Amiresmaeili et al. (2026) Evaluation of GRACE satellite data for drought monitoring and groundwater management in a small aquifer in Iran

Identification

• Journal: Acta Geophysica
• Year: 2026
• Date: 2026-02-03
• Authors: Vahidreza Amiresmaeili, Majid Rahimzadegan, S. Morteza Mousavi
• DOI: 10.1007/s11600-026-01797-5

Research Groups

• Department of Water Resources Engineering and Management, Faculty of Civil Engineering, K. N. Toosi University of Technology, Tehran, Iran

Short Summary

This study evaluated GRACE satellite data for drought monitoring and groundwater management in the small, arid Rafsanjan Plain, Iran, finding that the Modified Total Storage Deficit Index (MTSDI) is superior for drought assessment in anthropogenically impacted areas and that direct GRACE Total Water Storage Anomaly (TWSA) data effectively monitors regional groundwater changes without significant improvement from GLDAS component subtraction.

Objective

• To evaluate the applicability of GRACE satellite data (2002-2017) for calculating drought indices in arid and semi-arid regions with limited spatial extent, specifically the Rafsanjan Plain, Iran.
• To assess the performance of GRACE data in monitoring groundwater storage changes in this region.
• To investigate whether subtracting Global Land Data Assimilation System (GLDAS) components from GRACE data significantly improves groundwater storage estimations.

Study Configuration

• Spatial Scale: Rafsanjan Plain, Iran, with a total area of 12,513 square kilometers and an aquifer area of approximately 4,236 square kilometers.
• Temporal Scale: GRACE satellite data from April 2002 to January 2017 (15 years). Groundwater observation data for comparison also aligned to this period.

Methodology and Data

• Models used:
  • Drought Indices: Total Storage Deficit Index (TSDI), Modified Total Storage Deficit Index (MTSDI), Total Water Storage Deficit Index (TWSDI), Standardized Precipitation Index (SPI-12), Z-Score Index (ZSI-12), China-Z Index (CZI-12), Modified China-Z Index (MCZI-12).
  • Global Land Data Assimilation System (GLDAS) Noah model (for soil moisture, snow water equivalent, and plant canopy surface water).
• Data sources:
  • Satellite: Gravity Recovery and Climate Experiment (GRACE) mission monthly average data (from JPL, GFZ, CSR centers).
  • Observation: Groundwater level data from 30 piezometric wells (Kerman Regional Water Company); precipitation data from Anar and Kerman synoptic stations (Kerman Meteorological Organization).
  • Reanalysis: GLDAS Noah data with a spatial resolution of 0.25 degrees.

Main Results

• The Modified Total Storage Deficit Index (MTSDI) outperformed TSDI and TWSDI for drought assessment in the Rafsanjan Plain, as it effectively removed the influence of human activities (e.g., agricultural pumping) from the Total Water Storage Anomaly (TWSA) time series.
• TSDI and TWSDI showed very weak or negative correlations with traditional meteorological drought indices (SPI, ZSI, CZI, MCZI), indicating their limited effectiveness in capturing climate-driven drought conditions affecting groundwater.
• MTSDI exhibited a moderate correlation (approximately 0.3) with precipitation-based meteorological drought indices, suggesting a better representation of hydroclimatic drought variability.
• Subtracting GLDAS-modeled components (soil moisture, snow water equivalent, plant canopy surface water) from GRACE data did not significantly improve GRACE estimations of groundwater changes; correlation values with observed groundwater levels slightly decreased (mean correlation dropped from 0.75 to 0.71).
• Applying time lags (0 to 11 months) between GRACE data and observation well data did not lead to notable improvements in correlation.
• GRACE-derived TWSA showed a strong correlation (0.66 to 0.79) with observed groundwater levels in the 30 observation wells, confirming its robustness as a regional-scale indicator for groundwater monitoring in this arid, groundwater-dominated region.
• The Rafsanjan Plain experienced a persistent decline in regional water resources from 2002 to 2017, with GRACE TWSA indicating a -7.7% decline, GRACE-GLDAS showing -5.7%, and well-based groundwater storage anomalies revealing a significantly steeper decline of -22.1%, highlighting severe groundwater overdraft.

Contributions

• This study addresses a critical gap by evaluating the applicability of GRACE data for drought monitoring and groundwater management in a small, arid/semi-arid aquifer (Rafsanjan Plain), where previous GRACE studies often focused on larger basins.
• It demonstrates the superior performance of the Modified Total Storage Deficit Index (MTSDI) in regions with significant anthropogenic groundwater abstraction, providing a more reliable GRACE-based drought indicator by isolating climate-driven variability from human impacts.
• The research simplifies the methodology for GRACE-based groundwater monitoring in arid regions characterized by dominant groundwater abstraction and minimal surface water, showing that direct GRACE TWSA can be effectively used without systematic correction using GLDAS data.
• It provides quantitative evidence of strong correlations between GRACE-derived TWSA and in-situ groundwater levels in a highly stressed aquifer, reinforcing the value of GRACE data for regional water resource assessment in data-scarce environments.

Funding

Not applicable.

Citation

@article{Amiresmaeili2026Evaluation,
  author = {Amiresmaeili, Vahidreza and Rahimzadegan, Majid and Mousavi, S. Morteza},
  title = {Evaluation of GRACE satellite data for drought monitoring and groundwater management in a small aquifer in Iran},
  journal = {Acta Geophysica},
  year = {2026},
  doi = {10.1007/s11600-026-01797-5},
  url = {https://doi.org/10.1007/s11600-026-01797-5}
}