Xiliaohe Plain is located in the east of Xiliaohe River Basin and the west of Songliao Plain, covering an area of about 52,000 square kilometers, and basically located in Tongliao City, including Chifeng City, Xing 'an League, Siping City, Baicheng City, Songyuan City and parts of Shenyang City. The overall flow direction of the river is from west to east, with flat topography on both banks, hilly grassland and loess hilly landform widely distributed, with dry climate, concentrated rainstorm, poor vegetation, serious soil erosion and large river sediment concentration. Because Xiliaohe is located in the descending area of Songliao sag in the geotectonic structure, since the Quaternary, due to long-term settlement and river transportation, thick sediments have accumulated. The biggest feature of Xiliaohe River is that the mainstream swings, the flow direction changes and the mainstream rolls back and forth. There are more than 90 large, medium and small reservoirs in the basin, with a total designed storage capacity of 4 1. 200 million cubic meters. Hongshan Reservoir is the largest reservoir in Northeast China.
The West Liaohe River Basin is located on the slope from the Mongolian Plateau to the Liaohe Plain, starting from the watershed on the south side of Huolin River in the north and reaching Yanshan C in the south. The eastern part of Lamai (Tushan, Yiwulu Mountain and Nuruhu Mountain in seven old), the eastern part of Xiliaohe Plain and the western part of the southern section of Daxinganling. The mountain area is 580~ 1500m above sea level, covering an area of about 84,000 square kilometers, accounting for 6 1.8% of the total basin area. The elevation of the plain is 1 10580m, covering an area of about 52,000 square kilometers, accounting for 8.2% of the total basin area.
The West Liaohe Plain slopes slowly from west, southwest, northwest to east, southeast and northeast, and the ground slope is110001/2000, which is undulating. The northwest edge is the piedmont alluvial-diluvial platform of Daxing 'anling Mountains, with an altitude of 500-800 m, which inclines to the southeast. The northeast is the watershed between Songliao Plain and Songnen Plain, with an altitude of170 ~ 300 m; To the southwest is the Yanshan Mountains, with an altitude of 300 ~1000 m..
The main geomorphic types of the West Liaohe Plain are micro-undulating plain, floodplain, terrace, sand dune and sandy land. Except for the main floodplain and the first and second terraces, most of the plain areas are covered with aeolian sand, and there are low-lying lands between ridges, which can be used as natural pastures. The first unit of the main landform in the plain area is denudation and accumulation topography, with a slope plain with piedmont alluvial deposits near the mountain and an alluvial plain formed by Quaternary alluvial deposits in the east. The eastern part is a typical alluvial lacustrine plain, which is embodied in the eastern Daxing 'anling Mountains, alluvial platform, alluvial plateau, alluvial lake and alluvial lowlands on the northern slope of Yanshan Mountain. According to the classification system adopted by the national soil ethnography, there are 56 kinds of soils in the West Liaohe River Basin. There are mainly grassland aeolian sandy soil, chestnut soil, chestnut soil, chernozem, dark chestnut soil and so on. The above-mentioned main soil accounts for 60% of the basin area. Among them, grassland aeolian soil, fluvo-aquic soil and chestnut soil are mainly distributed in plain areas, while chestnut soil, chestnut soil and chernozem are mainly distributed in mountainous areas. Grassland aeolian sandy soil has the largest area of 29,200 square kilometers, accounting for 2 1% of the total area of the West Liaohe River Basin, mainly distributed in plain areas. Followed by chestnut soil, covering an area of 20,000 square kilometers, mainly distributed in mountainous areas.
Xiliaohe River Basin is located in semi-arid area, which belongs to grassland and sandy land farming and animal husbandry ecological zone. The ecological vegetation in the basin is mainly typical grassland vegetation, trees, shrubs, semi-shrub grassland vegetation and meadow vegetation. According to the remote sensing data in 2005, there are 23 types of land use in the West Liaohe River Basin, mainly including dry land (including cultivated land and unused land), grassland, woodland and building land. The dry land covers an area of 36,000 square kilometers, accounting for about 27% of the total area of the West Liaohe River Basin. 67,000 square kilometers of grassland, accounting for 52%; Woodland 1.8 million square kilometers, accounting for1.3%; The construction land is ***0.3 1 10,000 square kilometers, accounting for about 20%.
In the plain area of West Liaohe River, due to the influence of human activities, the grassland area decreased rapidly and the dry land area increased rapidly. According to the remote sensing data, from 1995 to 20 10, about 4,834.87 square kilometers of grassland in the West Liaohe Plain was converted into dry land, with the grassland area reduced by 25% and the dry land area increased by 4 1%. From 65438 to 0995, grassland was the main land use type in plain area, accounting for 44% in plain area and 34% in dry land. In 20 10, dry land has become the most important land use type in the plain area, accounting for about 47% of the plain area, and grassland has decreased to 32%. The decrease of grassland area reflects the problem of ecosystem degradation in plain areas. Most areas of the West Liaohe River Basin are located in arid and semi-arid climate zones. The average annual temperature is 5 degrees. 00℃~6。 At 50℃, the average sunshine hours are 2800~3 100h, the relative humidity is 45%~58%, the annual average rainfall is 300 ~ 400mm, and the evaporation is 1 199 ~ 2200 mm.
Xiliaohe Plain is mainly located in the semi-arid monsoon climate zone, which is characterized by dry and windy spring, hot and humid summer, cool autumn climate and cold and little snow in winter. The spatial and temporal distribution of precipitation is uneven, increasing from northwest to southeast in space, and 80% of precipitation occurs from June to September. The annual average evaporation decreases from northwest to southeast, with the maximum evaporation of 27 13.9mm and the minimum evaporation of1323.1mm. The annual average wind speed is 2.7 ~ 4.0m/s. In 2009, the total population of the West Liaohe River Basin was 7.74 million, including 3,049,600 urban residents and 4,690,400 rural residents. The urbanization rate is 39.40%, and the population density is 57.25 people /km2, concentrated in Tongliao City and Chifeng City. The total cultivated land area in the basin is 3.3 million/kloc-0.98 million mu, and the actual irrigated area is/kloc-0.3975 million mu.
In 2009, the total population of West Liaohe Plain was 4,722,900, and the cultivated land area was 2,0521.5 million mu, accounting for 19.47% of the plain area. The effective irrigated area is 654.38+0.5222 million mu, and the per capita cultivated land area is 4.35 mu/person, which is higher than the national average cultivated land level (654.38+0.5 mu/person). The industrial structure of the West Liaohe River Basin has gradually developed from agriculture and animal husbandry as the main body to an economic structure based on agriculture and animal husbandry, with industry as the leading factor and common development of agriculture, forestry and animal husbandry.
The gross domestic product (GDP) of West Liaohe Plain is 380 1 1 100 million yuan, and the per capita GDP is 8048.36 yuan. The output value of the primary industry is 65.438+04.507 billion yuan, the output value of the secondary industry is 65.438+065.438+0999 billion yuan, and the output value of the tertiary industry is 65.438+036.5438+04 billion yuan. The proportion of primary, secondary and tertiary industries is 1.2: 1: 1, and the plain economy is dominated by the primary industry.
Xiliaohe Plain has fertile soil and is known as the "northern granary", which is an important grain producing area in China. The main grain crops in the plain area are corn, soybean and wheat, and the cash crops are sunflower seeds, castor and sugar beet. Grain output reached119.8 billion Jin.
Horqin Grassland is an important animal husbandry production base in China, which is known as "the hometown of cattle" and "the hometown of Mawang in China". Animal husbandry in West Liaohe Plain is concentrated in Horqin grassland, with 4.802 million livestock (only), including 2.328 million large livestock and 2.474 million small livestock. The industry in the plain area is mainly concentrated in Horqin District, which has developed rapidly and begun to take shape, forming an industrial system with a certain foundation, scale and local characteristics, with the four leading industries of agricultural and sideline products processing, energy, medicine and chemical industry and building materials as the backbone.