RECENT DROUGHT IN NE THAILAND: REGIONAL VEGETATION DYNAMICS AND NDVI-RAINFALL RELATIONSHIPS

摘要

Northeast Thailand is the driest region in Thailand with a severe drought problem persisting for more than a decade. The impact of the drought on economy, environment and social well being is widely recognized and reported upon. Despite the importance of monitoring drought, most of previous studies have focused on drought risk and database creation. Therefore, to improve knowledge on vegetation response to precipitation at regional scale for drought monitoring, the objectives of this study were to determine the relationships between satellite-derived NDVI and rainfall over NE Thailand region, and to investigate the overall vegetation dynamics and inter-annual responses. Seven years (2000-06) of MODIS 16-day composite NDVI at 250m resolution and seven years (2000-06) of precipitation data from over 300 stations were used in this study. Spatial rainfall and NDVI anomalies as well as time lag relationships between rainfall and NDVI were analyzed. Results showed downward trends in 7-year NDVI temporal profiles with negative anomalies in rice, crops, orchards, and deciduous forest. This suggests that the impact of drought on vegetation can be seen in satellite observations. We found strong relationships between rainfall and one-month lag NDVI over the region. More detailed studies on the seasonal dynamics and rainfall relationships for major land cover types i.e. rice, crops, and forests are needed to improve drought monitoring and impact assessments.