2 | MATERIAL AND METHODS
Figure 1a shows the distribution of land wind power projects in 2019, indicating that a large number of projects are constructing in China, with 313 projects nationwide. It is distributed throughout the country, mainly in central and eastern China. As shown in Figure 1b, 4 typical clean energy projects from northwest to north China are selected as study cases. The study area is located in the eastern longitude 105 ° 09 ’-116 ° 16 ’ and northern latitude 36 ° 06 ’-38 ° 31 ’. The photovoltaic power project is located in Zhongning County, Ningxia Province, which is a type II region (Shen, 2014) with abundant solar energy in China. It is a typical example with the most abundant solar energy resources, low rainfall, and low vegetation cover in the northwest ecological embrittlement region of China. Its annual sunshine hours are 3000 ~ 3200 hours and the radiation amount is 586 ~ 670 × 104 kJ / cm2·a. Three wind farms are located in the Haiyuan County, Ningxia Province, Yu County, Shanxi Province, and Gucheng County, Hebei Province, involving the loess hilly-gully region in western China, the mountainous region in central China and the plains region in eastern China. Three wind farms are built on the loess hilltop, the top of the earth and rock mountain, and the open plain respectively, which almost react all kinds of typical situations to be faced in the construction of land wind farms. Due to technical reasons, some of the wind farms must be built on the top of the mountain or the hill to capture maximum wind energy resources, and therefore roads and land leveling must be completed before the construction of wind farms. These activities will cause interference on the surrounding areas widely, serious environmental problems will appear if the soil and water conservation measures have not been taken. Other wind farms are built in the open plains and these plains are fertile farmlands, so the construction of wind farms will cause relatively big disturbance to the farmland. From 2015 to 2019, we found some soil erosion and related environmental problems in the supervision process of a large number of principal parts of the clean energy projects, so we selected the above several representative construction projects for in-depth analysis.