Mapping Agricultural Drought-Prone Areas in Malang Regency Using MODIS and CHIRPS Data for Mitigation Planning

Agricultural drought is a recurring threat to food production in Malang Regency, yet monitoring at the subdistrict level is still hampered by the scarcity of rain gauges. This study aimed to map the frequency and spatial distribution of agricultural drought, examine its trends over 2001–2025, and assess how cropland vegetation responds to rainfall deficits across the 33 subdistricts of Malang Regency. Vegetation condition was expressed by the Vegetation Condition Index (VCI) derived from 250 m MODIS MOD13Q1 NDVI over cropland, while meteorological drought was expressed by the Standardized Precipitation Index (SPI) at 1, 3, and 6 month scales computed from CHIRPS rainfall. All images were processed in Google Earth Engine and analysed in R using the Mann–Kendall test, Sen’s slope, and Spearman correlation. Agricultural drought tended to decline: the number of drought months decreased by 0.088 months per year and dry-season VCI increased by 0.96 per year, both statistically significant, whereas the annual rainfall trend was not significant. The year 2003 was the driest on record. Agricultural drought frequency ranged from 4.1 to 22.1% among subdistricts and was not related to rainfall, suggesting that local land and water management conditions play a role; the highest frequencies occurred in Kalipare, Donomulyo, Gedangan, and Pujon. Vegetation responded to rainfall deficits within the same month, with weaker responses in subdistricts served by irrigation networks. The interannual correlation between VCI and SPI-3 remained strong after detrending (ρ = 0.833), indicating that VCI is suitable for subdistrict-level drought monitoring and for identifying priority areas for further mitigation planning.