Spatial-temporal variations of surface water area during 1986–2018 in Qinghai Province, northwestern China based on Google Earth Engine

Figures & data

Figure 1. The geographical situation of Qinghai Province.

Figure 2. Six basin zones in Qinghai Province, including the Hexi, Qaidam, Yellow, Yangtze, and Inner basin.

Figure 3. The distribution of the sampling points.

Table 1. The confusion matrix and accuracy assessment result for the extracted surface water map of Qinghai Province in 2018 based on the Google Earth Pro high-resolution image.

Google Earth Pro high-resolution image
Surface water data (2018)	Water	Not Water	Sum of Classified Pixels	User’s Accuracy
Water	198	8	206	96.12%
Not Water	52	492	544	90.44%
Sum of reference pixels	250	500		OA=92.00%
Producer’s accuracy	79.20%	98.40%		Kappa=0.81

Figure 4. Surface water maps of 1986 (a) and 2018 (b).

Figure 5. Surface water change from 1986 to 2018 in Qinghai Province. (a) Spatial distribution of surface water change; (b) the inter-annual variations of surface water area; and (c) the Mk test result.

Figure 6. The inter-annual variations of climate factors from 1986 to 2018 in Qinghai Province. (a) Air temperature (T). (b) Precipitation (P). (c) Potential evapotranspiration (ET₀).

Table 2. The correlation between surface water and climate factors in Qinghai Province and 3 river basins.

	T	P	ET0
Qinghai Province	0.51**	.46**	0.01
Qaidam	0.266	.362*	−0.137
Yangtze	0.541**	.387*	−0.131
Yellow	0.518**	.481**	−0.013

Note: * and ** indicate that the correlations passed the significance test at the 0.05 and 0.01 significant level, respectively.

Figure 7. A comparison among the surface water exacted in this study, the JRC yearly history data, and remote sensing images of four different type of water bodies. (a1–a3) Typical lake. (b1–b3) Lake groups. (c1–c3) River. (d1–d3) Artificial water bodies.

Data availability statement

The yearly surface water in Qinghai Province from 1986 to 2018 can be downloaded from https://doi.org/10.5281/zenodo.7532934.