He et al. (2026) Characterizing spatially concurrent hydrological drought and its response to meteorological drought under the impact of human activities

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2026
• Date: 2026-01-14
• Authors: Shaokun He, Qianxun Li, Kebing Chen, Lingling Zhu
• DOI: 10.1016/j.ejrh.2026.103129

Research Groups

• State Key Lab. of Water Resources Engineering & Management, Wuhan University, China
• Changjiang Institute of Survey, Planning, Design and Research Corporation, China
• Bureau of Hydrology, Changjiang Water Resources Commission, China

Short Summary

This study characterized the response of spatially concurrent hydrological droughts (HD) to meteorological droughts (MD) in two sub-regions of the upper Hanjiang River Basin, revealing that human activities significantly alter the MD-HD linkages from elementary to complex non-linear patterns, which can be probabilistically quantified using Copula functions.

Objective

• To characterize the response of spatially concurrent hydrological droughts (HD) to meteorological droughts (MD) in two sub-regions of the upper Hanjiang River Basin, specifically examining how human activities impact these inter-regional MD-HD linkages under both natural and human-influenced conditions.

Study Configuration

• Spatial Scale: Upper Hanjiang River Basin (UHRB) in China, divided into two sub-regions: S1 (upstream of Ankang reservoir, catchment area 35,700 km²) and S2 (between Ankang and Danjiangkou reservoirs, area 59,500 km²).
• Temporal Scale: Monthly data from 1961 to 2020, divided into a natural pre-change period (1961–1990) and a human-influenced post-change period (1991–2020).

Methodology and Data

• Models used:
  • Standardized Precipitation Index (SPI) for meteorological drought (MD).
  • Standardized Streamflow Index (SSI) for hydrological drought (HD).
  • Run theory for extracting drought characteristics (duration, magnitude, intensity).
  • Elementary functions (unary linear, polynomial, power, logarithmic, exponential) to model MD-HD magnitude relationships.
  • Copula functions (Gumbel-Hougaard, Frank, Clayton) for joint probability relationships of spatially concurrent HDs.
  • Model evaluation metrics: Nash-Sutcliffe efficiency (NSE), coefficient of determination (R²), percent bias (PBIAS), Kolmogorov-Smirnov (K-S) test, Bayesian information criterion (BIC), Akaike Information Criterion (AIC).
• Data sources:
  • Monthly precipitation data (1961–2020) from 18 meteorological stations, obtained from the China Meteorological Information Center. Basin-average precipitation estimated using the Thiessen polygon method.
  • Monthly streamflow data (1961–2020) from Ankang and Huangjiagang hydrological stations, provided by the Bureau of Hydrology of the Yangtze Water Resources Commission of China.

Main Results

• Drought Characteristics: Short-term (3-month) SPI and SSI series showed significant fluctuations, while long-term (12-month) series were smoother with fewer events but increased average duration and magnitude.
• Impact of Human Activities: In sub-region S2, hydrological drought (HD) magnitude significantly deteriorated in the post-change period, primarily due to the Middle Route of the South-to-North Water Diversion Project (diverting 9–10 billion cubic meters per year) and reservoir regulation, leading to a persistent decoupling between SPI and SSI. In S1, human activities intensified HD.
• MD-HD Linkages (Elementary Functions):
  • During the natural pre-change period, both S1 and S2 exhibited strong elementary functional relationships (R² > 0.8) between MD and HD magnitudes, with linear functions being optimal.
  • In the post-change period, human interventions disrupted these linkages. In S1, the relationship shifted from linear to a power function. In S2, elementary functions were unable to capture the complex, non-linear relationship due to intensive human activities.
• Spatially Concurrent HDs (Copula Functions):
  • The Copula framework successfully quantified the probabilistic linkage of concurrent HDs across regions.
  • In the pre-change period, the Frank copula was optimal. When S1 MD magnitude reached 1.16, HD onset occurred, and the S2 HD magnitude fell within a 70% probability interval of [0.58, 3.16] with a most likely value of 0.70.
  • In the post-change period, the Gumbel-Hougaard copula was superior, indicating a shift to upper tail dependence. For example, when S1 SSI-3 magnitude reached 5, the 70% probability interval for S2 SSI-3 magnitude narrowed from [1.89, 10.25] (pre-change) to [2.16, 4.22] (post-change), with most likely values around 4.

Contributions

• Explicitly investigated spatially concurrent hydrological droughts (HDs) across adjacent sub-basins, extending beyond previous single-region analyses.
• Contrasted pre- and post-change periods to reveal how human activities reshape meteorological drought (MD)–HD linkages, demonstrating a shift from elementary to more complex non-linear propagation patterns.
• Provided quantitative insight into cross-regional drought propagation using a Copula-based probabilistic framework.
• Offered practical implications for hydrological drought monitoring and management, particularly in data-scarce or regulated river basins.

Funding

• National Key R&D Program Funded Project (2023YFC3209502, 2023YFC3206005)
• National Natural Science Foundation of China (No. U2340217, 52269003, 52595704, 42577102)
• Basic Research Program of Jiangsu (BK20250013)
• China Postdoctoral Science Foundation (2022M711493)

Citation

@article{He2026Characterizing,
  author = {He, Shaokun and Li, Qianxun and Chen, Kebing and Zhu, Lingling},
  title = {Characterizing spatially concurrent hydrological drought and its response to meteorological drought under the impact of human activities},
  journal = {Journal of Hydrology Regional Studies},
  year = {2026},
  doi = {10.1016/j.ejrh.2026.103129},
  url = {https://doi.org/10.1016/j.ejrh.2026.103129}
}