刊首语

Wang Xiangrong

管子在《管子·水地》中说：“水者何也？万物之本原也。”水孕育了生命，也孕育了人类的文明。人类择水而居，建立聚落，发展为城市。水始终是城市生态、生活和经济的命脉。

北宋画家张择端在 “清明上河图”中描绘了北宋都城东京汴梁的市井风俗，也向我们传达了古代城市的运河景象。画面以汴河为中心，从疏林薄雾、阡陌纵横的郊外逐渐过渡到屋宇错落、百肆杂陈、车水马龙的城市。汴河之上，舟船往复，飞虹卧波，一派漕运繁忙的景象。张择端的另一幅画作 “金明池夺标图”，展现的是位于汴河畔的金明池水上娱乐的盛况。金明池在北宋初年是一片用于水军训练的人工湖，后成为重要的皇家园林。湖为方形，湖边栽植柳树，尽管是皇家领地，但在每年特定的时间也向汴梁的百姓开放。

张择端的这2幅画作都展现了北宋时期汴梁城市的水系景观，不过它们反映的仅是城市水环境的一个片段。实际上除了汴河外，东京汴梁还有蔡河、五丈河和金水河共4条人工运河贯穿城市内外；城市有三重城垣，每重城垣之外都有护城河环绕；城市内外还有金明池、琼林苑、玉津园、艮岳等园林湖池。从城市北部和西部流过的黄河和洛水为这些水体提供了水源。城外有陂湖和灌溉渠网，广浸民田；城内有排水沟渠，排洪泄涝。东京汴梁是人口超过百万的大都市，这些水网承担着城市蓄水、供水、分洪、调水、排水、灌溉、漕运，以及水上交通和园林等功能。水为汴梁带去繁荣与活力，也滋养了汴梁灿烂的文化。欧阳修、王安石、苏轼等都留下了描绘汴河、蔡河和金明池的风景诗篇，汴京八景中也有五景与水相关。

汴梁城水网只是城市水环境的一个范例。水是人类赖以生存的自然资源，但过多的水又会造成严重的灾难，所以当人类定居下来，就必然要梳理水系，让风雨顺轨，河网安流，以使农业稳产、聚落安全。中国是一个以农业为本的国家，由于农业灌溉的需要在很早就开始开渠筑堰，建造各种水利工程，而城市则在一定的农业经济单元中发展而来。各地依据不同的自然条件创造出的农业生产的支撑系统，如陂塘、运河、灌渠等，实际上也是城市的环境支撑系统。中国古代的城市往往位于河流边缘却又与之保持一定的距离，然后通过建造这些人工水系与天然水系连通，形成贯穿城市内外的安全和可控的水的系统。所以城市水环境问题，实际上是城市内外的整体水环境问题，是人居水环境问题。

在古代农业社会，我们的祖先创造了一套行之有效的城市水系统建造、使用和管理的方法，确保了历史上城市的安全和繁荣。今天，现代城市规划所遵循的工业革命之后的城市建设理论和经验，为应对不断膨胀的城市人口和城市规模、创造现代城市文明作出了巨大贡献。然而，现代城市把城市建设相关内容分解为规划、水利、市政、建筑、园林等诸多专业，并过于依赖采用工程手段解决城市问题，也造成了城市自然系统的割裂、自然过程的中断和生态条件的损害，并带来了非常严重的环境问题，其中之一就是城市水环境恶化。

在快速城市化过程中，城市水系的大量填埋和硬化，不仅削弱了城市防洪能力，阻断了地表水和地下水的交流，而且造成生境的丧失；城市中大量的硬化地面阻碍了天然降水的渗透，打断了水的上下循环，使地表径流量增加、地下水减少；大量被污染的水向河流湖泊排放，恶化了水质，破坏了生物栖息环境。城市水资源短缺、水系破碎化、水质污染、水生境破坏等造成了城市水环境的恶化，为城市安全和繁荣发展带来了诸多隐患。

在《管子·水地》中管子还谈道：“水者，地之血气，如筋脉之通流者也。”水是将地球上万物联系起来的纽带。水不仅存在于各种水体中，也存在于空气、土壤和动植物之中。城市水环境的问题，不仅仅局限于城市水体本身，也取决于区域水系统的健康和完善；城市水环境的建设，不仅要关注水自身的质和量，还要维护区域的山、林、田、草等自然生态系统的基本要素，涵养水源，保护生境，如此才能构建健康的城市水环境。

In his Guangzhi—Irrigated Land, Guanzi said: "What is water? The origin of all things."Water gives birth to life, and human civilization as well. Humans live by water, and establish settlements which develop into cities. Water is always the lifeblood of urban ecology, life and economy.

The Northern Song Dynasty painter Zhang Zeduan described the customs of the east capital Binliang in the Northern Song Dynasty in his painting The Riverside Scenes at the Qingming Festival, and also conveyed the canal scene of the ancient city to us. The scene is centered along Bian River, and it gradually transfer from the outskirts of woodland,forests, mists, and passes crisscrossed in the fields, to the cities of scattered and random houses, various shops, and crowded people and vehicles. Above Bian River, the boats and ships reciprocated and fluttered like rainbows, presenting a busy transporting scene. Zhang Zeduan's another painting, The Prize Capturing at Jinming Pool, shows the grand occasion of the water entertainment in Jinming Pool along Bian River. Jinming Pool was an artificial lake used for naval training in the early years of the Northern Song Dynasty and later became an important imperial garden. The lake is a square, planted with willows. Although a royal territory,it was open to the people of Bianliang during a specific period of time each year.

Both of Zhang Zeduan's paintings show the urban water landscape of Bianliang during the Northern Song Dynasty, but they reflect only a fragment of the urban water environment.In fact, there are four artificial canals in the city, including Cai River, Wuzhang River, and Jinshui River, and Bian River, running through the city. The city has three city walls, and there are moats around the city walls, one for each; there are Jinming Pool, Qionglin Court, Yujin Garden and Genyue Hill landscape inside and outside the city. The Yellow River and Luo River running through the north and west parts of the city provide whater for these water bodies. Outside the city, there are ponds and irrigation canal networks feeding the agricultural lands; inside the city, there are drainage ditches discharging flood. The east capital Bianliang was a metropolis with a population of more than one million, and these water networks shoulder such functions as water storage, water supply, flood distribution, water transfer, drainage, irrigation, goods and people transportation, and landscape. Water brings prosperity and vitality to Bianliang and it nourishes the splendid culture of Bianliang. Ouyang Xiu, Wang Anshi, and Su Shi all left landscape poems depicting Luo River, Cai River and Jinming Pool. Five out of the Eight Scenes of the East Capital Bianliang were related with water.

Bianliang city water network is just one example of urban water environment. Water is a natural resource on which mankind depends, but too much water can cause serious disasters. Therefore, when humans settle down, it will be necessary to sort out the water system, making winds and rains flow along the river network and keeping the river network safe, so that the agricultural production can be stabilized and settlements safe. China is an agricultural-oriented country, and due to the needs of agricultural irrigation, it began to open up canals and construct various water conservancy projects very early, while cities developed in certain agricultural economic units. The support systems for agricultural production that have been created based on different natural conditions, such as ponds, canals and irrigation channels, are actually the cities' environmental support systems. Ancient Chinese cities were often located on the edge of rivers but kept a certain distance from them. Then, by building these artificial water systems, they were connected with natural water systems to form safe and controllable water systems throughout cities. Therefore, the problem of urban water environment is actually an overall water environment problem inside and outside the city, and it is a human habitat water environment problem.

In ancient agricultural societies, our ancestors created an effective method of construction, use, and management of urban water systems, ensuring the safety and prosperity of cities in history. Today, the urban construction theory and experience after the industrial revolution followed by modern urban planning have made tremendous contributions to respond to the ever-expanding urban population and city scale, and the creation of modern urban civilization. However, modern cities decompose urban construction related contents into planning, water conservancy, municipal engineering, architecture, gardening and many other professions, rely too much on the use of engineering methods to solve urban problems.This has also resulted in the fragmentation of urban natural systems, disruption of natural processes, and damage of ecological conditions, and brings about very serious environmental problems, one of which is the deterioration of urban water environment.

In the process of rapid urbanization, the massive landfill and hardening of urban water systems not only weakened the city's ability to prevent floods, blocked the exchange of surface water and groundwater, but also caused the loss of habitats; a large amount of hardened ground in city hindered natural precipitation, and interrupted the upward and downward circulation of water, resulting in an increase in surface runoff and a decrease in underground water; a large amount of contaminated water was discharged to rivers and lakes,which deteriorated water quality and destroyed the habitat of living organisms. The shortage of urban water resources, the fragmentation of water systems, the pollution of water quality, and the destruction of aquatic habitat have caused the deterioration of urban water environment,bringing many hidden dangers to the safety and prosperity of city.

In his Guangzhi—Irrigated Land, Guanzi also said: "Water, the blood of the earth, is like the running flow in veins." Water is the link that connects everything on the earth. Water exists not only in various water bodies, but also in air, soil, plants and animals. The problem of urban water environment is not only confined to the urban water body itself, but also depends on the health and perfection of the regional water system. The construction of urban water environment needs not only to pay attention to the quality and quantity of water itself, but also to maintain the basic elements, such as mountains, forests, fields and grass, of regional natural ecological systems, to conserve water sources and protect habitats, so that a healthy urban water environment can be constructed.