Longchuan River

Longchuan River

Longchuan River is a tributary on the South Bank of Jinsha River. It is rich in water. It originates from puzaotang of yutula in the east of tianzimiaopo, Nanhua County, Chuxiong Yi Autonomous Prefecture. It flows from west to East through Nanhua County and Chuxiong City, then turns north into Lufeng County and Yuanmou County, crosses yuanmouba District, and finally joins Jinsha River in Jiangbian Township in the north of Yuanmou. The drainage area is 9240.7 square kilometers, and the total length is about 246 kilometers. The relative drop between the source and the estuary is more than 1600 meters, the average gradient of the riverbed is 4.8 ‰, and the average elevation of the basin is 1992 meters. The basin is dominated by mountains and hills, accounting for 95%, and valley basins and shallow hills account for about 5% of the basin area.

geographical position

The Longchuanjiang river basin is located in the transitional zone between Hengduan Mountains and Yunnan Guizhou Plateau. Most of the basin belongs to the original landform of Zhongshan Mountain. The mountains in the middle and upper reaches are high and steep, the river bed is deeply cut, and the terrain fluctuates greatly,

The terrain of the lower reaches is relatively gentle and belongs to basin topography.

Hydrological climate

Longchuan River belongs to low latitude plateau monsoon climate. In summer and autumn, it is affected by the warm and humid air flow in the southwest of bay of Bengal and the warm and humid air flow in the Beibu Gulf; in winter and spring, it is controlled by the dry and warm air flow from the Indian continent and the cold air from the south of the north. The climate types of the basin are subtropical monsoon, North tropical, north subtropical and south subtropical climate, with distinct dry and wet seasons, large daily temperature difference and small annual temperature difference, and the annual average temperature is 14.8-21.9 ℃.

The dry and wet seasons of Longchuan River are distinct, and the precipitation is less. The rainy area of the basin is in Wutai Mountain Area of Nanhua County, with an annual precipitation of about 1600mm; the less rainy area is in Jinsha River Valley, mainly in Jiangyi Township and Jiangbian township of Yuanmou County, with an annual precipitation of less than 800mm.

The flood in Longchuanjiang river basin is formed by rainstorm, and the seasonal variation of flood is consistent with rainstorm. The annual maximum flood occurs mostly in June, July and September, followed by August, and occasionally in October, but the magnitude is small. Due to the influence of topography, the regional difference and vertical change of climate are obvious, and the regional distribution of precipitation varies greatly with elevation and topography (the basin is mountainous, with an altitude of 940-3657m, and an altitude difference of 2717m, which determines the huge difference of precipitation at different altitudes: the average annual rainfall in the area below 1800m is about 835.2mm, and that in the eastern Lufeng and other three counties is 990mm The climate of Yuanmou dam area in the lower reaches is dry hot valley climate, known as "natural greenhouse". The annual average water surface evaporation is 1613.4mm, the annual average temperature is 15.6 ℃, the maximum temperature is 32.4 ℃, the minimum temperature is - 4.8 ℃, the annual average wind speed is 1.7m/s, and the maximum wind speed is 21m / S (wind direction is NE). Most places in the basin have large sunshine value, which is located in the high value area of Yunnan Province, and the annual average sunshine hours are 2549h.

Analysis on change trend of water resources in River Basin

Basin water resources refers to the dynamic water quantity formed by precipitation in the basin and can be updated year by year. Based on the data series of 48 years from 1960 to 2007 of Chuxiong and xiaokuiyuan hydrologic stations and the rainfall data of 33 stations (the rainfall data of some stations have been interpolated and extended), the analysis and calculation are carried out.

2.1 trend analysis of precipitation

Precipitation is the basis of runoff formation, and the runoff of Longchuan River is supplied by atmospheric precipitation, so precipitation is also the most direct and important factor affecting the formation of surface water resources. The basin is located in the area of low latitude and high altitude. Affected by the atmospheric circulation and monsoon, the dry and wet seasons are distinct, and the annual precipitation distribution is uneven. The precipitation from June to October in rainy season accounts for more than 80% of the annual precipitation, and single point rainstorm and disastrous rainstorm occur frequently. The seasonal distribution of precipitation varies greatly, and the regional distribution is also uneven.

According to the rainfall data of 33 stations in the basin (1961-2007 data series), the annual average precipitation of Longchuanjiang river basin is 847.2mm (881.7mm calculated from the precipitation contour map of Chuxiong water resources comprehensive planning, the data is up to 2000), which is equivalent to 7.815 billion cubic meters. The annual maximum precipitation is 1075.2mm, and the minimum precipitation is 634.6mm. According to the measured data of single station precipitation, the high precipitation area is located in tianzimiao area in the upper reaches of Longchuan River, the upper reaches of Zidian River in mouding, dabaicaoling area in Dayao and other high-altitude areas. The maximum annual precipitation measured by barnyard rainfall station is 1529.4mm, that of Tanhua Township rainfall station is 1580.0mm, the low precipitation area is Yuanmou dam area, and the minimum annual precipitation measured by xiaoguaiyuan station is 332.4mm.

The precipitation in the basin varies greatly from year to year, and there is a great disparity between the abundant and the dry. From the precipitation process since 1960s, the maximum annual precipitation is 440.6 mm more than the minimum annual precipitation, the maximum annual precipitation is 1.694 times of the minimum annual precipitation, and the minimum annual precipitation is only 74.9% of the average annual precipitation.

The annual precipitation of the basin has gone through five stages: normal ~ dry ~ dry ~ wet ~ normal; from the precipitation of each period, the normal wet period is in the 1960s, the normal dry period is in the 1970s and 1980s, and the wet period is in the 1990s.

According to the 5-year moving average hydrograph of precipitation in the basin, it has experienced a relative increase period from 1964 to 1970 and a relative decrease period from 1975 to 1989. Since the 1990s, it has shown an increasing trend as a whole, which is a relatively wet period.

Since the beginning of the 21st century, the precipitation in the basin has a slight decreasing trend, that is, the period from 2003 to 2006 is a relatively decreasing period. According to the existing data and trend analysis, it has entered the wet season since 2007, which should be paid attention to in the development and utilization of water resources, flood control and reservoir operation.

2.2 evaporation trend analysis

Evaporation is the main loss item of water resources in the basin. According to the evaporation observation data of Chuxiong and xiaokuiyuan hydrological stations and Nanhua, Chuxiong, Yuanmou, mouding, Yao'an, Dayao and Yongren meteorological stations, the annual average water surface evaporation of Longchuan River Basin is 1613.4mm, which is higher than the annual average of 5.4% and 3.5% in 1960s and 1970s, which is the same as the normal year in 1980s and the same in 1990s The precipitation is too much, and the water surface evaporation in the basin is lower than 8.2% of the annual average. According to the available data and trend analysis, the water surface evaporation in the basin in the 2000s was the same as that in the normal year, slightly less.

2.3 trend analysis of water resources

2.3.1 basin water resources

The runoff of Longchuan River is supplied by atmospheric precipitation, which is a poor area of water resources. Due to the large number of medium-sized reservoirs in the basin, the water consumption of industry, agriculture and life is large, and the runoff is greatly affected by human beings, the water reduction calculation is needed. According to the reduction calculation, the annual average natural water resources of Longchuanjiang river basin is 1.596 billion cubic meters, and the annual average water production modulus is 173000 cubic meters / square kilometers. There were more water resources in the 1960s and 1990s, less in the 1970s and 1980s, and the water volume in the 2000s was basically the same as that in the normal years. The water resources of the Longchuan River in each decade are shown in Table 1. The average annual runoff depth is 50.0-410.0 mm, the difference between the maximum and minimum is 8.2 times, and the CV value is 0.35-0.55. The distribution of water resources varies greatly. The annual average water production modulus of the upper reaches of the main stream and the major tributaries, as well as the northern and southern mountainous areas, is more than 250000 cubic meters per square kilometer. The water production modulus of Yuanmou Bazi Valley is smaller, ranging from 50000 to 150000 cubic meters per square kilometer. The water production modulus of Pingba District in other counties is 180000 to 250000 cubic meters per square kilometer. Generally speaking, the regional distribution of water resources is large in mountainous areas and small in basins and valleys.

Table 1 Statistics of water resources in Longchuan River

2.3.2 evaporation loss

The evaporation loss of Longchuan River is the land surface evapotranspiration of the whole basin. Land surface evaporation refers to the total evaporation of bare land, water body and plant transpiration, that is, the actual evaporation of a watershed. The land surface evaporation of the Longchuanjiang river basin is 674.2 mm by subtracting the average runoff depth from the average precipitation. According to the statistics of the observation data, the basic characteristics of the water surface evaporation in the Longchuan River Basin are that the water surface evaporation in the flat dam and valley is larger than that in the mountainous area, and that in the arid area is larger than that in the humid area. However, due to less precipitation and insufficient soil water supply in Pingba and valley areas, the land evaporation is less than that in mountainous areas.

2.3.3 change trend of production and domestic water consumption in the basin

Longchuanjiang river basin is the political and cultural center of Chuxiong Prefecture, and also the most developed area in economy and transportation. According to the statistical data of economic work manual for leading cadres of Chuxiong Prefecture, yearbook of Chuxiong Prefecture, bulletin of water resources of Chuxiong Prefecture and comprehensive planning of water resources of Chuxiong Prefecture, by the end of 2007, the total population of the basin was 1.436 million, the cultivated land area was 1.045 million mu, and the gross national product (GNP) increased It is worth 14.83 billion yuan. The population and farmland in the basin are concentrated, the industry and agriculture are developed, the runoff is greatly affected by human activities, and the water consumption of industry, agriculture and life is large.

(1) Agricultural irrigation water and consumption

Agricultural irrigation is a major water user in the basin. According to the effective irrigation area of Longchuanjiang River Basin from 1961 to 2007, the comprehensive irrigation quota is 563 m3 / mu and the water consumption rate is 85%. The average agricultural irrigation water consumption in the basin is 4

Chinese PinYin : Long Chuan Jiang