Geographical environment of Dehua county

The county has a high terrain and complex terrain. The landform is dominated by low mountains. With Dai Yun as the center, rivers are distributed in veins, belonging to Minjiang River system and Jinjiang River system. The mountains in the territory are continuous, mostly northeast-southwest, the valleys are cut sharply, the canyons are well developed, and there are obvious mountain views. In the meantime, there are occasional mountain basins and valley terraces scattered among them. Generally, the terrain is slightly inclined in all directions from the middle, layered and stepped down. Daiyun Mountain, the second peak in Fujian Province, is located in the middle, with an altitude of 1856 meters. The lowest point is only 2 17 meters.

The central part of Dehua County is towering, gradually descending in steps around, and the southeast is lower than the northwest. More than 75% of the villages in the county are 600 ~ 900 meters above sea level. Among them, the mountains with an altitude of 800- 1856 meters account for 39.24% of the total land area, about 13 12900 mu, mainly distributed in Chishui, Shang Yong, Guiyang, Gekeng, Tangtou, Daming, Leifeng, Cheng Nan and other towns; The mountainous area with an altitude of 500-800 meters accounts for 46.43% of the total land area, about 1553400 mu; Mountain hills, basins and valley terraces with an altitude of 2 17-500m only account for 14.3% of the total area, mainly distributed in Leifeng, Xunzhong, Sanban and other towns. The rivers in the territory are distributed around Daiyun Mountain in the form of veins, belonging to Minjiang River system and Jinjiang River system. The total length of streams in the county is 495.06 kilometers (the width of streams is more than10m), the density of river network is 0.222km/km2, the annual runoff depth is1000-1300mm, and the total runoff is 2.295 billion cubic meters.

There are 12 rainwater catchments with an area of 50 square kilometers and a length exceeding 10 kilometers, such as Chanxi, Yongxi, Dazhangxi and Xiaoyouxi. Among them, Chanxi and Yongxi have the largest rainwater collection area, the longest river and the largest flow. Rivers in the urban area include Zen Creek and its tributaries Dingxi and Yingxi, which pass through the central city.

Xu Xi: Located in the upper reaches of Dazhangxi, with a total length of10/km, it is the longest river in China. Originating from the southern slope of Daiyun Mountain, the surge mouth from the southeast of the county seat to Huban Village in Shuikou Township joins another major river in the northern part of the county seat, the surge creek, and flows into the Minjiang River through Yongtai and Minhou. The drainage area is 958 square kilometers, the average river ratio is reduced to 6.5‰, and the annual average runoff is 1, 65.438+0.72 billion cubic meters. It is the main water source of Dehua County.

Dingxi: Originated under the snowy mountain in Gede Township, it flows into Xu Xi through Fuyang, Ji You, Yingshan, Ding Qian and Dingxi Village, with a drainage area of 35 square kilometers. The river length is 13.4km, and the average riverbed gradient is 3 1.88%.

Yingxi: Originating at the foot of Gezai Jinji Mountain in Xunzhong Town, it flows through Fairyland, Han Long and Xunzhong Village and flows into Weixi, with a drainage area of 17 square kilometers, a river length of 8.6 kilometers and an average riverbed gradient of 44. 16‰.