Agricultural drought is alarmed by meteorological drought characterized by lower year-to-year rainfall. Under long period and continuous water deficits, plants may demonstrate stress symptoms and wilt or die. Furthermore, agricultural drought leads to crop failures and threaten the food security of an area. Progo Hulu sub-watershed is a major agricultural area in Temanggung Regency. Spatial-temporal pattern-based information about agricultural drought can be a basis for decision making in drought mitigation. This study aims to analyze spatial and temporal distribution patterns of drought, analyze the physical characteristics of land and their influence on drought pattern, and establish a prediction model of drought distribution patterns based on four physical characteristics of the land. Landsat 8 imagery is used to determine the spatial and temporal patterns of agricultural drought in Upper Progo watershed using an improved Temperature vegetation Dryness Index (iTVDI). Slope, land use, landform, and soil texture are the physical characteristics of land as the variables to determine the most influential factor of drought pattern. They are analyzed using multiple regression analysis techniques. Pixel samples are obtained through purposive sampling method based on land units. The results reveal that the spatial-temporal distribution of agricultural drought occurs rapidly on the slopes and foothills of Sumbing and Sindoro. These areas have the highest average value of the iTVDI index. Agricultural drought extends gradually in line with the number of days without rainfall. Landform is a physical characteristic that most influences the distribution of agricultural drought. The established model by utilizing four variables of physical characteristics generates an average value which almost similar to the iTVDI value produced by remote sensing data. The model can be useful to estimate drought distribution based on the number of days without rainfall.
Upper Progo watershed is one of the important agricultural areas in Temanggung Regency, Central Java. This research used the data obtained from Landsat 8 imagery to analyze the agricultural drought risk in the watershed. The hazard was analyzed using multi-temporal data every 16 days (to the Landsat 8’s temporal resolution) during the drought; from May to September 2015 combining the Landsat 8 imagery and the land’s physical condition. An agricultural drought hazard map was then created by summing the hazard class score in every recording time with overlay method. The crop’s vulnerability analyzed using NDVI difference, which indicates the crop’s ability to survive in dry conditions. The crop’s vulnerability was also analyzed every 16 days. A vulnerability map was then created by summing the vulnerability class of every recording time. The assessment of the drought risk was done by multiplying the hazard and the vulnerability scores. The result shows the high and very high classes of agricultural drought risk were located on the west research area which had a high class of hazard and vulnerability. Meanwhile, the moderate, low, and very low classes of agricultural risk were distributed evenly in the center and east area.
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