Drought and Vegetation Monitoring Using Geographic Information System and Remote Sensing in Rajasthan, India
Rainfall of Rajasthan is variable, seasonal, and unevenly distributed resultingfrequent occurrence of droughts, aridity and degradation of vegetation growth. Frequentoccurrences of droughts in Rajasthan have resulted in significant economical losses,ecological degradation and environmental deterioration. The objectives of the study are toassess potential of long-term time series of vegetation index from Advanced Very HighResolution Radiometer (AVHRR) as descriptor of drought, to study the spatial andtemporal pattern of drought and to analyze vegetation trends using long-tem NDVI fromAVHRR for drought and desertification monitoring. The NOAA-AVHRR 15 dayscomposites of GIMMS NDVI for 28 years (from1983), monthly rainfall data for the same28-years period over 102 rain gage stations and the crop statistics were used in this study.To monitor the drought and vegetation greenness variability annual, seasonal and monthlyNDVI and its mean, standard deviation, and NDVI Anomaly Index (NAI), integral NDVI(iNDVI) and rainfall ratio were computed in pixel level. To study the spatial and temporalpattern of meteorological drought condition, standardized precipitation index (SPI) werecomputed at different time scale for all 102 rain gauge stations and then SPI results wereinterpolated. The spatial pattern SPI during drought years are having higher negativeanomaly from July to September in greater part of Rajasthan. In 2000 drought, an extremevalue of SPI reaches up to -3.69 in September and –2.84 in August, which exhibits theseverity of drought condition. The trend and linear association between NAI and SPIshowed that there is a significantly strong high positive correlation in October in all agroecologicalzones in Rajasthan. The correlation between iNDVI (biomass) and rainfallreveal that, the relationship is relatively strong (>0.5) in the hyper arid and arid districts(i.e Jaisalmer, Bikaner, Churu), The trends of integral NDVI/RF ratio results suggest thatabout 35 % of study area has experienced decreasing trends of vegetation growth, ongoingdegradation, and desertification process.
Key words: AVHRR, NDVI, Vegetation, NAI, Drought, SPI
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