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Start Over Author "Si Jianhua" Journal environmental earth sciences
6 results on '"Si Jianhua"'

3. The changes of vegetation cover in Ejina Oasis based on water resources redistribution in Heihe River

Author

Feng Qi, Wang Yaobin, Su Yonghong, Chang Zongqiang, Si Jianhua, and Xi Haiyang

Subjects
Hydrology, Global and Planetary Change, Land use, Soil Science, Geology, Redistribution (cultural anthropology), Vegetation, Pollution, Arid, Vegetation cover, Water resources, Environmental Chemistry, Ecosystem, Heihe river, Earth-Surface Processes, Water Science and Technology
Abstract

The Ejina Oasis (EO), located in arid northwest China, is a typical arid area in the world. The ecosystem in the oasis has become worse since the 1990s. However, it began to improve after the Chinese government took the mandatory measure to redistribute the water in Heihe in 2000. To understand this change, the remote sensing images in 1990, 2000 and 2006 were selected, and exertion related Land Use/Cover Change (LUCC) model was employed. Results showed that: (1) non-vegetation cover was the main body of the vegetation cover in oasis, showing a trend of increase at the beginning and diminution later, while low, medium and high vegetation cover was the other way around; (2) the area of low, medium and high vegetation cover in 2006 was less than that in 1990; the status and trend index P t of oasis vegetation cover was 0.62 in 1990–2000, which means that the oasis ecosystem of Ejina was getting worse and was under an unbalanced status; P t was 0.27 in 2000–2006 indicating that the oasis ecosystem was restored obviously and the whole system tended to be balanced; (3) all of these changes should be attributed to the water resources redistribution in Heihe River, which played a leading role, as well as the measures and relevant policies taken by the local government, which promoted the rapid recovery of the medium and high vegetation.

Published
2011

6. Inland river terminal lake preservation: determining basin scale and the ecological water requirement.

Author

Si, Jianhua, Feng, Qi, Yu, Tengfei, and Zhao, Chunyan

Subjects
LAKE conservation, ARID regions ecology, WATER supply, WATERSHEDS, RUNOFF
Abstract

Inland lakes are a major water resource for arid regions. Determining basin scale is therefore an important indicator of variability for water resources in such regions. The goal of this study was to ascertain the appropriate Juyan Lake basin scale and its minimum ecological water requirement for the lake's continued preservation. This was accomplished in three parts. First, an analysis was carried out on the inflow of the lower reach of Heihe River and any subsequent water surface area change to Juyan Lake. Second, an optimum Juyan Lake basin scale was determined by establishing existing relationships between reservoir capacity and lake area, water level and lake area, and variation in lake area during different times of the year. Third, the ecological water requirement of the lake was determined. Results showed that the decrease in surface runoff and ceased flow of the channel resulted in the drying up of the terminal lake of Heihe River. It was determined that 35.6 km is the most stable Juyan Lake surface area, and 0.55 × 10 m is the minimum replenishment quantity in which to maintain Juyan Lake throughout the year without it drying up. [ABSTRACT FROM AUTHOR]

Published
2015
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