Variation Of Landscape Pattern Under The Influence Of Madushan Hydropower Station

Yunnan alpine and gorge region is heavy with hydraulic energy, and the increasingly striking energy problem has put the development of water conservancy and hydropower in this region on the agenda. Hydropower stations are usually situated in the vulnerable ecological environment, which to some extent will alter the landscape pattern of this region. What’s worse, these alterations will be likely to trigger some irrevocable changes in river basin ecosystem. Therefore, taking for example the Madushan Hydropower Station in the cascade-12 hydropower stations of Red River in Yunnan Province, this research analyzes the influence of hydropower construction on the regional landscape pattern based on the theory of landscape ecology in combination with 3S Technology, landscape index, transfer matrix of landscape area, and landscape dynamic degree. Then, based on the quantitative and qualitative analysis about landscape pattern, CA-Markov model is used to predict the future changing trend of landscape pattern in the area of Madushan Hydropower Station. Below are the major research results:(1) Analysis on landscape pattern:this research takes woodland, cropland, savanna, and water as the major landscapes types, which account for 90% of the entire landscape area. After the establishment of hydropower station, woodland is the landscape type that reduces largest area, and the decreased area is mainly turned into cropland, savanna, and garden land. Water is the landscape type whose proportion of landscape area changes most significantly. Its area after establishment of hydropower station rises by 67.7%, and the increased area is mainly constituted by woodland, savanna, bench land and cropland. The area of garden land, residential land, transportation land, and industrial land shows a rising trend. In respect of landscape type, water, bench land, and savanna are well improved from the perspectives of fragmentation and dispersion degrees, and their shapes tend to be simple. However, the increase in the fragmentation degree of the woodland and garden land is influenced by various factors:① Natural factors:during 2006 and 2011, Yunnan has undergone severe droughts for three years, which has led to the decline in woodland and garden land;② Artificial factors:the construction of hydropower stations has occupied partial woodlands and garden lands. In terms of landscape level, the fragmentation and dispersion degrees, diversity and uniformity of the whole landscape in the research area are increased, which suggests that the construction of the hydropower stations has not only diversified the landscape types in the research area, but also made the landscape structure more complicated.(2) The scope of the influence that construction of hydropower stations has on landscape type:according to the result of the gradient analysis on buffer zone, the scope of the influence that the construction of hydropower stations has on water, bench land, garden land, and industrial land is situated within 1000 meters of the buffer zone of the trunk streams in Red River. Within 200 meters of buffer zone, the dynamic degree of woodland reaches the largest negative growth value-17.0%. Under the influence of hydropower station building, savanna and residential land are situated within 500 meters of buffer zone. Cropland is remarkably affected by the construction of hydropower station within 1500 meters of buffer zone.(3) Prediction result of CA-Markov model:compared with 2011, the landscape pattern in 2016 will be changed significantly. Five years after the construction of hydropower stations in the research area, the landscape pattern will be basically restored and meanwhile will present a better development trend compared with 2006. Therefore, from a long-term perspective, the building of Madushan Hydropower Station plays a positive role in landscape pattern in the area. The major embodiments are as follows.① During 2011 and 2016, the significantly changed landscape types will be woodland, garden land, savanna, transportation land, and industrial land. Compared with 2011,2016 will see an increase in total woodland area that is basically equal to that before the establishment of hydropower station. However, the savanna area will suffer a decline, mainly changed into woodland. Nevertheless, the higher development level may lead to the decline in the area of industrial land. The area of water, cropland and bench land will present a stable trend.② From the perspective of landscape level, the fragmentation and dispersion degrees of the landscape in the research area will be decreased but superior to those in 2006. The landscape types in the research area will be also diversely and evenly distributed. ③ Landscape’s comprehensive dynamic degree may drop from 6.2% during 2006 and 2011 to the 5.3% during 2011 and 2016, which suggests that the landscape pattern five years after the establishment of hydropower station in the research area will become more stable.