Monitoring the changes of wetlands in the Source Region of Three Rivers with remote sensing data from 1976 to 2013

During the balancing process of the global ecology, the wetland plays an important role, which refers to various marsh and wet area locating on the land, water, still water, estuarine and marine systems. The Source Region of Three Rivers (SRTR), as the birthplace of Yangtze River, the Yellow River and Lancang River, is an important resource of wetlands in China and Asian, which also forms ecological security barrier for China's Qinghai-Tibet plateau. Here the wetlands information was extracted based TM data from 1976 to 2013. The results show that in 2013 the total area of wetlands, including the marsh, lake, river and reservoirs and pond, is 1.47 million hectares, nearly 5% of the whole SRTR. And the area of lake wetland is half of that of the total wetlands, 2.04 times than marsh wetland. From 1976 to 2013, the wetlands in SRTR have experienced a relatively large magnitude and speed of the variance. From the special perspective, the wetlands in the north and south of Yangtze River Basin vary greatly. The substantial reduction of marsh wetland impacts on the whole trend of the wetlands. And the lake wetland changes steady with a small addition, which lessens the magnitude and speed of the variance of the total wetlands area. In 1995 and 2000, with the smallest wetlands areas, the area of marsh wetland is obviously smaller than that of Lake Wetland. The wetlands in Yangtze River basin had been reducing obviously since 2004, while the Yellow River basin increasing. When it comes to the 18 national nature reserves within SRTR, the wetlands' area has a downward trend as the whole region, with significant fluctuation and relatively larger amplitude, especially the marsh wetland here reduces obviously. The change of wetlands' area is one of important indicators for ecological environment. The monitoring results can provide meaningful help and reference for government's decision-making and other researches.