Geographical environment of Huichang county

Huichang county belongs to a secondary structure of the second uplift belt of New China. Strata include Precambrian and Cambrian, Cretaceous, Jurassic, Quaternary, Carboniferous, Devonian, Permian, magmatic rocks and migmatite, among which Precambrian-Cambrian and Cambrian are the most, followed by magmatic rocks.

Precambrian-Cambrian and Cambrian: mainly distributed in Yunmenling, Dongtou, Gaopai, Nakamura, Yonglong, Zhantang, Fucheng, Youshui, Mazhou and Xiaolong. Area 1269.09 km2, accounting for 46.62% of the county's total area.

Cretaceous: mainly distributed in the county basin, Zhuangkou, Zhuangbu, Xiaomi, Xijiang and other towns and villages. It covers an area of 327.75 square kilometers, accounting for 12.04% of the total area of the county.

Jurassic: mainly distributed in small areas of Xiaomi, Yunmenling, Zhoutian and Qingxi. It covers an area of 78.94 square kilometers, accounting for 2.90% of the total area of the county.

Quaternary: mainly distributed from the county seat to Mazhou, Zhoutian Town and Xijiang Town in Xia Ying. It covers an area of 40.29 square kilometers, accounting for 1.48% of the total area of the county.

Carboniferous: mainly distributed in Xijiang, Xiaomi, Baie, Zhuangkou and other towns. It covers an area of 32.67 square kilometers, accounting for 1.2% of the total area of the county.

Devonian: mainly distributed in towns such as Bai 'e, Zhuangkou, Zhuangbu, Xijiang and Xiaomi. Area 12.25 square kilometers, accounting for 0.45% of the total area of the county.

Permian: scattered in Xijiang, Xiaomi, Zhuangkou and other towns. Area 10.34 km2, accounting for 0.38% of the county's total area.

Magmatic rocks: mainly distributed in Yunmenling, Qingxi, Zhoutian, Youshui, Dongtou, Zhongcun, Yonglong, Fucheng, Wenwuba, Gaopai, Zhu Lan and Baie. It covers an area of 950.85 square kilometers, accounting for 34.93% of the total area of the county.

Mixed rocks: distributed in towns and villages with Precambrian-Cambrian and Cambrian geology. Huichang county is surrounded by mountains on all sides, with a long and narrow middle part, which inclines from southeast to northwest. The Nanling residual vein spans the southwest, with the main peak Panguzhang 1 184 meters, which is a natural barrier on the border between Jiangxi and Guangdong. Wuyi Mountain is located in the east and southeast of the remaining vein, with the main peak of Cape Shi Yang at an altitude of1107.8m, which is the natural dividing line between Jiangxi and Fujian. The eastern and southwestern regions are relatively high in terrain, surrounded by low mountains and overlapping peaks. The north and northwest are low-lying, with rolling mountains and continuous slopes. Mountain area accounts for 25% of the county area, hills account for 69.7%, and basins account for 5.3%. Its main landforms are denudation tectonic mountains and erosion tectonic mountains.

(1) The landform of exposed structural hills can be divided into three types according to elevation and morphology: low hills, middle hills and high hills.

The elevation of low hills is less than 200m, the relative elevation is 40 ~100m, and the slope is15 ~ 20, which is a small or irregular banded basin. Area 144.23 square kilometers, accounting for 5.3% of the total area of the county. Mainly distributed in Zhoutian, Youshui, Mazhou, Wenwuba, Zhuangkou, Zhuangbu, Baie, Xijiang and other towns and villages.

Zhongqiu is 200 ~ 300m above sea level, with a relative altitude of 100m and a slope of 20 ~ 30, and it is distributed in a long and narrow torch shape. It covers an area of 528.5 square kilometers, accounting for 19.4% of the total area of the county. Mainly distributed in Yunmenling, Zhoutian, Zhantang, Youshui, Mazhou, Wenwuba, Zhu Lan, Zhuangkou, Zhuangbu, Baie, Xiaomi and Xijiang.

The high hills are 300-500m above sea level, with a relative elevation of100-200m and a slope of 30-40, and are distributed from northwest to southeast. Area 1368.8 square kilometers, accounting for 50.3% of the total area of the county. It is mainly distributed in Yunmenling, Zhoutian, Zhongcun, Zhantang, Yonglong, Fucheng, Youshui, Gaopai, Mazhou, Wenwuba, Zhu Lan, Zhuangkou, Zhuangbu, Baie, Xiaomi and Xijiang on the east and west sides of Zhong Qiu.

(2) The eroded structural mountainous counties only have low mountain landforms, which are distributed on the east and west sides of the southern part of the county, and spread in the northeast-south-southwest direction. 500 ~ 800 meters above sea level, 200 ~ 300 meters above sea level, with a slope of 35 ~ 45. It covers an area of 680.65 square kilometers, accounting for 25% of the total area of the county. The peaks above 800 ~ 1000 meters are mostly distributed in the low mountainous areas on the east and west sides. The lithology is mostly granite, metamorphic sandstone, slate and migmatite.

Before 1995, the land statistical area of Huichang County was 2722.438+08 square kilometers. 1996, Huichang county conducted the first land and resources survey after the founding of New China, with an investigation area of 2709.8+0 square kilometers. Among them, the woodland area is 210.0665 million hectares, accounting for 77.74% of the total area of the county, which is suitable for planting pine, fir, bamboo, camellia oleifera and citrus. The cultivated land area is 2 1.88 million hectares, accounting for 8% of the county's total area. Suitable for planting rice, sugarcane, flue-cured tobacco, beans, lotus roots and other crops. Among them, there are 20,700 hectares of paddy fields, accounting for 94.6% of the cultivated land area. There are 9,000 hectares of dry land, accounting for 4. 1% of the total cultivated land. Crops such as sweet potatoes, peanuts and soybeans can be planted. Unused land area 12500 hectares, accounting for 4.6% of the county's total area. surface water

Surface water resources are abundant. Huichang is abundant in rainfall, with an average annual precipitation of about 1600 mm and a maximum of 2000 mm. There are 3 19 rivers in the county, with a large river bed gradient, with a total length of 1726 km. The water area is 7363.63 hectares, the river network density is 0.64 km/km2, the annual average flow is 43.3 m3/s, and the catchment area is 73 13.7 km2. The annual average surface runoff is 210.98 billion cubic meters. The water output per square kilometer is 80.58 cubic meters. The county's theoretical hydropower reserves are1790,000 kilowatts, and the power generation capacity can be developed and utilized by 2180,000 kwh. The average water energy density is 65.8kW/km2, and the exploitable amount is 105kW, accounting for 58.6% of the reserves.

underground water

Groundwater resources are all over the county. According to the investigation of Jiangxi 909 Geological Brigade, the county produces 983,500 tons of groundwater per day and 359 million tons of water per year. 6.5438+0.4 million tons of groundwater have been developed and utilized, and 5 million tons of groundwater have been utilized annually. There are mineral springs and hot springs 18 in the county. The mineral water in Dongtou Township and Wanxing Village of Xijiang Town is pure and free of impurities. Junmenling town Chexin village hot pool hot spring contains sulfur, which is effective for skin diseases. According to the second-class forest resources survey in 2004, Huichang County has a forested area of 202 157.2 hectares (including bamboo forest 1240. 1 hectare). The county's standing timber volume is 627. 1039 cubic meters. There are 472 species in 82 families. Among them, rare plants are ginkgo and yew. Beautiful Chimonanthus praecox and Chimonanthus praecox, which are protected plants at the national level. The national second-class protected plants are Cinnamomum camphora, cypress and nanmu.

In 2009, there were 92 ancient trees 100 years old in the county. Among them, banyan 2 1, camphor tree 19, maple tree 27, ginkgo tree 5, yew 2, nanmu 2, Podocarpus 1, masson pine 6, fir tree 1, beef tendon tree 3, osmanthus tree 1, and lotus flower 4.

Huichang county is rich in mineral resources. According to the geological exploration, the metallic minerals include tin, copper, gold, rare earth, iron, bismuth, molybdenum, antimony, manganese, cobalt, lead, tungsten, zinc and titanium. In particular, Qingxi Township has the largest tin mine, with a reserve of 654.38 million tons and an average grade of 0.84%. Tin, tungsten, rare earth and copper have been developed and utilized. Non-metallic minerals include limestone, rock salt, fluorite, gypsum, clay, granite and anthracite. Zhoutian Town has the most rock salt, with a reserve of 21.400 million tons. Followed by Wenwuba and Junmenling Town, the fluorite reserves are 2.6 million tons. Limestone distributed in Xijiang Town and Xiaomi Township stretches for dozens of miles. The gypsum mine in Junmenling Town, which is being mined, has a reserve of 5,000 tons. The anthracite distributed in Xiaomi, Xijiang, Zhuangkou and Baie is 6.5438+0.75 million tons, and the clay distributed in Youshui and Wenwuba is 50 million tons. Tin, tungsten, limestone, rock salt, fluorite and gypsum have been developed and utilized. Among them, tin, rock salt and fluorite have been mined on a large scale.