课后作业参考答案

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1、Unit2WaterSources1.（1）（2）Becausetheflowofariverfluctuatesand,afterlongperiodsoflittleornorainoveritscatchmentarea,itmaydiminishtoatrickleorevencease.Itisessentialtobuildreservoirstokeepenoughwaterduringdryspellswhereawatersupplyschemedependsonariverasitssourc

2、e.3.(1)Waterisstoredandtransmittedthroughthehydrologicalcycle.Thewaterisheldtemporarilyin,andcanthereforebedrawnfromthegroundwatersystem,ponds,lakes,andstreamchannels.Duringdryweatherthedrainageofthesesubsystemsofthehydrologicalcycleprovidesthesupplyuponwhich

3、allhumanendeavordepends.Itneedstobestressedthatsurfacewaterandgroundwatersuppliesarerelated.Watercanflowfromonesubsystemtotheother,andtheuseofdisruptionofonecomponentcanimpairthevalueoftheother.水通过水文循环储存和传输，由于水具有流动性，只能在某一瞬间储存在地球上的不同空间位置，因此我们可以从地下水系统、池塘、湖泊、水渠中

4、抽取水。在干旱期，水文循环中这些子系统的出水量取决于人类的努力程度。需要注意的是地表水和地下水是相关的，水可以从一个子系统流动到另一个子系统，因此当其中一部分水被利用或补给中断后，另一部分的水量就会减少。4.(1)surfacewaterandgroundwater(2)theratioofthevolumeofwaterthatcanbedrainedbygravitytothegrossvolumeofsoil(3)freesurfaceofunconfinedaquiferandhydrostaticpre

5、ssureofconfinedaquifer(4)Bothwellsandinfiltrationgalleriesarecollectionworks.(5)Whenawellispumped,theconeofdepressionisencounteredinaquifer.Unit3Thepropertyofwater3.(1)Thebiologicalcharacteristicsofwater,relatedprimarilytotheresidentaquaticpopulationofmicroor

6、ganisms,impactdirectlyonwaterquality.Watermayserveasamediuminwhichliterallythousandsofbiologicalspeciesspendpart,ifnotall,oftheirlifecycles.Aquaticorganismsrangeinsizeandcomplexityfromthesmallestsingle-cellmicroorganismstothelargestfish.与水生微生物的含量密切相关的生物特征能够直接

7、影响水质。水可以作为生物的生活媒介，成千上万中生物在水里度过它们生命的某些阶段，有的甚至一生都在水里度过。水生生物的体积变化范围很大，组成也很复杂，既有世界上最小的单细胞微生物，也有世界上最大的鱼类。4（1）suchastheconcentrationsofthecompoundofcalciumhydroxide,magnesiumcarbonate,andsodiumbicarbonate（2）nonbiodegradableorganicmatter（3）tracenutrientsinwater（4）Pa

8、rametersassociatedwithphysicalcharacteristicsofwaterincludeodor,turbidityandsuspendedsolids.（5）Thetotalcoliformgroupisusuallyusedasindicatororganism.Unit5Water-supplysystem1(1)Itisthearea