Sustainable Groundwater Management Act.

Abstract

Drought has been called a creeping disaster because of the way itdevelops slowly. It can be defined according to meteorological,hydrological and agriculture criteria. Agricultural drought occurs whenthe rainfall and soil moisture are inadequate to meet the waterrequirements of crops. It is typically evident after meteorologicaldrought but before a hydrological drought. In 2005, several news hasreported severity of drought in Thailand, especially in north easternpart; however, there is still no well developed early warning system fordrought in Indo-China areas. It is therefore necessary to develop anapproach to identify agricultural drought area for early drought warningsystem. The aim of this study is to detect the agricultural drought areaand intensity in paddy fields. Burirum Province affected by droughtrecently is selected as study area. Firstly, temporal NDVIs (NormalizedDifference Vegetation Index) in paddy fields are calculated from MOD09product. Then two approaches are adopted to process temporal NDVIsnamely Local Maximum fitting (LMF) filtering and scale-space filteringrespectively. LMF filtering can extract the similar trend of thetemporal NDVIs through years, so it is used to create robust NDVI; onthe other hand, scale space filtering can well illustrate the change ofNDVI value in each year, such as drops affected by drought, so it isadopted to create sensitive NDVI. Finally, NDVI difference betweenrobust and sensitive NDVI is calculated and the drought risk map instudy area is created based on the various ranges of derived NDVIdifference. The final results show that this NDVI approach is reasonableand useful to detect the agriculture drought areas and intensity onagriculture according to field survey result. In the future,agricultural drought will be estimated in terms of water budgetcombining RS and meteorological data and compared to NDVI-based approachfor developing early drought warning system.