Devanand et al. (2025) The influence of lateral flow on land surface fluxes in southeast Australia varies with model resolution

Identification

• Journal: Hydrology and earth system sciences
• Year: 2025
• Date: 2025-09-19
• Authors: Anjana Devanand, Jason P. Evans, Andy Pitman, Sujan Pal, David Gochis, K. M. Sampson
• DOI: 10.5194/hess-29-4491-2025

Research Groups

• Australian Research Council Centre of Excellence for Climate Extremes, UNSW Sydney, Australia
• Climate Change Research Centre, UNSW Sydney, Australia
• CSIRO Environment, Canberra, Australia
• Environmental Science Division, Argonne National Laboratory, Lemont, Illinois, USA
• National Center for Atmospheric Research, Boulder, Colorado, USA
• Airborne Snow Observatories, Inc., Mammoth Lakes, California, USA

Short Summary

Lateral flow significantly increases evapotranspiration near major river channels in high-resolution (1 and 4 km) land surface simulations in southeast Australia, consistent with observations. This inclusion reveals resolution-dependent spatial patterns, such as drier ridges at 1 km, which are crucial for improved drought and water availability modeling.

Objective

• Quantify the influence of overland and shallow subsurface lateral flow on surface fluxes (evapotranspiration and surface water partitioning) in southeast Australia.
• Investigate how model resolution impacts the simulated influence of lateral flow on these surface fluxes.

Study Configuration

• Spatial Scale: Simulations performed over southeast Australia at Land Surface Model (LSM) resolutions of 1 km, 4 km, and 10 km, coupled with routing grids at 100 m and 250 m resolutions.
• Temporal Scale: Simulations covered the period from 2013 to 2017, with analysis focusing on December 2015 to November 2017 (2 years) after a 3-year spin-up period.

Methodology and Data

• Models used: WRF-Hydro version 5.2, coupled with the Noah-MP Land Surface Model (LSM).
• Data sources:
  • Geographic data: Global Hydrosheds Digital Elevation Model (DEM) (90 m resolution), Dynamic Land Cover Dataset version 2.1 (DLCDv2.1) (2014–2015), and default Food and Agriculture Organisation (FAO) soil data.
  • Meteorological forcing data: Hourly ERA5-Land reanalysis dataset, corrected to match monthly Australian Gridded Climate Data (AGCD) observations.
  • Calibration and evaluation data: Observed streamflow from four Hydrologic Reference Stations (HRS) in Australia, high-resolution (30 m) monthly actual evapotranspiration (ET) from the CMRSET (CSIRO MODIS Reflectance-based Scaling EvapoTranspiration) algorithm version 2.2, and coarser resolution (0.25°) observationally constrained ET from the Derived Optimal Linear Combination ET (DOLCE) version 3.

Main Results

• Lateral flow increases evapotranspiration (ET) near major river channels in LSM simulations at 4 km and 1 km resolutions, consistent with high-resolution observations.
• The largest ET changes (50% or more in some areas) occur in the warm season after a wet winter, particularly in the Murray Riverina region.
• At 1 km resolution, simulations exhibit a widespread pattern of drier ridges, which is absent or less prominent at 4 km and 10 km resolutions.
• At 10 km resolution, ET increases due to lateral flow are confined to mountainous regions, and the influence of drainage networks is not visible.
• Domain-average ET increases due to lateral flow are small (2% to 4% over 2 years), but lead to a reduction in domain-average total runoff by 11% to 22%.
• The inclusion of lateral flow results in cooler monthly maximum air temperatures (approximately 0.3 °C) in the Murray Riverina basin during summer (December 2016 to January 2017) at 4 km and 1 km resolutions.

Contributions

• This is the first study to quantify the influence of lateral flow on land surface states in regional Land Surface Models (LSMs) over southeast Australia.
• It demonstrates that the impact of lateral flow on land surface fluxes is highly dependent on model spatial resolution, becoming significant at resolutions higher than 10 km.
• The study provides evidence that incorporating lateral flow can improve simulations of droughts and future water availability by modulating runoff and extending ET dry-down periods, especially in downstream regions.
• It highlights the consistency of high-resolution lateral flow simulations with observed spatial patterns of ET near river channels, supporting the need for such processes in advanced models.
• The research identifies the emergence of hillslope-scale ecohydrological patterns (drier ridges, wet valleys) at 1 km resolution, which are crucial for the development of next-generation km-scale climate models.

Funding

• Australian Research Council Centre of Excellence for Climate Extremes (grant no. CE170100023)
• National Computational Infrastructure (NCI) (supported by the Australian Government)

Citation

@article{Devanand2025influence,
  author = {Devanand, Anjana and Evans, Jason P. and Pitman, Andy and Pal, Sujan and Gochis, David and Sampson, K. M.},
  title = {The influence of lateral flow on land surface fluxes in southeast Australia varies with model resolution},
  journal = {Hydrology and earth system sciences},
  year = {2025},
  doi = {10.5194/hess-29-4491-2025},
  url = {https://doi.org/10.5194/hess-29-4491-2025}
}