| Water resources are the basis for human survival and development.China faces severe serious water resource problems.The pollution and shortage of water resources deeply hinder the development of the national economy.Using the satellite remote sensing to monitor the annual and interannual changes and its distribution patterns of surface water resources in China are of great significance to the rational planning and utilization of China's water resources.In this study,the MODIS MOD09Q1 product was selected as the data source,and preprocessing operations such as format conversion,splicing,and clipping were performed to obtain an image with a spatial resolution of 250 m,a period of 8 days and 46 views per year.For the problems of cloud layer,cloud shadow and winter ice that often appear when the water surface is extracted,the upper threshold is set to effectively filter these factors.Utilizing team development combined with surface buffer zone boundary analysis to determine the optimal water extraction threshold from the surface of the water,the near-red band and slope mask data of the MOD09Q1 product image is programmed using IDL,and the water surface is automatically calculated to make the water surface and the land the most.Based on the best segmentation threshold,the spatial-temporal variation data set of the surface water surface of the country from 2000 to 2016 was extracted.The minimum water surface extracted by the data set was 0.5 km~2.The accuracy of the surface water surface data extracted from the three national land use/coverage maps in 2000,2005,and 2010 was used to evaluate the accuracy.The average accuracy of this data set was 92.76%.This study has improved the method of automatic water surface extraction and provided a set of key basic data sets and dynamic change analysis results for the continuous evaluation of the distribution of surface water resources throughout China.The main research findings include the following aspects:(1)From the Inter-annual changment of the water surface.The annual changes in surface water surface throughout the country show a strong seasonal pattern.Seasonal changes are slightly different in different areas,but generally water surface reaches the maximum value in autumn.The annual maximum and minimum water levels basically appear in September and February.The interannual variation of surface water area is intense,and is easy to be influenced by climate.(2)From the perspective of the country's largest annual water surface.From 2000 to2016,China's surface water area increased as a whole.In 2016,the area increased by 2185km~2 compared with 2000.The maximum and minimum areas were 977,523.8 km~2 in 2006and 127,808 km~2 in 2013 respectively.(3)From the perspective of the three surface water surface averages of 2000-2005,2006-2010,and 2011-2016.The overall surface water area in the country has increased.From the geographic scale analysis,the areas with the largest and the smallest surface water areas are southwest and south China,accounting for 29.88%and 3.06%,respectively.During this period,the area of surface water in the northwest,southwest and northeast areas increased,and the surface water area decreased in four regions of North China,South China,Central China,and East China.The area of northwestern China increased by a maximum of 2,725.18km~2,and the largest reduction occurred in East China,a total reduction of 1551.94 km~2.From the scale of the provincial administrative districts,Tibet and Ningxia accounted for the largest and smallest surface water area respectively,accounting for 27.68%and 0.04%of the country's surface water area respectively.In Qinghai and Tibet where surface water area increased the most,the increase was 2172.75km~2 and 1632.94km~2.The surface water area continued to increase in Shandong,Hubei,Shanxi and Ningxia provinces,and the surface water area in Shanxi,Hainan,Guangdong and Taiwan continued to increase.Reduction,other provinces increase or decrease alternately. |
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