According to the precipitation data from 1956 to 1979,
the average annual precipitation in this area is 637.7 billion cubic meters,
with an average precipitation depth is 510.8 mm. The differences are existed
in precipitation with the difference among the geographical latitude, inland and coastal.
The distribution characteristics of precipitation is large in southeast
and small in northwest, more precipitation is distributed in mountain than plain;
more precipitation is windward slope than leeward slope in mountain.
Based on regions and characteristics of regional precipitation,
the whole area could be divided into humid zone, subhumid zone and arid zone.