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<br /> <br />, <br />Many factors influence the amounts pf water consumed by plants. <br />Their effects differ with locality and fluc~te ftom year to yeat. <br />Important natural influences are climate, 'watet supply, .Iiloilsand <br />topography. Climaticfacto1'8 that particularly affect consumptive use <br />are precipitation, temperature; humidity,' wind movement ,md gtowing <br />season. The amount and rate of precipitation may have pronounced <br />effect on the amount of water used during i summer. The rate of con- <br />sumptive use is probably affected more by temperature than by any other <br />factor. L.ow temperatures may tetatd grjowth and high temperatures may <br />produce dormancy. Evaporation and tra~spirationare accelerated by <br />low humidity and slowed by high humidity:. <br /> <br />" <br /> <br /> <br />CONSUMPTIVE W A Tlj;R REOtJ;IREMENTS <br />IN THE COL.OItADO RIVER SASIN <br /> <br />Harry F. Blaney. Principal Irrigation Engineer. <br />Soil Conservation Service-Research,USDA ' <br /> <br />. <br /> <br />. <br /> <br />In this paper "consumptive use" includ~s all transpiration and <br />evaporation from lands on which there is groWth of crops 01' native <br />vegetation, plus evaporation. ftom bare l.and and watersUrlaces. It is <br />synonymous with" evapo-transpiration". It i's the best index of irriga- <br />tion requirements. <br /> <br />Consumptive use by crops and native vegetation is an important <br />factor in controversies over stream systems. Before equitable division <br />can be made of water available in a drainage, basin, cons.ideration must <br />be given to consumptive use requirements ini various sub-basins. In <br />design and construction of irrigation systemlil, the engineer should give <br />careful consideration to consumptive use by:crops and native vegetation, <br />and irrigation requirements of crops combined withloues., In arid <br />and semi-arid areas moisture rllquirements o,f n,tive vegetation are <br />uS)1ally satisfied before water become. available for other purposes. <br />The growing inadequacy of the water supply in these regions as popula- <br />tion increases creates strong demand forr~duction of evapo-transpita- <br />tion from native vegetation. Evaporation ir,omlakes, reservoirs and <br />rfvers aho becomes a major factor in oper$.tion of large river systems <br />such as the Colorado. Additionlll information on water consumption in <br />the COlorado River Basin still is needed in b.egotiations to allocate. water <br />rights among th.e states, irrigation districts, and cities involved. . <br />Measutements of evaporation and evapo-transpiration should be made <br />in areas not covered by previous studies. <br /> <br />This paper summarizes and reviews :results of investigations of <br />watllr consumption by the Division of Irrig~tion Engineering and Water <br />Conservation, Research Staff, Soil Conserjlation Service, in cooperation <br />with the U. S. Bw:eau of Iteclamation, Sta~e Enginee:rs, Agricultutal <br />Experiment Stations and other agencies in the Colorado River Basin. <br />Provisional.reports are completed for the Upper and L.ower Basins .and <br />each of the states. Specia1reports were made for areas in New Mexico, <br />Nev;l.da and. Utah. <br /> <br />. <br /> <br />I <br /> <br />Research Studies <br /> <br />. <br /> <br />-LZ- <br />