The climate in the north area of China will be drier, and combined
with the increased population, the development of industry and agriculture
and the deterioration of the environment, drought may will be the most harmful
natural disaster in our country. If there are no effective measures are taken,
the drought may extents to the Yangtze River in the middle of 21 century
and seriously affects the social sustainable development and
the implementation of the western development strategy.
4 quantitative indexes have been drawn up for the classification of drought disasters:
the affected area rate (affected area/sown area), the crops reduction rate
(the amount of reduction/common amount), the precipitation anomaly in summer (June to September)
and annual drought index (precipitation / crop water requirement).
The 1st index indicates the loss, while the others indicate the severity of the causes of disasters.
Considering the statistics, prevention and research of drought disasters are based on
administrative district unit, thus the grade division of drought disasters in Northeast China
is on the grounds of 4 provinces, Songhua River, Liaohe River basins and the whole region.
Each district has been comprehensive evaluated based on the 4 indexes above year by year.