本人主編英文國際期刊International Journal of Sediment Research 18年，還兼任其他三家國際期刊副主編多年。收到的期刊稿件近半數為中國作者所貢獻，有不少稿件內容不錯，僅由于英文太差不得不拒稿。為了改進研究生和青年研究工作者的專業英文寫作水平，我在清華大學開設了水利專業英語課Professional English for Hydraulic Engineering，受到研究生、青年教師和水利研究院工程師的歡迎，學生們踴躍參加。中國水利水電科學研究院及有關水利院系多次邀請本人到場講課。
本書是十多年來在教學和與聽課師生交流中不斷修改更新補充后的講義，貢獻出來供有關專業師生參考使用。本書第二作者Charles Steven Melching教授是多家國際期刊的副主編，具有很高的專業水平和豐富的編輯修改水利專業英文的經驗。他為本書貢獻了大量的資料并且審閱修改了全部英文。本書第三和第四作者也為本書的成稿與出版做出了重要貢獻。
為了幫助教師在課堂上講解專業詞匯，特別是詞典上難以查到或專業上有不同意義的單詞和詞組，在每小節后面增加了關鍵專業詞匯的中文注釋。在中國作者經常犯的錯誤（Common Habits of Chinese Writers)以及改進翻譯兩節，所有的實例都是來自本書作者們修改的稿件和教學實踐。每一小節后面用中文解釋了中文寫作的習慣與英文的差異。本書的聽力材料是國際廣播電臺(China Radio International)在舟曲泥石流災害發生后的采訪錄音，在清華大學的專業英語教學中用作聽力材料和聽力測驗。余在多年的教學實踐中發現，學生們在課堂第一個小時之后會感到疲倦，用英文笑話解除疲倦效果很好，本書特選取幾例供教師參考使用。
王兆印
2017年3月于清華園
王兆印，1951年10月出生，山東濟南人，清華大學水利水電工程系教授，主要從事高含沙水流、泥石流、植被侵蝕動力學、河流生態與恢復、以及河流綜合流域管理方面研究。獲得2011年度漢斯.阿爾伯特.愛因斯坦獎，這是首位大陸籍華人獲此殊榮。
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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