Agricultural drought monitoring in maligavila GN division based on normalized difference moisture index (NDMI) and vegetation health index (VHI)

The agricultural sector is pivotal to the economic development of Sri Lanka, particularly in the dry zone, where extensive agricultural lands are highly susceptible to drought. The "Yala" season, occurring annually, consistently experiences water deficits due to drought conditions. Drought is multifaceted and can be categorized into meteorological, hydrological, agricultural, and socio-economic droughts. Accurately assessing drought impacts requires multiple indices due to their complex nature. This study employs satellite-based Normalized Difference Moisture Index (NDMI) and Vegetation Health Index (VHI) to evaluate agricultural drought in the Maligavila GN division in Monaragala district, Sri Lanka. In 2015, the NDMI values for the region ranged from -0.103 to 0.311, reflecting variations in soil moisture content. By 2023, these values shifted significantly, ranging from -0.45 to 0.292, indicating a notable decrease in soil moisture. Similarly, VHI values, which assess vegetation health by combining the Vegetation Condition Index (VCI) and Temperature Condition Index (TCI), ranged from 12.33 to 91.82 in 2015 and from 11.442 to 86.966 in 2023. The decline in both NDMI and VHI values over this period suggests a marked increase in agricultural drought conditions. The analysis reveals that agricultural drought in Maligavila GN division has intensified from 2015 to 2023. The broader implications of these findings are significant for the agricultural sector in the dry zone of Sri Lanka. The increasing drought conditions necessitate the implementation of sustainable land management practices and efficient water resource management strategies. By enhancing soil moisture retention and supporting vegetation health, these measures can help mitigate the adverse impacts of drought and contribute to the resilience of the agricultural sector in the region.