Modelling dissolved organic carbon dynamics in Krycklan catchments in Sweden using the SWAT-C model
(2025) In Student thesis series INES NGEM01 20251Dept of Physical Geography and Ecosystem Science
- Abstract
- Understanding the spatial and temporal dynamics of dissolved organic carbon (DOC) in boreal catchments is essential for improving water quality models and assessing carbon fluxes. This study applies the SWAT-C (Soil and Water Assessment Tool for Carbon) model to the Krycklan catchment in northern Sweden (67.9 km²), a well-instrumented boreal watershed characterized by forests, wetlands, and peatlands. The primary objectives of this study were to (1) test the model’s ability to simulate streamflow using in-situ measurements for validation; (2) assess the model’s performance in reproducing observed DOC concentrations; (3) examine the spatial and temporal variability of simulated DOC concentrations. These objectives aim to evaluate the... (More)
- Understanding the spatial and temporal dynamics of dissolved organic carbon (DOC) in boreal catchments is essential for improving water quality models and assessing carbon fluxes. This study applies the SWAT-C (Soil and Water Assessment Tool for Carbon) model to the Krycklan catchment in northern Sweden (67.9 km²), a well-instrumented boreal watershed characterized by forests, wetlands, and peatlands. The primary objectives of this study were to (1) test the model’s ability to simulate streamflow using in-situ measurements for validation; (2) assess the model’s performance in reproducing observed DOC concentrations; (3) examine the spatial and temporal variability of simulated DOC concentrations. These objectives aim to evaluate the capacity of the SWAT-C model to accurately represent key hydrological and biogeochemical outputs, thereby providing a basis for its application in future studies of water quality and carbon export.
Model performance was assessed at three representative subcatchments (C5, C12, and C16), corresponding to upstream, midstream, and downstream subcatchments. Calibration (2011-2016) and validation (2017-2022) results showed that the model performed best in the midstream subcatchment (C12), with NSE and KGE values exceeding 0.65 and relatively low prediction bias. In contrast, upstream and downstream subcatchments exhibited persistent biases and higher uncertainties, likely due to incomplete watershed delineation, spatial heterogeneity, and limitations in climate forcing and soil parameterization. Uncertainty analysis using SUFI-2 indicated acceptable p-factor and r-factor values for streamflow simulations, but greater variability for DOC, particularly in C16.
The study highlights the importance of accurate watershed representation, optimized HRU thresholds, and high-resolution meteorological input in improving DOC simulations. While SWAT-C effectively captured mid-catchment dynamics, performance in headwater and downstream areas requires enhanced spatial and process-based refinements. These findings provide insights into DOC mobilization mechanisms and inform future improvements in hydrological-carbon modeling in boreal environments. (Less) - Popular Abstract
- Carbon in the landscape is constantly moving. Rain and melting snow wash organic carbon from soils, wetlands, and peatlands into streams. In its dissolved form – dissolved organic carbon (DOC) – it affects water quality and the global carbon cycle. High DOC can complicate drinking water treatment, alter aquatic ecosystems, and transfer carbon from land to oceans or the atmosphere.
As climate and land use change, it becomes vital to understand how DOC is mobilized and transported.
The Krycklan catchment in northern Sweden offers an ideal test site. This 68 km² forest and wetland area has decades of high-quality monitoring data. In this project, I used the SWAT-C model (Soil and Water Assessment Tool for Carbon) to simulate how water... (More) - Carbon in the landscape is constantly moving. Rain and melting snow wash organic carbon from soils, wetlands, and peatlands into streams. In its dissolved form – dissolved organic carbon (DOC) – it affects water quality and the global carbon cycle. High DOC can complicate drinking water treatment, alter aquatic ecosystems, and transfer carbon from land to oceans or the atmosphere.
As climate and land use change, it becomes vital to understand how DOC is mobilized and transported.
The Krycklan catchment in northern Sweden offers an ideal test site. This 68 km² forest and wetland area has decades of high-quality monitoring data. In this project, I used the SWAT-C model (Soil and Water Assessment Tool for Carbon) to simulate how water and DOC move through the catchment.
The model describes how rainfall and snowmelt travel through soils and vegetation before reaching streams. I evaluated its performance at three points: upstream, midstream, and downstream, comparing model outputs with measurements.
The best results were obtained in the midstream area, where water flow and DOC matched observations reasonably well. Accuracy was lower in headwaters and downstream, likely due to greater complexity and limited data in those areas.
These findings show both the promise and the limitations of current models. SWAT-C can reveal important links between water and carbon export, but its reliability depends on detailed data and careful setup.
With better climate inputs, soil information, and calibration, models like SWAT-C can help scientists and policymakers anticipate future changes in water quality and carbon transport. This is essential for protecting northern waters, managing ecosystems, and understanding how boreal regions contribute to the Earth’s carbon balance. (Less)
Please use this url to cite or link to this publication:
http://lup.lub.lu.se/student-papers/record/9211574
- author
- Duan, Yujia LU
- supervisor
-
- Zheng Duan LU
- Renkui Guo LU
- organization
- course
- NGEM01 20251
- year
- 2025
- type
- H2 - Master's Degree (Two Years)
- subject
- keywords
- Geography, dissolved organic carbon (DOC), SWAT-C, Krycklan, streamflow
- publication/series
- Student thesis series INES
- report number
- 730
- language
- English
- id
- 9211574
- date added to LUP
- 2025-09-03 09:38:28
- date last changed
- 2025-09-03 09:38:28
@misc{9211574,
abstract = {{Understanding the spatial and temporal dynamics of dissolved organic carbon (DOC) in boreal catchments is essential for improving water quality models and assessing carbon fluxes. This study applies the SWAT-C (Soil and Water Assessment Tool for Carbon) model to the Krycklan catchment in northern Sweden (67.9 km²), a well-instrumented boreal watershed characterized by forests, wetlands, and peatlands. The primary objectives of this study were to (1) test the model’s ability to simulate streamflow using in-situ measurements for validation; (2) assess the model’s performance in reproducing observed DOC concentrations; (3) examine the spatial and temporal variability of simulated DOC concentrations. These objectives aim to evaluate the capacity of the SWAT-C model to accurately represent key hydrological and biogeochemical outputs, thereby providing a basis for its application in future studies of water quality and carbon export.
Model performance was assessed at three representative subcatchments (C5, C12, and C16), corresponding to upstream, midstream, and downstream subcatchments. Calibration (2011-2016) and validation (2017-2022) results showed that the model performed best in the midstream subcatchment (C12), with NSE and KGE values exceeding 0.65 and relatively low prediction bias. In contrast, upstream and downstream subcatchments exhibited persistent biases and higher uncertainties, likely due to incomplete watershed delineation, spatial heterogeneity, and limitations in climate forcing and soil parameterization. Uncertainty analysis using SUFI-2 indicated acceptable p-factor and r-factor values for streamflow simulations, but greater variability for DOC, particularly in C16.
The study highlights the importance of accurate watershed representation, optimized HRU thresholds, and high-resolution meteorological input in improving DOC simulations. While SWAT-C effectively captured mid-catchment dynamics, performance in headwater and downstream areas requires enhanced spatial and process-based refinements. These findings provide insights into DOC mobilization mechanisms and inform future improvements in hydrological-carbon modeling in boreal environments.}},
author = {{Duan, Yujia}},
language = {{eng}},
note = {{Student Paper}},
series = {{Student thesis series INES}},
title = {{Modelling dissolved organic carbon dynamics in Krycklan catchments in Sweden using the SWAT-C model}},
year = {{2025}},
}