RETRIEVING SURFACE SOIL MOISTURE FROM OPTICAL SATELLITE IMAGERY OVER MEDAN AND SURROUNDING

The Earth’s environmental surface have change in local, regional and also global scale in any environmental parameter. Medan, one of big city or region in Indonesia, has fluctuated tropical climate in hydrological cycle. Soil moisture is a key variable in the hydrologic processes that play an important role in determining the availability of water as a fundamental element in human life. Soil moisture is an important parameter for many processes’ hydrology, biology and biogeochemistry. The aim of this study to integrated soil moisture over land area in Medan and surrounding. One of the existing methods to obtain information about soil moisture is Temperature-dryness Vegetation Index (TVDI). TVDI a drought index that is determined based on the empirical parameters of the relationship between surface temperature (TS) and vegetation index (NDVI). The index is associated with soil moisture and obtained only by the input of satellite remote sensing information. Dataset use Landsat 5 TM during 2005 to 1989, Landsat 7 ETM image for 2011, and Landsat 8 OLI for 2014 - 2016. Vegetation index value calculation using InfraRed band (4 to Landsat 5 TM and Landsat 7 ETM or 5 for Landsat 8 OLI) and Band Shortwave InfraRed (5 for Landsat 5 TM and Landsat 7 ETM or 6 for Landsat 8 OLI). The result will be classified from low to high value TVDI. TVDI maximum value each period of the years showed value above > 0.5 that means from moderate to high moisture. From the linear function of TVDI shows the decreasing soil moistures during those time period that assumes assumed the source of soil moisture decreasing conditions due to the surface runoff that resulting in a change in vegetation area and surface temperatures. Reduction of a soil’s capacity to accept, retain, release and transmit water reduces biomass productivity, whether of crops, pasture species, shrubs or trees.