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Evaporation fractionation in a peatland drainage network affects stream water isotope composition

Sprenger, M, Tetzlaff, D, Tunaley, C, Dick, JJ and Soulsby, C (2017) Evaporation fractionation in a peatland drainage network affects stream water isotope composition. Water Resources Research, 53 (1). pp. 851-866. ISSN 0043-1397

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There is increasing interest in improving understanding of evaporation within a catchment for an enhanced representation of dominant processes in hydrological models. We used a dual‐isotope approach within a nested experimental design in a boreal catchment in the Scottish Highlands (Bruntland Burn) to quantify the spatiotemporal dynamics of evaporation fractionation in a peatland drainage network and its effect on stream water isotopes. We conducted spatially distributed water sampling within the saturated peatland under different wetness conditions. We used the lc‐excess—which describes the offset of a water sample from the local meteoric water line in the dual‐isotope space—to understand the development of kinetic fractionation during runoff in a peatland network. The evaporation fractionation signal correlated positively with the potential evapotranspiration and negatively with the discharge. The variability of the isotopic enrichment within the peatland drainage network was higher with higher potential evapotranspiration and lower with higher discharge. We found an increased evaporation fractionation toward the center of the peatland, while groundwater seepage from minerogenic soils influenced the isotopic signal at the edge of the peatland. The evaporation signal was imprinted on the stream water, as the discharge from a peatland dominated subcatchment showed a more intense deviation from the local meteoric water line than the discharge from the Bruntland Burn. The findings underline that evaporation fractionation within peatland drainage networks affects the isotopic signal of headwater catchments, which questions the common assumption in hydrological modeling that the isotopic composition of stream waters did not undergo fractionation processes.

Item Type: Article
Uncontrolled Keywords: 0905 Civil Engineering, 0907 Environmental Engineering, 1402 Applied Economics
Subjects: G Geography. Anthropology. Recreation > GE Environmental Sciences
T Technology > TA Engineering (General). Civil engineering (General)
Divisions: Natural Sciences & Psychology (closed 31 Aug 19)
Publisher: American Geophysical Union
Related URLs:
Date Deposited: 23 Oct 2018 08:45
Last Modified: 04 Sep 2021 02:19
DOI or ID number: 10.1002/2016WR019258
URI: https://researchonline.ljmu.ac.uk/id/eprint/9528
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