| Urbanization is an important indicator to measure the economic and social development of a country or region,and it is also the only way to promote social development and improve people’s living standards.After nearly 50 years of urbanization construction,about 60%of the population in China now lives in cities.However,due to the lagging of the concept of ecological protection and sustainable development,problems such as unreasonable planning and blindly expanding the scale of cities exist in the process of promoting urbanization in China.Various ecological problems have accumulated in the process of urban development,such as the lack of water resources in urban areas,the loss of rainwater resources,the increase of runoff pollution and the frequent occurrence of urban waterlogging disasters,which seriously restricts the health and sustainable development of urban areas.Sponge City is regarded as an advanced concept and effective measure to solve the current urban water ecological problems in China.It advocates harmonious coexistence and development between city and nature,restores urban water ecological environment with low-cost rainwater and flood management measures,and further restores the ecological system balance of the whole region and river basin.Since 2013,the Chinese government has vigorously advocated and promoted the construction of sponge cities,which set off a series of attempts and research upsurge in the construction of sponge cities.However,most of the research and practice focused on the economically developed,humid and semi-humid areas in the central and eastern part of China,and the attention paid to the construction of sponge cities in arid and semi-arid regions is far from enough.The global arid and semi-arid area accounts for about 36%of the total land area,involving more than 80 countries and 40%of the global population.And China’s situation is even more serious.Arid and semi-arid areas account for 53%of the total land area,covering a large area of Inner Mongolia,North China,northwest and southwest.These regions are not only the important ecological barriers in China,but also are the core corridor of"one belt and one road"initiative in China.And they are also act as the many node cities area,so the geographical position is very important.At the same time,under the influence of global climate change,the world is facing the continuous and rapid expansion in arid areas,and the trend of the higher temperatures,frequent extreme weather events.Due to the fragile ecological environment and weak disaster resistance,arid and semi-arid areas are very sensitive to climate change and human activities,and will certainly face more serious effects of drought and climate warming.Therefore,it is of great significance to explore how to reasonably plan and build sponge cities in arid and semi-arid areas for the protection of ecological environment and the development of social economy.This study takes the arid and semi-arid regions of China as the research area.Firstly,the conceptual framework of sponge city construction in arid and semi-arid regions based on the theory of catchment agriculture is discussed from the perspectives of the problems and challenges faced by urban construction in arid and semi-arid regions,the connotation of sponge city construction,the mechanism of combining catchment agriculture with sponge city construction and the theoretical support.Secondly,based on the short-term,medium-term and long-term objectives of sponge city construction in arid and semi-arid regions,it then puts forward the scheme design of sponge city construction in arid and semi-arid region based on catchment agriculture theory from three levels of micro-sponge unit scale,meso-city scale and macro-watershed scale.Thirdly,this study chooses Lanzhou City as an empirical analysis area,and puts forward the design idea of sponge city construction in Lanzhou City according to the actual situation of Lanzhou City.Taking Xingang City District of Cheng Guan District of Lanzhou City as an example,the catchment volume and the value of urban ecological service promotion were predicted from the perspective of the district and the construction area of the city respectively,and the feasibility of the construction scheme was analyzed.Finally,according to the empirical research and the present situation of sponge city construction,the countermeasures and suggestions of sponge city construction in arid and semi-arid regions are put forward.The main results are as follows:1.On the theoretical level,urban construction in arid and semi-arid areas should focus on water ecology problems,and the concept of sponge city construction in arid and semi-arid regions should fully consider the rich practice and theoretical experience of catchment agriculture theory in solving the problem of uneven spatial and temporal distribution of water resources in arid and semi-arid regions,organically combining with the concept of sponge city construction.It is supposed to be supported by the basic low-impact development measures and the principle of sponge cities adapting to local conditions,and taking the collection,purification,saving and utilization of precipitation resources as the main contents,in order to improve the urban water ecological problems in arid and semi-arid regions and realize livability in arid and semi-arid regions and accomplish the goal of city and ecological watershed construction.2.At the operational level,the sponge city construction in the micro-scale arid and semi-arid area is taken as the concrete sponge unit construction,and the landscape design scheme is mainly combined to increase the urban greening rate and collect rainwater resources as much as possible;taking the construction of sponge cities in arid and semi-arid regions at meso-scale as a foothold,focusing on land use control planning and urban design,forming a solid urban sponge system;the construction of sponge cities in arid and semi-arid regions on a macro scale focuses on the construction of a unified planning and management system of the river basin and the construction of a water ecological security pattern at the river basin level.3 Empirically,considering the characteristics of Lanzhou city,such as narrow area,high building density,geography and climate,etc.,the sponge unit construction in Lanzhou should focuses on green roof construction,and fully taps the construction potential of other sponge facilities.The study shows that,based on the built-up area of Lanzhou City in 2017and the building density of 37%,under ideal conditions,the development of green roof can increase the urban green space area of Lanzhou City by 117.41 km~2.In addition,the total area of sponge unit in Lanzhou will reach 207.01 km~2,and the contribution to ecosystem service value will increase by about 364-389 million yuan.The ideal annual water harvesting value of Lanzhou will reach 86 million m~3 after the implementation of the renovation scheme,which is basically equivalent to the ecological environment water consumption of Lanzhou.4.On the suggestion level,taking the problem as the guidance,the paper puts forward the relevant countermeasures and suggestions for the construction of sponge cities in arid and semi-arid regions as follows:(1)Change the concept of urban development,abandon the concept of urban construction which destroys the ecology and only seeks development,and establish the concept of sustainable development of harmonious coexistence between cities and nature;(2)Establish and perfect relevant legal system to build sponge cities for water resources utilization,water environment protection and sponge city construction;(3)Insist on the"three simultaneous"of urban construction planning and water-saving facilities and ecological environmental protection,that is,simultaneous design,construction and use,should be problem-oriented,technical measures should be in line with the conditions of the construction site;(4)Strengthen the construction of basic stations,promote transparency and openness of basic data;(5)Encourage public participation,draw wisdom and strengthen supervision;(6)Optimize investment and financing channels and innovate investment and financing modes. |
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