2.3　Groundwater Resources

Quantity of groundwater resources refers to the annual renewed quantity of groundwater in aquifers, i.e., recharge from infiltration of precipitation and surface water. Quantity of groundwater resources in mountainous and hilly areas is calculated in terms of groundwater discharges, including river base flow, piedmont lateral seepage discharge, evaporation from water table and net consumption via groundwater abstraction, and total quantity of discharges is taken as the quantity of groundwater resources. Quantity of groundwater resources in plain areas is calculated in terms of groundwater recharges, including recharge by direct precipitation infiltration, recharge by surface water infiltration, recharge by piedmont lateral seepage and recharge by well irrigation, and total recharge minus recharge by well irrigation is taken as the quantity of groundwater resources. The quantity of groundwater resources in a water resources or administrative region is calculated by deducting the overlap between mountainous and hilly areas and plain areas in quantity of groundwater resources from the sum for the two types of areas.

Figure 8 Composition of plain groundwater recharge in northern Class I WRRs, 2014

The national calculation area of shallow groundwater resources with a mineralization degree equal to or less than 2 g/L is 8.41 million km2 and the annual quantity of groundwater resources in 2014 was 774.50 billion m3, 4.0% less than normal, in which plain area occupies 1.65 million km2 of calculation area and had 161.65 billion m3 of groundwater resources in 2014; mountainous and hilly area occupies 6.76 million km2 of calculation area and had 640.78 billion m3 of groundwater resources in 2014; and the overlap in the quantity of groundwater resources between the two types of areas in that year was 27.93 billion m3. See Table 5 for the quantity of groundwater resources in the Class I WRRs and Table 6 for that in the PARs in 2014. The calculation area of plain shallow groundwater resources in the Northern Six Regions is 91% of the national total plain area and had 137.03 billion m3 of groundwater recharge in 2014, providing an important source for water supply in northern China. The total groundwater recharges in the plain areas of the northern regions in 2014 were: 27.31 billion m3 in the Songhua; 9.97 billion m3 in the Liaohe; 12.44 billion m3 in the Haihe; 16.12 billion m3 in the Yellow; 28.03 billion m3 in the Huaihe; and 43.16 billion m3 in the Northwest Rivers. Of the total groundwater recharge in the plain areas of the Northern Six Regions, recharge by direct precipitation infiltration accounted for 50.4%, recharge by surface water infiltration 35.8%, recharge by piedmont lateral seepage 8.1%, and recharge by well irrigation 5.7%. Recharge by direct precipitation infiltration is the major source of groundwater resources in the Yellow-Huaihe-Haihe plain and Songhua-Liaohe plain, accounting for about 70% of total recharge; and recharge by surface water infiltration is the major source of groundwater resources in the Northwest Rivers plain, accounting for about 71% of total recharge. See Figure 8 for the composition of groundwater recharge in the plain areas of the Northern Six Regions in 2014.