【文章內(nèi)容簡介】 th century, when men such as Hortan, Mead, and Sherman began to explore the field. The great expansion of activity in flood control, irrigation, soil conservation, and related fields which began about 1930 gave the first real impetus to organized research in hydrology, as need for more precise design data became evident. Most of today’s concepts of hydrology date from 1930. 印度早在公元前4世紀(jì)就測量降水量了，但是令人滿意的測量河道流量的方法很遲才得到發(fā)展。公元97年，羅馬水利專員福朗堤努斯只按橫斷面面積估算流量，而不考慮流速。在美國，有組織地測量降水量是1819年在陸軍軍醫(yī)總監(jiān)領(lǐng)導(dǎo)下開始的，1870年移交給通信兵團(tuán)，最后，在1891你那移交給新改組的美國氣象局，該局于1970年改名為國家氣象局。早在1848年密西西比河上就進(jìn)行分散的河道流量測量了，但是，直到1888年美國地質(zhì)調(diào)查局承擔(dān)這項工作時，才開始實施系統(tǒng)的觀測計劃?；舻?、米德和謝爾曼等人在20世紀(jì)早期剛開始對這一領(lǐng)域進(jìn)行探索，因此，在這時期之前，在水文方面沒有進(jìn)行什么定量工作是不足為奇的。大約從1930年起，由于在防洪、灌溉、土地改良和有關(guān)領(lǐng)域中開展了大量活動，第一次為有組織地研究水文學(xué)提供了真正的動力，因為需要更精確的設(shè)計資料，這已是十分明顯的事了。大多數(shù)現(xiàn)代水文學(xué)的概念從1930年就開始有了。2 hydrology in engineering水文學(xué)在工程中的應(yīng)用Hydrology is used in engineering mainly in connection with the design and operation of hydraulic structures. What flood flows can be expected at a spillway or highway culvert or in a city drainage system ? What reservoir capacity is required to assure adequate water for irrigation or municipal water supply during droughts? What effects will reservoirs, levees, and other control works exert on flood flows in a stream? These are typical of questions the hydrologist is expected to answer.在工程上，水文學(xué)主要用于水工建筑物的設(shè)計和運行，溢洪道、公路涵洞、或者城市排水系統(tǒng)會期望有什么樣的洪水流量？需要多大的水庫庫容才能保證干旱季節(jié)里有足夠的灌溉水量或城市供水呢？水庫、堤壩或其他控制工程對河流洪水流量有什么影響？這些典型的問題等待水文學(xué)家去解答。Large organization such as federal and state water agencies can maintain staffs of hydrologic specialists to analyze their problems, but smaller offices often have insufficient hydrologic work for fulltime specialists. Hence, many civil engineers are called upon for occasional hydrologic studies. It is probable that these civil engineers deal with a larger number of projects and greater annual dollar volume than the specialists do. In any event, it seems that knowledge of the fundamentals of hydrology is an essential part of the civil engineer’s training.像聯(lián)邦和州轄水利機構(gòu)這樣的大型組織，擁有一批水文專家來分析他們的問題，但較小的單位往往沒有足夠的水文工作給專職水文專家做。因此，許多土木工程師們應(yīng)邀進(jìn)行臨時的水文研究。這些土木工程師處理的工程和年費用可能比水文專家還多。無論如何，水文學(xué)的基礎(chǔ)知識看來是培訓(xùn)土木工程師所必不可少的一部分。3 subject matter of hydrology水文學(xué)研究的主要內(nèi)容Hydrology deals with many topics. The subject matter as presented in this book can be broadly classified into two phases: data collection and methods of analysis. Chapter 2 to 6 deals with the basic data of hydrology. Adequate basic data are essential to any science, and hydrology is no exception. In fact, the plex features of the natural processes involved in hydrologic phenomena make it difficult to treat many hydrologic processes by rigorous deductive reasoning. One can not always start with a basic physical law and from this determine the hydrologic result to be expected. Rather, it is necessary to start with a mass of observed facts, analyze these facts, and from this analysis to establish the systematic pattern that governs these events. Thus, without adequate historical data for the particular problem area, the hydrologist is in a difficult position. Most countries have one or more government agencies with responsibility for data collection. It is important that the student learn how these data are collected and published, the limitations on their accuracy, and the proper methods of interpretation and adjustment.水文學(xué)研究很多問題。本書所介紹的主要內(nèi)容可大致分成兩個方面：收集資料和分析方法。2～6章研究水文學(xué)的基本資料。充足的基本資料是任何一個一門科學(xué)所不可少的，水文學(xué)也不例外。事實上，水文現(xiàn)象中也包含著許多自然過程的復(fù)雜特征，用嚴(yán)密的推理來處理許多水文現(xiàn)象是困難的。人們并不總是能夠從基本的自然法則出發(fā)，并由此來推求預(yù)期的水文結(jié)果。相反，從大量觀察的事實出發(fā)，分析這些事實，并根據(jù)分析建立控制這些事件的系統(tǒng)模型確實十分必要的。因此，對于沒有足夠歷史資料的特殊疑難地區(qū)，水文學(xué)家就將陷入困境。大多數(shù)國家有一個或更多的政府機構(gòu)負(fù)責(zé)收集資料，重要的是要讓學(xué)生學(xué)會這些資料是如何收集和刊出的，了解這些資料的精確度的局限性，學(xué)會整理分析和校正這些資料的專門的方法。Typical hydrologic problems involve estimates of extremes not observed in a small data sample, hydrologic characteristic at locations where no data have been collected (such locations are much more numerous than sites with data), or estimates of the effects of man’s actions on the hydrologic characteristics of an area. Generally, each hydrologic problem is unique in that it deals with a distinct set of physical conditions within a specific river basin. Hence, quantitative conclusions of one analysis are often not directly transferable to another problem. However, the general solution for most problems can be developed from application of a few relatively basic concepts.典型的水文問題包括估算小的數(shù)據(jù)樣本中無法觀測到的極值及估算無資料地區(qū)（這種地區(qū)比有資料的地區(qū)多得多）的水文特征值，或者估算人類活動對該地區(qū)水文特征值的影響。一般來說，每一個水文問題都是不同的，因為它涉及到特定流域內(nèi)特有的自然條件。因此，某種分析所得的定量結(jié)論常常不能直接移用到另一個問題上。然而，應(yīng)用一些比較基本的概念可以得出大多數(shù)問題都適用的一般解決方法。 Lesson 4 underground water 地下水Of all the earth’s water 97% is found in the oceans, 2% in glaciers and only 1% on land. Of this 1% almost all (97%) is found beneath the surface and called subsurface or underground water. Most of this water eventually finds its way back to the sea either by underground movement or by rising into surface streams and lakes.地球上的總水量中，97%在海洋，2%在冰川，只有1%在陸地上。陸地上的水幾乎全部（97%）埋藏在地面一下，稱為地下水。大部分地下水或通過地下流動，回到海洋；或先進(jìn)入河流或湖泊，最終又回到海洋。These vast underground water deposits provide much needed moisture for dry areas and irrigated districts. Underground water acts in similar ways to surface water, also performing geomorphic work as an agent of gradation.這些廣闊的地下含水層為干旱地區(qū)和灌溉區(qū)域提供了迫切需要的水分。地下水的作用和地表水的作用類似，也以均夷作用塑造著地貌。Even though man has been aware of subsurface water since earliest times, its nature, occurrence, movement and geomorphic significance have remained obscure. Recently, however, some answers have been found to the perplexing questions about underground water’s relationship to the hydrological cycle.盡管人類自古以來就知道地下水，但對它的特性、發(fā)生、運動和地貌意義還不清楚。然而，近來關(guān)于地下水和水文循環(huán)關(guān)系的這些錯綜復(fù)雜的問題已找到了一些答案。1 source of underground water地下水資源Since the days of Vitruvius at the time of Christ, many theories have been presented to explain the large volume of water underneath the earth’s surface. One theory was that only the sea could provide such large quantities, the water moving underground from coastal areas. Vitruvius was the first to recognize that precipitation