Laserfiche WebLink
<br />003f.\96 <br /> <br />SECCION IV - GEOHIDROLOGfA <br /> <br />91 <br /> <br />t"" " ',. ?< ,f. <br />"';:"'''';';,':!>>' <br /> <br />'fi;},;',ti:';}"G,,:>.,<> " <br />". <br /> <br />charge and diverting it for beneficial use. Conveying the water of streams <br />through areas of ripariau phreatophyte growth hy means of pipes or liued <br />ditches also reduces consumptive waste:. <br />The efficieucy of water consumption may he increased hy suhstituting plants <br />of higher economic value for plants of low economic value. In the United States <br />this has heen done, fo.r example, hy suhstituting alfalfa for an association of <br />greasewood, rahhithrush, and saltgrass (White, 1932), As yet, the practice is <br />not widespread. Before replacement can he accomplished, however, it is necessary <br />to rid the area of the existing vegetation-not as easy task, especially when deal- <br />ing with aggressive plants such as saltcedar. <br />An entirely different method, hut one that may prove feasihle, is increasiug <br />the efficiency of the water consumptiou through the development of a higher <br />economic use for the existing phreatophytes, This method would he most valu. <br />ahle in areas where the water has a high mineral content and is not suitahle <br />for most uses. Some examples of possihle higher economic uses are: rahhithrush <br />as a source of rubber, saltcedar as a source of tannins, and mezquite as a source <br />of high.quality charcoal. Intensive research doubtless would reveal other uses. <br /> <br />"'.~';'.~Z>';;';,{':;> ,";' <br /> <br />.;<, ..<'{' '"", <br />. .:',: .... ',"i,":,.. <br />~:,/,,:,:~,;\""" .",:.,; <br />','J> .:.,::;>';::Y'~;' <br /> <br />t::!';;(;~:;'2/ "',:.> :":;;s\:~ <br />.'. ", \<::;):':.2< <br />..::,(1\(;" 'E~,',:;,:'(1 <br />.~\;:;?",,~.;,,?, ".,,{' <br />:1~\';::':5i:':;,,:,:}; <br />.,.,i" ,)j"'i' <br /> <br />RELATION OF PHREATOPHYTES TO FLOOD AND SEDIMENTATION <br /> <br />;; <br /> <br /><',.'t:;:, <br />',>,.;:': ", 'V' '{" <br />"'..,'; .;>\:\; <br />',:,'" :,:' "",.,"" ,Hi\< <br />:':c.. ;"": .'..,::", <br />::,,;,::[,;:i~"" :}::::;,:::;',;,:; <br />.1;'" 'l;:'~;'~':'I:'i ". ,,( ~:;! <br />";',,; <br />"-. <br />,.:.">, >,; <br /> <br />r::},:~~::l'..,t;; ';':,'::;~,:;: <br /> <br />:;,.",:".<:"',~". """.'::.:; ie" <br />"\, ::::. ": <br />~',., '< ", <br /> <br />;'<:"'.'.,.,," <br /> <br />:> <br /> <br />Some species of phreatophytes grow so dimsely ou the flood plans of streams <br />as to form a partial barrier or dam to flood flows. As a result, in times of <br />flood the water spreads over and inundates areas that normally would not be <br />flooded, endangering lives and demaging property. Saltcedar is a prime of. <br />fender in this respect, followed closely by willow and other riparian vegetation~ <br />Examples of. streams that present flood hazards as the result of phreatophyte <br />growth in the United States are the Salt and Gila River in Arizona, and the <br />Rio Grande in Texas and New Mexico and along the International Boundary <br />hetween the United States and Mexico. <br />Floodwaters are nearly always silt laden. The damming or ponding effect <br />of dense phreatophytic growth reduces the velocity of the water, and at the <br />same time reduces its power to carry the full silt load, As a result there is de, <br />position of silt in areas of phreatophyte growth. Such deposition as occurred, <br />for example, on the flood plain of the Rio Grande and the Pecos River in New <br />Mexico and the Gila River in Arizona, In the delta area ahove Lake McMillan <br />a man.made reservoir on the Pecos River, it is estimated that in places as much <br />as 15 feet of silt may have heen deposited as the result of saltcedar growth. In <br />this situation the dense growth acted as a desilting agent to reduce the amount <br />of silt entering Lake McMillan and at the same time to prolong the life of the <br />reservoir. The effectiveness of the saltcedar as a desiIting agent is shown by "_:::'>." <br /> <br />. ';,,<~.'. ". ..;.... <':?I;:,:::.:~,~~~:f <br />.' ':<:',::',.i;'::~j:,;';S::' <br />. ..' "'::\:~';,:::':';',":'S<":: <br />':.'ii<';:.:':";:;;'''':: .' ...?; . ....... ...... j'"::""",,,:';';" ..... ..\: j;',:r:':.""\,'{::!l.,.,..'::" .<>.;,..:~<:'X, . "C". ..' ...;;:1',';,,:: <br />""".: .' ,... ";';::/' ,\ic,'......./;;, ::'.C:;:'::;:">':,::>' <br />............... ........ ......};:' ".:.;".:t:::;;'::<;~:" ...... '......H .""";~::>.'." ..../'T. ..:.. . <br /> <br /> <br />;,.,.g,;/:\;';" ,;",,:':\",,",":.!; '.,'-::':;:::'". ,X,{.."'.:,,,.......:,: <br />.:";..;:.,.1r.;;.i . ".,.,. .:":.,,.("','/": .. ...:.';..<";,\.... " ,K,">, ?~./\...",;.; ,~i <br />: '" i"" :'.... .'\""";,::' .'" .'" fe'.. <. .., '.' ....,J..;>c: ':' <br />.' '. .... .. . . ..1 <br /> <br />.'; <br />'r' <br /> <br />;,k"'J"~ <br />