Colloquium

Discovering trends in drought on the island of Savu, Indonesia - using time series of weather data and vegetation indices

Organisator Laboratory of Geo-information Science and Remote Sensing
Datum

vr 4 september 2015 10:00 tot 10:30

Locatie Lumen, building number 100
Droevendaalsesteeg 3a
100
6708 PB Wageningen
+31 317 481 700
Zaal/kamer 2

By Peter Hooiveld (the Netherlands)

Abstract
Indonesia suffers from a lack of water, due to a growing population, industrial, and agricultural sector. On the island of Savu in southern Indonesia increasing lack of water has become a concrete problem. To examine the meteorological and hydrological causes and the consequences of increasing drought on vegetation indices, this thesis research two component of drought: Hydrological drought and meteorological drought. Analysis are done with Climate Hazards Group InfraRed Precipitation (CHIRPS) precipitation data and GIMMS, MODIS and Landsat Normalized Difference Vegetation Index (NDVI) time series data. For analysis of the precipitation data the Standardized Precipitation Index (SPI) is used. To analyse the NDVI data a tool called Breaks For Additive Seasonal and Trend (BFAST) is used. The research is divided in three research scales: global, regional and local. On global and regional scale precipitation data and NDVI time series data are used to detect trends in drought. On local scale the effect of water basins, caused by dams, on surrounding vegetation NDVI values has been examined.
Precipitation analysis, only possible to analyse on global scale, showed no increasing drought trend. A correlation has been found between precipitation and the El Niño of 36%. On global scale vegetation GIMMS NDVI analysis also showed no indications for increasing drought trends. On regional scale the general vegetation MODIS NDVI analysis showed no indications for an increasing drought trend. In contrast to the results of the general vegetation MODIS NDVI analysis, results from vegetation MODIS NDVI time series classification showed on local scale indications for increasing drought. However, this increasing drought has been detected for less than 20% of the island. On local scale only one dam has been examined, the results give clear indications for an increasing vegetation growth in the irrigated areas.
The results showed that no increasing drought is caused by a lack of precipitation and no increasing drought could be detected in the vegetation NDVI time series on global and regional scale. Irrigation from water reservoirs have a positive impact on the vegetation NDVI value. For further examination socio economic and agricultural drought could be researched. The influence of irrigation from dams on vegetation can be examined more detailed by using other satellite data sources. The influence of the El Niño effect on Savu should be examined more extensively.

Keywords: Savu; hydrological drought; meteorological drought; El Niño; MEI; CHIRPS; SPI; GIMMS; MODIS; Landsat; NDVI; BFAST; BFAST classification.