International Geologiical Congress - Oslo 2008

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GTR-01 General contributions to geological remote sensing - Part 1

 

Research on the reasons for Anguli Lake's shrinkage and drying up using satellite remote sensing

 

Yanxiao Qiao, Remote Sensing Centre of Hebei Province (China)
Shengmin Liu, Hebei Geological Society (China)
Youyi Ma, Hebei Provincial Bureau of Geology And Mineral Resources (China)
Yuesheng Hao, Remote Sensing Centre of Hebei Province (China)
fengjun Lu, Remote Sensing Centre of Hebei Province (China)
 

 

Anguli Lake that enjoys the biggest inland lake in north China, located in the northwest of Hebei province, belonging to a part of the Inner Mongolia Plateau, had dried up since the autumn of 2004. The area of Anguli Lake is located in the temperate zoon and enjoys continental monsoon climate. The annual average precipitation is 300-350mm. The character of climate is drought , windy and sandy. After the lake dried up, it is compared to a second Lop Nur Lake by some experts. They said that this is a warning that the Mother Nature gave to man.To sum up, there are only following three reasons for Anguli Lake's shrinkage and drying up. One is because of the successive years of drought and rainless. Second is the exploitation of large quantity of groundwater in order to irrigate crop ,vegetables and trees. Third lies in a hybrid cause that consists of drought, rainless and the exploitation of a large quantity of groundwater. Are they right? Landsat7-TM image data acquired in 1999 was used as a main remote sensing image data in the project. Image processing methods include fusion, false composition and supervised classification.
Through interpretation image carefully, we find a group of arc lines in the remote sensing image, which are not only parallel to each other, but also to the lake east shore. We consider that the area surrounded by the outmost arc line is exactly the lake water area in history. These arc lines that are parallel to the current lake shore are precisely the vestiges of Anguli Lake's shrinkage, which are some troughs made by water waves lapping against the lake band in the stages of the lake water stability. Accordingly, we calculate that the largest acreage of Anguli Lake had ever been about 187 km2 in history. It is 3.6 times the present lake area. From the original shrinkage to the final drying up, the lake went through 8 cycles from one shrinkage to one steady state at least. Satellite remote sensing study shows that Anguli Lake experienced a long-term course from the initial shrinkage to the final drying up in the past. So, all the reasons above mentioned for Anguli Lake's drying up are not correct. What on earth is the main cause for Anguli Lake's drying up? A careful study shows that the global climate change is the main cause .Nowadays, the global temperature keeping on rise is a established fact during nearly one hundred years. In China, the Earth's surface temperature has risen 0.5-0.8° since 1950's. In Hebei Province, the temperature has risen 1.0-2.1° since 1950's. Especially, the temperature of Anguli Lake region even rose 2.1°. Meanwhile, the annual average precipitation dropped by 62.1mm. So, we consider that the shrinkage and drying up of Anguli Lake experienced a long-term course from initial shrinkage to final drying up in the past, and the main reason for Angulu Lake's shrinkage and drying up is the global temperature keeping on rise. As for other reasons, they are only minor effect at most.

 

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