DETECTING CHANGES IN IRRIGATED AREA USING MULTI-TEMPORAL MODIS AND LAND SURFACE MODEL SURFACE TEMPERATURE WITHIN AMU DARYA DELTA

抄録

 The Amu Darya delta is an irrigation intensive region located in an arid drought-prone part of the Aral Sea basin. Due to irrigation which is characterized by high water application rates, the groundwater level is high and has resulted in secondary salinization. This coupled with the frequent droughts causes the irrigation area to constantly change for farmers to adapt to cropping environmental problems and the changing annual climate. However, obtaining an accurate report of the actual distribution of the irrigated area has proven to be difficult even to the local government and local agricultural institutes. This study aims to assess the potential of using Land Surface Temperature (LST) from MODIS and a Land Surface Model (LSM) to detect annual changes in irrigated area. 3 indices were developed using LST by MODIS and LSM based on the concept of heat capacity difference between water and soil. The LSM provides LST for ideal conditions while MODIS provides the actual LST. A combination of the two enables the elimination of external influence on LST such as rainfall and geological variations which may impact on the LST. A distributed map of all the 3 indices shows the potential of LST in detecting drought. The irrigation fraction during a drought year was observed to be lower as compared to that of a normal year. This was true especially further away from the water source due to water scarcity. In addition, a comparison of the sum of all the meshes in the study area for each of the 3 indices with the volume of water released from the Tuyamuyun reservoir shows a similar trend. Tuyamuyun is indicative of water availability in this drought-prone region, therefore, the indices developed can be used to indicate irrigation activity here.