Eslami et al. (2025) Climatic, topographic, and groundwater controls on runoff response to precipitation: evidence from a large-sample data set

Identification

• Journal: Hydrology and earth system sciences
• Year: 2025
• Date: 2025-10-13
• Authors: Zahra Eslami, Hansjörg Seybold, James W. Kirchner
• DOI: 10.5194/hess-29-5121-2025

Research Groups

• Department of Environmental Systems Science, ETH Zurich, Zurich, Switzerland
• Swiss Federal Research Institute WSL, Birmensdorf, Switzerland
• Department of Earth and Planetary Science, University of California, Berkeley, CA, USA

Short Summary

This study utilized ensemble rainfall-runoff analysis (ERRA) across 189 Iranian catchments to quantify how climatic, topographic, and groundwater factors control peak runoff response to precipitation, revealing that steeper slopes, smaller catchment areas, shallower groundwater, and more humid climates lead to higher peak runoff.

Objective

• To investigate how topographic, climatic (aridity index), and groundwater depth variables, and their interactions, influence runoff response in catchments.
• To determine how variations in groundwater depth influence runoff response when accounting for other relevant factors, such as slope or catchment size.

Study Configuration

• Spatial Scale: 189 Iranian catchments with diverse climates and topographies; topographic data at 90 meter resolution. Groundwater depths ranged from 1 meter to 92 meters.
• Temporal Scale: Daily streamflow and rainfall time series; monthly groundwater depth time series spanning 2000–2018. Runoff response was analyzed for lags up to 10 days.

Methodology and Data

• Models used: Ensemble Rainfall–Runoff Analysis (ERRA), a data-driven, nonparametric, and model-independent approach for quantifying rainfall–runoff relationships.
• Data sources:
  • Daily streamflow data from 1549 hydrometric stations (Iranian Water Resources Management Company, IWRMC, 2018).
  • Topographic data from the Shuttle Radar Topography Mission (SRTM) at 90 meter resolution (Jarvis et al., 2008).
  • Daily rainfall and potential evapotranspiration time series from CHELSA’s global precipitation downscaling reanalysis (Karger et al., 2017).
  • Monthly groundwater depth time series from 13 538 wells (IWRMC, 2018).

Main Results

• Peak runoff response (RRD peak height) is generally higher in catchments with shallower groundwater (1–14 meters depth) compared to those with deeper groundwater (27–92 meters depth).
• A negative Spearman rank correlation (ρ = -0.22, p < 0.001) was found between RRD peak height and groundwater depth, indicating deeper groundwater is associated with smaller runoff peaks.
• A positive Spearman rank correlation (ρ = 0.43, p < 0.001) was observed between RRD peak height and mean topographic slope, suggesting steeper terrain leads to higher runoff peaks.
• A negative Spearman rank correlation (ρ = -0.21, p < 0.001) was found between RRD peak height and catchment area, implying larger catchments tend to have lower runoff peaks.
• A positive Spearman rank correlation (ρ = 0.27, p < 0.001) was noted between RRD peak height and the climatic aridity index (P/PET), indicating higher runoff response in more humid climates.
• Partial regression analysis revealed that topographic slope is the strongest control on RRD peak height, followed by catchment area and groundwater depth, with the aridity index showing a statistically insignificant trend after accounting for other drivers.

Contributions

• This study provides a comprehensive understanding of how topographic, climatic, and groundwater variables interact to shape runoff response, particularly addressing a notable gap in research for arid and semi-arid environments.
• It highlights the importance of considering multiple interacting factors for effective water resource management and flood risk mitigation in vulnerable regions.
• The application of Ensemble Rainfall–Runoff Analysis (ERRA) in a large-sample study across a diverse region like Iran offers novel insights into nonlinear hydrological responses.

Funding

• Swiss Government Excellence Scholarship (to Zahra Eslami)

Citation

@article{Eslami2025Climatic,
  author = {Eslami, Zahra and Seybold, Hansjörg and Kirchner, James W.},
  title = {Climatic, topographic, and groundwater controls on runoff response to precipitation: evidence from a large-sample data set},
  journal = {Hydrology and earth system sciences},
  year = {2025},
  doi = {10.5194/hess-29-5121-2025},
  url = {https://doi.org/10.5194/hess-29-5121-2025}
}