| The climate in Central Asia is arid,the ecological environment is fragile,and it is sensitive to climate change.The basin is the area where the interaction between humans and nature is the strongest,especially in the middle and lower reaches.The oasis in this area has a prosperous agriculture,high population density,rapid urbanization,frequent land use/cover changes,and the transboundary nature of the watershed,which has caused more prominent and complex water and soil resource disputes and ecological and environmental issues.Studying the status of land use/cover change in this area and its relationship with water resources is of great significance to the rational allocation of water and soil resources and the restoration of the ecological environment.Therefore,this paper takes the middle and lower reaches of the three typical river basins in Central Asia as the study area,and uses long-term land use/cover and surface water remote sensing data from 1995 to 2018 to extract land use/cover and surface water area information in the study area,using a variety of dynamics change model to reveals the spatiotemporal evolution characteristics,transfer laws and landscape pattern characteristics of land use/cover,explores the driving mechanism that causes the spatiotemporal changes of land use/cover,and conducts coupling analysis of land use/cover change and water resources in combination with relevant hydrological data.The main research results are as follows:(1)Dynamic monitoring and analysis of land use/cover spatiotemporal changes in study area based on land use degree index,information entropy,equilibrium degree,and transfer model:The expansion of cultivated land in the study area has led to changes in land use/cover pattern and has obvious phase characteristics.From 1995 to2005,the cultivated land in the middle and lower reaches of the Syr River and Balkhash Lake increased rapidly(1226.21 km~2 and 10956.7 km~2),and the vegetation showed a decrease.From 2005 to 2018,the arable land in the two watersheds showed a slow increase,forest land,grassland and water bodies have recovered to a certain extent,bare land continued to decrease,water bodies and towns continued to increase.However,the cultivated land and vegetation in the middle and lower reaches of the Amu Darya River Basin showed opposite changes,the water body continued to decrease significantly(78.83%).The rapid expansion of urban areas in each river basin by invading other land types.A large amount of water has been reduced and turned into bare land in Amu Darya River Basin,and the arable land in the other two basins has been transferred to increase in a large amount of forest,grass and bare land.(2)According to the calculation results of the landscape pattern index of each river basin:The water body is gradually fragmented in Amu Darya River Basin,and the towns are relatively scattered but intensified.As a whole,the landscape patches tend to gather,and the diversity and uniformity of the landscape are reduced;the cultivated land gradually shows a contiguous distribution in Syr River Basin,while the degree of fragmentation of the naked land is deepened.The overall landscape pattern tends to become more complicated;The forest land and grassland in the middle and lower reaches of the Balkhash Lake basin dominate,and the overall landscape pattern changes relatively stable.(3)Using the correlation analysis method to analyze the driving forces of regional land use/cover changes.It is concluded that the overall climate in the study area is changing from cold and wet to warm and dry,and the impact of climatic factors on land use/cover changes is more complex and insignificant.Population and night lights play an important role in land use/cover changes,indicating that population growth and economic development are the main driving forces for the evolution of land use/cover.(4)Using dynamic degree and rate of change methods to analyze the temporal and spatial dynamic evolution trend of surface water resources in the study area,it is concluded that seasonal water in the middle and lower reaches of the Amu Darya River has increased significantly,with an increase of 156.10%in 24 years.The permanent water showed a continuous decreasing trend,with an overall decrease of76.71%.Both the seasonal water and permanent water in the middle and lower reaches of the Syr River and Balkhash Lake Basin showed an increasing trend.Among them,the seasonal water increased the most,with an increase of 137.25%and351.60%respectively;the middle and lower reaches of the Balkhash Lake had the highest seasonal water dynamics(15.29%),the changes are the most active;the significant changes of seasonal water and permanent water are concentrated in the Amu Darya River,Ili River,Aral Sea and Balkhash Lake,and the phenomenon of permanent water conversion to seasonal water is obvious.(5)Using multiple regression analysis to explore the coupling relationship between land use/cover and water resources,it is concluded that the coupling degree of cultivated land,town and water resources index is high in the Amu Darya and Syr Darya,which is the main influencing factor of regional water diversion,river water quality,rainfall and evaporation.The expansion of arable land,population growth and improvement of living standards have increased the consumption of water resources and produced a large amount of agricultural non-point source pollution and production and domestic sewage,together with the backward sewage system,the water quality of rivers has gradually deteriorated and the ecological environment is becoming more fragile. |
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