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affects hydrology at scales that are regional (basinwide) to subregional (e.g., delivery <br />area for an irrigation canal). <br />9.2 ETa from Ve~etation/Water Surface Incidental to Irrigation <br />Figures 5 and 6 are reproduced as Figure 10 for illustration. The DOQQ data displayed <br />on the left-hand image (bottom center) shows a series of small lakes and seeps that are <br />down-gradient of Prewitt Reservoir. These lakes and seeps were not included in the <br />analysis of ET in this effort because they are not part of the riparian corridor. Instead, <br />they exist through reservoir seepage through dune deposits. Likewise in the right-hand <br />image, strips and clumps of verdant vegetation (bright red) can be seen projecting <br />through the partially transparent green irrigation mask. This verdant vegetation is also <br />maintained on edges of fields by farm runoff, tailwater from flood irrigation, sprinkler <br />overspray, or by seepage from unlined irrigation canals. The water use of such features is <br />best identified statistically using photo-interpretive techniques within the GIS. Judging <br />from their representation in this system, an approximation of their water use is between <br />10,000 and 20,000 of/yr (lx and 2x of the small water body ET (Tables 5 and 6)). <br />Also, as noted earlier in the caption to Figure 6 (right hand image), some obvious areas of <br />phreatophyte ET that lay outside of the alluvial extent polygon (portrayed in dark blue) <br />were excluded from consideration. A gross estimate of the magnitude of this consumptive <br />use (judging by comparative area and average rate) may be on the order 0.5-1.0 times the <br />ET that is incidental to irrigation. <br />Figure 10. images illustrating high ET incidental to irrigation. <br /> <br /> 4 ~ ; ~ia <br />~ <br /> ~ A - <br />i~ ! <br /> ~ ,T a <br />~j ~' /J~a <br /> - <br />' <br />.. . <br />' ~. <br /> a'~ <br />y <br />y <br />~ ~ . <br />' <br />~ ~. JN <br />r <br /> ~y <br />; <br />.. <br />~ pit , <br />~ .- <br />~. 1~~, "R ~ ~ _ '~ <br />' + <br /> <br /> s <br /> ~ ~~ L ~ ~ _ i. ~°x.. .rt'e` - - <br /> <br /> ~ <br /> ~~T ~ ~~"3 ~ <br />~ y.~ ` <br />to kf ~~ '~ P y ~y. <br /> $ <br /> <br /> r, <br /> Background ~JSGS pC}Q Mosa ~+ `~ <br /> Background;. LandSat TM false Cofor <br /> ~ Phreatophyte Boundary Phreatophyte Boundary <br /> DAluvial Extent N <br />0 Alu+rial Extent <br /> Irrigated Lands ~ 2 ~ 5 ~:, U5 , <br />Irrigated Lands <br /> Ki9ometers x~iome.e,s <br /> <br />