Indramayu Regency plays a crucial role in Indonesia’s food security as one of the country’s primary rice granaries. Farmers traditionally depend on predictable rainfall during the main planting season (Rendengan) between December and March. However, climate variability associated with events such as El Niño has increasingly disrupted rainfall distribution, making traditional planting calendars less reliable.
The study shows that rainfall volume alone is no longer an adequate indicator of water availability. Even months that receive more than 100 millimeters of rain may still experience meteorological drought if precipitation falls significantly below historical averages. These hidden rainfall deficits can delay planting, increase irrigation costs, and raise the risk of widespread crop failure.
Satellite Data Reveal Hidden Climate Risks
Rather than relying solely on ground-based weather stations, the researchers analyzed satellite-derived rainfall observations using Climate Hazards Group InfraRed Precipitation with Station (CHIRPS) data. The dataset covered January 2014 through December 2024, providing monthly rainfall information across Indramayu Regency.
To identify rainfall anomalies, the research team applied the one-month Standardized Precipitation Index (SPI-1), a widely used climate indicator that compares monthly rainfall against long-term historical patterns. This approach detects meteorological drought based on rainfall probability rather than absolute rainfall totals, allowing hidden drought conditions to be identified even during the rainy season.
The study focused on regional rainfall trends over an eleven-year period and classified drought severity according to internationally recognized SPI categories.
Extreme Drought Occurred During the Rainy Season
One of the study’s most significant findings is that the strongest drought anomaly occurred in December 2023, a month that normally marks the beginning of the wet season.
Although December 2023 recorded 110.97 mm of rainfall, the month produced an SPI value of -2.48, placing it in the Extremely Dry category because rainfall was far below the historical December average.
Another severe anomaly occurred in February 2024, when rainfall reached 222.85 mm, yet the SPI value still dropped to -1.81, indicating Severely Dry conditions.
The five most severe drought events identified during the study period were:
- December 2023: SPI -2.48 (Extremely Dry)
- April 2021: SPI -2.19 (Extremely Dry)
- June 2015: SPI -2.10 (Extremely Dry)
- February 2024: SPI -1.81 (Severely Dry)
- April 2018: SPI -1.78 (Severely Dry)
Remarkably, four of these five extreme drought events occurred during months that still received more than 100 millimeters of rainfall. This finding demonstrates that apparent rainfall abundance does not necessarily guarantee sufficient water for rice cultivation.
Implications for Rice Farming and Food Security
The researchers explain that rainfall shortages during the beginning of the rainy season are particularly damaging because they coincide with the early vegetative stage of rice growth. Farmers depend on adequate rainfall to prepare fields, establish nurseries, and support young rice plants.
When rainfall arrives below historical expectations, planting schedules are delayed, irrigation demand increases, and production costs rise sharply. Farmers may also be forced to pump water from rivers or irrigation canals, increasing fuel expenses and financial pressure.
The study also identified vulnerability during the transition to the second planting season. Rainfall deficits in April can expose newly planted rice to water stress earlier than expected, making successful harvests increasingly dependent on effective reservoir and irrigation management.
Dynamic Planting Calendars Could Reduce Crop Failure
According to the authors, Indonesia's agricultural sector can no longer rely on fixed seasonal calendars because climate patterns have become increasingly unpredictable.
Instead, the researchers recommend replacing static planting schedules with dynamic planting calendars supported by climate probability forecasts such as the Standardized Precipitation Index. They also encourage irrigation managers to prepare water reserves not only for the dry season but also for unexpected rainfall deficits during the wet season.
Future research should integrate rainfall indicators with satellite vegetation measurements such as the Normalized Difference Vegetation Index (NDVI) to better estimate crop damage and agricultural losses across affected regions.
As Marthin Abednego Gultom and colleagues from Universitas Cenderawasih emphasize, the findings demonstrate that meteorological drought is no longer confined to the dry season. Hidden rainfall deficits during the rainy season can have even greater consequences because they disrupt the earliest and most critical stages of rice cultivation, requiring a fundamental shift toward climate-informed agricultural planning.
Author Profiles
Marthin Abednego Gultom is a researcher from the Department of Geological Engineering, Faculty of Engineering, Universitas Cenderawasih, Jayapura, Indonesia. His research focuses on environmental geology, climate analysis, and geospatial applications for natural resource management.
Rafael Buwana is a lecturer and researcher in the Department of Geological Engineering, Faculty of Engineering, Universitas Cenderawasih. His expertise includes geological sciences, environmental assessment, and spatial data analysis.
Chrisostommi Wirayudha Tuhumena is affiliated with the Department of Management, Faculty of Economics and Business, Universitas Cenderawasih. His academic interests include management, regional development, and socio-economic aspects of sustainable development.
Source
Article Title: Characteristics of Rainfall Deficit Anomalies During the Main Rice Planting Season in Indramayu Regency Based on the Standardized Precipitation Index (SPI) 2014–2024
Authors: Marthin Abednego Gultom, Rafael Buwana, Chrisostommi Wirayudha Tuhumena
Journal: Indonesian Journal of Agriculture and Environmental Analytics (IJAEA)
Publication Year: 2026
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