TY - JOUR

T1 - Groundwater travel times predict DOC in streams and riparian soils across a heterogeneous boreal landscape

AU - Jutebring Sterte, Elin

AU - Lidman, Fredrik

AU - Sjöberg, Ylva

AU - Ploum, Stefan W.

AU - Laudon, Hjalmar

N1 - Funding Information: We thank the crew of the Krycklan Catchment Study (KCS) funded by SITES (VR) for advice and data collection. Krycklan Catchment Study is funded by SITES (VR), Svensk Kärnbränslehantering AB (SKB), Swedish University of Agricultural Sciences, the Knut and Alice Wallenberg Foundation through Branch-Point and Future Silviculture, Swedish Research Council, FORMAS and Kempe foundation. We want to give special thanks to SKB , who funded this study, and DHI Sweden AB for consulting and modeling support. Publisher Copyright: © 2022 The Authors

PY - 2022

Y1 - 2022

N2 - Dissolved organic carbon (DOC) in surface waters is an important component of the boreal landscape carbon budget and a critical variable in water quality. A dominant terrestrial DOC source in the boreal landscape is the riparian zone. These near stream areas play a key role in regulating DOC transport between land and aquatic ecosystems. The groundwater dynamics at this interface have been considered a major controlling variable for DOC export to streams. This study focuses on the regulating role of groundwater levels and mean travel times (MTT) on riparian DOC concentrations and, subsequently, stream DOC. This is done by comparing them as explanatory variables to capture the spatial and intra-annual variability of the stream and riparian groundwater DOC. We used a physically based 3D hydrological model, Mike SHE, to simulate DOC concentrations of the riparian zones for 14 sub-catchments within the Krycklan catchment (Sweden). The model concept assumes that DOC concentrations will be higher in groundwater moving through shallow flow paths. In the model, this can be linked to the position of the groundwater table at a point of observation or the travel time, which will generally be shorter for water that has travelled through shallow and more conductive soil layers. We compared the results with both observed stream and groundwater concentrations. The analysis revealed that the correlation between modelled and observed annual averages of stream DOC increased from r = 0.08 to r = 0.87 by using MTT instead of groundwater level. MTT also better captured the observed spatial variability in riparian DOC concentrations and more successfully represented seasonal variability of stream DOC. We, therefore, suggest that MTT is a better predictor than groundwater level for riparian DOC concentration because it can capture a greater variety of catchment heterogeneities, such as variation in soil properties, catchment size, and input from deep groundwater sources.

AB - Dissolved organic carbon (DOC) in surface waters is an important component of the boreal landscape carbon budget and a critical variable in water quality. A dominant terrestrial DOC source in the boreal landscape is the riparian zone. These near stream areas play a key role in regulating DOC transport between land and aquatic ecosystems. The groundwater dynamics at this interface have been considered a major controlling variable for DOC export to streams. This study focuses on the regulating role of groundwater levels and mean travel times (MTT) on riparian DOC concentrations and, subsequently, stream DOC. This is done by comparing them as explanatory variables to capture the spatial and intra-annual variability of the stream and riparian groundwater DOC. We used a physically based 3D hydrological model, Mike SHE, to simulate DOC concentrations of the riparian zones for 14 sub-catchments within the Krycklan catchment (Sweden). The model concept assumes that DOC concentrations will be higher in groundwater moving through shallow flow paths. In the model, this can be linked to the position of the groundwater table at a point of observation or the travel time, which will generally be shorter for water that has travelled through shallow and more conductive soil layers. We compared the results with both observed stream and groundwater concentrations. The analysis revealed that the correlation between modelled and observed annual averages of stream DOC increased from r = 0.08 to r = 0.87 by using MTT instead of groundwater level. MTT also better captured the observed spatial variability in riparian DOC concentrations and more successfully represented seasonal variability of stream DOC. We, therefore, suggest that MTT is a better predictor than groundwater level for riparian DOC concentration because it can capture a greater variety of catchment heterogeneities, such as variation in soil properties, catchment size, and input from deep groundwater sources.

KW - Concentration

KW - Dissolved organic carbon

KW - Groundwater level

KW - Hydrologic transport

KW - Modelling

KW - MTT

U2 - 10.1016/j.scitotenv.2022.157398

DO - 10.1016/j.scitotenv.2022.157398

M3 - Journal article

C2 - 35872199

AN - SCOPUS:85135692373

VL - 849

JO - Science of the Total Environment

JF - Science of the Total Environment

SN - 0048-9697

M1 - 157398

ER -