*4.2. Ground Composition*

Using the above methods, this experiment carries on the ground pixel classification to Daihai basin and Huangqihai basin. In order to be more suitable for the study of the causes of lake water changes, the surface categories are divided into six categories. Specific classified data are shown in Tables 4 and 5.


**Table 4.** Statistics of ground classification in Daihai basin.

**Table 5.** Statistics of ground classification in Huangqihai basin.


The area of the construction increased in Daihai basin year by year. Before 2010, the area was stable relatively and expanded 10-fold from 2010 to 2018 (Figure 8). Distribution of the construction are mainly located at Liangcheng county in southwest of the lake, which began to scatter around the lake and the county after 2010. The farmland area was stable about 150 km<sup>2</sup> until 2010, but the area of 1998 showed a three times increase compared to 1993. Because the local governmen<sup>t</sup> adopted the project of the expansion of planting area in order to increase economic income. The woodland area has been stable relatively between 50 km<sup>2</sup> and 150 km<sup>2</sup> except in 1998. The local government's excessive afforestation plan gave rise to the burst increase of the water consumption in the basin. Regrettably, the growth resulted in excessive water consumption in the region, which cannot sustain the growth of these trees. This is the reason why trees withered in a large area in 2001. The nudation area, accounting for more than 85% of the whole basin, includes bare mountains and arable land without growing crops, which is enough to show that the soil and water conservation capacity of the land is low. In addition to the main Daihai Lake, the water area also includes reservoirs, dams, and some water in the river, which shows a downward trend. Saline–alkali area are more volatile, mainly around the lake and part of the dry beach, which is related to direct human production and vegetation cover at that time.

**Figure 8.** Ground classification of Daihai basin.

Because there are three larger cities in the Huangqihai basin and the economy is more developed than Daihai basin (Figure 9). Thus, the construction area is much larger than that in the Daihai basin. Similarly, the building area also had a huge increase in the Huangqihai basin after 2010. Farmland area fluctuated before 2010. In 1998, there was still a burst of growth, unlike Daihai basin, which lasted until 2001, but the area did not drop sharply until 2006. Next, there has been a steady upward trend. Woodland area has remained at a low level relatively except in 1998, 2001, and 2018. Great fluctuations are evident in excessive human intervention. Nudation reached previous level again in 2006 after a decline in 1999. The water area of the basin has been declining because of the gradual drying up of the Huangqihai Lake. It rebounded in 2014, but fell again in 2018. Saline–alkali land is mainly saline–alkali land formed by the residual salt of bare land after the removal of lake. With the change of lake water area and artificial intervention, the area of saline–alkali land is also changing.

**Figure 9.** Ground classification of Huangqihai basin.
