In recent years, the population size and scale of the Shiyang River Basin unceasingly expanding lead to a series of ecological environment: surface water reducing, land desertification and Ground water levels fall, etc. Research evolution characteristics of population distribution and migration growth of Shiyang River Basin contribute to river water resources and the industrial development of the comprehensive management. The article using the distribution of population structure index, population distribution center of gravity model and the population migration growth analysis model analyzes the distribution of the population evolution characteristics and population migration growth characteristics of Shiyang River Basin in 2000 to 2010. The results show that: 1) Considering Shiyang River Basin, population density is generally low, population distribution difference is bigger and concentration distribution in the middle corridor plain and three big population distribution center of Minqin oasis area, presenting a “point-areas-ribbon” structure characteristics. 2) The population distribution trend of Shiyang River Basin is constantly concentration, but the change is slow; the population distribution of Minqin is in the highest concentration degree, but the trend has been declining. 3) The focus of population density in river basin locates in Liangzhou district of Daliu country; in ten years, it migrates about 1209 m to southwest Wuwei City direction, but migration along the direction things is bigger than the north and south direction. The focus of population density and the basin geometry center is far away. 4) For ten years, at the township for basic statistics unit, each level population migration change within the overall is not significant: township level > prefecture-level cities level > counties level. 5) For ten years, there are significant changes in population migration between watershed township units, Wuwei City and Gulang Town are the two main concentrations of population centers.
Generally, population distribution refers to manifestations of the population process in the space, and characterization of population groups in the geo-spatial distribution, distribution, and portfolio position [
At present, the study of domestic population distribution is more concentrated at the national provincial unit [
Shiyang River Basin is one of three inland river basins in the Hexi Corridor, the basin area is 4.06 × 104 km2, located at 101˚07' - 104˚15'E, 37˚07' - 39˚27', the river basin administrative divisions include Liangzhou of Wuwei City, Minqin County, Gulang County and some areas of the Tianzhu Tibetan Autonomous County, Jinchuan District of Jinchang City, Yongchang County, and all Sunan Autonomous County of Zhangye City. There are two major river systems: Tai Jing River and West River, as well as the East river, West Camp River, Golden Tower River, Zamu River, Gazelle River, Gulang River as the main body of River System. The basin is arid continental inland climate zones, with less precipitation and precipitation variability, uneven distribution of the year, evaporation and drought periods significantly. In 2009, there was a total population of 1748.8 thousand, achieved a GDP of 17.929 billion yuan, the total grain output reached 950,800 tons, the per capita net income of farmers reached 3972 yuan.
Graphic data set used in this paper is provided by Environmental and Ecological Science Data Center for West China, National Natural Science Foundation of China (http://westdc.westgis.ac.cn). Because the river township zoning unit is frequently adjusted, collecting various of information and data validation, merger and name on the part of the township area, and ultimately get 97 township units. Townships appeared in the paper are the name after mergerring. In the year of 2000 and 2010, demographic data comes from counties Bureau of Statistics Statistical Yearbook and various statistical data within the basin: 2010 preliminary data of Liangzhou comes from Sixth Census; 2010 population data of Tianzhu is calculated and adjusted based on 2000-2005 population; 2010 population data of Minqin is 2009 data, although there is discrepancy of population data within a small area, it does not affect the overall population distribution of the basin as a whole.
Population distribution structure index [
U: imbalance index, C: concentration index, n: the Administrative Region of the number, yi: each administrative unit population accounts for the proportion of the total population of the region, xi: each administrative unit land area accounts for the proportion of the total area of the region as a whole. Population imbalance index U and the concentration index C are greater, indicating that the population distribution is more concentrated; otherwise, it showed that the more balanced population distribution.
Gravity model of population distribution [
x and y represent barycentric coordinates of the population distribution of the study area, pi, xi, yi, respectively represents population and the population distribution barycentric coordinates of the various administrative units in the study area. Because the administrative center adjusts frequently, (xi, yi) is the center coordinates of each administrative unit. When the property value of pi is the area of the administrative unit, the Barycentric coordinates becomes the geometric center of the region, and accordingly it can study the stability of the regional population distribution center of gravity.
Population shift growth analysis [
ABSFRi, SHAREi, SHIFTi relatively is the amount of absolute growth, the amount of share growth and the amount of offset growth of i administrative unit (township) in (t0, t1,) time. VLISHIFTintra is the growth of the total offset between the different administrative units within the same county (township). VOLSHIFTinter is the growth of the total offset between the different counties. VOLSHIFTtotal is the total amount of the offset growth between the various administrative units of the entire study area (township). m is the number of Counties, n is the number of township units, r is the number of counties contained within county districts.
Analysis of basin population distribution. In 2010, the total population of Shiyang River Basin is 2.28 million people, the population density is 60 persons/square kilometer, the average population density of 97 township- level unit (including a variety of public places, etc.) is 341 persons/square kilometer. Using Quartile method to classify the basin population density (expressed as a percentage), and take the population density outside the scope of [FU ± 3(FU − FL)] as outliers and individually graded, including FU for the last four scores, FL for the next four scores. As shown in
three major cities as the center and population diffusion distribution area that Dajing River, midstream plain corridor area of the six river systems, midstream plain corridor area of the West River, the core area of Minqin Oasis as the center and presenting a “point-areas-ribbon” structure characteristics that State Road 312, Provincial Highway 211 and 212, Lan-Xin Railway as transport corridors. Population density within the Basin distributes quite differently: The population density of Wuwei City (formerly Chengguan Town area in Wuwei City) reaches 16905.09 people/sq. km becoming the highest one; followed is Jingyang Town of Liangzhou and Sanlei Town of Minqin County, the population respectively is 1345.34 people/sq. km and 711.56 people/sq. km. The east and west sides of Minqin oasis belongs to vast desert area inaccessible, upstream Qilian Mountains are mostly the ethnic communities and the population density is relatively small.
Except Wuwei City, Jinyang Town, and Sanlei Town, YongChang Town, Gaoba Town (including the original Liuba Town), Wunan Town, Qingshui township and Yangxiaba Town (including the original Zhongba Town) located in Liangzhou together form eight high population density and the value of the anomalous areas.
Population distribution structure index analysis. Use of imbalance index and concentration index model of population distribution calculated population distribution structure index change table of the basin sub-counties, as shown in
Analysis the focus of migration of population distribution. Using calculation model of population centers and ArcGIS9.3 software calculated the location of population distribution center of gravity and the geometric center, as shown in
Index type | Year | Basin | Jinchang | Wuwi | Liangzhou | Minqin | Gulang | Tianzhu |
---|---|---|---|---|---|---|---|---|
Imbalance index | 2000 | 0.0188 | 0.0812 | 0.0248 | 0.0440 | 0.0905 | 0.0472 | 0.0686 |
2010 | 0.0193 | 0.0812 | 0.0254 | 0.0473 | 0.0897 | 0.0478 | 0.0691 | |
Increase/decrease | + | 0 | + | + | − | + | + | |
Concentration index | 2000 | 0.6294 | 0.4426 | 0.6501 | 0.4641 | 0.8611 | 0.3913 | 0.3680 |
2010 | 0.6299 | 0.4491 | 0.6501 | 0.4968 | 0.8470 | 0.3908 | 0.3732 | |
Increase/decrease | + | + | 0 | + | − | − | + |
about 1209 meters. The geometric center coordinates of the basin is (102.772˚E, 38.286˚N), in the northern Cai Qi township and near Hongyashan Reservoir, distance of the focus of population density changes from 36,364 meters in 2000 to 37,115 meters now, deviated more about 751 meters in ten years. The distance of the population density center of gravity and geometric center was far, mainly caused by the natural and geographical environment of the basin. North-south direction of the movement of the focus of population density is mainly due to Minqin oasis Hongyashan upstream of the reservoir area immigrants and Qilian Mountains population down placement; East-west direction of the movement is mainly due to the gathering role of the center in Jinchang city and Wuwei City. This shows that the urbanization development speed of Wuwei and Jinchang is faster ten years. In addition, it also can be found that the center of gravity position and direction of movement of the population direction of movement of the focus of population density is completely different. This is mainly due to desert and other natural division of the Shiyang River Basin, and township-level administrative divisions of the shape and size difference causes. Therefore, when analysis of population distribution center of gravity changes, it can not use population center of gravity to instead of population distribution in the center of gravity.
Population shift growth analysis. The change of the regional distribution of population is caused by the internal region offset growth, so it can study the reasons for the change of population distribution by the population offset growth of the basin. The offset growth of the Shiyang River Basin population in the decade 2000- 2010 is calculated by taking use of the population offset growth analysis model, as shown in
For the population migration growth among the township units, we take use of the standard deviation approach to classification and visualization, shown in
Index | 2000-2010 | Index | 2000-2010 |
---|---|---|---|
Total population growth of the Shiyang River Basin (ABSGR) | 4.37 | Tianzhu County (VOLSHIFT (intra Tianzhu County)) | 0.07 |
Percentage in the initial years | 1.95% | Liangzhou Area (VOLSHIFT (intra Liangzhou Area)) | 7.76 |
The total migration growth among the townships of the basin (VOLSHIFT (total)) | 11.85 | Yongchang County (VOLSHIFT (intra Yongchang County)) | 0.51 |
The total migration growth among 5 counties and 2 regions (VOLSHIFT (inter)) | 1.06 | The total migration growth among the internal township unit of 3 prefecture-level cities (VOLSHIFT (intra 3 cities)) | 11.73 |
The total migration growth among the internal township unit of 5 counties and 2 regions (VOLSHIFT (intra)) | 10.79 | Among: | |
Among: | Wuwei City (VOLSHIFT (intra Wuwei City)) | 10.81 | |
Gulang County (VOLSHIFT (intra Gulang County)) | 1.78 | Jiangchang City (VOLSHIFT (intra Jiangchang City)) | 0.93 |
Minqin County (VOLSHIFT (intra Minqin County)) | 0.66 | The total migration growth among 3 prefecture-level cities (VOLSHIFT (inter 3 cities)) | 0.12 |
trend is obvious: for combined Gaoba Town (history including Gaoba Town and Liuba County), which is close to Wuwei City and greatly influenced by Wuwei City urbanization, population migration growth absolute value is the largest, the Value achieving to −14292.11 and the rate of decrease of population is the fastest; followed by combined Zhangyi Town (history including the Zhangyi Town, Zhonglu County and Shangquan County), population offset growth amounted to −11572.54. In addition, for the desert area, Qilian high mountain area, and part towns in Gulang County, outside the basin population distribution concentrated area, the growth of population offset is positive, the demographic changes is in the growth trend. But only for Sanlei Town in Minqin, Chengguan Town in Yongchang County, Huangyang Town and Jinta Town in Wuwei, and part towns in Gulang County, the population offset growth is larger, the rest of the regions, offset growth in the amount of the population is relatively small.
This paper studied population distribution characteristics of space and time of the Shiyang River Basin from 2000 to 2010, by analysis of population distribution, population distribution structure index analysis, population distribution center of gravity model and population offset growth analysis model, and mainly drew the following conclusion:
1) Shiyang River Basin population density is low, concentrated in the middle reaches corridor plains area and three population distribution centers of Minqini oasis region, and forms the “point-areas-ribbon” structure characteristics, regional centers, plain corridor areas and transportation corridors as the basis. Basin internal population distribution is quite different, and there are eight high-value anomaly areas, especially Wuwei City, the population density is the largest.
2) The Basin population density of the center of gravity is located in the Liangzhou Daliu country territory; it offset about 1209 m to south-west Wuwei City direction from 2000 to 2010 which offset to east-west direction that was larger than north-south direction. At the same time, the distance of the population density center of gravity from the geometric the center of the basin is relatively far away; for 10 years, it offset about 751 m. The distance of the population center of gravity and the center of gravity of population density is relatively close. But, it can’t use the population center of gravity instead of population density of gravity to analyze the changes of population distribution centre of gravity.
3) In ten years, each level of Shiyang River Basin, townships as the basic statistical unit, in the overall population changes are not significant: for township level, population change is the biggest, population growth rate differences is also the largest; units at all levels as the basic statistical unit, population changes are very great, changes in population growth rate decrease rapidly with the increasing level of Administrative Region (SAR) level. Meanwhile, for Prefecture level, the population offset growth of the basin was mainly concentrated in Wuwei City; for county district level, it mainly concentrated in Gulang County the population offset growth of the basin. In other words, in the concentrated area of population distribution, Wuwei City and Gulang Town as the center, the rate of population growth is relatively fast; while in population distribution sparse areas and desert areas, the rate of population growth is relatively low.
4) For ten years, among the basin township units, there are significant changes in population migration. Wuwei City and the Gulang Town are two distinct population migration destination area and population agglomeration area, and there, the population offset growth is also the fastest. Within the Midstream plain corridor area of the basin, except Wuwei City, Gulang Town and some towns of Gulang County, in other towns, the population offset growth is negative, obviously offset to concentrated area of population; In most towns in the sparsely populated area, mainly in Minqin desert area and Qilian mountain area, the population offset growth is positive, but in most towns, the total amount of the offset is relatively small.
Overall, population distribution of the Shiyang River Basin has a significant spatial clustering and population offset growth characteristics. Relying on local unique landscape environment formed its own unique “point- area-ribbon” distribution structure and for ten years, basin population changes showed obvious characteristics of offsetting to the Wuwei City and Gulang Town. However, in the analysis of the basin, a series of questions will bring some degree of difficulty, such as different shape and area of the township units, frequent changes of administrative divisions, lack of statistical data and inconsistent statistical standards. Characteristics of population distribution are affected by a variety of natural and anthropogenic factors, especially water and traffic impact. Therefore, it needs to consider all relevant factors to faithfully reflect the characteristics of basin population distribution, providing strong support to achieve coordinated development of population and environment.
This work was financially supported by China’s National Natural Science Foundation (No. 40971078). The graphic data set is provided by Environmental and Ecological Science Data Center for West China, National Natural Science Foundation of China (http://westdc.westgis.ac.cn).