Remote sensing–based assessment of seasonal agricultural drought dynamics using the integration of soil moisture and vegetation health index in Waghimra Zone, Ethiopia

Agricultural drought poses a critical threat to food security in rainfed regions such as Ethiopia. To address the lack of high-resolution, multi-seasonal drought assessments, this study integrates soil moisture and vegetation health indicators to characterize the spatiotemporal dynamics of agricultural drought in the Waghimra Zone, Ethiopia. Using Landsat time-series data (TM, ETM+, OLI, and OLI-2) from 2000 to 2025, we developed an integrated Soil Moisture–Vegetation Health Index (SM–VHI) to assess drought conditions across Spring, Winter, and Autumn, excluding Summer because of persistent cloud cover. Winter was the most consistently vulnerable season, with more than 50% of the study area experiencing agricultural drought stress during most years, whereas Autumn showed the highest drought-free conditions (64.65–68.68%) in 2019, 2020, and 2025. In 2001, 2012, and 2023, severe agricultural drought occurred across all seasons, with 49–54.22% of the study area classified as drought-affected, indicating that agricultural drought recurrence occurs on a decadal timescale (approximately every 10 years). The seasonal relationship between soil moisture and vegetation health showed correlation coefficients (r = 0.49–0.90), indicating a significant positive relationship. The determination coefficients (R² = 0.24–0.81) indicated that 24–81% of the variability in vegetation health was explained by soil moisture conditions. The SM–VHI provides an effective, spatially explicit framework for agricultural drought monitoring, providing valuable information to support season-specific early-warning systems and climate adaptation strategies aimed at strengthening food security.