the best experts on this subject based on the ideXlab platform.
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interception effects on stable isotope driven Streamwater transit time estimates
Geophysical Research Letters, 2015Co-Authors: Michael Stockinger, Andreas Lucke, Jeffrey J Mcdonnell, Bernd Diekkruger, Harry Vereecken, Heye BogenaAbstract:Previous studies of Streamwater transit time distributions (TTDs) used isotope tracer information from open precipitation (OP) as inputs to lumped watershed models that simulate the stream isotopic composition to estimate TTD. However, in forested catchments passage of rainfall through the canopy will alter the tracer signature of throughfall (TF) via interception. Here we test the effect of using TF instead of OP on TTD estimates. We sampled a 0.39 km2 catchment (Wustebach, Germany) for a 19 month period using weekly precipitation and stream isotope data to evaluate changes in stream isotope simulation and TTDs. We found that TF had different effects on TTDs for δ18O and δ2H, with TF leading to up to 4 months shorter transit times. TTDs converged for both isotopes only when using TF. TF improved the stream isotope simulations. These results demonstrate the importance of canopy-induced isotope tracer changes in estimating Streamwater TTDs in forested catchments.
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where does Streamwater come from in low relief forested watersheds a dual isotope approach
Hydrology and Earth System Sciences, 2014Co-Authors: J. Klaus, Jeffrey J Mcdonnell, C. R. Jackson, E. Du, N. A. GriffithsAbstract:The time and geographic sources of Streamwater in low-relief watersheds are poorly understood. This is partly due to the difficult combination of low runoff coefficients and often damped Streamwater isotopic signals precluding tra- ditional hydrograph separation and convolution integral ap- proaches. Here we present a dual-isotope approach involv- ing 18 O and 2 H of water in a low-angle forested watershed to determine Streamwater source components and then build a conceptual model of streamflow generation. We focus on three headwater lowland sub-catchments draining the Savan- nah River Site in South Carolina, USA. Our results for a 3- year sampling period show that the slopes of the meteoric water lines/evaporation water lines (MWLs/EWLs) of the catchment water sources can be used to extract information on runoff sources in ways not considered before. Our dual- isotope approach was able to identify unique hillslope, ripar- ian and deep groundwater, and streamflow compositions. The streams showed strong evaporative enrichment compared to the local meteoric water line ( 2 HD 7.15 18 OC9.28 ‰) with slopes of 2.52, 2.84, and 2.86. Based on the unique and unambiguous slopes of the EWLs of the different wa- ter cycle components and the isotopic time series of the in- dividual components, we were able to show how the riparian zone controls baseflow in this system and how the riparian zone "resets" the stable isotope composition of the observed streams in our low-angle, forested watersheds. Although this approach is limited in terms of quantifying mixing percent- ages between different end-members, our dual-isotope ap- proach enabled the extraction of hydrologically useful infor- mation in a region with little change in individual isotope time series.
