Geographical Environment of Huanjiang Maonan Autonomous County

The maximum horizontal distance from the east to the west around the Yangtze River is 89 kilometers, and the maximum vertical distance from the north to the south is 90 kilometers. The county covers an area of 4,572 square kilometers, accounting for 1.93% of the total area. It is the fifth largest county in Guangxi, with forest coverage rate of 59.2% and cultivated land area of 24.7 thousand hectares. It is one of the key counties of agriculture, forestry and mining in Guangxi. Huanjiang Maonan Autonomous County is located on the slope of the southern edge of the central Guizhou Plateau. The overall terrain is high in the north and low in the south, surrounded by mountains on all sides, with hills to the south of the central part, with a slightly higher elevation of 1693 m and the lowest elevation of 149 m. Northeast Mountain in Huanjiang Maonan Autonomous County is a part of 90,000 mountain systems, with the highest peak of Phoenix Mountain, with an altitude of 1.693 meters. In the northern mountainous area, Dagezhai is the main peak (elevation 1460m), which extends southward and becomes the watershed of large and small rivers. The main mountain peak in the northwest mountainous area is Jin 'ao Mountain (elevation 106 1.4), which extends from northwest to south. The west and south are dominated by karst mountains, with earth mountains, semi-earth mountains and semi-stone mountains in the middle. Qifeng is steep, and the highest peak is Xiaodongpo in Mulun Township, with an altitude of 740.0 meters. Baxian Mountain is the highest mountain in southern Central China, with an altitude of 73 1.9 meters.

The appearance of the county is controlled by lithology and geological structure. Carbonate rocks are widely distributed, mainly karst landforms, accounting for 39.9% of the county's total area. According to the basic forms and causes of landforms, counties can be divided into three categories: structural erosion landforms, erosion and denudation landforms and karst landforms. Huanjiang Maonan Autonomous County belongs to the subtropical monsoon climate zone, with mild climate, abundant rain and sunshine, no severe cold in winter, no heat in summer, the same season of rain and heat, and a long frost-free period. The annual average temperature in southern Qiu Ling is 19.9℃,15.7℃; In the northern mountains. 1 monthly average temperature 10. 1℃, and the average temperature in July is 28℃; ; The lowest temperature over the years is-5.2℃, the frost-free period is 290, and the annual average sunshine hours 145.438+0 hours. The annual solar radiation is 98.89 kcal/cm2.

The average annual rainfall is1.750mm in the north and 1.389. 1 mm in the south, which is concentrated from April to September, accounting for 70% of the annual rainfall. The minimum rainfall over the years is 922.8 mm, evaporation 1. 1mm, and the average relative humidity of the air is 79.

Huanjiang River is located in the north of Guangxi and the southeast of Yunnan-Guizhou Plateau. The overall terrain is high in the north and low in the south, surrounded by mountains, with hills in the middle and a little basin. Located on the northern edge of the Tropic of Cancer, the county belongs to the monsoon climate zone of transition from south subtropical zone to middle subtropical zone. The southern margin belongs to the northern margin of the south subtropical zone, and the central and southern parts and the large and small river basins belong to the middle subtropical valley climate. These two areas have mild climate, abundant rainfall, abundant sunshine, long frost-free period, the same season of rain and heat, and crops can be harvested three times a year. The northern part belongs to subtropical mountainous climate, characterized by cool climate, wet and rainy, rainy and hot in the same season, and the heat condition can be harvested twice a year. Due to the complex terrain and geographical location, the disastrous weather in this county is frequent, such as drought, waterlogging, wind hail and frost, which has a great impact on the industrial and agricultural production and people's life in this county. The county's water resources are 3,596.6 million cubic meters, including 3,336.3 million cubic meters of surface water and 260.3 million cubic meters of groundwater. According to the recent needs of people's life, industry and agriculture, the water demand is 235.9 million cubic meters, including 228.6 million cubic meters for agriculture and 07.3 million cubic meters for industry and life. Water resources mainly come from three rivers such as Huanjiang River, Zhongzhou River (also known as Xiaohuanjiang River) and Dagou River, and four streams such as Ping 'an, Sancai, Dacai and Wenping. Water diversion irrigation, water storage irrigation of Shantang Reservoir, electric irrigation and water pump irrigation have been developed and utilized. Farmland water consumption is 228.6 million cubic meters, and industrial and domestic water consumption is 0.10.30 billion cubic meters. The total area of the county is 4572.3 1 km2, and the total area of the basins of Huanjiang and Zhongzhouhe counties is 3644.26 km2, accounting for 80% of the total area of the county.

Dahuanjiang River: total length 147.2km, county boundary 136.5km, drainage area of 2850km2, maximum flow of 3020s cubic meters (1970) and minimum flow of 3. 1s cubic meters (1963).

Xiaohuanjiang River: the total length is 136.5km, the county boundary is 94. 1km, the drainage area is 2328km2, and the annual average flow is 39.25s cubic meters.

Zhongzhou River: total length 136.5km, county boundary 17. 1km, with an average annual flow time of 39.45 seconds cubic meters.

Dagou River: Dagou River is located in the west of the county seat, separated from Nandan County, with a total length of 26 kilometers. Huanjiang is rich in mineral resources, with the characteristics of wide distribution, many types, large reserves and high grade. More than 20 kinds of minerals have been found for development, and there are more than 30 mineral deposits. The proven mineral resources amount to 1 16 10000 tons, with a potential value of 8.095 billion yuan. There are mainly 28 kinds of minerals such as coal, limonite, pyrite, copper, lead, zinc, phosphorus, gypsum, asbestos, talc, dolomite, crystal, manganese, realgar, tin, silver, sulfur, uranium, porcelain clay, calcite, marble, Iceland spar and mercury. Among them, the reserves and grade of lead-zinc ore are the first in Guangxi.