Wang Xiangrong

管子在《管子·水地》中說：“水者何也？萬物之本原也。”水孕育了生命，也孕育了人類的文明。人類擇水而居，建立聚落，發(fā)展為城市。水始終是城市生態(tài)、生活和經(jīng)濟的命脈。

北宋畫家張擇端在 “清明上河圖”中描繪了北宋都城東京汴梁的市井風(fēng)俗，也向我們傳達了古代城市的運河景象。畫面以汴河為中心，從疏林薄霧、阡陌縱橫的郊外逐漸過渡到屋宇錯落、百肆雜陳、車水馬龍的城市。汴河之上，舟船往復(fù)，飛虹臥波，一派漕運繁忙的景象。張擇端的另一幅畫作 “金明池奪標(biāo)圖”，展現(xiàn)的是位于汴河畔的金明池水上娛樂的盛況。金明池在北宋初年是一片用于水軍訓(xùn)練的人工湖，后成為重要的皇家園林。湖為方形，湖邊栽植柳樹，盡管是皇家領(lǐng)地，但在每年特定的時間也向汴梁的百姓開放。

張擇端的這2幅畫作都展現(xiàn)了北宋時期汴梁城市的水系景觀，不過它們反映的僅是城市水環(huán)境的一個片段。實際上除了汴河外，東京汴梁還有蔡河、五丈河和金水河共4條人工運河貫穿城市內(nèi)外；城市有三重城垣，每重城垣之外都有護城河環(huán)繞；城市內(nèi)外還有金明池、瓊林苑、玉津園、艮岳等園林湖池。從城市北部和西部流過的黃河和洛水為這些水體提供了水源。城外有陂湖和灌溉渠網(wǎng)，廣浸民田；城內(nèi)有排水溝渠，排洪泄?jié)?。東京汴梁是人口超過百萬的大都市，這些水網(wǎng)承擔(dān)著城市蓄水、供水、分洪、調(diào)水、排水、灌溉、漕運，以及水上交通和園林等功能。水為汴梁帶去繁榮與活力，也滋養(yǎng)了汴梁燦爛的文化。歐陽修、王安石、蘇軾等都留下了描繪汴河、蔡河和金明池的風(fēng)景詩篇，汴京八景中也有五景與水相關(guān)。

汴梁城水網(wǎng)只是城市水環(huán)境的一個范例。水是人類賴以生存的自然資源，但過多的水又會造成嚴重的災(zāi)難，所以當(dāng)人類定居下來，就必然要梳理水系，讓風(fēng)雨順軌，河網(wǎng)安流，以使農(nóng)業(yè)穩(wěn)產(chǎn)、聚落安全。中國是一個以農(nóng)業(yè)為本的國家，由于農(nóng)業(yè)灌溉的需要在很早就開始開渠筑堰，建造各種水利工程，而城市則在一定的農(nóng)業(yè)經(jīng)濟單元中發(fā)展而來。各地依據(jù)不同的自然條件創(chuàng)造出的農(nóng)業(yè)生產(chǎn)的支撐系統(tǒng)，如陂塘、運河、灌渠等，實際上也是城市的環(huán)境支撐系統(tǒng)。中國古代的城市往往位于河流邊緣卻又與之保持一定的距離，然后通過建造這些人工水系與天然水系連通，形成貫穿城市內(nèi)外的安全和可控的水的系統(tǒng)。所以城市水環(huán)境問題，實際上是城市內(nèi)外的整體水環(huán)境問題，是人居水環(huán)境問題。

在古代農(nóng)業(yè)社會，我們的祖先創(chuàng)造了一套行之有效的城市水系統(tǒng)建造、使用和管理的方法，確保了歷史上城市的安全和繁榮。今天，現(xiàn)代城市規(guī)劃所遵循的工業(yè)革命之后的城市建設(shè)理論和經(jīng)驗，為應(yīng)對不斷膨脹的城市人口和城市規(guī)模、創(chuàng)造現(xiàn)代城市文明作出了巨大貢獻。然而，現(xiàn)代城市把城市建設(shè)相關(guān)內(nèi)容分解為規(guī)劃、水利、市政、建筑、園林等諸多專業(yè)，并過于依賴采用工程手段解決城市問題，也造成了城市自然系統(tǒng)的割裂、自然過程的中斷和生態(tài)條件的損害，并帶來了非常嚴重的環(huán)境問題，其中之一就是城市水環(huán)境惡化。

在快速城市化過程中，城市水系的大量填埋和硬化，不僅削弱了城市防洪能力，阻斷了地表水和地下水的交流，而且造成生境的喪失；城市中大量的硬化地面阻礙了天然降水的滲透，打斷了水的上下循環(huán)，使地表徑流量增加、地下水減少；大量被污染的水向河流湖泊排放，惡化了水質(zhì)，破壞了生物棲息環(huán)境。城市水資源短缺、水系破碎化、水質(zhì)污染、水生境破壞等造成了城市水環(huán)境的惡化，為城市安全和繁榮發(fā)展帶來了諸多隱患。

在《管子·水地》中管子還談道：“水者，地之血氣，如筋脈之通流者也?！彼菍⒌厍蛏先f物聯(lián)系起來的紐帶。水不僅存在于各種水體中，也存在于空氣、土壤和動植物之中。城市水環(huán)境的問題，不僅僅局限于城市水體本身，也取決于區(qū)域水系統(tǒng)的健康和完善；城市水環(huán)境的建設(shè)，不僅要關(guān)注水自身的質(zhì)和量，還要維護區(qū)域的山、林、田、草等自然生態(tài)系統(tǒng)的基本要素，涵養(yǎng)水源，保護生境，如此才能構(gòu)建健康的城市水環(huán)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.