1312 水利工程學(二) 鄭國渠和靈渠 02/12/2025
一. "鄭國渠"
"鄭國渠"
是中國在戰國時期的水利學家鄭國，於秦王政元年（前246年）為秦國所築的灌溉河渠。 河渠長三百里，位於今日 陝西省 涇陽縣 上然村涇出口一帶。 為紀念 韓國 工程師鄭國而得名。 建造經過: 鄭國渠由韓國水工鄭國 主持修建。 鄭國原本是西去秦國的奸細 ，本是去勸說 秦王政興修水利工程，企圖使秦國把經費消耗, 免去攻擊韓國.
秦王得知該陰謀後, 不但沒有殺他, 反而支持他去克工. 使原本廢棄的含塩和鹼的涇河與洛水之間一大塊土地得到大量灌溉水, 而使土壤大大改變, 得以豐收. 却不料使秦國因該水利工程更大大的強盛. 十數年後韓國還是被消滅. 該工程一直使用至今. 留德研究水利工程的李儀祉大師, 更使 "鄭國渠" 的功效發揮廣大, 為編輯者忠心佩服. |
| "鄭國渠" 是始於秦國, 由涇水谷口開始至洛水(漢代加建白渠的終點) |
1133 都江堰 Have a mercy on me, O Lord. 求主憐憫. 15/11/2025
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| 敬愛的徐世大老師 |
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| 編輯者Stephen Lei |
1.1 洪災消減措施(flood mitigation plan)
洪災消減措施的工程出發點來自以隣(上游比較不重要之低窪地區)為暫時疏導洪水破口, 因為洪水總要找出口瀦蓄. 美國1931及1997 mississippi river (密西西比河)兩次大洪水都是用在上游人口稍少, 房屋不多的地區爆破已有的堤防, 使下游正在搶救的沙包新堤防得以不使洪水過頂, 造成大的洪災損害.
恩師台灣大學土木系水利組徐世大教授於1946年工程師節演講, 談到大禹的治水用疏而成功，这是因为沼泽的功用，而 “鲧陻洪水” —— 而失败，乃是因當時建大垻工程技术不够水準。鯀用陻 (大埧) 的方法，大概他想拦河筑坝，想暫時把 水資源 - 洪水留住, 不让洪水流到下游太快，因为建築大埧工程浩大，器具不夠, 技术也欠缺, 所以筑了九年之久，但因那时没有筑大坝的技术，也沒建築大埧的重型機械設備可供使用, 無法遏止下流猛烈水性之洪流，故未成功.
而現在《洪范》说他 “汩陈其五行”，现在工程技术昌明时代，黄河下游又无沼泽，我们正应该用鲧所用的方法，把黄河的水陻于山中，一面让泥沙得以沉淀，一面利用高水头来开发水力电（据當時估计, 仅河曲到孟津就可開發得八九百万马力的水力發電的電能），一面存贮洪水以免泛滥成灾。而在发电以后，或用电力引水以灌高地，或下输以通航运，这正是禹所未了之功绩，要待现在的工程师来完成的。(古賢大埧的興建, 幸甚國人看見!)
[註]: 編輯者引自民国35年（1946年）《水利》第三期第十四卷. 供我國工程師作為參考.
引言
編輯者蒙恩師徐世大耳提面命的教導, 並以愛來激勵. 故立志一身致力於水利工程的研究, 並教導學生國家需要他們致力於拯救辛苦農民出於窮苦生活途徑. 再者編輯者出生於長江九江河畔, 適逢1931年發生最大洪災, 我只有半歲, 上帝憐憫孩子, 插手差遣天使 - 美國美以美會傳教師. Rev. William Richard Johnson, 拯救我於14萬的死亡災民之中. 又於1943祂又插手賜智慧於當時的党國元老空軍總司令周至柔將軍有遠見, 創辦空軍幼年學校於四川灌縣(現稱都江堰市)蒲陽河畔的蒲陽場. 編輯者有機會從三千哩外的江西贛州來到舉世聞名, 離開幼校約20哩的都江堰灌溉工程畔, 學習飛行. 決心學成後, 打下殘酷的小日本空軍.
編輯者在台灣大學土木系水利組教授水文. 需用水文知識最多的是洪災消減措施(flood mitigation plan). 今分:
1. 洪災消減措施的重要.
二. 靠人的智慧, 能斷定有沒有 "大禹"治洪水的事嗎?
恩師徐世大教授在重慶工程師節演講: ......讲到大禹，就联想到治水，我们知道各民族都有洪水的传说——有人就据此以为现代民族出于一源之证。但对于洪水的起源和终了，各处传说并不完全一样。希伯来民族的传说，是上帝要消灭一切恶人而只留挪亚一家。中华民族的洪水起源，传说似乎只是水灾，而洪水的终了，是大禹王的治导的成功，中间还经过禹的父亲鲧治水的失败。《孟子》上说禹治水的故事：
“当尧之时，天下犹未平，洪水横流，泛滥于天下。……尧独忧之，举舜而敷治焉。舜使……禹疏九河，瀹济漯，而注诸海；决汝汉，排淮泗，而注之江，然后中国可得而食也。”
[註]: 引自民国35年（1946年）《水利》第三期第十四卷 --- 恩師徐世大教授在重慶工程師節(斯時以大禹生日訂為工程師節)的演講. 這裡講到兩次洪水事件, 可見大洪水曾經發生過的, 因考查其發生的時代, 都是在紀元前4000年左右. 由此可見大洪水的發生是必然的事實. 再以編輯者是基督信仰者, 2000年前基督的降世為人的實存(reality), 仍有數十億的信徒, 對挪亞遵照上帝的旨意造方舟, 完成上帝使用洪水消灭一切希伯来民族的恶人, 而只留挪亚一家 (註: 恩師他不是道聽途說, 他可能讀過聖經, 為的是要完成他張寫一本有關中國的水利工程, 內容中絕對缺不了大禹治洪水這典故。他讀的古典文書極多. 霣𩂣 (在上三段可以覆製這字)即他在
三. 造成洪水災害的主要原因為海水及河川.
1. 海嘯(surge) : 因海底地震或火山暴發等原因產生的海嘯.
2. 河川 : 河川上游發生的暴雨或因颱風帶來的暴雨, 及在河川當地的暴雨所形成.
1924, 7月,15日, 洞庭湖土埧在岳陽附近的華容縣埧垮, 編輯者是半歲從洪水中逃生的人, 一生研究防洪的事件. 在台大土木系恩師徐世大教授耳提面命的教導下, 千叮萬囑要告訴國人不要與洪水爭地的自然法則, 即所謂與大自然共存的和諧. 中國長江水系的兩個大湖, 鄱陽湖及洞庭湖是上帝安排的兩個供長江洪水氾濫的地方, 不要去開墾. (註: 該此洪水不是三峽大埧泄洪, 而是當地的四月至七月的長江下游的梅雨, 不過今年成了暴雨, 且多了些. 以至堤防無法承受水持久的壓力而破裂.)
下圖對三峽大埧防洪功能顯示得很清楚. 更能回答這個問題 —— 三峽大埧為何無視下游洪成災! 是事實還另有隱情? (註: 該問題寫在圖中, 徐小刀工程師已經回答得很完滿. 編輯者只加以學術上的補充.)
三峽大埧能控制的洪水災害理應是自大埧以上的河道發生的洪水. 至於自武漢以下的洪災, 它擋不住長江中, 下游的洪水為災, 是顯而易見的事. 就是說事實上三峽工程無法控制下游的洪水. 以水文學的觀點來說更為明顯. 下游的洪水多來自4-7月的強烈的東南梅雨季節的氣流所造成. 像1931年的長江氾濫成災, 近14萬災民的死亡, 應歸咎於東南含豐富水汽的季節氣流所致. 因強烈的東南溫濕季節氣流直衝到長江上游, 暴雨從上游開始, 洪峯重疊, 造成極高的洪水位, 使堤防潰決, 造成極大洪災. 這是天然的事實災害. 若早在1931年前就建好三峽大埧, 可能災情不如報導的那麼嚴重. 肯定的. 因為攔阻部分洪水, 使洪峯不致重疊, 洪水位就下降很多.
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| 該圖取自徐小刀工程師的視頻, 敬以致謝. |
求主耶穌賜恩, 一天做一頁, 不要貪心. 主阿, 祢的恩典夠孩子用. 阿們.
河川水力學
要治理黃河必須用河川水力學. 因為它是河川, 很多水力學的理論不能完全適用. 例如, 濕周 (wetted boundary) 有誰真能下河去度量黃河的 濕周 . 所以要把治黃河的水力學的理論套牢在渠道水力學上, 必定是得不償失, 差距太大. 但是使用 河川水力學的公式, 就必大大的加以修正.
如何度量黃河的流速, 就是問題.( ????) 編輯者譯述的工程流體力學---第230頁---第七章---渠道水力學有約柬( bounded flows )與有自由水面流體的不同, 在渠道流之流體, 其橫斷面不能由約束限界決定, 而由動力原則定其連續性質來決定其橫斷面. 目前先討論正常流( normal flow) 或均流 (uniform flow ) .
均流
均流有恆定水深. 只發生在幾何的均恆斷面渠道. 均恆斷面 ( uniform cross section ) 即斷面不變. 若渠道斷面水深恆定且為定量流, 則渠道全段的平均流( uniform velocity)必為常數. 它的摩擦損失亦必為常數. 該能量的損失, 必須與能量的獲得相平衡. 換句話說, 均流可看成垂直作用在河床上的流體重量所形成的加速度, 使其速度變成平均速度, 其時河床邊與底的摩擦剪力與其平衡, 不再使其速度加大. ( 示如圖7. 1 )
Aor sini 是流體重量垂直作用在河床上的分力. 1:PO 是河床邊界摩擦力[ A是流體斷面積, T是河床邊界摩擦剪應力, P 是濕周wetted boundary]. 若流體速度
為常數, 亦即
wA ax sin i = TPaX T=WA
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Froude 福祿氐定則: 但若 n 假定為 2, 則ｋ與ｖ的指數有關。 故必須假設 ｎ為 ２， 因避免小數的指數。
WATER RESOURCES MANAGEMENT Water supply management Biological sciences Ecology Entomology Fisheries Food technology Forestry Horticulture Limnology Marine science Microbiology Plant science Public health Zoology Engineering Agriculture Chemical Civil Environmental Industrial Mechanical Systems Physical sciences Chemistry Climatology Computer science Geology Hydrology Mathematics Meteorology Oceanography Physics Soil science Statistics Social sciences Economics Education Geography History Law Planning Political science Public administration Resource development Sociology Water excess management Figure 1.1.1 Ingredients of water resources management (from Mays (1996))
Water resources engineering not only includes the analysis and synthesis of various water problems through the use of the many analytical tools in hydrologic engineering and hydraulic engineering but also extends to the design aspects. Water resources engineering has evolved over the past 9000 to 10,000 years as humans have developed the knowledge and techniques for building hydraulic structures to convey and store water. Early examples include irrigation networks built by the Egyptians and Mesopotamians (see Figure 1.1.2) and by the Hobokam in North America (see Figure 1.1.3). The world’s oldest large dam was the Sadd-el-kafara dam built in Egypt between 2950 and 2690 B.C. The oldest known pressurized water distribution (approximately 2000 B.C.) was in the ancient city of Knossos on Crete (see Mays, 1999, 2000, for further details). There are many examples of ancient water systems throughout the world (see Mays (2007, 2008, 2010) and Mays et al. (2007)).
1.3 WATER USE IN THE UNITED STATES Dziegielewski et al. (1996) define water use from a hydrologic perspective as all water flows that are a result of human intervention in the hydrologic cycle. The National Water Use Information Program (NWUI Program), conducted by the United States Geological Survey (USGS), used this perspective on water use in establishing a national system of water-use accounting. This accounting system distinguishesthe following water-use flows: (1) water withdrawals for off-stream purposes, (2) water deliveries at point of use or quantities released after use, (3) consumptive use, (4) conveyance loss, (5) reclaimed wastewater, (6) return flow, and (7) in-stream flow (Solley et al., 1993). The relationships among these human-made flows at various points of measurement are illustrated in Figure 1.3.1. Figure 1.3.2 illustrates the estimated water use by tracking the sources, uses, and disposition of freshwater using the hydrologic accounting system given in
B B Groundwater Groundwater Surface water B B B C C C D D A A EXPLANATION A Withdrawal B Delivery C Release D Return flow A-B = Conveyance loss (also C-D) B-D = Consumptive use Figure 1.3.1 Definition of water-use flows and losses (from Solley et al. (1993)). Table 1.3.1 Major Purposes of Water Use Water-use purpose Definition Domestic use Water for household needs such as drinking, food preparation, bathing, washing clothes and dishes, flushing toilets, and watering lawns and gardens (also called residential water use). Commercial use Water for motels, hotels, restaurants, office buildings, and other commercial facilities and institutions. Irrigation use Artificial application of water on lands to assist in the growing of crops and pastures or to maintain vegetative growth in recreational lands such as parks and golf courses. Industrial use Water for industrial purposes such as fabrication, processing, washing, and cooling. Livestock use Water for livestock watering, feed lots, dairy operations, fish farming, and other on-farm needs. Mining use Water for the extraction of minerals occurring naturally and associated with quarrying, well operations, milling, and other preparations customarily done at the mine site or as part of a mining activity. Public use Water supplied from a public water supply and used for such purposes as firefighting, street washing, municipal parks, and swimming pools. Rural use Water for suburban or farm areas for domestic and livestock needs, which is generally self-supplied. Thermoelectric power use Water for the process of the generation of thermoelectric power. Source: Solley et al. (1993). 1
1.5 THE FUTURE OF WATER RESOURCES The management of water resources can be subdivided into three broad categories: (1) water-supply management, (2) water-excess management, and (3) environmental restoration. All modern multipurpose water resources projects are designed and built for water-supply management and/ or water-excess management. In fact, throughout human history all water resources projects have been designed and built for one or both of these categories. A water resources system is a system for redistribution, in space and time, of the water available to a region to meet societal needs (Plate, 1993). Water can be utilized from surface water systems, from groundwater systems, or from conjunctive/ground surface water systems. When discussing water resources, we must consider both the quantity and the quality aspects. The hydrologic cycle must be defined in terms of both water quantity and water quality. Because of the very complex water issues and problems that we face today, many fields of study are involved in their solution. These include the biological sciences, engineering, physical sciences, and social sciences (see Figure 1.1.1), illustrating the wide diversity of disciplines involved in water resources. In the twenty-first century we are questioning the viability of our patterns of development, industrialization, and resources usage. We are now beginning to discuss the goals of attaining an equitable and sustainable society in the international community. Looking into the future, a new set of problems face us, including the rapidly growing population in developing countries; uncertain impacts of global climate change; possible conflicts over shared freshwater resources; thinning of the ozone layer; destruction of rain forests; threats to wetland, farmland, and other renewable resources; and many others. These problems are very different from those that humans have faced before. The fact that there are so many things undiscovered by the human race leads me to the statement by Sir Isaac Newton, shortly before his death in 1727: I do not know what I may appear to the world, but to myself I seem to have been only like a boy playing on the sea shore, and diverting myself in now and then finding a smoother pebble or a prettier shell than ordinary, while the great ocean of truth lay all undiscovered before me.
2.1 WHAT IS WATER RESOURCES SUSTAINABILITY? Traditionally, sustainability explores the relationships among economics, the environment, and social equity, using the three-legged stool analogy that includes not only the technical, but also the economic and social issues. The term “sustainable development” was defined in 1987 by the World Commission on Environment and Development as “development that can meet the needs of the present generation without compromising the ability of future generations to meet their own needs. Some of the questions related to sustainable systems and sustainable design are: . What are the characteristics of sustainable systems? . How does the design process encourage sustainability? . What is sustainable water resources development? . What are the components of sustainable development? 2.1.1 Definition of Water Resources Sustainability We live in a world where approximately 1.1 billion people lack safe drinking water, approximately 2.6 billion people lack adequate sanitation, and between 2 and 5 million people die annually from water-related diseases (Gleick, 2004). The United Nations Children’s Fund’s (UNICEF) report, “The State of the World’s Children 2005: Childhood under Threat,” concluded that more than half the children in the developing world are severely deprived of various necessities essential to childhood. For example, 500 million children have no access to sanitation and 400 million children have no access to safe water. One might ask how sustainable is this? The key to sustainability is the attention to the survival of future generations. Also important is the global context within which we must think and solve problems. The future of water resources thinking must be within the context of water resources sustainability. The overall goal of water resources management for the future must be water resources sustainability. Mays (2007) defined water resources sustainability as follows: “Water resources sustainability is the ability to use water in sufficient quantities and quality from the local to the global scale to meet the needs of humans and ecosystems for the present and the future to sustain life, and to protect humans from the damages brought about by natural and human-caused disasters that affect sustaining life.”
The Brundtland Commissions’s report, “Our Common Future” (World Commission on Environment and Development,WCED), defined sustainability as focusing on the needs of both current and future generations. A development is sustainable if “it meets the needs of the present without compromising the ability of future generations to meet their own needs.” Because water impacts so many aspects of our existence, there are many facets that must be considered in water resources sustainability including: . Water resources sustainability includes the availability of freshwater supplies throughout periods of climatic change, extended droughts, population growth, and to leave the needed supplies for the future generations. . Water resources sustainability includes having the infrastructure, to provide water supply for human consumption and food security, and to provide protection from water excess such as floods and other natural disasters. . Water resources sustainability includes having the infrastructure for clean water and for treating water after it has been used by humans before being returned to water bodies. . Water sustainability must have adequate institutions to provide the management for both the water supply management and water excess management. . Water sustainability must be considered on a local, regional, national, and international basis. . To achieve water resources sustainability, the principles of integrated water resources management (IWRM) must be implemented. Sustainable water use has been defined by Gleick et al. (1995) as “the use of water that supports the ability of human society to endure and flourish into the indefinite future without undermining the integrity of the hydrological cycle or the ecological systems that depend on it.” Seven sustainability requirements are presented in Section 11.1. 2.1.2 The Dublin Principles The following four simple, but yet powerful messages, were provided in 1992 in Dublin and were the basis for the Rio Agenda 21 and for the millennium Vision-to-Action: 1. Freshwater is a finite and vulnerable resource, essential to sustain life, development and the environment, i.e. one resource, to be holistically managed. 2. Water development and management should be based on a participatory approach, involving users, planners, and policy-makers at all levels, i.e. manage water with people—and close to people. 3. Women play a central role in the provision, management and safeguarding of water, i.e. involve women all the way! 4. Water has an economic value in all its competing uses and should be recognized as an economic good, i.e. having ensured basic human needs, allocate water to its highest value, and move towards full cost pricing, rational use, and recover costs. Poor water management hurts the poor most! The Dublin principles aim at wise management with focus on poverty. 2.1.3 Millennium Development Goals (MDGs) The Millennium Development Goals (MDGs), adopted in September 2000 during the Millennium Summit of the United Nations General Assembly, is comprised of eight goals (see Table 2.1.1). All of the goals can be translated directly or indirectly into water-related terms (Gleick, 2004). For example, Goal No. 1—“Eradicate extreme poverty and hunger”—and No. 7—“Ensure 1
Table 2.1.1 UN Millennium Development Goals and Targets for Goal 7 Goal
1 Eradicate Extreme Hunger and Poverty Goal
2 Achieve Universal Primary Education Goal
3 Promote Gender Equality and Empower Women
Goal 4 Reduce Child Mortality
Goal 5 Improve Maternal Health
Goal 6 Combat HIV/AIDS, Malaria, and Other Diseases
Goal 7 Ensure Environmental Sustainability Target 9 Integrate the principles of sustainable development into country policies and programs and reverse the loss of environmental resources. Target 10 Halve, by 2015, the proportion of people without sustainable access to safe drinking water and basic sanitation. Target 11 Achieve by 2020 a significant improvement in the lives of at least 100 million slum dwellers. Goal 8 Develop a Global Partnership for Development Source: http://www.mdgmonitor.org/browse_goal.cfm
environmental sustainability” have direct relevance to water; whereas Goal No. 2—“Achieve universal primary education” and No. 3—“Promote gender equality and empower women” are water-related as millions of women and young girls spend many hours every day to fetch water. The health related Goals 4, 5, and 6 also have strong relevance to water, or the lack of it. The MDG Goal 7, target 10 of halving, by the year 2015, the proportion of people without sustainable access (to reach or to afford) to safe drinking water seems unlikely to be met. The international community has made little progress to meet the similar part of target 10—to halve, also by 2015, the proportion of people without access to basic sanitation—adopted at the World Summit on Sustainable Development (WSSD), in Johannesburg in 2002 (United Nations, ). An interesting fact is that this goal did not specifically emphasize wastewater treatment and disposal, because in many parts of the world wastewater treatment does not exist even though sanitation services exist and the sewage is used to irrigate agricultural crops. It is estimated that in Latin America 1.3 million hectares of agricultural land is irrigated with raw wastewater and has related health and disease issues. In countries with water shortages, the reuse of untreated wastewater will likely increase in the future. 2.1.4 Urbanization – A Reality of Our Changing World Urban populations demand high quantities of energy and raw material, water supply, removal of wastes, transportation, etc. Urbanization creates many challenges for the development and management of water supply systems and the management of water excess from storms and floodwaters. Many urban areas of the world have been experiencing water shortages, which are expected to explode this century unless serious measures are taken to reduce the scale of this problem (Mortada, 2005). Most developing countries have not acknowledged the extent of their water problems, as evidenced by the absence of any long-term strategies for water management. Changes Caused by Urbanization Urbanization is a reality of our changing world. From a water resources perspective, urbanization causes many changes to the hydrological cycle including radiation flux, amount of precipitation, amount of evaporation, amount of infiltration, increased runoff, etc. Changes brought about by urbanization can be summarized briefly as follows (Marsalek et al., 2006): . Transformation of undeveloped land into urban land (including transportation corridors); . Increased energy release (i.e., greenhouse gases, waste heat, heated surface runoff); and . Increased demand on water supply (municipal and industrial). 2.2 CHALLENGES TO WATER RESOURCES SUSTAINABILITY Urban populations are growing rapidly around the world with the addition of many mega-cities (populations of 10 million or more inhabitants). In 1975 there were only four mega-cities in the world and by 2015 there may be over 22 mega-cities in the world (Marshall, 2005). Other cities that will not become mega-cities are also growing very rapidly around the world. By 2010, more than 50% of the world’s population is expected to live in urban areas (World Water Assessment Program, 2006). Mega-cities mean mega problems of which urban water supply management and water excess management are among the largest. Mega-cities and other large cities will be a drain on the Earth’s dwindling resources, while at the same time significantly contributing to the environmental degradation. Many of the large cities around the world are prone to water supply shortages, others are prone to flooding, and many are prone to both. A large number of the cities of the world do not have adequate wastewater facilites and most of the waste is improperly disposed or used as irrigation of agricultural lands. As the Earth’s population continues to grow, so will the growth of cities continue across the globe, stretching resources and the ability to cope with disasters such as floods and droughts. These factors, coupled with the consequences of global warming, create many challenges for future generations. There are many factors that affect water resources sustainability including: urbanization, droughts, climate change, flooding, and human-induced factors. Developed areas of the world such as the United States are not exempt from the need for water resources sustainability. Figure 2.2.1 shows areas in the western United States with potential water supply crisis by 2025.
2.2.1 Urbanization The Urban Water Cycle The overall urban water cycle is illustrated in Figure 2.2.2 showing the main components and pathways. How does the urbanization process change the water budget from predevelopment to developed conditions of the urban water cycle in arid and semi-arid regions? This change is a very complex process and very difficult to explain. Urban Water Systems Urban water system implies that there is a single urban water system and the reality of this is that it is an integrated whole. The concept of a single “urban water system” is not fully accepted because of the lack of integration of the various components that make up the total urban water system. For example, in municipalities it is common to plan, manage, and operate urban water into separate entities such as by service, i.e. water supply, wastewater, flood control, and stormwater. Typically there are separate water organizations and management practices within a municipality, or local or regional government because that is the way they have been historically. Grigg (1986) points out that integration could be achieved by functional integrationand area-wide integration. There are many linkages of the various components of the urban water system with the hydrologic cycle being what connects the urban water system together. There are many reasons for considering the urban water system in an integrated manner. Two of the principal reasons are (a) the natural connectivity of the system through the hydrologic cycle and (b) the real benefits that are realized through integrated management rather than by independent action. The urban water management system is considered herein as two integrated major entities, water supply management and water excess management. The various interacting components of water excess and water supply management in conventional urban water infrastructure are: Water Supply Management
Sources (groundwater, surface water, Transmission
Water treatment (WT)
Distribution system
Wastewater collection
Wastewater treatment (WWT)
Reuse Water Excess Management
Collection/drainage systems
Storage/treatment
Flood control components (levees, dams, diversions, channels) Sustainable Urban Water Systems Sustainable urban water systems are being advocated because of the depletion and degradation of urban water resources coupled with the rapid increases in urban populations around the world. Marsalek et al. (2006) defined the following basic goals for sustainable urban water systems: . Supply of safe and good-tasting drinking water to the inhabitants at all times. . Collection and treatment of wastewater in order to protect the inhabitants from diseases and the environment from harmful impacts. . Control, collection, transport, and quality enhancement of stormwater in order to protect the environment and urban areas from flooding and pollution. . Reclamation, reuse, and recycling of water and nutrients for use in agriculture or households in case of water scarcity. In North America and Europe many of the above goals have been achieved or are within reach. In many developing parts of the world these goals are far from being achieved. Climate change will be a major factor in both the developed and undeveloped parts of the world that has not been addressed for the future of water resources sustainability. The Millennium Development Goals put a strong emphasis on poverty reduction and reduced child mortality. Urban Stormwater Runoff Urban stormwater runoff includes all flows discharged from urban land uses into stormwater conveyance systems and receiving waters. Urban runoff includes both dry-weather, non-stormwater sources (e.g., runoff from landscape irrigation, dewatering, and water line and hydrant flushing) and wet-weather stormwater runoff. Water quality of urban stormwater runoff can beaffected by the transport of sediment and other pollutants into streams, wetlands, lakes, estuarine 18 Chapter 2 Water Resources Sustainability and marine waters, or groundwater. The costs and impacts of water pollution from urban runoff are significant and can include fish kills, health concerns of human and/or terrestrial animals, degraded drinking water, diminished water-based recreation and tourism opportunities, economic losses to commercial fishing and aquaculture industries, lowered real estate values, damage to habitat of fish and other aquatic organisms, inevitable costs of clean-up and pollution reduction, reduced aesthetic values of lakes, streams, and coastal areas, and other impacts (Leeds et al., 1993). Increased stormwater flows from urbanization have the following major impacts (FLOW, 2003): . acceleration of stream velocities and degradation of stream channels, . declining water quality due to washing away of accumulated pollutants from impervious surfaces to local waterways, and an increase in siltation and erosion of soils from pervious areas subject to increased runoff, . increase in volume of runoff with higher pollutant concentrations that reduces receiving water dilution effects, . diminished groundwater recharge, resulting in decreased dry-weather flows; poorer water quality of streams during low flows; increased stream temperatures; and greater annual pollutant load delivery, . increased flooding, . combined and sanitary sewer overflows due to stormwater infiltration and inflow, . damage to stream and aquatic life resulting from suspended solids accumulation, and increased health risks to humans from trash and debris which can also endanger, and . destroying food sources or habitats of aquatic life (FLOW, 2003).
Groundwater Changes Urbanization often causes changes in groundwater levels as a result of decreased recharge and increased withdrawal. In rural areas, water supplies are usually obtained from shallow wells, while most of the domestic wastewater is returned to the ground through cesspools or septic tanks. Thus the quantitative balance in the hydrologic system remains. As urbanization occurs many individual wells are abandoned for deeper public wells. With the introduction of sewer systems, stormwater, and (treated or untreated) wastewater are discharged to nearby surface water bodies. Three conditions disrupt the subsurface hydrologic balance and produce declines in groundwater levels. 1. Reduced groundwater recharge due to paved surface areas and storm sewers 2. Increased groundwater discharge by pumping wells 3. Decreased groundwater recharge due to export of wastewater collected by sanitary sewers Groundwater quality is certainly another challenge to water resources sustainability resulting in many cases from urbanization. Groundwater quality can be affected by residential and commercial development as illustrated in Figure 2.2.3. The U.S. Geological Survey’s National Water Quality Assessment (NAWQA) program (http://water.usgs.gov/nawqa) seeks to determine how shallow groundwater quality is affected by development (Squillace and Price, 1996). Residential developments have taken up very large tracts of land, and as a consequence, have widespread influence on the quality of water that recharges aquifers, streams, lakes, and wetlands. Liquids discharged onto the ground surface in an uncontrolled manner can migrate downward to degrade groundwater. Septic tanks and cesspools are another source of groundwater pollution. Polluted surface water bodies that contribute to groundwater recharge are sources of groundwater pollution.
2.2.2 Droughts and Floods Droughts Droughts continue to be one of the most severe weather-induced problems around the world. Droughts can be classified into different types: meteorological droughts refer to the lack of precipitation; agricultural droughts refer to the lack of soil moisture; and hydrological droughts refer to the reduced streamflow and/or groundwater levels. Figure 2.2.4 presents the progression of droughts and their impacts. Section 11.6 addresses drought management including management options, drought severity indices, and economic effects of water shortage. Figure 2.2.5 shows an example of the U.S. Drought Monitor. The following is a definition of drought from the “Colorado River Basin Management: Evaluating and Adjusting to Hydroclimatic Variability” (from Water Science and Technology Board (2007)): A basic concept invoked in understanding drought is that of a water budget. Water is held in storage buffers such as soil root zones, aquifers, lakes, reservoirs, and surface stream flows. These buffers act as water supplies, are subject to demands, and are replenished and lose water at varying rates. When losses exceed replenishment, impacts are experienced and, at Natural Climate Variability Precipitation deficiency (amount, intensity, timing) High temperature, high winds, low relative humidity, greater sunshine, less cloud cover Reduced infiltration, runoff, deep percolation, and groundwater recharge Increased evaporation and transpiration Soil water deficiency Plant water stress, reduced biomass and yield Reduced streamflow, inflow to reservoirs, lakes, and ponds; reduced wetlands, wildlife habitat Economic Impacts Social Impacts Environmental Impacts Time (duration) Hydrological Drought Agricultural Drought Meteorological Drought Figure 2.2.4 Progression of droughts and their impacts. (Source: National Drought Mitigation Center
lower storage levels, become increasingly severe. In essence, drought is defined by its impacts on both natural and manmade environments because without impacts there is no drought, no matter how dry it might be. Drought infers a relationship between supply rates and demand rates; drought is not simply a supply-side phenomenon, but also depends on water demands. Without demands, there is no drought, whether a given supply of water is big, small, or even zero. Floods Urban flood management (also referred to as water excess management herein) will be effected by the rapid urbanization and climate change among other factors and must be considered within the framework of water resources sustainability, which will require the principles of integrated urban water management. The impact of floods to cities can devastate national economies and industrial markets, even at the international level. Urban flood management must capture the following concepts that: (a) floods are part of the natural resources that should be considered within the scope of integrated urban water resources management (IUWRM); (b) water resources sustainability captures IUWRM; (c) and the realization that floods never can be fully controlled. Urban flood management in developing countries is affected by development with little or no planning; high population concentration in small areas; lack of stormwater and sewage facilities; polluted air and water; difficulty of maintaining water supply with growing population; and poor public transportation among other things. The urban poor are often forced to settle in flood prone areas and they lack the adaptive capacity to cope with flood events. The unplanned urbanization and poverty are dramatically increasing the vulnerability to floods. Increase in vulnerability of cities to flood disasters arises predominantly from the systematic degradation of natural ecosystems, increased urban migration, and unplanned occupation, and unsustainable planning and buildingUrban flood disasters are not only prevalent in developing countries but have also impacted urban areas significantly in developing countries. In Europe, during the 10-year time period of 1973–1982, there were 31 flood disasters, and during the ten-year time period of 1993 to 2002, there were 179 flood disasters (Hoyois and Guha-Sapir, 2003). The Mississippi River flooding (see photos in Figure 14.1.1) and particularly the St. Louis area (see Figure 2.2.6) are used as examples of flooding problems. The Mississippi River flood of 1993 caused major flood damage in nine Midwestern states in which 75 towns and millions of acres offarmlands disappeared under the floodwaters. Approximately 50 people died, and tens of thousands of people were temporarily or permanently evacuated. Thousands of homes were completely destroyed and hundreds of flood levees failed. Flood damage estimates ranged from $10 to $20 billion. Houston, Texas, is an example of poor urban flood management in a large city in a developed country. A combination of poor urban planning, poor floodplain management, poor stormwater management, and lack of integrated floodplain and stormwater management has caused billions of dollars of flood damage over the last couple of decades. Subsidence has been a factor, but minimal compared to the effects of poor floodplain and poor stormwater management in Houston. Tropical Storm Allison is one of the several examples with damage estimates of up to $5 billion. Hurricane Katrina in the Gulf of Mexico coastal region of the U.S. brought unprecedented death and destruction over a 90,000 m2 . Not only were the costs (estimates vary between $100 and $200 billion) and deaths (over 1200 lives) unprecedented, but a very large number of the residents who evacuated before the storm have not yet returned. Even to this date many of the essential city services have not yet been restored to pre-Katrina levels. Many lessons were learned (Kahan et al., 2006). . Government officials need to consider policies and plans that are more robust against a wider range of disaster scenarios (e.g. on the Gulf of Mexico coast, storm surges had been anticipated, but not at the level of Katrina even though they had anticipated catastrophic flooding and levee failures). . Failure to anticipate the widespread regional breakdown in infrastructure and services and the disabling of first-response and public safety programs was the biggest blind spot throughout the region (e.g. the planning for regional infrastructure and services must cover total catastrophic breakdown and must include secondary, contingency responses that can be invoked when primary responses are overwhelmed). . Detection of the storm was adequate, but the detection of structural weakness, soil anomalies, and impending failure was not, as no monitoring was in place which was (remedied through extensive deployment of sensors on all structural features of the flood protection system). . Reconstruction efforts are strongly influenced by the answer to the question, what will the level of protection be in the future? Complicating this is the fact that many flood victims have chosen not to return and economic recovery remains uncertain. . Integrated urban water management from the perspective of flood control includes conceding land to the water from time to time (somewhat psychologically and politically difficult).
2.2.3 Climate Change
Definitions The United Nations Intergovernmental Panel on Climate Change (IPCC) defines climate change as “a change in the state of the climate that can be identified (e.g. using statistical tests) by changes in the mean and/or the variability of its properties, and that persists for an extended period, typically decades or longer. It refers to natural variability or as a result of human activity.” The United Nations Framework Convention on Climate Change (UNFCC) defines climate change as “a change in climate that is attributed directly or indirectly to human activity that alters the composition of the global atmosphere and that is in addition to natural climate variability observed over comparative time periods.” A schematic framework representing anthropogenic drivers, impacts of and responses to climate change, and their linkages, is shown in Figure 2.2.7. 24 Chapter 2 Water Resources Sustainability In the last (fourth) assessment report of the United Nations Intergovernmental Panel on Climate Change (IPCC), the Working Group I states that “warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.” The IPCC report also stated it is “very likely” that human activities are responsible for most of the warming of recent decades. The IPCC shared the 2007 Nobel Peace Prize with Al Gore. The climate system is an interactive system consisting of five major components: the atmosphere, the hydrosphere, the cryosphere, the land surface, and the biosphere, forced or influenced by various external forcing mechanisms, the most important of which is the sun. The effect of human activities on the climate system is considered as external forcing. Climate change predictions are based on computer simulations using general circulation models (GCMs) of the atmosphere. The limitations of state-of-the-art climate models are the primary sources of uncertainty in the experiments that study the hydrologic and water resources impact of climate change. Future improvement to the climate models, hopefully resulting in more accurate regional predictions, should greatly improve the types of experiments to more accurately define the hydrologic and hydraulic impacts of climate change.
The impacts associated with global average temperature change will vary by the rate of temperature change, the extent of adaptation of humans, and the social-economic pathway. Water will be affected in general as follows: . Increased water availability in moist tropics and high latitudes. . Decreasing water availability and increasing droughts in mid-latitudes and semi-arid low latitudes. . Hundreds of millions of people exposed to increased water stress. Hydrologic Response Future precipitation and temperature are the primary drivers for determining future hydrologic response. Because of the uncertainties of the predictions of the future precipitation and temperatures, the hydrologic responses of various river basins are uncertain, resulting in uncertainties of our future urban water resources, particularly in arid and semi-arid regions, In general, the hydrologic effects are likely to influence water storage patterns throughout the hydrologic cycle and impact the exchange among aquifers, streams, rivers, and lakes. In arid and semi-arid regions, relatively modest changes in precipitation can have proportionately larger impacts on runoff, and higher temperatures result in higher evaporation rates, reduced streamflows, and increased frequency of droughts (Mays, 2007). The effects of climate change on groundwater sustainability include (Alley et al., 1999) (a) changes in groundwater recharge resulting from changes in average precipitation and temperature or in seasonal distribution of precipitation; (b) more severe and longer droughts (c) changes in evapotranspiration resulting from changes in vegetation; and (d) possible increased demands of groundwater as a backup source of water supply. As an example, we can consider in general the hydrologic effects of climate change on the Pacific Northwest United States (e.g. the Columbia River) as summarized in Figure 2.2.8. Starting in the winter, changes in temperature and precipitation during the winter affects the snowpack during the winter. The winter snowpack in turn affects the stream flow during the spring and summer. The streamflow affects the quantity, quality, and timing of the water supply, which in turn affects
Figure 2.2.8 Dominant impact through which changes in regional climate are manifested in the Pacific Northwest (from Miles et al., 2000) hydropower production, aquatic ecosystems, agriculture, forests, municipal and industrial water supply. Both the winter snowpack and the spring/summer streamflow affect the groundwater recharge, the soil moisture, and the evapotranspiration which have terrestrial effects on the forests, agriculture, etc. Hamlet and Lettenmaier (1999) and Miles et al. (2000) provide a more detailed discussion of the Columbia River Basin. Some Realities of Climate Change In the Fourth World Water Forum in March 2006, the Co-operative Programme on Water and Climate (CPWC) pointed to “the alarming gap between international recognition of the risks posed by climate change and the general failure to incorporate measures to combat those risks into national and international planning strategies (McCann, 2006). The CPWC findings and recommendations to cope with climate extremes were encompassed within the following five key messages: . Strategies for achieving the 2015 Millennium Development Goals (MDG) do not account for the climate variability and change. . Climate-related risks are not sufficiently considered in water sector development and management plans. . Investment in climate disaster risk reduction is essential. . The trend of increasing costs has to be reversed through the safety chain concept (prevention, preparation, intervention, risk spreading, recondition, reconstitution). . Coping measures need to combine a suite of technical/structural and nonstructural measures. The first message addresses the fact that climate impacts on hydrological systems and on livelihoods threaten to undo decades of development efforts. The second message relates to the fact that to meet MDG targets, there will need to be substantial long-term investments in structural and nonstructural approaches to water management. Structural measures include storage, control, and conveyance; and nonstructural measures include demand-side management, floodplain management, service delivery, etc. The third message relates to the fact that the costs of disasters, especially those related to water, are increasing and substantial efforts are needed in mainstream climate reduction. The fifth message advocates a combination of both structural and nonstructural measures. Structural measures include dams, dikes, and reservoirs; and nonstructural measures include early flood warning systems, spatial planning, “living with water” insurance, etc. The reality is that climate change impacts are already with us and manifesting in increasing occurrences of and intensity of climate extremes such as droughts and floods, and climate variability. From the water supply perspective, there are both supply-side and demand-side options that could be considered for urban water supply. Table 2.2.1 summarizes some supply-side and demand-side adaptive options for the urban water-use sector. 2.2.4 Consumption of Water – Virtual Water and Water Footprints In Section 1.2 we stated that some of today’s most acute and complex problems are related to the rational use and protection of water resources in order to supply humankind with clean freshwater. Table 1.2.3 presents the dynamics of water use in the world by human activity and Table 1.2.4 presents the annual runoff and water consumption by continents and by physiographic and economic regions. Chapter 11 discusses in detail water withdrawals and uses. Various types of uses include consumptive use, instream use, and offstream use. Tables 11.1.2 and 11.1.3 list water requirements for various industries; Table 11.1.4 lists the water requirements for municipal establishments; Table 11.1.5 lists typical household water use in the US; Table 11.2.1 and Table 11.2.2 list consumptive water use for energy production and electricity production, respectively; and Table 11.3.6 lists crop water requirements and crop evapotranspiration for agriculture.
Consumptive use is defined in Table 11.1.1 as “that part of water withdrawn that is evaporated, transpires, incorporated into products or crops, consumed by humans or livestock, or otherwise removed from the immediate water environment”. It is difficult to imagine that to produce one cup of coffee requires 140 liters of water and to produce 1 kg of beef requires 16,000 liters of water. A discussion of the human consumption of water required to produce commodities and services follows. The concepts of virtual water and water footprints are both important to the understanding of water resources sustainability. We are familiar with the concept of “ecological footprint” that quantifies the land area needed to sustain people’s living. The water footprint indicates the water required to sustain a population. To define the water footprint we must first discuss the concept of virtual water. Virtual water is the volume of water required to produce a commodity or service, as introduced by Allen (1993, 1994). The global average virtual water content of some selected products, per unit of product is listed in Table 2.2.2. The water footprint concept was introduced by Hoekstra and Hung (2002) as a consumption indicator of water use in addition to the traditional production-sector indicators of water use. Figure 2.2.9 shows the contribution of some major crops to the global water footprint. Rice has the largest footprint, which is about 21%, and wheat has the second largest footprint, which is about 12%. The total volume of world rice production is approximately the same as wheat production, but with a much higher evaporative demand for rice production. Global average virtual water content of rice (paddy) is 2291 m3 /ton, and wheat is 1334 m3 /ton. The water footprint of a nation is the total volume of freshwater that is used to produce goods and services consumed by the people of the nation (Hoekstra and Chapagain, 2007). Figure 2.2.10 shows the contribution of major consumers to the global water footprint. Obviously not all goods consumed in a country are produced in that country, so the water footprint consists of the use of domestic water resources of that country plus the water used outside the borders of that country. The water footprint indicates the water required to sustain a population, therefore the connection to water resources sustainability. The total water footprint of a nation is composed of the internal water footprint and the external water footprint. Internal water footprint is the volume of water used from domestic water resources. External water footprint is the volume of water used in other countries to produce
二. 上帝在我幼年時賜憐憫:
上帝讓我幸運的考上空軍幼年學校, 為的是要與小日本空軍拼個他死我活, 因為他們太殘忍, 不分日夜的來我國後方轟炸, 甚至轟炸到四川灌縣蒲陽河畔我們的學校, 太沒有人性. 那時我是住在江西省12歲的兒童, 要跋涉三千多里到四川省成都灌縣蒲河畔當小空軍, 可見我是多麼的恨小日本軍閥入骨。雖然現今已是94歲的老人, 猶記得小日本軍閥是多麼的殘忍. 他們日夜不斷的轟炸我國首都重慶, 三千多人被閉死在防空洞裡, 因為警報信號及警鈴無法消除, 故防空洞門無法打開。 至於他們為什麼要飛那麼遠, 來轟炸四川灌縣蒲陽河, 猜測他們是想炸毀都江堰, 企圖餓死我們。 因為都江堰所產的糧食, 養活後方億萬預備捨身反攻小日本的中國人。
在台灣大學極度艱苦的日子裡, 是靠恩師愛心的鼓勵。1959年畢業,1962年回母校任趙國華教授研究助理, 1966恩師為我修改所撰寫的論文, "台灣新店溪地水補注" 。經台大教員升等審核委員會通過, 升格為講師.
1971年經恩師推薦, 由國科會資助, 出國深造, 恩師代我教授水文學課一年, 回國後沒有感謝他老人家的愛心, 真是忘恩負義的人。於今在感恩節日, 才想起撰寫 "懷念都江堰" 一文, 以表達思念恩師愛之心。
當年我在蒲陽場受訓，每年盼望的日子，就是清明節步行去灌縣參加都江堰開堰盛典。自1943年住進唐二院，至1949年離開蒲陽場，共連續五年看到這稱譽世界的偉大水利工程。上帝是這樣的愛我們中華民族，在二千二百五十多年前就為我們預備了李冰太守，為旱澇無常的成都平原設計這舉世聞名的 “都江堰”，使成都平原為旱澇從人的“天府之國”。 是它在抗日戰爭中養活了當時在大後方成千上萬的同胞。讓我們八年的抗日戰爭得到最後的勝利，打倒想吞噬我中華民族的倭冦.
國內聞名的余秋雨先生在 “文化苦旅”一書中特別撰寫一篇 “都江堰”，他以歷史的觀點來比較中國古代極著盛名的兩大土木工程 “都江堰” 和 “ 長城”。 他說，“ ‘長城’的社會功用早已廢弛，而 ‘都江堰’ 至今還在爲無數民衆輸送汩汩清流。有了它，旱澇無常的四川平原成了天府之國，每當我們民族有了重大灾難，天府之國，總是沈著地提供庇護和濡養。因此，可以毫不誇張地說，它永久性地灌溉了中華民族。……說得近一點，有了它，抗日戰爭中的中國才有一個比較安定的後方…”.
本來成都平原不是旱澇從人的 “天府之國”，而是水旱頻仍，饑饉時見，民不潦生的地方。 少雨則旱，多雨則洪水成災。 因為岷江水源絶大部分是，來自青城山流域，經春天氣溫升高融化的雪水，水量豐富湧猛，若無都江堰的 “魚嘴”(分水堤)，“飛沙堰”(溢洪道)、寶瓶口(引水口)三重要工程來控制岷江水流(示如下圖)，則水害就常常發生，非澇則旱.II. God's Mercy in My Childhood:
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| 敬愛的徐世大老師 |
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| 編輯者Stephen Lei |
