For the importance of water security, the area of extremely
important is 67,987.98hm2, accounting for 21% of the total area
(see Table 2). These areas are extremely valuable for the
maintenance of local water security, including water resource
conservation and flood regulation and storage. Fig. 5(a) shows that
the key spaces maintaining water security mainly consist of
woodlands and regional river systems, which located in the
northern and southern mountains in the study area. There are good
quality and significant functions of water conservation for the
woodlands in these areas, and the lake-river system in these areas
plays a vital role in flood control.