Natural disasters in Heihe river basin

Drought is the main obstacle to the economic and social development in this area and the main reason for the extremely fragile ecological environment. Hexi Corridor, located on the north side of Qinghai-Tibet Plateau, is controlled by the descending airflow on the edge of large terrain and the northwest airflow on the east coast of Asia, and it is one of the driest areas in the same latitude in the world. Heihe river basin is located at the intersection of temperate climate zone and warm temperate arid desert climate zone, with annual precipitation of 200 mm- 100 mm in the middle reaches and 0/00 mm in the lower reaches.

Frost is one of the main agrometeorological disasters that endanger the growth of crops and natural pastures in a large area. The lowest temperature in frost can reach -2.0℃ ~-6.2℃, which makes the affected area of corn, wheat and cash crops reach more than 80%, resulting in a large area of agricultural crop failure and a decline in natural pasture. From the frequency of frost occurrence, the probability of frost occurrence in mountainous areas is the highest in the middle and late May, reaching 29% and 3 1.9% respectively, followed by early June, reaching 21.7%; In the plain area, late April and early May are the high incidence periods, and the occurrence probability reaches 29. 1% and 20.8%, and frost hardly occurs in June.

As a common natural disaster in arid areas, dry hot wind is also a common meteorological disaster phenomenon in Heihe River Basin. It is characterized by low wind speed, high temperature and abnormal dryness, which can quickly evaporate the water in crops and soil, resulting in a large amount of water loss of crops and reduced production. Dry-hot wind is more harmful to the vast plains below 1800 meters above sea level, with an average of more than 5.5 days a year, while dry-hot wind is less harmful to the upper edge of alluvial fans and foothills at 1800-2000 meters above sea level, with an average of more than 3.0 days a year.

Strong wind means that the instantaneous speed is greater than 17m/s, which is equivalent to a wind of magnitude 8 or above. Due to the influence of anticyclone in Mongolia-Siberia Plateau, gale is a common weather phenomenon in arid areas of China, one of the common disasters that endanger the normal growth of crops, forests and grasses, and also the main driving force of regional desert passages and sandstorms. Gale weather occurs in all parts of Heihe River Basin, generally more in plain areas than in mountainous areas, and generally shows a decreasing trend from northwest to southeast. The average number of windy days in the middle reaches is 20-30 days, and that in the lower reaches is 40-50 days. Sandstorm is the main form of sandstorm hazard, which is different from sand blowing or floating dust weather. It can erode the topsoil of soil and bury farmland, but it can drive away sand dunes, destroy farms, bury fields and destroy forests, often causing damage to channels, cottages and railways, and even causing human and animal casualties. This is a devastating natural disaster unique to arid areas.

Sandstorms are very harmful. Take1993 "5.5" sandstorm as an example. Eastern Xinjiang, Hexi Corridor in Gansu, most of Ningxia, western Mongolia and other places were seriously affected, with 5.6 million mu of crops affected, 85 people were killed and 264 people were injured,/kloc-0.2 million livestock were killed or injured, and some road and railway transportation and power supply lines were interrupted, resulting in economic losses of 5.5%. Hexi Corridor and the southwest edge of Tengger Desert are one of the high-frequency areas where sandstorms occur in northwest arid areas, and they are also the hardest hit areas. In most areas, the number of sandstorm days exceeds 13, and as high as 20 days in Jinta and Ejina Banner.

The earliest ice flow time in the upper reaches of Heihe River is165438+1the first ten days of October, and1the river channel is frozen from the first ten days of October to the end of February, and it begins to thaw in the middle and late March. The maximum shore ice thickness is 1. 14m, and the maximum river ice thickness is 0.88m ..