 |
| Titel |
The O and H stable isotope composition of freshwaters in the British Isles. 2. Surface waters and groundwater |
| VerfasserIn |
W. G. Darling, A. H. Bath, J. C. Talbot |
| Medientyp |
Artikel
|
| Sprache |
Englisch
|
| ISSN |
1027-5606
|
| Digitales Dokument |
URL |
| Erschienen |
In: Hydrology and Earth System Sciences ; 7, no. 2 ; Nr. 7, no. 2, S.183-195 |
| Datensatznummer |
250004527
|
| Publikation (Nr.) |
 copernicus.org/hess-7-183-2003.pdf |
|
|
|
|
|
| Zusammenfassung |
| The utility of stable isotopes as tracers of the water molecule has a long
pedigree. The study reported here is part of an attempt to establish a comprehensive
isotopic "baseline" for the British Isles as background data for a range of applications.
Part 1 of this study (Darling and Talbot, 2003) considered the isotopic composition of
rainfall in Britain and Ireland. The present paper is concerned with the composition of
surface waters and groundwater. In isotopic terms, surface waters (other than some upland
streams) are poorly characterised in the British Isles; their potential variability has
yet to be widely used as an aid in hydrological research. In what may be the first study
of a major British river, a monthly isotopic record of the upper River Thames during 1998
was obtained. This shows high damping of the isotopic variation compared to that in
rainfall over most of the year, though significant fluctuations were seen for the autumn
months. Smaller rivers such as the Stour and Darent show a more subdued response to the
balance between runoff and baseflow. The relationship between the isotopic composition
of rainfall and groundwater is also considered. From a limited database, it appears that
whereas Chalk groundwater is a representative mixture of weighted average annual rainfall,
for Triassic sandstone groundwater there is a seasonal selection of rainfall biased
towards isotopically-depleted winter recharge. This may be primarily the result of
physical differences between the infiltration characteristics of rock types, though other
factors (vegetation, glacial history) could be involved. In the main, however,
groundwaters appear to be representative of bulk rainfall within an error band of
0.5‰ δ18O. Contour maps of the δ18O and
δ2H content of recent groundwaters in the British Isles show a
fundamental SW-NE depletion effect modified by topography. The range of measured
values, while much smaller than those for rainfall, still covers some ‰ for
δ18O and 30‰ for δ2H. Over lowland areas the
"altitude effect" is of little significance, but in upland areas is consistent with
a range of –0.2 to –0.3‰ per 100 m increase in altitude. Groundwaters dating from
the late Pleistocene are usually modified in δ18O and
δ2H owing to the effects of climate change on the isotopic composition
of rainfall and thus of recharge. Contour maps of isotopic variability prior to
10 ka BP, based on the relatively limited information available from the British Isles,
allow a first comparison between groundwaters now and at the end of the last Ice Age.
The position of the British Isles in the context of the stable isotope systematics of
NW Europe is reviewed briefly.
Keywords: Stable isotopes, surfacewaters, groundwater, British Isles |
| |
|
| Teil von |
|
|
|
|
|
|
|
|