VEGETATION COVER ANNUAL CHANGES BASED ON MODIS/TERRA NDVI IN THE 
THREE GORGES RESERVOIR AREA 
Sun Xiaoxia 3 ' b ’*, Zhang Jixian 3 , Liu Zhengjun 3 
3 Key Laboratory of Mapping from Space of State Bureau of Surveying and Mapping, Chinese Academy of Surveying 
and Mapping, Beijing, P.R.China -sunxx@casm.ac.cn 
b China University of Mining and Technology, Xuzhou, P.R.China 
Commission VII, ICWG VII/IV 
KEY WORDS: Vegetation, Change, Analysis, Remote Sensing, Multi-temporal, Accuracy 
ABSTRACT: 
Vegetation coverage change is a very important indication of the ecological enviroment change. In this paper, we detected the 
vegetation cover change by retrieving the fraction of the vegetation coverage, using the Normalized Difference Vegetation Index 
(NDVI) data from MODIS/Terra imagery in recent years from 2000 to 2006, the period before and after the Three Gorges Dam 
construction. In addition, the accuracy of vegetation fraction retrieval was assessed by the classification data from SPOT5 images. 
Based on these results, we analyzed the annual vegetation change quantitatively, and it was shown that the vegetation cover took on a 
little increase in the Three Gorges Reservoir Area in recent seven years, and the vegetation cover grades was transforming from low 
coverage to high coverage. 
1. INTRODUCTION 
Along with the construction of the Three Gorges’ dam and 
hydropower station, the eco-environment in the Three Gorges 
Reservoir Area has been given full attention by local 
government and scientific community. The main potential 
environmental problem such as Land use and land cover 
changes (LUCC), water pollution, geological disasters, soil 
erosion, and the subsequent impact on the microclimate and 
biodiversity, have been recognized. In which, LUCC has been 
considered as one of the dominant causes of ecological 
environment changes, and that vegetation cover changes are one 
of the important components of LUCC (Zhang, 2008). In the 
Three Gorges Reservoir Area, the vegetation cover is changing 
year by year. The project constructed, emigration moving and 
factories built made the vegetation cover reducing, and moreover, 
some retrieval policies such as enclosing the hills for natural 
afforestation, and conversion from cropland to forest, brought 
an increase in vegetation cover. Therefore, the researches on 
change detection and change assessment of vegetation, as well 
as subsequent impact on environment are necessary for future 
regional planning and governmental policy-making. Here we 
used NDVI data from MODIS/Terra sensor to retrieve the 
fraction of vegetation coverage, obtaining and analyzing the 
recent vegetation cover changes in the Three Gorges Reservoir 
Area from 2000 to 2006. 
2. STUDY AREA 
Reservoir Area (TGRA) locates at latitude 
28°56'N-31°44'N and longitude 106°16'E -111°28'E, central 
China (Fig.l), lower section of the upper reaches of the Yangtze 
River at the boundary of Sichuan and Hubei with the area of 58 
000 square kilometers and with the population of almost 20 
million (Meng, 2005). The TGRA consists of submerged 
The Three 
portions at 175 meters water level and resettlement area 
involved in 21 counties and cities of Chongqing city and Hubei 
province, which stretches along the Yangtze River fom Jiangjin 
City to Yichang City (Zhang, 2008). The reservoir area is very 
narrow and where the geography is complex. The mountainous 
areas represent 74% of the region only with 4.3% plain area in 
the river valley and 21.7% hilly area. Sloping lands of the 
gradients greater than 5 degree are accounting for 90 percent in 
the whole fields, and the average slope value is more than 25 
degree. The climate of the Three Gorges Reservoir Area is the 
subtropical monsoon climate. The vegetation are abundant and 
various, but self-sown plants are reducing instead of manual 
plants in farming area, because of a long reclaiming history. 
Compared to farming area, the self-sown vegetation are more in 
woodland area, however, the area and types are reducing 
quickly because of the over-felling, as a result, water and soil 
erosion in some area are serious. Moreover, the increasing 
population is destroying the natural plants continuously, and the 
slope croplands are reclaimed severely. 
Figure 1 . Location of study area 
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