本人主编英文国际期刊International Journal of Sediment Research 18年，还兼任其他三家国际期刊副主编多年。收到的期刊稿件近半数为中国作者所贡献，有不少稿件内容不错，仅由于英文太差不得不拒稿。为了改进研究生和青年研究工作者的专业英文写作水平，我在清华大学开设了水利专业英语课Professional English for Hydraulic Engineering，受到研究生、青年教师和水利研究院工程师的欢迎，学生们踊跃参加。中国水利水电科学研究院及有关水利院系多次邀请本人到场讲课。
本书是十多年来在教学和与听课师生交流中不断修改更新补充后的讲义，贡献出来供有关专业师生参考使用。本书第二作者Charles Steven Melching教授是多家国际期刊的副主编，具有很高的专业水平和丰富的编辑修改水利专业英文的经验。他为本书贡献了大量的资料并且审阅修改了全部英文。本书第三和第四作者也为本书的成稿与出版做出了重要贡献。
为了帮助教师在课堂上讲解专业词汇，特别是词典上难以查到或专业上有不同意义的单词和词组，在每小节后面增加了关键专业词汇的中文注释。在中国作者经常犯的错误（Common Habits of Chinese Writers)以及改进翻译两节，所有的实例都是来自本书作者们修改的稿件和教学实践。每一小节后面用中文解释了中文写作的习惯与英文的差异。本书的听力材料是国际广播电台(China Radio International)在舟曲泥石流灾害发生后的采访录音，在清华大学的专业英语教学中用作听力材料和听力测验。余在多年的教学实践中发现，学生们在课堂第一个小时之后会感到疲倦，用英文笑话解除疲倦效果很好，本书特选取几例供教师参考使用。
王兆印
2017年3月于清华园
王兆印，1951年10月出生，山东济南人，清华大学水利水电工程系教授，主要从事高含沙水流、泥石流、植被侵蚀动力学、河流生态与恢复、以及河流综合流域管理方面研究。获得2011年度汉斯.阿尔伯特.爱因斯坦奖，这是首位大陆籍华人获此殊荣。
1BASIC CONCEPTS
All land is part of a watershed or river basin.Figure 1 shows the landscape sculptured by erosion in Greece and the very dry land in Egypt. Indeed，rivers are such an integral part of the land that in many places it would be as appropriate to talk of riverscapes as it would be of landscapes. Rivers are much more than merely water flowing to the sea. Rivers carry downhill not just water，but just as importantly sediments，dissolved minerals，the nutrientrich detritus of plants and animals. Their evershifting beds and banks and the groundwater below are all integral parts of rivers. Even the meadows，forests，marshes and backwaters of floodplain can be seen as part of the rivers—and the rivers as part of them.
Figure 1(a) The landscape sculptured by erosion (Greece)； (b) river flow is the main drive for development of geomorphology (Norway)
The main functions of rivers are draining floods，supplying drinking water，maintaining ecology，irrigating farmland，transporting sediment，supplying power，providing habitat for fish，assimilating wastewater，and providing navigation. Humans exploit the resources of rivers by constructing dams and waterdiverting channels，developing navigation channels，and harvesting fish，which result in changes in the river hydrology，runoff，sediment transport，riparian and stream habitats，and water quality.
Watersheds start at mountain peaks and hilltops. Snowmelt and rainfall wash over and through the high ground into rivulets which drain into fastflowing mountain streams. As the streams descend，tributaries and groundwater add to their volume and they become rivers. As they leave the mountains，rivers flow and start to meander and braid，developing channels within the valleys with alluvial floors laid down by millennia of sedimentladen floods. Eventually rivers will flow into a lake or ocean. Where the river carries a heavy sediment load and the land is flat，the alluvial sediments may form a delta. Estuaries，the places where the fresh water of rivers mix with the oceans salt，are among the most biologically productive parts of rivers and of seas. Most of the worlds fish catch comes from species that are dependent for at least part of their lifecycle on a nutrientrich estuarine habitat.
Figure 2 shows the components of a river system，materials transported，and the aspects affected by the rivers and transported materials. Rivers can be recognized as mountain rivers，alluvial rivers，and estuaries. A mountain river is the most upstream part of the river，including the river source and the upstream tributaries of the river，where the river system flows through mountainous areas and the flow is confined by mountains. Usually the channel bed of a mountain river is composed of gravel. Mountain rivers receive most of the sediment，nutrientrich detritus of plants and animals，dissolved materials，and usually more than half of the water.
Figure 2River system，transported materials，and aspects affected by rivers and the transported materials
For a large river the upstream reaches compose the inputpart of the river and are directly affected by the watershed or drainage area. Erosion control and vegetation development are the most challenging tasks for researchers and watershed managers. Erosion induced landslides and debris flows are disastrous in the upstream reaches. Mountain rivers are quite often incised rivers and degradation of the channel bed causes many problems. Therefore，erosion control and vegetation development over the watershed，landslides and debris flows，and control of channel bed incision are major topics of mountain river studies.
An alluvial river is defined as a river with its boundary composed of the sediment previously deposited in the valley，or a river with erodible boundaries flowing in selfformed channels. Over time the stream builds its channel with sediment it carries and continuously reshapes its cross section to obtain depths of flow and channel slopes that generate the sedimenttransport capacity needed to maintain the stream channel. Alluvial rivers are mostly perennial streams and the channel bed is composed mainly of sand and silt. A large river usually originates from mountains and flows over floodplains before it pours into the ocean，therefore，it is a mountain river in its upper reaches and an alluvial river in its lower reaches.
Many alluvial rivers are large rivers or flatland sections of large rivers，such as the lower reaches of the Yellow River and the middle and lower reaches of the Yangtze River.These alluvial rivers are confined within the valley defined by human constructed or artificially reinforced levees. The river morphology and river patterns depend mainly on the sediment transportation and deposition.Rivers are the main source of water resources for agriculture，urban use，and industry.
River flood are major natural disasters accounting for 1/3 of the total loss due to natural hazards. The quality of river water is important for human health. Flood and sediment transportation are natural processes in these rivers and water diversion，channelization，and navigation are human disturbance，to the rivers. Thus，sediment transportation，water resources development，and flood defense are the most important issues in the alluvial river management.
The estuary is the connection part of a river with the sea or the ocean into which it flows，including the river mouth，a river section affected by the tide，and the water body area affected by the river flow. Sediment is deposited for land creation and very often a delta develops in the area. In recent years，the need for sustainable development of coastal cities and marine resources has given rise to challenging environmental problems. Examples include the environmental impact assessment of dredging and sludge/spoil dumping and the transport and transformation of nutrients and heavy metals at the sedimentwater interface. Urban development including largescale land reclamation and population growth induced increase in sewage discharge puts the estuary ecosystem under stress.
Red Tide is a phenomenon in which the seawater is discolored by high algal biomass. Some algal species produce potent toxins，which accumulate in shellfish that feed on those algae，resulting in poisoning in human consumers. There has been a significant expansion of red tide episodes and impacts throughout the world over the last several decades. Very unusual red tides have occurred in the Bohai Sea，East China sea，and South China sea in the past decades. Delta and coastal processes，eutrophication，and algal blooms are the major challenges for the management of estuaries.
A variety of riveruses was the driving force of societal development in the past and now is even more important in economic and cultural development. Rivers，and the rich variety of plants and animals which they sustain，provided huntergatherer societies with water for drinking and washing，and with food，drugs and medicines，dyes，fibers，and wood. Farmers reap similar benefits as well as，where needed，irrigation for their crops. For pastoral societies，who graze their herds over wide areas of often parched plains and mountains，perennial vegetation along the banks of rivers provides lifesustaining food and fodder during dry seasons and droughts. Towns and cities use and misuse rivers to carry away their wastes. Rivers also served as roadways for commerce，exploration，and conquest. The role of rivers as the sustainers of life and fertility is reflected in the myths and beliefs of a multitude of cultures.
Many countries have taken an increasing interest in integrated river management coordinating various sectors of river issues. A developing country，like China，now strongly emphasizes the goal of flood control，water resources development，and protecting environment in addition to reducing poverty by supporting efficient and sustainable development of agriculture and light industries.
Water is acknowledged to have a significant impact on the economic development potential of individuals through agriculture，water supply and sanitation，public health，power generation，flood mitigation，etc. In addition，water sustains ecological systems，which also have economic value，and in turn generate a healthy hydraulic system. Poor people can improve their welfare by having access to water. In turn，people who are wealthier and better educated are better able under stress conditions to make cautious use of water，thus，not preempting the next generation from having similar benefits from the same water system.
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