首页
外语
计算机
考研
公务员
职业资格
财经
工程
司法
医学
专升本
自考
实用职业技能
登录
外语
Water will evaporate from any wetted surface. A .significantly large fraction of the rainfall that falls on land is returned to
Water will evaporate from any wetted surface. A .significantly large fraction of the rainfall that falls on land is returned to
admin
2011-04-26
68
问题
Water will evaporate from any wetted surface. A .significantly large fraction of the rainfall that falls on land is returned to the atmosphere in this fashion. In addition water is assimilated by root systems of growing plants and is later transpired from the leaf surfaces by a process essentially identical to evaporation. The two effects, evaporation and transpiration, cannot be individually discriminated for their effectiveness in returning rainfall to the atmosphere, but their sum contribution can be evaluated and is usually called the evapotranspiration factor. The fraction of rain falling on the United States that is returned to the atmosphere by evapotranspiration, for example, is 70 percent; for the world as a whole, approximately 62 percent. In arid countries such as Australia the fraction is larger, and in less arid areas such as the United Kingdom it is lower. Water returned to the atmosphere by evapotranspiration is unavailable to man, except in, the sense that useful plants may be grown in the place of useless ones. It cannot be trapped and redistributed for industrial or other purposes.
In regions of low rainfall, plant cover will develop to a point where all precipitation is used in evapotranspiration and none remains for stream now. Seasonal rainfalls provide a qualifier for this statement because streams will flow even in the most arid areas during periods of maximum rainfall. In general, if the potential evapotranspiration—that which would result from the maximum plant cover a region could support under ideal circumstances—should exceed the precipitation, overland stream flow ceases. Conversely, if evapotranspiration is less than precipitation, runoff is generated.
The amount by which precipitation exceeds evapotranspiration is the perennial yield of stream flow water, and this is the usable fraction of rain and snowfall. Across the entire United States the water yield amounts to 30 percent of the total rainfall, or approximately 1.77×1015 liters per year. But when we consider the distribution of water deficiencies and surpluses we find that essentially the entire eastern half of the United States, together with a small region in the Pacific northwest, enjoys water surplus, while most of the country to west of the Mississippi is water- deficient and arid.
It can be inferred from the passage that ______.
选项
A、more than 30% of total rainfall can yield stream flow in the United States
B、the water in the entire eastern haft of U. S.A. goes beyond its necessary need
C、west part of U. S. A.doesn’t have perennial yield of stream flow water
D、the yield of stream flow water is ’unevenly distributed in the United States
答案
D
解析
转载请注明原文地址:https://kaotiyun.com/show/zo6O777K
0
考博英语
相关试题推荐
MayfieldCollegeItalianforBusiness5xthree-hourlessonstwiceweeklybeginningTuesday28SeptemberEachlessonwilllast
Lookatthelistbelow.ItshowsthecontentsofaWeb.Forquestions6-10,decidewhichpart(A-H)eachpersonshouldvisit.F
Lookattheorganizationchartbelow.Itshowstheresponsibilityofeachmanager.Whoseresponsibilitydoeseachsentence(11-1
Whileincomefromadvertisementsrosesteadilythroughouttheperiod,incomefromsalesincreasedinJunebutthenfelltobelow
Readthearticlebelowaboutaservicewhichhelpscompaniesindifficulties.Foreachquestion(23-28)ontheoppositepage,cho
Readtheadvertisementbelowforahotdrinksmachine.Aresentences16-22"Right"or"Wrong"?Ifthereisnotenoughinform
Itisnotunusualforchiefexecutivestocollectmillionsofdollarsayearinpay,stockoptions,andbonuses.Inthelastfif
Asshehasakindly,outgoingnature,sheisa______hostessandhasawidecircleofverygoodfriends.
Contradictorytopopularbelief,recentsurveysshowthatbesideshousewives,manycollegestudentsarealso______tosoapoper
WiththeUSeconomyslowingdown,layoffsareeverywhere.Noindustryisspared.Ifyouenduphavingtostartover,inaddition
随机试题
设y=sin(lnx),则y’(1)=_________。
膀胱炎患者的尿液具有哪些特征
患者,女,48岁。有口腔黏膜粗涩感,进刺激食物感疼痛半年,检查发现其舌背左右各一黄豆大小白色病损,浅淡,表面乳头消失、质软。双颊自口角至颊脂垫尖处广泛白色角化网纹,基底充血发红。双舌缘舌腹也可见类似病损。询问病史及临床检查时应注意以下几点,不包括
1,2,3,…,25这25个数字中的质数个数为().
市场经济运行的基本规律包括()。
某单位因施工需要,须砍伐单位内的几株梧桐树,在给所在街道办事处绿化办公室行文时,宜用()。
下面的三角形表示某省五种产业的数量按地域划分(城区、郊区、乡村)所占百分比。图上的字符表示各种工业,三角形的顶点表示100%,与该顶点相对的基线表示0%。例如,该省所有的加工企业中,约有70%地处城市,5%位于乡村,25%在郊区。大约有百分之几的服务
中国历史上第一个全国性的专职警察机构是清朝的()。
调查表明,使得大学生学习成绩下降的一个重要因素是:很多大学生玩网络游戏。为了提高大学生的学习成绩,学校作出决定:禁止在校园网上玩网络游戏。以下哪项最能对学校的决定进行质疑?
数据是企业中最【】的因素,它又是企业所有运行活动的数字化特征。
最新回复
(
0
)