Cruz et al. (2025) Long-term basin trends confirm a record 2022–2024 hydrological drought and water-storage losses in western Amazonia

Identification

• Journal: Journal of Hydrology Regional Studies
• Year: 2025
• Date: 2025-11-20
• Authors: Gustavo De la Cruz, Renato Collado-Tello, Eduardo Chávarri-Velarde, Waldo Lavado‐Casimiro, Jhan Carlo Espinoza
• DOI: 10.1016/j.ejrh.2025.102951

Research Groups

• Doctorado en Ingeniería y Ciencias Ambientales, Universidad Nacional Agraria La Molina, Lima, Peru
• Servicio Nacional de Meteorología e Hidrología (SENAMHI), Lima, Peru
• Doctorado en Recursos Hídricos, Universidad Nacional Agraria La Molina, Lima, Peru
• IRD, CNRS, Grenoble INP, Institut des Géosciences de l’Environnement (IGE, UMR 5001), Université Grenoble Alpes, Grenoble, France
• Instituto de Investigación sobre la Enseñanza de las Matemáticas, Pontificia Universidad Católica del Perú, (PUCP), Lima, Peru

Short Summary

This study quantifies long-term hydrological trends (1981-2024) in Western Amazonia and diagnoses the unprecedented 2022-2024 hydrological drought, revealing significant delays in high-runoff season onset, decreased low-flow discharge, and record-low terrestrial water storage. The findings underscore the region's increasing vulnerability and the urgent need for adaptive water resource management.

Objective

• To quantify long-term trends in annual basin-wide precipitation (1981–2024), mean runoff (1984–2024), and the timing of the high-runoff season (1984–2024) in the Tamshiyacu basin.
• To characterize rainfall patterns during the 2022–2024 drought episode by mapping monthly anomalies.
• To assess the intensity, duration, and hydrological impacts of the 2022–2024 drought using standardized indices and anomalies of runoff, terrestrial water storage, and groundwater storage.

Study Configuration

• Spatial Scale: Western Amazonia, specifically the contributing basin of the Tamshiyacu hydrological station (Peruvian and Ecuadorian Amazon-Andes transition zone), covering approximately 726,400 km².
• Temporal Scale:
  • Long-term trend analysis: 1981–2024 for precipitation, 1984–2024 for runoff and high-runoff season timing.
  • Rainfall anomaly characterization: September 2022 – August 2024 (relative to 1981–2010 baseline).
  • Drought diagnosis (SRI, TWS, GWS): 2022–2024 (TWS and GWS anomalies relative to 2002–2020 baseline).

Methodology and Data

• Models used:
  • Non-parametric Mann–Kendall test and Sen’s slope estimator for trend analysis.
  • Standardized Runoff Index (SRI-6 and SRI-12) calculated using a Gamma probability distribution.
  • Terrestrial water balance for isolating groundwater storage anomalies.
• Data sources:
  • Observed daily discharge records (1984–2024) from the Tamshiyacu station (SENAMHI, Peru).
  • Satellite precipitation estimates: The Climate Hazards Group InfraRed Precipitation with Stations (CHIRPS v2.0) (0.05° spatial resolution, 1981–2024).
  • Terrestrial Water Storage (TWS) anomalies: GRACE (2002–2017) and GRACE-FO (2018–2024) mascon solutions from NASA/JPL.
  • Groundwater Storage (GWS) anomalies: Derived from TWS minus land surface water storage and soil moisture components from the NASA Global Land Data Assimilation System (GLDAS Version 2.2) (0.25° spatial resolution, 2002–2024).

Main Results

• A significant delay in the onset of the high-runoff season was observed at a rate of approximately 12 days per decade (1.28 days per year).
• A significant decrease in low-flow season discharge was detected at a rate of -116.3 m³ s⁻¹ yr⁻¹.
• Annual basin-wide precipitation showed a significant positive trend of 8.3 mm yr⁻¹, primarily driven by an increase during the wet season (5.8 mm yr⁻¹).
• The hydrological year 2022–2023 recorded the shortest high-runoff season duration in the historical record (121 days).
• The 2022–2024 drought was identified as the most prolonged (24 consecutive months for SRI-6) and exceptionally intense event in the past four decades in the Peruvian and Ecuadorian Amazon.
• Standardized Runoff Index (SRI-6) values dropped below -2.5 in 2024, and SRI-12 values fell below -2, marking the lowest levels ever recorded.
• Terrestrial Water Storage (TWS) anomalies reached a record low, falling below -15 cm during the 2023–2024 hydrological year.
• Groundwater Storage (GWS) anomalies also showed a marked decline from late 2022 into 2023–2024.
• River discharge at Tamshiyacu fell below 10,000 m³ s⁻¹ by August 2024, comparable to the 2010 extreme drought.
• Persistent precipitation deficits from September 2022 to August 2024, particularly severe in 2023 and early 2024, were linked to the transition from La Niña to El Niño and anomalously warm tropical North Atlantic sea-surface temperatures.

Contributions

• Establishes critical long-term hydroclimatological trends (1981–2024) in the Tamshiyacu basin, providing essential historical context for recent hydrological events.
• Delivers an integrated diagnosis of the unprecedented 2022–2024 hydrological drought in western Amazonia, detailing its severity, timing, and drivers through a combination of long-term trends and water storage changes.
• Highlights the increasing vulnerability of the Western Amazon to climate change, emphasizing the urgent need for adaptive water resource management strategies.
• Offers generalizable insights for researchers and policymakers, including the potential of hydrological season shifts as early drought indicators and the importance of integrated monitoring systems for proactive water allocation and resilience building.

Funding

Not explicitly mentioned in the provided text.

Citation

@article{Cruz2025Longterm,
  author = {Cruz, Gustavo De la and Collado-Tello, Renato and Chávarri-Velarde, Eduardo and Lavado‐Casimiro, Waldo and Espinoza, Jhan Carlo},
  title = {Long-term basin trends confirm a record 2022–2024 hydrological drought and water-storage losses in western Amazonia},
  journal = {Journal of Hydrology Regional Studies},
  year = {2025},
  doi = {10.1016/j.ejrh.2025.102951},
  url = {https://doi.org/10.1016/j.ejrh.2025.102951}
}