87Sr/86Sr as an indicator of flowpaths and weathering rates in the Plynlimon experimental catchments, Wales, U.K.

Shand, Paul; Darbyshire, D. P. F.; Gooddy, Daren C.; Haria, Atul H.

doi:10.1016/j.chemgeo.2006.09.012

Cited by 62 publications

(32 citation statements)

References 34 publications

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“…Stable isotopes of Sr, O and H have been used to show that pre-event groundwater dominates stream flow generation during storm episodes in the forested catchment, and that the flow-path for rainfall is via fracture flow rather than flow through the soil zone (Shand et al, 2007;Neal and Rosier, 1990). O and H stable isotopes have also shown that soil pipeflow during storm events in the Gwy catchment has a significant proportion of pre-event water (Sklash et al, 1996).…”

Section: Introductionmentioning

confidence: 99%

Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales

Lapworth

Shand

Abesser

et al. 2008

Science of The Total Environment

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The importance of upland groundwater systems in providing a medium for nitrogen transformations and processes along flow paths is investigated within the Afon Gwy moorland catchment, Plynlimon, mid-Wales. Dissolved organic nitrogen (DON) was found to be the most abundant form of dissolved nitrogen (N) in most soils and groundwaters, accounting for between 47 and 72% of total dissolved nitrogen in shallow groundwater samples and up to 80% in deeper groundwaters. A significant correlation between dissolved organic carbon (DOC) and DON in the shallow groundwater system suggests that during the autumn and winter months the flux of DON from the soil zone may be regulated by the wetting up and release of soil organic matter. DON needs to be taken into account when considering catchment N balances otherwise N export from upland catchments could be significantly underestimated. DON may also be an important source of bio-available N in surface waters and marine systems fed by upland catchments. A conceptual model of N processes is proposed based on a detailed study along a transect of nested boreholes and soil suction samplers within the interfluve zone. Shallow groundwater N speciation reflects the soil N speciation implying a rapid transport mechanism and good connectivity between the soil and groundwater systems. Median dissolved inorganic N concentrations were an order of magnitude lower within the soil zone (10-25 mg/L-N) than in the shallow groundwaters (100-750 mg/L-N).Given the rapid hydrostatic response of the groundwater level within the soil zone, the shallow groundwater system is both a source and sink for dissolved N. Results from dissolved N2O, N2/Ar ratios and dissolved N chemistry suggests that microbial N transformations (denitrification) may play an important role in controlling the spatial variation in soil and groundwater N speciation. Reducing conditions within the groundwater and saturated soils of the wet-flush zones on the lower hillslopes, a result of relatively impermeable drift deposits, are also important in controlling N speciation and transformation processes.

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Section: Introductionmentioning

confidence: 99%

Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales

Lapworth

Shand

Abesser

et al. 2008

Science of The Total Environment

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“…Studies in the UK and Australia reveal that there is significant groundwater flow through both shallow 60 and deep fractured bedrocks which could provide much of stream input even during periods of high 61 flow (Banks et al, 2009;Shand et al, 2007). Despite these studies providing different results with 62 regard to the role of shallow and deep groundwater for streamflow generation which probably reflects 63 specific differences in hydrogeological settings, all studies underline the importance of fractured hard 64 rock systems in terms of transferring water and associated pollutants (e.g., nitrate) to surface water 65 bodies (e.g., Paulwels et al, 2001; Pawar and Shaikh, 1995) .…”

Section: Introduction 27mentioning

confidence: 99%

Analysis of groundwater-level response to rainfall and estimation of annual recharge in fractured hard rock aquifers, NW Ireland

Cai¹,

Ofterdinger

2016

Journal of Hydrology

101

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Please cite this article as: Cai, Z., Ofterdinger, U., Analysis of groundwater-level response to rainfall and estimation of annual recharge in fractured hard rock aquifers, NW Ireland, Journal of Hydrology (2016), doi: http://dx.doi.org/ 10. 1016/j.jhydrol.2016.01.066 This is a PDF file of an unedited manuscript that has been accepted for publication. As a service to our customers we are providing this early version of the manuscript. The manuscript will undergo copyediting, typesetting, and review of the resulting proof before it is published in its final form. Please note that during the production process errors may be discovered which could affect the content, and all legal disclaimers that apply to the journal pertain. Despite fractured hard rock aquifers underlying over 65% of Ireland, knowledge of key processes 7 controlling groundwater recharge in these bedrock systems is inadequately constrained. In this study, 8 we examined 19 groundwater-level hydrographs from two Irish hillslope sites underlain by hard rock 9 aquifers. Water-level time-series in clustered monitoring wells completed at the subsoil, soil/bedrock 10 interface, shallow and deep bedrocks were continuously monitored hourly over two hydrological 11 years. Correlation methods were applied to investigate groundwater-level response to rainfall, as well 12 as its seasonal variations. The results reveal that the direct groundwater recharge to the shallow and the relationship between the rainfall intensity and water-table rise reveal that the low rainfall intensity 22 group (≤ 1 mm/h) has greater impact on the groundwater recharge rate than other groups (> 1 mm/h). 23This study shows that the combination of the time-series analysis and the water-table fluctuation 24 method could be an useful approach to investigate groundwater recharge in fractured hard rock 25 aquifers in Ireland.

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“…(Green and Marsh, 1997;Marc and Robinson 2007;Neal, 1997Neal, , 2004. This study focuses on a small stream, the Hafren, which drains one of the main subcatchments of the Plynlimon catchment and forms the headwaters of the River Severn Shand et al, 2007Shand et al, , 2005. The Hafren catchment has an area of 3.6 km 2 (of which the Upper Hafren is 1.2 km 2 ) with an altitudinal range of 355-670 m (Brandt et al, 2004;Marsh and Hannaford, 2008).…”

Section: Introductionmentioning

confidence: 99%

Upland streamwater nitrate dynamics across decadal to sub-daily timescales: a case study of Plynlimon, Wales

et al. 2013

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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 and high-frequency data from 7-hourly samples (2007)(2008)(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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87Sr/86Sr as an indicator of flowpaths and weathering rates in the Plynlimon experimental catchments, Wales, U.K.

Cited by 62 publications

References 34 publications

Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales

Groundwater nitrogen composition and transformation within a moorland catchment, mid-Wales

Analysis of groundwater-level response to rainfall and estimation of annual recharge in fractured hard rock aquifers, NW Ireland

Upland streamwater nitrate dynamics across decadal to sub-daily timescales: a case study of Plynlimon, Wales

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