2 Quantity of Water Resources
2.1 Precipitation
The average annual precipitation in China was 660.8 mm in depth in 2015,which is equivalent to 6,256.94 billion m3 in quantity,2.8% more than normal and 3.7% more than that in 2014.The variation of annual precipitation during 1956—2015 is shown in Figure 1,the regional distribution of the 2015 annual precipitation is shown in Figure 2,and that of the difference between the 2015 annual precipitation and normal is shown in Figure 3.
Figure 1 Variation of annual precipitation in China during 1956—2015
Among the first-class water resources regions(Class I WRRs),the Songhua,Liaohe,Haihe,Yellow,Huaihe and Northwest Rivers(Northern Six Regions for short)had an average annual precipitation of 322.9 mm,which is 1.6% less than normal and 1.9% more than that in 2014;and the Yangtze(including the Taihu Lake Basin),Southeast Rivers,Pearl and Southwest Rivers(Southern Four Regions for short)had an average annual precipitation of 1,260.3 mm,which is 5.0% more than normal and 4.6% more than that in 2014.Among the ten Class I WRRs,the Liaohe,Southwest Rivers,Yellow,Haihe and Huaihe had an annual precipitation less than normal,in which the Liaohe had an annual precipitation 12.2% less than normal,Songhua had a value almost equal to normal,and all the other regions had a value more than normal,in which the Southeast Rivers and Pearl had an annual precipitation 23.8% and 12.7% more than normal,respectively.Compared with 2014,except that the Yellow,Southwest Rivers and Songhua had a decreased annual precipitation,all the regions had an increased annual precipitation to a varying extent,in which the Haihe and Southeast Rivers had an annual precipitation 21.0% and 15.6% more than that in 2014,respectively.Table 1 shows comparison of the 2015 precipitation with the 2014 precipitation and normal by Class I WRR.
Figure 2 Isopleth map of annual precipitation in China,2015(Unit:mm)
Figure 3 Anomaly map of annual precipitation in China,2015(%)
Table 1 Comparison of 2015 precipitation with 2014 precipitation and normal by Class I WRR
Note:The calculation area of the Northwest Rivers accounts for 55.5% of the total area of the Northern Six Regions,and that of the Yangtze accounts for 52.2% of the total area of the Southern Four Regions.
Among the provincial administrative regions(PARs),12 had an annual precipitation more than normal,in which Shanghai,Zhejiang,Jiangxi,Jiangsu and Guangxi had a quantity over 20% more than normal;Hubei,Ningxia and Qinghai had an annual quantity close to normal;and 16 had an quantity less than normal,in which Hainan,Liaoning and Shandong had a quantity over 15% less than normal.See Table 2 and Figure 4 for comparison of the 2015 precipitation with the 2014 precipitation and normal by PAR.
Table 2 Comparison of 2015 precipitation with 2014 precipitation and normal by PAR
Figure 4 Comparison of 2015 precipitation with normal by PAR