Detecting groundwater discharge dynamics from point-to-catchment scale in a lowland stream

Combining hydraulic and tracer methods

J. R. Poulsen*, E. Sebok, C. Duque, D. Tetzlaff, P. K. Engesgaard

*Corresponding author for this work

Research output: Contribution to journalArticle

14 Citations (Scopus)
4 Downloads (Pure)

Abstract

Detecting, quantifying and understanding groundwater discharge to streams are crucial for the assessment of water, nutrient and contaminant exchange at the groundwater-surface water interface. In lowland agricultural catchments with significant groundwater discharge this is of particular importance because of the risk of excess leaching of nutrients to streams. Here we aim to combine hydraulic and tracer methods from point-to-catchment scale to assess the temporal and spatial variability of groundwater discharge in a lowland, groundwater gaining stream in Denmark. At the point-scale, groundwater fluxes to the stream were quantified based on vertical streambed temperature profiles (VTPs). At the reach scale (0.15-2 km), the spatial distribution of zones of focused groundwater discharge was investigated by the use of distributed temperature sensing (DTS). Groundwater discharge to the stream was quantified using differential gauging with an acoustic Doppler current profiler (ADCP). At the catchment scale (26-114 km2), runoff sources during main rain events were investigated by hydrograph separations based on electrical conductivity (EC) and stable isotopes 2H/1H. Clear differences in runoff sources between catchments were detected, ranging from approximately 65% event water for the most responsive sub-catchment to less than 10% event water for the least responsive sub-catchment. This was supported by the groundwater head gradients, where the location of weaker gradients correlated with a stronger response to precipitation events. This shows a large variability in groundwater discharge to the stream, despite the similar lowland characteristics of sub-catchments indicating the usefulness of environmental tracers for obtaining information about integrated catchment functioning during precipitation events. There were also clear spatial patterns of focused groundwater discharge detected by the DTS and ADCP measurements at the reach scale indicating high spatial variability, where a significant part of groundwater discharge was concentrated in few zones indicating the possibility of concentrated nutrient or pollutant transport zones from nearby agricultural fields. VTP measurements confirmed high groundwater fluxes in discharge areas indicated by DTS and ADCP, and this coupling of ADCP, DTS and VTP proposes a novel field methodology to detect areas of concentrated groundwater discharge with higher resolution.

Original languageEnglish
Pages (from-to)1871-1886
Number of pages16
JournalHydrology and Earth System Sciences
Volume19
Issue number4
Early online date21 Apr 2015
DOIs
Publication statusPublished - 21 Apr 2015

Fingerprint

tracer
catchment
hydraulics
groundwater
Acoustic Doppler Current Profiler
temperature profile
method
nutrient
temperature
runoff
agricultural catchment
pollutant transport
hydrograph
water
electrical conductivity
stable isotope
leaching
spatial distribution
surface water
methodology

ASJC Scopus subject areas

  • Earth and Planetary Sciences (miscellaneous)
  • Water Science and Technology

Cite this

Detecting groundwater discharge dynamics from point-to-catchment scale in a lowland stream : Combining hydraulic and tracer methods. / Poulsen, J. R.; Sebok, E.; Duque, C.; Tetzlaff, D.; Engesgaard, P. K.

In: Hydrology and Earth System Sciences, Vol. 19, No. 4, 21.04.2015, p. 1871-1886.

Research output: Contribution to journalArticle

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