Geographical environment of Qingjian county

Qingjian belongs to the hilly and gully region of the Loess Plateau. Qingjian County has a small area of Sichuan tableland and remnant tableland, most of which are ravines in Mao Liang. The terrain is high in the northwest (elevation 900 ~ 1200m) and low in the southeast (elevation 570 ~ 900m). Bounded by the Wuding River, it can be divided into two parts: east and west.

The eastern region, bordering the Yellow River in the east, is a canyon and hill with obvious geographical significance. The east is closer to the Yellow River than the west to the Wuding River, and the erosion benchmark is low. The relative cutting depth of the river channel is150 ~ 200m. The valley is narrow with a slope of 35 ~ 75. Serious soil erosion.

The loess layer in the western region is thick, and the relative cutting depth is100 ~ 200 m. There are many headlands, short headlands, few headlands, developed gullies and broken ground. The flowing water and gravity erosion are serious, the middle and lower reaches of the valley cut into bedrock, and there are often first-class alluvial platforms and diluvial platforms at the bottom of the valley. Xiuyan River and Wuding River (above Alex Gao Village) are alluvial rivers with flat terrain. Qingjian county belongs to the warm temperate continental monsoon semi-humid climate zone. It is characterized by four distinct seasons. In spring, the heating mass gradually strengthens and moves northward, resulting in higher temperature and more precipitation. The daily temperature difference is large, which is prone to cold wave, frost and strong wind. In summer, affected by subtropical high, rainfall is concentrated, mostly thunderstorms, accompanied by strong winds. Rainfall distribution is extremely uneven. Continuous rainy weather often occurs in early autumn. Winter is controlled and invaded by strong Siberian cold air, with cold and dry climate and little precipitation.

The annual average temperature in Qingjian County is 9.6℃65438+ 10, the monthly average temperature is -6.8℃, the July average temperature is 23.8℃, the annual average maximum temperature is 16.5℃, the annual extreme high temperature is 38. 1℃, the annual average minimum temperature is 3.7℃, and the annual extreme low temperature is-22.

The average annual precipitation in Qingjian County is 505 mm, the maximum precipitation is 735.3 mm (1964), and the minimum precipitation is 254.7 mm. The rainfall is mainly concentrated in June-August, accounting for about 80% of the annual precipitation. The rivers in Qingjian County belong to the Yellow River Basin. The Yellow River is a first-class river, Wuding River is a third-class river, Xiuyan River is a fourth-class river, and there are 295 rivers below the fourth level, with a total length of 662 kilometers. The river density is 0.3km/km2, and the annual runoff is 30.88 billion cubic meters, including 90 million cubic meters.

The largest river in Qingjian County is the Yellow River, which runs from Shang Ping Village in Shipan Township to Hejiapan Village in Shuangmiao River Township, and flows through Shipan, Jiejiagou, Alex Gao Village, Yujiahe and Shuangmiao River. The domestic flow is 57 kilometers, the basin area is 407.8 square kilometers, the average flow is 933.32 cubic meters per second, and the annual total flow is 29.43 billion cubic meters. The main tributary is the Wuding River, with a domestic flow of 69.9 kilometers, which flows into the Yellow River in Hekou Village, Alex Gao; Xiuyan River, with a domestic flow of 28.7 kilometers.