Gorugantula et al. (2026) An integrated water deficit index to evaluate multifaceted impacts of drought in a semi-arid river basin

Identification

• Journal: Natural Hazards
• Year: 2026
• Date: 2026-02-17
• Authors: Sai Srinivas Gorugantula, B.V.N. P. Kambhammettu
• DOI: 10.1007/s11069-025-07862-4

Research Groups

• Department of Civil Engineering, Indian Institute of Technology Hyderabad, Hyderabad, Telangana, India

Short Summary

This study developed an Integrated Water Deficit Index (IWDI) by combining climatic water deficit (SPEI) and terrestrial water storage deficit (TWSI) using a Clayton copula function to holistically characterize drought in a large, semi-arid river basin. The IWDI revealed distinct spatiotemporal drought patterns, with upper sub-basins experiencing longer, more severe droughts, and quantified significant reductions in water bodies (15%) and crop production (25%) during drought events.

Objective

• Understand spatiotemporal variation in climatic water and terrestrial water storage deficits in a semi-arid river basin.
• Develop a copula-based, integrated drought index that considers the effects of meteorological, agricultural, and hydrological droughts.
• Track internal propagation of integrated drought using variable motion studies.
• Investigate the role of hydrometeorological variables on integrated drought.

Study Configuration

• Spatial Scale: Krishna River Basin (KRB), India, covering 258,948 km², divided into seven sub-basins (Upper Bhima, Lower Bhima, Upper Krishna, Middle Krishna, Lower Krishna, Upper Tungabhadra, Lower Tungabhadra). Data resolutions include 0.25° for precipitation and GRACE TWSA, and 500 m for MODIS ET.
• Temporal Scale: Monthly data for the period 2002–2017.

Methodology and Data

• Models used:
  • Integrated Water Deficit Index (IWDI) developed using the Clayton copula function.
  • Standardized Precipitation Evapotranspiration Index (SPEI).
  • Terrestrial Water Storage Index (TWSI).
  • Run theory for drought event identification and characterization (duration, severity, intensity).
  • Variable motion studies for tracking internal drought propagation (Instantaneous Development Speed, Instantaneous Recovery Speed, Development Duration, Recovery Duration).
  • Structural Equation Modeling (SEM) under multilinear regression to ascertain the role of controlling variables (P, PET, SF, SM, GWL on SPEI, TWSA, IWDI).
  • Correlation studies to quantify the role of external factors on IWDI.
• Data sources:
  • Monthly precipitation (P): India Meteorological Department (IMD) daily gridded data (0.25°).
  • Potential evapotranspiration (PET): Moderate Resolution Imaging Spectroradiometer (MODIS) 8-day composite ET (500 m).
  • Terrestrial Water Storage Anomalies (TWSA): GRACE-derived data (0.25°) from Jet Propulsion Laboratory (JPL).
  • Auxiliary variables (soil water volume, surface pressure, soil moisture, runoff, evaporation): ERA-5 and GLDAS reanalysis data.
  • Streamflows (SF): Central Water Commission (CWC).
  • Groundwater levels (GWL): Central Groundwater Board (CGWB).
  • Crop production data: Ministry of Agriculture and Farmers Welfare.
  • Land Use Land Cover (LULC) and Normalized Difference Vegetation Index (NDVI): MODIS.

Main Results

• A clear spatiotemporal variation in drought characteristics was observed across the Krishna River Basin.
• Upper sub-basins exhibited prolonged drought durations (> 22 months) and higher severity (< -15), with longer development (12 ± 6 months) and recovery periods (13 ± 8 months).
• Lower sub-basins experienced more frequent, short-term droughts (duration > 15 months) with lower severity (< -10), attributed to low precipitation despite adequate resources.
• The Integrated Water Deficit Index (IWDI) effectively captured the combined effects of climatic water and terrestrial water storage deficits, showing lower intensities than marginal distributions and better representing extreme drought events.
• Devastating droughts occurred across the basin during 2002–2004 and 2015–2017.
• Incoming fluxes (precipitation, terrestrial water storage anomalies, soil moisture) and storage components showed a positive association with IWDI, indicating they reduce drought intensity.
• Outgoing fluxes (potential evapotranspiration, evaporation, maximum/minimum temperature) showed a negative association with IWDI, indicating they intensify droughts.
• Drought events during 2002–2017 were correlated with a 15% reduction in water bodies and a 25% reduction in crop production (e.g., rice, Jowar).

Contributions

• Development of a novel copula-based Integrated Water Deficit Index (IWDI) that holistically combines climatic water deficit (SPEI) and terrestrial water storage deficit (TWSI) for large-scale, semi-arid river basins, addressing limitations of existing indices.
• Comprehensive characterization of drought events, including their internal propagation (development and recovery speeds and durations), using run theory and variable motion studies.
• Detailed investigation of the influence of various hydrometeorological variables and external factors on integrated drought using Structural Equation Modeling and correlation analysis.
• Quantification of the multifaceted impacts of drought on hydrological reserves (water bodies) and agricultural productivity (crop production), providing actionable insights for water resource management and mitigation strategies.

Funding

The authors declare that no funds, grants, or other support were received during the preparation of this manuscript.

Citation

@article{Gorugantula2026integrated,
  author = {Gorugantula, Sai Srinivas and Kambhammettu, B.V.N. P.},
  title = {An integrated water deficit index to evaluate multifaceted impacts of drought in a semi-arid river basin},
  journal = {Natural Hazards},
  year = {2026},
  doi = {10.1007/s11069-025-07862-4},
  url = {https://doi.org/10.1007/s11069-025-07862-4}
}