An Introduction to the Recycling of Water Resources and Sustainable Development Planning in Urban Watersheds (Paper Sharing)

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　I’m not sure if this will work; please let the moderator correct me! Introduction to the Recycling and Sustainable Development Planning of Water Resources in Urban Watersheds. Source: China Thesis Download Center. Author: Yang Qingshan. Abstract: As urbanization accelerates worldwide, cities face increasing water demands, worsening water pollution, and an increasing number of cities suffering from shortages due to resource constraints or poor water quality. Traditional or current planning approaches for urban water supply and drainage are no longer sufficient to prevent water pollution in urban watersheds and the degradation of the regional natural water environment. A new concept for the recycling of water resources and sustainable development planning in urban watersheds is proposed, with the aim of establishing a modern approach to water supply and drainage planning, thereby laying the foundation for building cities that are resource-efficient and environmentally friendly in order to achieve energy conservation and emission reduction. 　　Keywords: water resources ； Planning ； Water supply and drainage ； Recycling 　　　　Abstract: With the advancement of urbanization, urban water demand continues to rise, while water pollution becomes increasingly severe. Nowadays, water shortages caused by water resource limitations or poor water quality are on the increase; therefore, the traditional concepts of urban water supply and drainage planning are no longer sufficient to ensure the protection of urban water resources and the regional natural water environment. This paper proposes a new concept for urban water supply and drainage planning, aiming to establish a modern approach to such planning and to provide a foundation for achieving energy savings and emission reductions, as well as for building resource-efficient and environmentally friendly cities. As urbanization progresses globally, urban water demand keeps increasing, water pollution worsens, and water shortages are shifting from those resulting from insufficient water volume to those caused by resource limitations and poor water quality. This paper proposes the concept of circular utilization of water resources and sustainable development planning for urban watersheds, primarily based on an exploration of a conceptual shift in the current professional planning for urban water supply and drainage. 　　The basic requirement of traditional or current professional planning for urban water supply and drainage is: how to meet the city’s needs for water for production and daily use, as well as to ensure rapid and safe wastewater disposal ； The concept of water resource recycling and sustainable development planning for urban watersheds is as follows: in addition to ensuring the needs and safety of water for urban production and daily life, it involves treating the water supply as well as sewage and wastewater in a city or region as resources. Such resources are then systematically planned to be processed and recycled in an appropriate manner, so as to achieve balance in the water environment of that region or watershed, sustain social and economic development, and create cities that are resource-efficient and environmentally friendly. 　　 　　1 Concept of water resource cycle 　　 Water is a cyclical resource, as well as a renewable resource. Based on its objective laws and patterns of circulation, we can divide it into natural cycles and social cycles. 　　1.1 Natural water cycle Water exists in nature in three states: solid, liquid, and gas, and it is in a continuous cycle of movement within the hydrosphere, atmosphere, lithosphere, and biosphere. Under the influence of solar radiation and gravity, water evaporates from the oceans to form clouds (water vapor), which then fall back to the ground as rain or snow. Some of this water evaporates again, while some seeps into the ground or becomes part of surface runoff, eventually returning to the oceans. This continuous cycle of water movement is known as the natural cycle of water. 　　Characteristics of the natural water cycle: ① The natural water cycle is a relatively stable yet complex dynamic system; whether it is a large-scale cycle or a small-scale one, it is related to natural factors such as climate, soil, geology and topography, and vegetation conditions. It is also affected by human factors such as mountain ponds and reservoirs. The quality and quantity of water resources, as well as their distribution, are products of natural historical development ； ②In the natural cycle of water, there is not only a balance in water volume but also a dynamic balance in water quality, that is, the renewability of water quality. 　　Under the conditions of natural circulation, the global water cycle is balanced. According to recent reports, the global volume of circulating water is 496,000 km3. Of this, the amount of water evaporating from the oceans is 425,000 Km3, while the amount of water evaporating from land areas (including surface waters and land itself) is 71,000 Km3 ； Global water evaporation volume: 496,000 Km3 ； Rainfall over the sea surface is 385,000 Km3, rainfall on land is 111,000 Km3, and the total global precipitation volume is 496,000 Km3. The total amount of rainfall is balanced by the total amount of evaporation. Furthermore, in terms of the water balance between marine and terrestrial areas, precipitation on land exceeds evaporation from land by 40,000 Km3, and this amount of water constitutes the runoff that flows into the sea. The evaporation from the sea surface is 40,000 Km3 greater than the rainfall on the sea surface; the lost water volume is replenished by the runoff flowing into the sea, thus maintaining a water balance. 　　Based on the storage volumes of seawater, surface water, and groundwater, as well as their circulation volumes, it is not difficult to estimate the volume circulation patterns of these various water bodies and the average cycle time for one complete exchange. Under normal circumstances, water stored in the atmosphere and river water are the bodies of water with the most active exchange, with average exchange cycles of 10 days and 11 days respectively. The average exchange cycle for ice caps and glaciers is the longest, at 8,000 years per cycle. 　　1.2 Social water cycle The social water cycle refers to the process in which, within the natural water cycle, humans continuously utilize groundwater flow or surface water flow to meet the needs of their living and industrial activities. The circulatory system is mainly composed of three subsystems: the water supply system, the water use system, and the drainage system. The water supply system and the drainage system are like the arteries and veins of a city or region; neither can be neglected. If too much water is drawn from the water supply system, the ecological water needs of rivers cannot be met; moreover, untreated or inadequately treated wastewater will affect the natural water cycle. 　　 　　1.3 The relationship between the social water cycle and the natural water cycle The social water cycle is an additional component of the natural water cycle; it exerts a strong interactive influence on the latter, altering the movement of water around the world to varying degrees. The development and utilization of water resources represent a direct way for humans to intervene in their spatial and temporal distribution. While large-scale water management projects by humans have brought significant benefits in terms of production and energy, the negative impacts of the human-induced water cycle on the natural water cycle are becoming increasingly apparent. It is mainly manifested in the following aspects: ① The pathways of water circulation are altered (through spatial and temporal changes). Water conservancy projects such as artificial reservoirs, canals, dams, and long-distance inter-basin water transfers intercept large amounts of water on a large scale, changing the pathways of water circulation. This results in reduced water flow in downstream river sections, or even their drying up, leading to a sharp decrease in the amount of water that rivers supply to groundwater. Water transfer across river basins increases the dispersion of water flow within the surface water subsystems, which may affect the renewal cycle and movement patterns of surface water ； ②The water circulation volume has changed. The runoff extracted by humans accounts for about 10% of the world’s renewable water resources each year, significantly altering the volume of water flowing into surface rivers and causing substantial changes in the water cycle at various spatial scales. ③Changes in water quality: As water bodies are affected by human water use cycles, there is a significant increase in both the types and quantities of chemical substances present in them. Sources of pollution include untreated sewage, chemical emissions, and agricultural chemicals that are washed away from farmlands or seep into the ground. 　　 　　2 The Current Status of the Social Water Cycle in China and Reflections on Traditional Urban Water Supply and Drainage Planning Concepts At present, overall in China, the social water cycle still operates on a crude, unidirectional basis. That is, water is taken from the upstream of the watershed or groundwater aquifers, and after being used once by consumers, most of it is discharged into downstream water bodies. Throughout the entire water cycle, water is utilized only once, and no negative feedback mechanism is established. 58% of the total exploitable water resources in the country have already been used, and the growing demand for water in industrial and agricultural activities as well as for domestic use is met by increasing the extraction of water resources. However, these are used in agriculture, and the wastewater from agricultural irrigation as well as runoff from farmlands carry large amounts of fertilizers and pesticides back into water bodies. Meanwhile, the large volume of sewage generated by urban users is mostly discharged directly, continuously disrupting the natural water cycle and thus creating a sharp conflict between the two. It is estimated that, without taking into account water transferred from the southwest and after deducting the water required for ecological and environmental purposes, the amount of water available for exploitation nationwide is around 8000–9500×10^8 m³. By 2050, the country’s water demand could reach 7000–8000×10^8 m³, at which point it will be close to the limit of exploitable water resources. By the middle of the 21st century, it is expected that urban sewage in our country will continue to increase significantly, as shown in Table 1; among this increase, the rise in domestic sewage accounts for a large proportion of the total increase. 　　As can be seen from Table 1, the volume of urban sewage (wastewater) discharged nationwide will continue to increase in the future, and the pollutant load resulting from this urban sewage discharge will pose a severe challenge to urban drainage systems. If rapid expansion of wastewater treatment facilities, as well as improvements in treatment efficiency, the rate of advanced and ultra-advanced wastewater treatment, and the utilization rate of recycled water, cannot be achieved, the situation regarding water circulation will become even more severe in the future. Therefore, the traditional concepts of urban water supply and drainage planning can no longer meet the requirements of the social water cycle; it is necessary to rethink these planning concepts from the perspective of water resource recycling and sustainable development in urban watersheds. 　　In terms of traditional urban water supply planning, the goal is to meet the city’s water demand and ensure the quality of the water supply, with an emphasis often placed on finding suitable water sources. However, due to the pollution of regional water resources, or temporary contamination, the water quality of these sources does not meet the standards required for urban water supply. When it is difficult to find an ideal water source in the short term, many cities do not focus on finding ways to treat and prevent pollution in the regional watersheds; instead, they continue to draw water from the sources at the upstream end. Overall, the approach to water acquisition and use in urban development has always followed a linear pattern: when water is unavailable locally, it is drawn from upstream sources or surrounding areas, and then discharged and discarded after use ； When water resources are still insufficient, consider transferring water from further away. The prevalence of this way of thinking has led to the construction of increasingly large-scale and long-distance water diversion projects in many places, turning urban rivers into natural sewers. This water use strategy relies increasingly on the availability of water sources from the upstream areas of rivers in the urban hinterland. But this availability is facing increasing challenges. In particular, water usage is increasing in the upper reaches of rivers, while the available water resources in the lower reaches are declining, and water quality is also worsening. 　　The disadvantages of this traditional water use pattern are: ① A large number of long-distance water transfer projects result in ever-increasing costs, imposing a growing financial burden and leading to higher water prices ； ②The available water supply will continue to decline, and water quality safety cannot be guaranteed ； ③River life will gradually disappear, and landscapes and landforms will change more rapidly ； ④Conflicts and potential disputes between cities and regions will increase increasingly. 　　In terms of traditional drainage systems, urban drainage serves to prevent flooding caused by rainwater, remove and treat urban wastewater, and protect the urban environment as well as the water quality of the local river basins. It is generally believed that wastewater is harmful and should be discharged as quickly as possible downstream from the city. The outcome of this mindset is often the protection of local living environments at the expense of larger river basin areas. The disadvantages of this traditional drainage approach are as follows: ① There is an unclear understanding of the concepts behind urban drainage planning, and the planning is rather rudimentary. Drainage planning simply involves dividing drainage areas based on land use plans and urban road plans, determining the drainage system, and roughly outlining the locations of main drainage lines and wastewater treatment plants. Necessary evaluations of regional water resources and comprehensive coordination are lacking, and there is no scientific and reasonable comparison of different options ； ②Traditional urban drainage planning is limited to simple discharge processes and lacks the concept of water resource recycling and sustainable development; it does not recognize that rainwater and wastewater are also resources that should be utilized first before being discharged ； ③Drainage planning is limited to the local city or region, lacking an approach to comprehensive development and utilization of river basins ； ④There is a lack of effective coordination and cooperation between urban drainage planning and the construction of municipal sewage and rainwater treatment facilities ； ⑤There is a lack of technical support measures for the recycling of rainwater and wastewater. 　　In short, in the traditional concepts of urban water supply and drainage planning in our country, there is a strong influence from ideas such as \"transforming nature\" and \"man can conquer nature.\" Humans are not considered as part of the ecosystem within a river basin; instead, an emphasis is placed solely on meeting the needs of human societal development, which in turn disrupts or even destroys the harmony and balance of the ecosystem in that basin or region. 　　 　　The concept of social water cycle for the sustainable development of 3 cities In fact, in urban agglomerations located within river basins, most cities are built near water bodies. Through years of development, they become functionally integrated with one another, such that the downstream area of one city serves as the upstream area for another city. A good water environment refers not to a local area but to the entire watershed. 　　In a city, a healthy water cycle requires a comprehensive water supply and drainage system. This includes a safe and reliable water supply system that provides residents with clean drinking water, as well as systems for collecting, treating, further purifying, effectively utilizing, and disposing of wastewater. 　　How to establish a concept of a social water cycle for sustainable urban development involves, compared to traditional urban drainage systems, at least three fundamental changes in terms of approach. 　　3.1 Systematic concept Systematicity is a characteristic that is inherent in things in nature. The urban water supply and drainage systems discussed earlier, from water extraction and purification to use and discharge, actually constitute a complete systematic project. If we re-examine our urban drainage systems from a systematic way of thinking and perspective, it may bring us closer to understanding certain objective laws governing the development of nature and human society, thereby providing a more comprehensive and feasible strategy to address the water crisis facing urban development today. The concept of water resource recycling and sustainable development planning for urban watersheds involves treating the urban water system as a unified whole, considering in an overall manner issues such as urban water demand, water use, recycling, drainage, as well as residents’ living conditions and food supply. Instead of addressing the problems arising from urban development in isolation, it focuses on systematically ensuring the rational distribution and sustainable development of water flows, nutrient flows, and energy flows within the urban watershed. 　　3.2 The concept of resource recycling 　　There are no wastes in nature; all materials should be able to be recycled. Establishing a resource-recycling system in urban water systems engineering represents a new attempt and effort in urban water supply and drainage systems. It is not a one-way flow that is used once and then discharged, as in traditional urban water supply and drainage concepts, but rather a closed-loop system for recycling. The wastewater after its first use will be collected and treated to produce reclaimed water that meets certain functional requirements. This reclaimed water is then supplied, through specialized water distribution systems, to urban industrial and municipal water users for repeated and cyclic use. 　　3.3 The Concept of Intrinsic Sustainability In the 20th century, we continuously built dams, constructed water diversion channels, and implemented long-distance water transport projects in order to find more new water sources to meet the needs of urban expansion and population growth. This leads to an increasingly degraded water environment and a growing shortage of water resources, resulting in greater impacts and pressures from urban development on the surrounding environment. The social water cycle has gradually become a heavy burden for the development of human society. A sustainable water resource system must not only meet the needs of modern people but also those of future generations. It is a philosophical concept, rather than a concrete state of existence. The sustainability of urban water supply and drainage systems is an inherent characteristic of modern urban water systems; it is an inevitable requirement for the development of human society and essential for a healthy cycle of water use in society. 　　In line with the concept of sustainable development of urban water resources, the utilization of water resources will shift from the past one-way open flow of \"water extraction – water transmission – use by users – discharge\" to a feedback-based circular process of \"restricted water extraction – water transmission – efficient water use – recycled water circulation\". 　　 　　4 Concepts of Water Resource Recycling and Sustainable Development Planning in Modern Urban Watersheds The concept of water resource recycling and sustainable development planning in urban watersheds was proposed as an exploration of a shift in the planning philosophy behind current urban water supply and drainage plans. It is key to realizing modern concepts for urban water supply and drainage planning. The transition from traditional to modern concepts in this field can be summarized in the following aspects: ① A shift from an approach where humans exploit nature to one that emphasizes harmonious coexistence with nature, as well as more efficient utilization of the renewable characteristics of water resources ； ②Shifting from supply driven by demand to demand driven by supply ； ③A shift from focusing on managing water quality at the factory level to managing water quality for end-users ； ④Shifting from acting independently and pursuing individual interests to resource sharing and integrated management of river basins ； ⑤Shift from conventional treatment processes to highly intensified treatment processes ； ⑥Shifting from a focus on both opening up resources and conserving them to giving priority to conservation, emphasizing pollution control, managing resource opening up scientifically, and achieving comprehensive utilization ； ⑦Shift from strict compliance with discharge standards for wastewater to its resource utilization ； ⑧Shift from focusing solely on end-processing to emphasizing both end-processing and upstream management ； ⑨Shifting from mere rainwater flood control and drainage to strengthening the management and utilization of rainwater from the perspective of water resource utilization ； ⑩There is a shift from traditional management to information-based management, socialized services, legal oversight, and diversified investment. In the planning and design of modern urban water supply systems, the new approach to water supply planning is to give priority to protecting the water sources in the respective river basins; to conduct a scientific analysis of the volume of water available in these sources as well as their environmental capacity, with the aim of improving the efficiency of water use ； In water-scarce cities and regions, it is necessary to approach the local **and planning authorities to adjust the industrial structure and control land use, restrict the development of industries with high water consumption, and increase the rate of recycled water use in industry ； In the agricultural areas upstream that are in conflict with urban water supply, it is necessary to actively develop water-saving agriculture, including adjusting the planting and industrial structures to match the available resources, as well as adopting water-saving irrigation methods, in order to provide downstream cities with an adequate water resource environment ； In the prediction of urban water consumption, industrial water-saving indicators should be taken into account, and the key indicator for controlling water savings, namely the rate of recycled industrial water, should be effectively implemented ； Urban water intake planning should be based on utilizing the water resources from local rivers, minimizing the need for water transfer over long distances, and controlling the scale of water intake while ensuring an adequate supply for ecological purposes. It is generally considered appropriate for the water withdrawal amount not to exceed 40% of the runoff volume ； In areas suffering from severe water scarcity, when the water withdrawal volume has to exceed 40% of the runoff volume, it is necessary to use reclaimed water for supplementation in order to meet the qualitative and quantitative requirements of river ecosystems for water, thereby increasing the amount of water allocated for ecological purposes ； The water use and wastewater discharge in upstream cities do not affect the water supply in downstream cities, enabling resource sharing. Each city needs to limit both the amount of water it draws and the quantity and quality of its wastewater discharge, so as not to pollute the lower reaches of the river, thereby ensuring sustainable utilization of water resources throughout the entire river basin. 　　The characteristics of this new concept for water supply planning are: ① a model for the integrated utilization of water resources on a watershed basis. Managing on a watershed basis is in line with the natural properties and systemic characteristics of water resources. This new approach to water extraction emphasizes that water use within each watershed should be addressed within that watershed itself; it ensures that water needs in the watershed are met by taking into account the requirements of cities, humans, and the river ecosystem both upstream and downstream, thereby promoting greater fairness and sharing of water resources within the watershed. ②Sharing and recycling of water resources. To ensure that the main sources of water for urban use come from the local river basins, it is necessary to change the one-time-use model of water consumption, and to achieve the utilization, regeneration, and recycling of water within the urban watershed ； ③An economic and secure water supply system. The sustainable development of local water resources can reduce dependence on water from external basins, thereby enhancing the reliability of local water supply. At the same time, the new watershed water use model enhances the security of urban water supply; if cities achieve the recycling of wastewater, it can to some extent mitigate the impacts of sudden natural disasters. 　　In the planning and design of modern urban drainage systems, their function should shift gradually from preventing flooding and pollution-related disasters in the past to the recycling of sewage and nutrients, thereby restoring a healthy water environment and promoting the sustainable use of water resources. In collection, processing, regeneration, and recycling, it is necessary to emphasize not only the quantity of materials that are recycled but also the quality of these recycled resources. 　　With the development of society and an increasing awareness of environmental issues, water pollution control in our country has gone through two stages: treatment of single pollution sources and ensuring that wastewater meets discharge standards, followed by comprehensive regional prevention and control as well as total amount control. However, the operation rate, utilization rate, and pollutant removal efficiency of the wastewater treatment equipment in most cases are not high, and many of these devices fail to perform their functions. At the same time, there is insufficient attention paid to urban sewage treatment plants, especially a lack of the concept of sewage reuse and recycling. 　　In the new concepts for drainage planning, the first thing to consider is how to protect the water sources in the respective river basins. It is necessary to scientifically analyze the water environmental capacity of these sources, divide the areas into different drainage zones based on topographical and geomorphological characteristics, determine the drainage system, establish discharge standards and treatment processes, set goals for energy conservation and emission reduction, and improve the efficiency of water resource utilization. 　　When formulating urban master plans, it is necessary to develop regional water resources plans in a timely manner. Drainage planning should change the previous approach and methodology, which always involved subordinating itself to the overall plan and passively adapting to the city’s overall layout. Proactive efforts should be made to put forward reasonable suggestions for the master plan that are closely related to regional water resources planning and drainage planning. For example, in order to meet the requirements of regional water resources planning, the master plan should clearly specify the natural waterways that need to be preserved, as well as the road designs and elevation plans required to satisfy drainage needs ； It is necessary to actively coordinate with specialized plans for water resources management and urban flood control in order to make rational use of water resources. It is necessary to adopt a watershed perspective, break down administrative boundaries, and consider urban and regional drainage planning from the perspective of the entire watershed ； 　　To adapt to the changes in the functions of modern drainage systems, today’s urban drainage systems consist of a sewage collection system, a sewage treatment and reuse system, a reclaimed water supply system, and a high-quality treated water discharge system. Compared with traditional drainage systems, it includes elements of wastewater reclamation and reuse, improving the level of wastewater treatment from secondary treatment to advanced treatment or even ultra-advanced treatment, thereby meeting the requirements for reclaimed water. A thorough investigation should be conducted into the functional zoning of the entire city, the distribution of industries, the drainage network, and the current state of wastewater treatment. The geographical locations of existing and potential reclaimed water users, as well as their requirements regarding water volume and quality, should be identified, and these findings should be reflected in the specialized planning. Treat sewage treatment plants as reclaimed water plants, changing the traditional practice of locating them at the farthest downstream point in the city for highly centralized treatment. 　　When planning a sewage treatment plant, the following points should be considered: ① It is necessary to take into account the needs for sewage reuse both in the short and long terms, select an advanced sewage treatment system, and reserve space for the development of such advanced treatment facilities, so as to minimize the total investment in sewage treatment, advanced treatment systems, and reuse systems ； ②Location and number of sewage treatment plants. According to traditional planning methods, the location of a wastewater treatment plant is determined based on factors such as pollution emission control targets, urban layout, and the functions and flow rates of the receiving water bodies; generally, it is placed as far downstream as possible in river systems or in the suburbs of cities. However, this system layout places wastewater treatment plants far away from reclaimed water users, resulting in higher costs for the pipelines required to transport the reclaimed water, which hinders the recycling of wastewater. Therefore, when determining the location of sewage treatment plants, it is also necessary to conduct surveys and analyses of users who require reclaimed water. Based on the demand for reclaimed water, several sewage treatment (reclaimed water) plants should be established in appropriate locations within the city to collect urban sewage from upstream and nearby areas. After treating this sewage according to the requirements for reutilized water, it can be reused locally, thereby creating a layout plan for sewage reuse plants in the city that combines large, medium, and small-scale facilities as well as those for short-term and long-term use. In this way, it facilitates the reuse of wastewater, reduces the burden on urban drainage systems, allows for phased construction, and is in line with China’s national conditions. ③When selecting treatment processes, various combinations of water treatment units should be considered based on the quality of the wastewater and the requirements of the users who will receive the reclaimed water; an economically viable and technologically advanced wastewater treatment process is then chosen through technical and economic comparisons. Economic analysis is conducted on the premise of meeting all the requirements regarding water quality of the effluent. In addition to factors such as costs and technology, it is also necessary to consider whether this approach facilitates wastewater recycling; that is, on top of the existing technical and economic analysis factors, a comparative factor related to the suitability for wastewater and material recycling is added. 　　Traditional urban municipal management, in order to ensure city safety, tends to treat rainwater as a \"dangerous force,\" adopting as its primary principle \"draining surface rainfall into urban drainage systems as quickly as possible and then into rivers and seas,\" ignoring the idea that rainwater is also a valuable natural resource. In fact, storage and regulation are the hydrological cycle mechanisms for conserving groundwater and replenishing surface water flow during dry periods. In modern cities, apart from the park greens and natural water bodies scattered throughout the urban area, the entire city is almost covered by an impermeable barrier that prevents rainwater from penetrating into the soil beneath the city, blocking groundwater flow. This severely affects the hydrological cycle of rainwater in urban areas, resulting in flooding during the rainy season and dried-up rivers during the dry season. At present, many **place great emphasis on the collection and utilization of rainwater. In water-scarce areas of our country, there is consideration being given to making use of rainwater, but it has not yet been widely accepted. Reasonable collection, storage, regulation, and utilization are highly beneficial for improving the climate conditions in urban areas, reducing peak flood levels in urban watersheds, and minimizing the impact of surface pollution on these watersheds. To make full use of rainwater resources, the following aspects should be considered: ① It is necessary to scientifically and reasonably derive calculation formulas for storm intensity suitable for urban development, adopt appropriate retention and infiltration measures to increase groundwater infiltration and reduce surface runoff ； ②Select appropriate drainage standards, and take necessary flood control measures to ensure urban flood safety. ③Raise the standards for flood control in rivers to ensure that rainwater can flow into them without being blocked ； ④Plan the construction of urban rainwater storage and treatment facilities in a rational manner, and integrate rainwater collection with reuse effectively ； ⑤Where possible, adopt a separate drainage system for rainwater and sewage to reduce pollution in urban water bodies. 　　 　　5 Conclusion The purpose of this research on the recycling of water resources in urban watersheds and sustainable development planning is to propose new concepts for urban water supply and drainage planning, building upon traditional approaches in this field. In the face of the increasingly severe water crisis facing humanity today, taking more measures to recycle water resources in urban watersheds lays a solid foundation for building cities that are resource-efficient and environmentally friendly, enabling better sustainable development for humanity and society. 　　 　　References: 　　 Wang Xiqin. Theory, Methods, and Applications of Ecological Water Demand for Rivers. 　　 Ren Bozhi et al. Water Resource Utilization and Protection. 　　 Zhang Jie et al. Principles and Applications of Water Health Circulation. 　　 Wu Qunhe et al. Regional Cooperation and Comprehensive Improvement of Water Environment. Reposted from China Thesis Download Center http://www.studa.net