1 Quantity of Water Resources

1.1 Precipitation

In 2017,the average precipitation^[1]of China was 664.8 mm,which was 3.5%more than normal and 8.3%less than that in 2016.The isohyetal map of the annual precipitation in 2017 is shown in Figure 1,the anomaly map of 2017 precipitation^[2]is shown in Figure 2 and the variation of annual precipitation during 1956-2017 is shown in Figure 3.

Among the Class I water resources regions (WRRs),the six regions of Northwest Rivers,Yellow,Pearl and etc.had an annual precipitation more than normal,in which the Northwest Rivers had an annual precipitation 13.7%more than normal;and the other four regions all had an annual precipitation less than normal,in which the Liaohe and Songhua had an annual precipitation 15.6%and 10.6%less than normal,respectively.Compared with 2016,except that the Southwest Rivers and Yellow had an annual precipitation 3.5%and 1.3%more,respectively,all the other regions had a less annual precipitation to a varying extent,in which the Southeast Rivers and Liaohe had an annual precipitation 31.2%and 23.7%less,respectively.Table 1 shows the 2017 precipitation and comparison with 2016 and normal by Class I WRRs.

Among the provincial administrative regions (PARs),18 had an annual precipitation more than normal,in which Xinjiang and Shaanxi had a quantity over 20%more than normal;Guizhou had a quantity close to normal;and 12 had a quantity less than normal,in which Inner Mongolia and Liaoning had a quantity 26.2%and 19.8%less than normal,respectively.See Table 2 for the 2017 precipitation and comparison with 2016 and normal by PARs.

Figure 1 Isohyetal map of annual precipitation in China in 2017(Unit:mm)

Figure 2 Anomaly map of annual precipitation in China in 2017(%)

Figure 3 Variation of annual precipitation in China during 1956-2017

Table 1 The 2017 precipitation and comparison with 2016 and normal by Class I WRRs

Notes:1.The Northern Six Regions are the Songhua,Liaohe,Haihe,Yellow,Huaihe and Northwest Rivers.

2.The Southern Four Regions are the Yangtze (including the Taihu Lake),Southeast Rivers,Pearl and Southwest Rivers.

3.The calculation area of the Northwest Rivers accounts for 55.5%of that of the Northern Six Regions,and the calculation area of the Yangtze accounts for 52.2%of that of the Southern Four Regions.

Table 2 The 2017 precipitation and comparison with 2016 and normal by PARs