Aadhar et al. (2026) Role of hydrometeorological variables and catchment area to flood generation over the monsoonal climate region of India

Identification

• Journal: Hydrology and earth system sciences
• Year: 2026
• Date: 2026-11-02
• Authors: Saran Aadhar, Efrat Morin, Utkarsh Gupta
• DOI: 10.5194/hess-30-6747-2026

Research Groups

• Civil and Infrastructure Engineering, Indian Institute of Technology (IIT) Jodhpur, Jodhpur, India
• The Fredy & Nadine Herrmann Institute of Earth Sciences, Hebrew University of Jerusalem, Jerusalem, Israel

Short Summary

This study investigates the hydrometeorological and catchment-scale drivers of flood generation in India's Godavari River basin, revealing how temporal precipitation properties and specific catchment areas contribute to flood events across different aridity regimes. It differentiates between short-duration, single-event floods in semi-arid regions and long-duration, multi-event floods in semi-humid areas, identifying key flood-dominant sub-basins.

Objective

• To understand the major flood-generating mechanisms across different aridity regimes within the Godavari River basin, one of the largest river basins in the Indian Subcontinent.
• To examine the temporal variability of hydrometeorological variables (precipitation and surface runoff) before peak streamflow events to identify dominating flood processes.
• To evaluate the spatial variability of hydrometeorological variables to identify flood-dominant catchment areas associated with downstream flood events.

Study Configuration

• Spatial Scale: Godavari River basin (drainage area of approximately 312,800 km²), covering six Indian states. Analysis focused on five sub-basins/streamflow stations: Mancherial (84,375 km²), Tekra (90,625 km²), Pathagudam (35,625 km²), Perur (226,250 km²), and Polavaram (257,500 km²). Gridded data at 0.25° spatial resolution.
• Temporal Scale: 1967–2019 for meteorological forcing and simulations, with streamflow data for 1967–2014. Daily timescale for hydrometeorological variables. Flood events identified using a peak-over-threshold approach with a 10-day separation. Precipitation and runoff accumulation durations ranged from 1 to 20 days, with lag times of 0 to 7 days.

Methodology and Data

• Models used:
  • Variable Infiltration Capacity (VIC) model: A physically based, land surface, grid-based hydrologic model for simulating energy and water fluxes.
  • Stand-alone routing model (Lohmann et al., 1996): Routes VIC-simulated surface runoff and baseflow using a unit hydrograph method and linearized Saint-Venant equation.
• Data sources:
  • Observed daily 0.25° gridded precipitation data from the India Meteorological Department (IMD).
  • Observed daily 1° gridded maximum and minimum temperature data from IMD, regridded to 0.25°.
  • Reanalysis wind speed data at 0.25° spatial resolution from the National Centers for Environmental Prediction-National Center for Atmospheric Research (NCEP-NCAR).
  • Daily streamflow discharge data from the Central Water Commission (CWC) for five gauging stations.
  • Vegetation parameters from Advanced Very High-Resolution Radiometer (AVHRR) global land-cover information (1 km spatial resolution).
  • Soil parameters from the Harmonized World Soil Database (HWSD).
  • Basin and sub-basin delineation and flow direction computed from Shuttle Radar Topography Mission (SRTM) elevation data.
  • Empirical Orthogonal Function (EOF) analysis: Used to identify dominant modes of spatio-temporal variability in precipitation and surface runoff.
  • Pearson correlation coefficient: Quantified coupling between Principal Component (PC) time series from EOF and peak discharge anomaly.

Main Results

• The majority of high-intensity precipitation and streamflow events occurred during the Indian summer monsoon (June–September), with a higher ratio of high streamflow to high precipitation in the late monsoon (August–September) due to wetter antecedent soil moisture conditions.
• Floods in the semi-arid Mancherial sub-basin were predominantly associated with short-duration (2 days) accumulated precipitation and mean runoff, often triggered by a single high-intensity precipitation day.
• In contrast, floods in the semi-humid sub-basins (Tekra, Pathagudam, Perur, and Polavaram) were linked to long-duration (10–11 days) accumulated precipitation and 7–8 days mean runoff, characterized by multiple high-intensity precipitation events.
• Empirical Orthogonal Function (EOF) analysis revealed that the central and downstream areas of the Godavari basin dominantly contribute to flood generation, producing substantially higher runoff.
• The Tekra sub-basin exhibited the highest runoff coefficient values across all analyzed durations and soil moisture conditions, highlighting its significant role in downstream flooding within the Godavari River basin.

Contributions

• Provides a sub-basin and spatially explicit understanding of flood-generating mechanisms in a large, climatically heterogeneous river basin, moving beyond basin-averaged flood attribution.
• Differentiates flood types and their hydrometeorological drivers based on aridity regimes, identifying distinct short-duration, single-event floods in semi-arid areas versus long-duration, multi-event floods in semi-humid regions.
• Identifies specific flood-dominant catchment areas (central and downstream Godavari, particularly the Tekra sub-basin) through advanced spatial analysis (EOF and correlation), which is crucial for targeted flood management.
• Offers practical insights for duration-informed flood forecasting (e.g., need for 10–11 day precipitation forecasts in semi-humid regions) and catchment-scale flood management strategies, including the importance of real-time soil moisture monitoring and natural flood management methods in high-runoff areas like Tekra.

Funding

• Anusandhan National Research Foundation (grant no. 20230091) under the Startup Research Grant (SRG).

Citation

@article{Aadhar2026Role,
  author = {Aadhar, Saran and Morin, Efrat and Gupta, Utkarsh},
  title = {Role of hydrometeorological variables and catchment area to flood generation over the monsoonal climate region of India},
  journal = {Hydrology and earth system sciences},
  year = {2026},
  doi = {10.5194/hess-30-6747-2026},
  url = {https://doi.org/10.5194/hess-30-6747-2026}
}