Malmquist et al. (2026) Soil moisture and evapotranspiration in four temperate agricultural catchments of Southern Sweden under future climatic conditions

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2026
• Date: 2026-09-21
• Authors: Louise Malmquist, Magdalena Bieroza, Fernando Jaramillo, Jennie Barron
• DOI: 10.1016/j.ejrh.2026.103992

Research Groups

• Department of Soil and Environment, Swedish University of Agricultural Sciences, Uppsala, Sweden
• Department of Physical Geography, Stockholm University, Stockholm, Sweden

Short Summary

This study assessed the impact of current and future extreme weather on soil moisture availability and evapotranspiration in four temperate agricultural catchments in southern Sweden, finding significant drying trends in both topsoil and subsoil, particularly in the subsoil, and reduced evapotranspiration under future climate scenarios, primarily driven by temperature increases.

Objective

• To assess how current and future extreme weather impacts soil moisture availability and evapotranspiration in temperate agricultural catchments in southern Sweden.
• To quantify changes in soil moisture surplus and deficit in the root zone under extreme events in current and projected future climate.
• To quantify consecutive effects of low soil moisture on crop/vegetation actual evapotranspiration (ETa).

Study Configuration

• Spatial Scale: Four agriculturally dominated catchments in southern Sweden: Tidan (696 km²), Enköpingsån-Örsundaån (995 km²), Saxån-Braån (359 km²), and Gamlebyån-Loftaån (725 km²).
• Temporal Scale: Reference period (1991–2023) compared with future climate scenarios (2024–2040 and 2041–2060). Soil moisture dynamics were evaluated weekly.

Methodology and Data

• Models used:
  • Soil and Water Assessment Tool (SWAT+) for water balance modeling.
  • LARS-WG (weather generator) for generating future climate scenarios.
• Data sources:
  • Climate data: Observed historical weather records from SMHI (Swedish Meteorological and Hydrological Institute) stations, and CMIP6 SSP2–4.5 and SSP5–8.5 emission scenarios generated by LARS-WG using the ACCESS-ESM1–5 global climate model.
  • Elevation map: Swedish Land Survey.
  • Land cover: Nationella marktäckesdata (NMD) from the Swedish Environmental Protection Agency, and Sentinel 2A/2B satellite data.
  • Soil data: References from Malmquist and Barron (2023).
  • Stream network, water bodies, ditch network: National agencies.
  • Tile drainage: Tabular data on the share of total cropland that is tile drained from the Swedish Board of Agriculture.
  • Groundwater level: SGU (Geological Survey of Sweden) measurement stations.
  • Structural mitigation measures: Data from local water councils and Swedish County Administrative Boards.
  • Actual Evapotranspiration (ETa): MODIS (MOD16A v006 and v061, 500 m, 8-day temporal resolution).
  • Discharge: Monthly streamflow data from SMHI and local water associations.
• Indices used:
  • Soil Moisture Deficiency Index (SMDI) for topsoil (10–20 cm) and subsoil (50–60 cm).
  • Evapotranspiration Deficiency Index (ETDI).
  • Standardized Precipitation Index (SPI) (weekly).
  • TX90p (share of days above the 90th percentile of maximum temperature) (weekly).

Main Results

• Significant drying trends (p < 0.05) were observed in both topsoil and subsoil in three of the four catchments.
• Enhanced drying was particularly evident in the subsoil, with an earlier onset of drying in catchments at higher latitudes.
• Reduced actual evapotranspiration (ETDI) coincided with the soil moisture reduction, mainly occurring from July to September.
• The drying trends were primarily temperature-driven, as the climate scenarios showed significant temperature increases but non-significant changes in precipitation volume or days.
• The northernmost catchment (Enköpingsån-Örsundaån) showed a non-significant change towards wetter conditions in the topsoil and subsoil (for SSP2–4.5).
• The average soil moisture content corresponding to no anomaly (SMDI=0) ranged from 45 ± 9% to 55 ± 16% of field capacity, indicating limited easily accessible water for plants.
• The area with soil moisture below the wilting point (dry area) increased by up to +26% in the topsoil in western and southern catchments, and up to +60% in the subsoil of the southernmost catchment towards the end of the cropping season.
• The area with soil moisture above 90% of field capacity (saturated area) remained stable or reduced in future scenarios, except for a slight increase in the northernmost catchment.

Contributions

• Provides novel insights into subsoil unsaturated domain responses to climate change in agricultural landscapes, complementing existing topsoil studies.
• Utilizes a weather generator (LARS-WG) for climate change scenario input, exploring its implications for current and future climate.
• Employs multi-parameter calibration and validation of a catchment-scale water balance model (SWAT+) using actual evapotranspiration (ETa) from satellite products, which is a less common approach.
• Highlights the importance of using multiple, crop-relevant indices (SMDI, ETDI, SPI, TX90p) to understand the chain of impact from weather to soil moisture and evapotranspiration, crucial for agricultural adaptation.
• Identifies specific regional vulnerabilities in southern Sweden, suggesting increasing needs for improved soil water management and irrigation, particularly in eastern and southern catchments.

Funding

• Faculty of Natural Resources and Agricultural Sciences, Swedish University of Agricultural Sciences (SLU).
• EU EJP SOIL Programme within the European Union Horizon 2020 research and innovation programme [Grant agreement No. 862695 EJP SOIL].

Citation

@article{Malmquist2026Soil,
  author = {Malmquist, Louise and Bieroza, Magdalena and Jaramillo, Fernando and Barron, Jennie},
  title = {Soil moisture and evapotranspiration in four temperate agricultural catchments of Southern Sweden under future climatic conditions},
  journal = {Journal of Hydrology Regional Studies},
  year = {2026},
  doi = {10.1016/j.ejrh.2026.103992},
  url = {https://doi.org/10.1016/j.ejrh.2026.103992}
}