水利水電工程專業(yè)英語-水文與水資源篇

實(shí)用文檔實(shí)用文檔水利水電工程專業(yè)英語——水文與水資源篇1.HydrologicalCycleandBudget水文循環(huán)與預(yù)算Hydrologyisanearthscience.Itencompassestheoccurrence,distribution,movement,andpropertiesofthewatersoftheearthandtheirenvironmentalrelations.Closelyalliedfieldsincludegeology,climatology,meteorologyandoceanography.水文學(xué)是一門地球科學(xué)。它包含地球水資源的發(fā)生、分布、運(yùn)動(dòng)和特質(zhì)，以及其環(huán)境關(guān)系。與之密切相關(guān)領(lǐng)域包括地質(zhì)學(xué)，氣候?qū)W，氣象學(xué)和海洋學(xué)。Thehydrologiccycleisacontinuousprocessbywhichwateristransportedfromtheoceanstotheatmospheretothelandandbacktothesea.Manysub-cyclesexist.Theevaporationofinlandwateranditssubsequentprecipitationoverlandbeforereturningtotheoceanisoneexample.Thedrivingforcefortheglobalwatertransportsystemisprovidedbythesun,whichfurnishestheenergyrequiredforevaporation.Notethatthewaterqualityalsochangesduringpassagethroughthecycle;forexample,seawaterisconvertedtofreshwaterthroughevaporation.水文循環(huán)是一個(gè)連續(xù)的過程，在這個(gè)過程中水從海洋被運(yùn)輸?shù)酱髿庵校德涞疥懙?，然后回到海洋。有很多子循環(huán)存在。內(nèi)陸水域的蒸發(fā)機(jī)器后在回到海洋前在陸地上的將于就是一個(gè)例子。全球水運(yùn)輸系統(tǒng)的運(yùn)行動(dòng)力由太陽提供，通過蒸發(fā)這個(gè)過程賦予水運(yùn)動(dòng)能量。需要注意的是，水質(zhì)在水循環(huán)通道中也會(huì)改變，比如，海水在蒸發(fā)后就會(huì)轉(zhuǎn)變成淡水。Thecompletewatercycleisglobalinnature.Worldwaterproblemsrequirestudiesonregional,national,international,continental,andglobalscales.Practicalsignificanceofthefactthatthetotalsupplyoffreshwateravailabletotheearthislimitedandverysmallcomparedwiththesaltwatercontentoftheoceanshasreceivedlittleattention.Thuswatersflowinginonecountrycannotbeavailableatthesametimeforuseinotherregionsoftheworld.Modernhydrologistsareobligatedtocopewithproblemsrequiringdefinitioninvaryingscalesofsignificantorderofmagnitudedifference.Inaddition,developingtechniquestocontrolweathermustreceivecarefulattention,sinceclimatologicalchangesinoneareacanprofoundlyaffectthehydrologyandthereforethewaterresourcesofotherregions.完整的水循環(huán)在自然界中是全球性的。世界水問題需要在區(qū)域，國家，國際，洲際和全球范圍的研究。地球上可利用的淡水總量與海洋中的咸水相比是有限的，并且非常少，這個(gè)重要的顯示尚未得到人們足夠關(guān)注。因此，在一個(gè)國家流動(dòng)的水源并不能同時(shí)在世界的其他區(qū)域被利用。現(xiàn)代水文學(xué)應(yīng)該著力解決顯著數(shù)量級(jí)的差異在不同尺度上的定義問題。此外，發(fā)展控制天氣的技術(shù)必須得到密切關(guān)注，因?yàn)橐粋€(gè)地區(qū)的氣候變化能夠深刻地影響到其他地區(qū)的水文循環(huán)進(jìn)而影響到其水資源。Becausethetotalquantityofwateravailabletotheearthisfiniteandindestructible,theglobalhydrologicsystemmaybelookeduponasclosed.Openhydrologicsystemmaybelookeduponasclosed.Openhydrologicsubsystemsareabundant,however,andtheseareusuallythetypeanalyzed.Foranysystem,awaterbudgetcanbedevelopedtoaccountforthehydrologiccomponents.因?yàn)榈厍蛏峡衫玫乃渴怯邢耷也豢杀苊獾?，所以全球的水文循環(huán)系統(tǒng)可以被看成是閉合的。開放性的水文循環(huán)系統(tǒng)可以被看成是閉合的。開放的水文子系統(tǒng)內(nèi)容豐富，然而這些系統(tǒng)也是經(jīng)常被分析到的。對(duì)于任何系統(tǒng)，水預(yù)算都能夠轉(zhuǎn)變到對(duì)水文組成的計(jì)算。Figures1and2showahydrologicbudgetforthecoterminousUnitedStates.Thesefiguresillustratethecomponentsofthewatercyclewithwhichahydrologistisconcerned.Inapracticalsense,somehydrologicregionisdealtwithandabudgetforthatregionisestablished.Suchregionsmaybetopographicallydefined(watershedsandriverbasinsareexamples),politicallyspecified(e.g.countryorcitylimits),orchosenonsomeothergrounds.Watershedsordrainagebasinsaretheeasiesttodealwithsincetheysharplydefinesurfacewaterboundaries.Thesetopographicallydeterminedareasaredrainedbyariver/streamorsystemofconnectingrivers/streamssuchthatalloutflowisdischarged through asingleoutlet.Unfortunately,itisoftennecessarytodealwithregionsthatarenotwellsuitedfortrackinghydrologiccomponents.Fortheseareas,thehydrologistwillfindhydrologicbudgetingsomewhatofachallenge.ifi--1-'I!'HlJ'V.；■Jbc^lm后注皿ifi--1-'I!'HlJ'V.；■Jbc^lm后注皿grmiriflMAHr(towboowiiihtV-lpVKUClLlILrmuuHlM'ir同'山一":--?! ■■. 1. !.：二tnutxLiki^制00(1明E.v^XX^1KN>IirJMiphiAhumbofefclun^surfecemidxtiKinifnj 地ittfi；■中Pi2jme1171ydiPi2jme1171ydi101c典bu岫MofaatHininmiUnitolSttilcMU￡Qm1響ESumy，F(xiàn)igure；Iliehytbutogjccycle:兀iwn用irabon;^evupcMMifHi;f+predpi曜km；岫■"hilion pa7圖1和圖2展示了美國毗連地區(qū)的水文循環(huán)。這些圖展示了考慮水文的水循環(huán)的過程。從實(shí)際意義上講，一些水文區(qū)域被處理并且建立了預(yù)算。 這些區(qū)域可以是在地形上確定（如流域和河流盆地）、在政治上確定（如根據(jù)國家或者城市限制），或以其他因素確定。流域或者排水流域是最容易確定的， 因?yàn)樗鼈兠黠@地限定了地表水的邊界。 這些地形上確定的區(qū)域由一條河流/溪流或者相連的河流/溪流排水，因此所有的出流都從某個(gè)單一的出口排出。 不幸的是，我們經(jīng)常會(huì)處理到不適合通過跟蹤水文組成部分的區(qū)域。 對(duì)于這些區(qū)域，水文學(xué)家

會(huì)在不同程度上挑戰(zhàn)地進(jìn)行水文預(yù)算。Theprimaryinputinahydrologicbudgetisprecipitation.Someoftheprecipitation(e.g.rain,snow,hail)maybeinterceptedbytrees,grass,othervegetation,andstructuralobjectsandwilleventuallyreturntotheatmospherebyevaporation.Onceprecipitationreachestheground,someofitmayfilldepressions(becomedepressionstorage),partmaypenetratetheground(infiltrate)toreplenishsoilmoistureandgroundwaterreservoirs,andsomemaybecomesurfacerunoff,thatis,flowovertheearth’ssurfacetoadefinedchannelsuchasastream.在水文預(yù)算中首要的輸入是降水。部分降水(如雨、雪、冰雹)會(huì)被樹木、草地、其它植被以及建筑物截留，并最終會(huì)通過蒸發(fā)返回大氣。若降水到達(dá)地面，其中一些會(huì)在洼地儲(chǔ)存(成為洼地存水)，部分會(huì)入滲到地下(滲透)補(bǔ)充含水層和地下儲(chǔ)水，一些會(huì)成為地表徑流，即流過地表進(jìn)入到已有的通道中，比如溪流。Waterenteringthegroundmaytakeseveralpaths.Somemaybedirectlyevaporatedifadequatetransferfromthesoiltothesurfaceismaintained.Thiscaneasilyoccurwhereahighgroundwatertable(freewatersurface)iswithinthelimitsofcapillarytransporttothegroundsurface.Vegetationusingsoilmoistureorgroundwaterdirectlycanalsotransmitinfiltratedwatertotheatmospherebyaprocessknownastranspiration.Infiltratedwatermaylikewisereplenishsoilmoisturedeficienciesandenterstorageprovidedingroundwaterreservoirs,whichinturnmaintaindryweatherstreamflow.Importantbodiesofgroundwaterareusuallyflowingsothatinfiltratedwaterreachingthesaturatedzonemaybetransportedforconsiderabledistancesbeforeitisdischarged.Groundwatermovementissubject,ofcourse,tophysicalandgeologicalconstraints.水進(jìn)入地表后可能有幾個(gè)途徑（被利用）。如果土壤水到地表的轉(zhuǎn)移能夠得到保證，一些可能被直接蒸發(fā)。這種現(xiàn)象很容易發(fā)生在毛細(xì)現(xiàn)象運(yùn)輸?shù)竭_(dá)地表限制水位內(nèi)的高地下水位情況下。植被直接利用的土壤水或地下水可通過所謂的“蒸騰”過程把如深水轉(zhuǎn)換到大氣中去。入滲水同樣可以補(bǔ)充不足的土壤水且接入到地下水庫提供的容量中，這些水反過來會(huì)在干燥天氣保持水流運(yùn)動(dòng)。重要的地下水體一般都在流動(dòng)，因此到達(dá)飽和區(qū)域的入滲水可能會(huì)在被運(yùn)輸了相當(dāng)遠(yuǎn)的距離后才被排出。地下水的運(yùn)動(dòng)自然地會(huì)受到物理和地質(zhì)條件的限制。Waterstoredindepressionswilleventuallyevaporateorinfiltratethegroundsurface.Surfacerunoffultimatelyreachesminorchannels（gullies,rivulets,andthelike）,flowstomajorstreamsandfinallyreachesanocean.Alongthecourseofastream,evaporationandinfiltrationcanalsooccur.儲(chǔ)存在洼地的水會(huì)最終蒸發(fā)或入滲到地表。地表徑流最終到達(dá)小的通道（溝渠，溪流等），流向大的溪流，最后到達(dá)海洋。在水流動(dòng)的過程中，蒸發(fā)和滲流也同時(shí)發(fā)生著。UnitHydrographs單位線Waystopredictfloodpeakdischargesanddischargehydrographsfromrainfalleventshavebeenstudiedintensivelysincetheearly1930s.Oneapproachreceivingconsiderableuseiscalledtheunithydrographmethod.ItderivesfromamethodofunitgraphsemployedbySherman,in1932.Theunitgraphisdefinedasfollows:ifagivenX-hourrainfallproducesa10cmdepthofrunoffoverthegivendrainagearea,thehydrographshowingtheratesatwhichtherunoffoccurredcanbeconsideredaunitgraphforthatwatershed.自20世紀(jì)30年代早期就已經(jīng)深入研究了降雨事件中預(yù)測洪峰流量和流量過程線的方法。一個(gè)應(yīng)用廣泛的方法被稱為單位線法。它源于謝爾曼在 1932年使用的單位曲線的方法。該單位曲線定義如下：如果在給定的X小時(shí)內(nèi)，給定的流域上產(chǎn)生了10cm深的徑流，則在該流域出口斷面形成的地面徑流過程線即為單位線。Itisincorrecttodescribeaunithydrographwithoutspecifyingtheduration,Xofthestormthatproducedit.AnX-hourunithydrographisdefinedasadirectrunoffhydrographhavinga10cm.Volumeandresulting fromanX-hourstormhavingasteadyintensityof10/Xcm/hr.A2-hrunithydrographwouldbethatproducedbya2-hrstormduringwhich10cmofexcessrunoffwasuniformlygeneratedoverthebasin.A1-dayunithydrographwouldbeproducedbyastormhaving10cmofexcessrainuniformlyproducedduringa24-hrperiod.ThevalueXisoftenafractionof1hr.如果不指明單位線的降雨歷時(shí) X，那么描述單位線是不正確的。 X小時(shí)的單位線被定義為具有10厘米的直接徑流的過程線。一個(gè)X小時(shí)的暴雨有著穩(wěn)定的10/X厘米/小時(shí)的體量和結(jié)果。一個(gè)2小時(shí)的單位線將由在流域內(nèi)均勻產(chǎn)生 10厘米過量徑流的2小時(shí)暴雨所產(chǎn)生。一個(gè)1日單位線將由在 24小時(shí)期間內(nèi)均勻產(chǎn)生的具有 10厘米過量降雨的暴雨所產(chǎn)生的。X值通常是1小時(shí)的幾分之一。ApplicationanX-hourunitgraphtodesignrainfallexcessamountsotherthan10cmisaccomplishedsimplybymultiplyingtherainfallexcessamountbytheunitgraphordinates,sincetherunoffordinatesforagivendurationareassumedtobedirectlyproportionaltorainfallexcess.A3-hrstormproducing20cmofnetrainwouldhaverunoffrates2timesthevaluesofthe3-hrunithydrograph.5cmin3hrwouldproduceflowshalfthemagnitudeofthe3-hrunithydrograph.Thisassumptionofproportionalflowsappliesonlytoequaldurationstorms.采用X小時(shí)的單位線來計(jì)算并非等于 10厘米的徑流過程，可簡單地用凈雨深乘以單位線的縱標(biāo)，因?yàn)閷?duì)一個(gè)給定時(shí)段，單位線假定徑流與凈雨直接成正比。一個(gè)產(chǎn)生 20厘米凈雨的3小時(shí)暴雨的徑流速率值將是 3小時(shí)單位線的2倍。3小時(shí)內(nèi)5厘米將會(huì)產(chǎn)生 3小時(shí)單位線一半的量。該成比例徑流假設(shè)僅適用于相同歷時(shí)的暴雨。IfthedurationofanotherstormisanintegermultipleofX,thestormistreatedasaseriesofendtoendX-hourstorms.First,thehydrographs fromeachXincrementofrainaredeterminedfromtheX-hourunithydrograph.Theordinatesarethenaddedatcorrespondingtimestodeterminethetotalhydrograph.如果另一個(gè)暴雨的歷時(shí)是 X的整數(shù)倍，那么該暴雨就被視作一系列首尾相連的X小時(shí)暴雨系列。首先，每個(gè) X降雨增量的過程線由X小時(shí)單位線確定。然后在相應(yīng)的時(shí)間疊加到縱軸，以確定總的過程線。Implicitinderivingtheunithydrographistheassumptionthatrainfallisdistributedinthesametemporalandspatialpatternforallstorms.Thisisgenerallynottrue;consequently,variationsinordinatesfordifferentstormofequaldurationcanbeexpected.在推導(dǎo)單位線隱含的假設(shè)是所有暴雨中降雨都按照相同的時(shí)間和空間類型而分布。這通常并不是真實(shí)的；因此，可以預(yù)期對(duì)于相同歷時(shí)的不同暴雨中的縱坐標(biāo)的變化。TheconstructionofunithydrographsforotherthanintegermultiplesoftheThederiveddurationisfacilitatedbyamethodknownastheS-cedureemploysaunithydrographtoformanS-hydrographresultingfromacontinuousappliedrainfall.Theunithydrographtheorycanbeappliedungaugedwatershedsbyrelatingunithydrographfeaturestowatershedcharacteristics.Asaresultoftheattemptedsynthesisofdata,theseapproachesarereferredtoassyntheticunithydrographmethods.Theneedtoalterdurationofaunithydrographencouragedstudiestodefinetheshortestpossiblestormduration,thatis,aninstantaneousunitrainfall.Theconceptofinstantaneousunithydrograph(IUH)canbeusedinconstructionunithydrographsforotherthanthederivedduration.The對(duì)于歷時(shí)不是整數(shù)倍的單位線的建立，引入了一個(gè)被稱為“S曲線”的方法。該過程引入了一個(gè)單位線以組成一個(gè)自所引用連續(xù)降雨產(chǎn)生的S曲線。單位線理論可以通過將單位線特征與流域特性相關(guān)聯(lián)而應(yīng)用到無水文資料流域。作為數(shù)據(jù)的嘗試合成的結(jié)果，這些方法被稱為“綜合單位線法”。改變單位線歷時(shí)的需要鼓勵(lì)研究確定最短的風(fēng)暴歷時(shí)，即，瞬時(shí)單位的降雨量?！八矔r(shí)單位線”(IUH)的概念可以被用于構(gòu)建非引用歷時(shí)的單位線。Methodsofderivingunithydrographsvaryandaresubjecttoengineeringjudgment.Thelevelofsophisticationemployedtounraveltheproblemdependslargelyonthekindofissueinquestion.Severalmethodsusefulinthedeterminationofunithydrographswillbediscussed.TheyaresubdividedintostartingwithunithydrographsobtainedfromfielddataandmanipulatingthembyS-hydrographmethodsandconstructingsyntheticunithydrographs.獲得單位線的方法各異且受工程師判斷的影響。用來解開問題的復(fù)雜程度在很大程度它們細(xì)分為開上取決于所討論的那種問題。在確定單位線的過程中將討論很多有用的方法。始從現(xiàn)場數(shù)據(jù)獲得單位線，然后用S曲線方法操作它們并構(gòu)建綜合單位線。它們細(xì)分為開Datacollectionpreparatorytoderivingaunithydrographforagaugedwatershedcanbeextremelytimeconsuming.T odevelopaunithydrograph,itisdesirabletoacquireasmanyrainfallrecordsaspossiblewithinthestudyareatoensurethattheamountanddistributionofrainfalloverthewatershedisaccuratelyknown.Preliminaryselectionofstormstouseinderivingaunithydrographforawatershedshouldberestrictedtothefollowing ：Stormsoccurringindividually,thatis,simplestormstructure.Stormshavinguniformdistributionofrainfallthroughouttheperiodofrainfallexcess.Stormshavinguniformspatialdistributionovertheentirewatershed.獲得一個(gè)有水文資料流域的單位線的數(shù)據(jù)收集準(zhǔn)備會(huì)相當(dāng)?shù)刭M(fèi)時(shí)。為了建立一個(gè)單位線，最好是獲得盡可能多的研究區(qū)域內(nèi)的降水記錄，以確保準(zhǔn)確知曉流域內(nèi)降雨的數(shù)量和分布。要用于流域獲得單位線的降雨初步選擇應(yīng)該嚴(yán)格遵循如下：)暴雨獨(dú)立地發(fā)生，即，單獨(dú)的暴雨結(jié)構(gòu)。2)在整個(gè)過量降雨期間，暴雨具有均勻的降雨分布。)降雨在整個(gè)流域內(nèi)具有均勻的空間分布。Theserestrictionsplacebothupperandlowerlimitsonsizeofthewatershedtobeemployed.Anupperlimitofwatershedsizeofapproximately2000km2isovercautious,althoughgeneralstormsoversuchareasarenotunrealisticandsomestudiesofareasupto3000km2haveusedtheunithydrographtechnique.Thelowerlimitofwatershedextentdependsonnumerousotherfactorsandcannotbepreciselydefined.Ageneralruleofthumbistoassumeabout10km 2.Fortunately,otherhydrologictechniqueshelpresolveunithydrographsforwatershedsoutsidethisrange.這些約束限制了要應(yīng)用流域大小的上限和下限。2000平方公里左右的流域大小的上限是過于謹(jǐn)慎的，盡管在這些區(qū)域的通常暴雨并非不切實(shí)際并且一些面積達(dá)到3000平方公里地區(qū)的研究也應(yīng)用了單位線技術(shù)。流域范圍的下限取決于眾多的其他因素，并不能被準(zhǔn)確定義。一般的經(jīng)驗(yàn)是假設(shè)約10平方公里。幸運(yùn)的是，其它過程線技術(shù)可以幫助解決在這個(gè)范圍外的流域單位線。Thepreliminaryscreeningofsuitablestormsforunithydrographformationmustmeetmorerestrictivecriteriabeforefurtheranalysis:Durationofrainfalleventshouldbeapproximately10%-30%ofthedrainagearealagtime.Directrunofffortheselectedstormshouldbegreaterthan5cm.Asuitablenumberofstormsshouldbeanalyzedtoobtainanaverageoftheordinatesforaselectedunithydrographduration.ModificationsmaybemadetoadjustunithydrographdurationsbymeansofS-hydrographsofIUHprocedures.Directrunoffordinatesforeachstormshouldbereducedsothateacheventrepresents10cmofdirectrunoff.Thefinalunithydrographofaspecificdurationforthewatershedisobtainedbyaveragingordinatesofselectedeventsandadjustingtheresulttoobtain10cmofdirectrunoff.在進(jìn)一步分析之前，單位線形成的合適暴雨的初步篩選必須滿足以下更加嚴(yán)格的標(biāo)準(zhǔn)：）降雨事件的歷時(shí)應(yīng)該大約是流域面積延遲時(shí)間的10%-30%。）所選擇的暴雨的直接徑流應(yīng)該大于 5厘米。）應(yīng)該分析合適數(shù)量的暴雨以獲得一個(gè)所選單位線歷時(shí)的平均縱標(biāo)?？梢酝ㄟ^ IUH過程的S曲線法來調(diào)整修改單位線歷時(shí)。4）每場暴雨的直接徑流縱標(biāo)應(yīng)該被減少，所以每場降雨代表 10厘米的直接徑流。5）流域特定歷時(shí)的最終單位線是通過平均所選擇降雨事件的縱標(biāo)和調(diào)整結(jié)果以獲得10厘米的直接徑流而得到的。Constructiontheunithydrographinthiswayproducestheintegratedeffectofrunoffresultingfromarepresentativesetofequaldurationstorms.Extremerainfallintensityisnotreflectedinthedetermination.Ifintensestormsareneeded,astudyofrecordsshouldbemadetoascertaintheirinfluenceuponthedischargehydrographandactualhydrographsfromintensestorms.用這種方式構(gòu)建單位線產(chǎn)生了徑流的綜合效應(yīng)，這來自一個(gè)代表系列的相同歷時(shí)的暴雨。極端暴雨強(qiáng)度不會(huì)再?zèng)Q定中反映出來。如果需要強(qiáng)暴雨，就要研究記錄以判明它們對(duì)流量過程線的影響以及強(qiáng)暴雨的實(shí)際過程線。Essentialstepsindevelopingaunithydrographforanisolatedstormfollow:Analyzethestreamflowhydrographtopermitseparationofsurfacerunofffromgroundwaterflow.Measurethetotalvolumeofsurfacerunoff（directrunoff）fromthestormproducingtheoriginalhydrographequaltotheareaunderthehydrographaftergroundwaterbaseflowhasbeenremoved.Dividetheordinatesofdirectrunoffhydrographbytotaldirectrunoffvolumeininchesandplottheseresultsversustimeasunitgraphforthebasin.Finally,theeffectivedurationoftherunoff-producingrainforthisunitgraphmustbefoundfromthehyetograph（timehistoryofrainfallintensity）ofthestormused.建立一個(gè)獨(dú)立暴雨單位線的基本過程如下：1）分析徑流過程線以允許將地表徑流和地下徑流分離。2）在移除地下水基流后，測量暴雨產(chǎn)生的地表徑流（直接徑流）的總量，該暴雨產(chǎn)生了與過程線下該地區(qū)相等的原始過程線。3）以英尺為單位劃分直接徑流總量的直接徑流過程線縱標(biāo)，并將這些結(jié)果和時(shí)間繪制成一個(gè)流域的單位線。4）最后，必須從所用暴雨的雨量計(jì)圖來建立產(chǎn)流降雨的有效歷時(shí)。Proceduresotherthanthoselistedarerequiredforcomplexstormsorindevelopingsyntheticunitgraphswhenfewdataareavailable.Unithydrographscanalsobetransposedfromonebasintoanotherundercertaincircumstances.更復(fù)雜的暴雨或者當(dāng)有很少可用資料情況下建立綜合單位線時(shí)會(huì)需要除上述列出以外的步驟。在某些情況下，也可以將一個(gè)流域的單位線移用到另外一個(gè)流域。3.FloodRouting3.洪水演算Floodforecasting,reservoirdesign,watershedsimulation,andcomprehensivewaterresourcesplanninggenerallyutilizesomeformofroutingtechnique.Routingisusedtopredictthetemporalandspatialvariationsofafloodwaveasittraversesariverreachorreservoir,oritcanbeemployedtopredicttheoutflowhydrographfromawatershedsubjectedtoaknownamountofprecipitation.Routingtechniquesmaybeclassifiedintotwocategories-hydrologicroutingandhydraulicrouting.洪水預(yù)測、水庫設(shè)計(jì)、流域仿真和水資源綜合規(guī)劃通常應(yīng)用某種形式的演算技術(shù)。演算被用來預(yù)測一個(gè)洪峰在通過一個(gè)河段或水庫時(shí)的時(shí)間和空間變化，或者它可以被用于預(yù)測受到一個(gè)已知量降水的流域的出流過程線。演算技術(shù)可以分為兩類：水文演算和水力演算。Hydrologicroutingemploystheequationofcontinuitywitheitherananalyticoranassumedrelationbetweenstorageanddischargewithinthesystem.Hydraulicrouting,ontheotherhand,usesboththeequationofcontinuityandtheequationofmotion,customarilythemomentumequation.Thisparticularformutilizesthepartialdifferentialequationsforunsteadyflowinopenchannels.Itmoreadequatelydescribesthedynamicsofflowthandoesthehydrologicroutingtechnique.水文演算應(yīng)用了連續(xù)性方程，表達(dá)系統(tǒng)內(nèi)儲(chǔ)蓄和排放之間的一個(gè)分析或假設(shè)的關(guān)系。另一方面，水力演算既應(yīng)用連續(xù)性方程，也應(yīng)用運(yùn)動(dòng)方程，習(xí)慣上是動(dòng)量方程。這種特殊的形式使用偏微分方程來表達(dá)明渠的非恒定流。它比水文演算技術(shù)更充分地描述水流動(dòng)力情況。Applicationsofhydrologicroutingtechniquestoproblemsoffloodprediction,evaluationsoffloodcontrolmeasures,andassessmentstheeffectsofurbanizationarenumerous.Mostfloodwarningsystemsincorporatethistechniquetopredictfloodstagesinadvanceofaseverestorm.Itisthemethodmostfrequentlyusedtosizespillwaysforsmall,intermediate,andlargedams.Additionally,thesynthesisof

runoffhydrographsfromgaugedandungaugedwatershedsispossiblebytheuseofthisapproach.水文演算技術(shù)在洪水預(yù)測問題、防洪措施評(píng)估以及城鎮(zhèn)化影響評(píng)價(jià)中有很多應(yīng)用。大它是確定小型、中多數(shù)洪水預(yù)警系統(tǒng)引入了該項(xiàng)技術(shù)以在一場劇烈暴雨之前預(yù)測洪水過程。它是確定小型、中型和大型大壩溢洪道尺寸的最常用方法。 此外，在可測量和無測量資料的流域中徑流水文過程的綜合可能使用這種方法。Hydrologicriverroutingtechniquesareallfoundedupontheequationofcontinuity?2d??

=-?2d??whereIistheinflowratetothereach,whereIistheinflowratetothereach,Oistheoutflowratefromthereach,dS/dtistherateofchangeofstoragewithinthereach.水文河流演算技術(shù)都建立在連續(xù)性方程的基礎(chǔ)上??-d??d??(1)??-d??d??(1)其中I是到達(dá)該河段的入流速率， O是河段的出流速率，dS/dt是河段內(nèi)蓄水的變化速率。Storageinastableriverreachcanbeexpectedtodependprimarilyonthedischargeintoandoutofareachandonhydrauliccharacteristicsofthechannelsection.Thestoragewithinthereachatagiventimecanbeexpressedas(2)??=，？??]??+(1-??????[a(2)Constantsaandnreflectthestagedischargecharacteristicsofcontrolsectionsateachendofthereach,andbandmmirrorthestage-volumecharacteristicsofthesection.ThefactorXdefinestherelativeweightsgiventoinflowandoutflowforthereach.穩(wěn)定河段中的蓄水量主要取決于該河段的入流和出流，以及河流斷面的水力特征值。在給定時(shí)間點(diǎn)的河段內(nèi)蓄水量可以被表示為TOC\o"1-5"\h\z??=b[???????+(1-???*?] (2)a常數(shù)a和n反映每個(gè)河段兩端的階段排放特性，且b和m反映了河段的階段體積特性。因素X確定了河段入流和出流的相對(duì)權(quán)重。TheMuskingummethodassumesthatm/n=1andletsb/a=K,resultingin??=??????(1-???? ⑶whereKisthestoragetimeconstantforthereach,Xisaweightingfactorthatvariesbetween0and0.5.馬斯京根法假設(shè)m/n=1且令b/a=K,得到??=??????(1-???? (3)其中K是河段存儲(chǔ)時(shí)間常數(shù)， X是在0-0.5之間的權(quán)重因數(shù)。Applicationofthisequationhasshownthat KisusuallyreasonablyclosetothewavetraveltimethroughthereachandXaveragesabout0.2.該方程的應(yīng)用已經(jīng)表明 K通常合理地接近于水流通過河段流動(dòng)的時(shí)間，且 X平均值約0.2。Behaviorofthefloodwaveduetochangesinthevalueofweightingfactor Xisreadilyapparent.Theresultingdownstreamfloodwaveiscommonlydescribedbytheamountoftranslation,thatis,thetimelagandbytheamountofattenuationorreductioninpeakdischarge.ThevalueX=0.5resultsinapuretranslationofthefloodwave.權(quán)重因數(shù)X的值的變化很明顯地影響著洪峰的表現(xiàn)。所得的下游洪峰通常被描述為移

動(dòng)量，即，時(shí)間滯后和衰減量或洪峰流量的減少。 X=0.5時(shí)導(dǎo)致了洪峰的單純的平移。ApplicationofEqs.(1)and(3)toariverreachisastraightforwardprocedureifKandXareknown.Theroutingprocedurebeginsbydividingtimeintoanumberofequalincrements,At,andexpressingEq.(1)infinitedifferenceform,usingsubscripts1and2todenotethebeginningandendingtimesforAt.Thisgives(4)如果K和X已知，那么方程（1）和（3）At.Thisgives(4)如果K和X已知，那么方程（1）和（3）在河段中的應(yīng)用就是非常簡單的流程。演算過程開始于將時(shí)間分成一定數(shù)量的相同增量，At,并將方程（1）表達(dá)為有限差分的形式，使用下標(biāo)1和2表示At的開始和結(jié)束時(shí)間。由此得出(4)TheroutingtimeintervalAtisnormallyassignedanyconvenientvalue(4)TheroutingtimeintervalAtisnormallyassignedanyconvenientvalue??+????+?? ?q-??betweenthelimitsofK/3andK.演算時(shí)間間隔At通常被指定為K/3和K的界限之間的任何方便的值。ThestoragechangeintheriverreachduringtheroutingintervalfromEq.(3)is??-??=??????-演算時(shí)間間隔At通常被指定為K/3和K的界限之間的任何方便的值。ThestoragechangeintheriverreachduringtheroutingintervalfromEq.(3)is??-??=??????-??)+(1-??(??-??)]andsubstitutingthisintoEq.(4)resultsintheMuskingumroutingequation??=?3??+????+????(6)Inwhich-????0.5??????-???+05????.??=????0.5??????-???+05????.??=??-????05????.??-???+05????.NotethatKandAtmusthavethesametimeunitsandalsothatthethreecoefficientssumto1.0.方程（3）中演算間隔中河段內(nèi)的蓄水變化為馬斯京根方程??-??=??????-??)+(1-??(??-??)] (5)將此式帶入方程(4)中得到??=????+????+???? (6)其中-???+0.5?????7= 0 ??-???+05????.???+0.5??????= ??-???+05????.??-????05????.??2= ??-???+05????.注意K和At必須有相同的單位且三個(gè)系數(shù)和為 1.0。TheoreticalstabilityofthenumericalmethodisaccomplishedifAtfallsbetweenthelimits2KXand2K(1-X).ThetheoreticalvalueofKisthetimerequiredforanelemental(kinematic)wavetotraversethereach.Itisapproximatelythetimeintervalbetweeninflowandoutflowpeaks,ifdataareavailable.Ifnot,thewavevelocitycanbeestimatedforvariouschannelshapesasafunction ofaveragevelocityVforanyrepresentativeflowrateQ.VelocityforsteadyuniformflowcanbeestimatedbyeithertheManningorChezyequation.如果At在2KX和2K(1-X)之間，那么數(shù)值計(jì)算方法就滿足理論穩(wěn)定性。 K的理論值是一個(gè)元素(運(yùn)動(dòng))峰穿過河段所需的時(shí)間。如果可以獲得數(shù)據(jù)，那么它大約是流入及流出峰值之間的時(shí)間間隔。如果不是，波速可以對(duì)不同的渠道形狀作為代表性流量 Q的平均速率的函數(shù)來估算。穩(wěn)定均勻流的速度可以通過曼寧或謝才公式來估算Since,I1andI2areknownforeverytimeincrement,routingisaccomplishedbysolvingEq.(6)successivetimeincrementsusingeach O2asO1forthenexttimeincrement.因此，I1和I2是已知的每個(gè)時(shí)間增值，并通過將 O2作為下個(gè)時(shí)間增量的O1來解決方程( 6)的連續(xù)的時(shí)間增量，從而完成演算。4.WaterQualityModels4.水質(zhì)模型Becausewaterqualityisinextricablylinkedtowaterquantity,itisimportantforthehydrologisttounderstandthesignificanceofdevelopingmodelingtechniquesthatcanaccommodatebothfeatures.由于水質(zhì)與水量密不可分，因此了解開發(fā)能夠適用于兩個(gè)特性的建模技術(shù)對(duì)水文學(xué)家來說是很重要的。Awaterqualitymodelisamathematicalstatementorsetofstatementsthatequatewaterqualityatapointofinteresttocausativefactors.Ingeneral,waterqualitymodelsaredesignedto(1)acceptasinput,constituentconcentrationversustimeatpointsofentrytothesystem,(2)simulatethemixingandreactionkineticsofthesystem,and(3)synthesizeatime-distributedoutputatthesystemoutlet.水質(zhì)模型是一個(gè)或一系列的數(shù)學(xué)表達(dá)，描述了所關(guān)注點(diǎn)的誘發(fā)因素的水質(zhì)。通常來講，2）模擬混合及水質(zhì)模型被設(shè)計(jì)于(1)作為輸入條件，在系統(tǒng)入口處濃度與時(shí)間的關(guān)系，系統(tǒng)的動(dòng)力學(xué)反應(yīng)，以及（32）模擬混合及Eitherstochastic(containingprobabilisticelements)ordeterministicapproachesmaybetakenindevelopingmethodsforpredictingpollutionalloads.Theformertechniqueisbasedondeterminingthelikelihood(frequency)ofaparticularoutputqualityresponsebystatisticalmeans.Thisissimilartofrequencyanalysisoffloodsorlowflows.Waterqualityrecordsshouldbeavailableforatleast5years(andpreferablymuchlonger)ifestimatesofreturnperiodsforinfrequenteventsaretobereliable.隨機(jī)(包含概率元素)或確定性方法都可能被用于開發(fā)預(yù)測污染負(fù)荷的方法。前者技術(shù)基于通過統(tǒng)計(jì)方法確定的一個(gè)特定的輸出質(zhì)量響應(yīng)的可能性(頻率)。這類似于洪水或低流量的頻率分析。如果要求可靠的偶發(fā)事件重現(xiàn)期的估計(jì)，那么就要至少獲得 5年(最好更長)的水質(zhì)記錄。Thedeterministicapproach(outputexplicitlydeterminedforagiveninput)requiresthatamodelbedevelopedtorelatewaterqualityloadingtoaknownorassumedhydrologicinput.Suchamodelcanrangefromanempiricalconcentrationdischargerelationtoaphysicalequationrepresentingthehydrochemicalcycle.Theultimatemodelingtechniqueisthatwhichbestdefinestheactualmechanismtriggeringthewaterqualityresponse.Thecauseofagivenstateofpollutioncanthenbespecificallyidentified.確定性方法(對(duì)于給定的輸入明確地確定輸出)要求一個(gè)模型被開發(fā)于將水質(zhì)負(fù)荷與一個(gè)已知的或假設(shè)的水文輸入關(guān)聯(lián)起來。這樣的一個(gè)模型可以從一個(gè)濃度流量的經(jīng)驗(yàn)關(guān)系到一個(gè)物理方程，描述水化學(xué)循環(huán)。最終的建模技術(shù)最好地定義了觸發(fā)水質(zhì)響應(yīng)的實(shí)際機(jī)制。隨后即可具體確定給定污染狀態(tài)的起因。Water quality modelsvaryintheir complexity.Theirnature dependsontheapplication tobe madeofthemodel, theavailabilityofdata, andthe levelofunderstandingofthehydrochemicalandhydrobiologicalprocessesinvolved.Unfortunately,thecomplexitiesoftheseprocesses,whicharegreat,makethedifficultiesassociatedwithhydrologicalmodelingseemsmallincomparison.水質(zhì)模型的復(fù)雜性各有不同。其本質(zhì)取決于作為模型的應(yīng)用、數(shù)據(jù)的可獲得性以及對(duì)于所涉及的水化學(xué)和水生物學(xué)過程的理解程度?？上?，這些過程巨大的復(fù)雜性使得與水文模擬相關(guān)聯(lián)的復(fù)雜性看起來相對(duì)較小。Ingeneral,waterqualitymodelsshouldpermitacceptanceofinputsintermsofpollutant(constituent)concentrationversustimeatpointsofentryintothesystem,descriptionofthemixingandreactionkineticsinthestreamelementorgroundwaterelementofconcern,andsynthesisofatime-distributedoutputindicatingpollutantconcentrationattheoutletoftheelement(segment) beingmodeled.Ananalogymaybedrawntothestreamflowrouting,whichisperformedinadownstreamsequencefromonestreamchannelsegmenttoanother.Inthecaseofwaterqualitymodeling,thecommonrepresentationisthecalculationofchangeinconstituentconcentrationasitpassesthroughsuccessivestatesofthewaterbodybeingmodeled.通常來講，水質(zhì)模型應(yīng)該允許在系統(tǒng)進(jìn)口處的污染物(組分)濃度相對(duì)時(shí)間的輸入形式，所關(guān)注的水流元素或地下水元素混合和反應(yīng)動(dòng)力學(xué)的描述，以及綜合成一個(gè)隨時(shí)間分布輸出，該輸出描述所模擬的出口元素(分段)的污染物濃度?？梢詫?duì)水流演算打個(gè)比喻，這發(fā)生在向下游的從一個(gè)向另一個(gè)的水流通道段中。在水質(zhì)模擬的情況下，通常的表達(dá)是對(duì)在通過被模擬連續(xù)水體時(shí)組分濃度變化的計(jì)算。發(fā)生在向下游的從一個(gè)向另一個(gè)的水流通道段中。Asinthecaseofotherwaterresourcesmodelingprocesses,theapproachmaybedeterministicorstochastic.Inthecaseofwaterqualitymodels,thestochasticapproachisoftenruledoutbecauseactualrecordsofwaterqualityparametersareunavailableforlongenoughperiodstopermitfrequencymethodstobeused.Ofcourse,generatedsequencescanbeusedforthispurposeifadequatemathematicalstatementsrepresentingthekineticsofthesystemcanbedevelopedandtheirparametersdetermined.對(duì)于其它水資源模擬過程，其方法可以是確定性或隨機(jī)性的。對(duì)于水質(zhì)模型，隨機(jī)方法往往被排出在外，因?yàn)椴荒塬@得足夠長時(shí)段內(nèi)的水質(zhì)參數(shù)的實(shí)際記錄，所以不允許應(yīng)用概率方法。當(dāng)然，如果可以開發(fā)表示該系統(tǒng)的動(dòng)力學(xué)適當(dāng)?shù)臄?shù)學(xué)命題，且它們的參數(shù)可以確定，那么所產(chǎn)生的序列可以被用于此目的。Thedeterministicapproachtowaterqualitymodelingrequiresthatrelationsbetweenwaterqualityloadingandthefloworhydraulicfeaturesofthesystembeestablishedandthattheappropriatechemicaland/orbiologicalreactionsbetractableforsolutions.Wheretheory-basedrelationscannot beemployed,empiricalrelationsareoftenused.Theoptimummodeltousewouldbetheonebestdefiningtheactualwaterqualityresponseofthesystem.Manymodelshavebeendeveloped.水質(zhì)模擬的確定性方法須要建立水質(zhì)負(fù)荷與系統(tǒng)水流或水動(dòng)力特性之間的關(guān)系，以及對(duì)于解決方案已預(yù)處理的合適的化學(xué)和/或生物反應(yīng)。其中，不能使用基于理論的公式，但很多模型已經(jīng)是經(jīng)常應(yīng)用經(jīng)驗(yàn)公式。要應(yīng)用的最佳模型將最好地限定系統(tǒng)的實(shí)際水質(zhì)響應(yīng)。被建立起來。很多模型已經(jīng)Pollutantsmaybeclassifiedasconservativeornonconservative(constituentshavingtime-dependentdecays);somewhatmorespecificallyasorganic,inorganic,radiological,thermal,orbiological;andfinallytheymaybecategorizedbyspecificformssuchasBOD,phosphorus,nitrogen,bacteria,viruses,andspecifictoxicsubstances.Thesepollutantsmaybeloadedintoawatercourseorgroundwatersystemfromeitherpointornonpointsources.污染物可以分為保守型和非保守型(組分隨時(shí)間衰減)；稍微更具體地為有機(jī)、無機(jī)、放射性、溫度或生物；且最終它們可以被分為具體的形式，如BOD、磷、氮、細(xì)菌、病毒和具體的有毒物質(zhì)。這些污染物可能通過點(diǎn)源或非點(diǎn)源被加入水體或地下水系統(tǒng)中。Thetimerateofdeliveryofapollutantmustbedeterminedifitscharacteristicsaretobemodifiedbymanagementpracticesoritsimpactonsomeelementofthesystemevaluated.Forexample,theconsequencesofsom