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<br />, .: .. <br /> <br />. <br /> <br />. <br /> <br />GVWM Flow Protection Plan <br /> <br />December 19, 1994 <br />4:02pm <br /> <br />DRAFT <br /> <br />Potential for Reallocation <br />The potential quantity that could be reallocated is controlled by two factors. The fIrst is how <br />much water could be conserved through the canal improvements. The second is what type of <br />water year is experienced. If it isn't possible to stay above the GMR targets, it will not be <br />possible to reallocate GMR storage. <br /> <br />Computation of Conserved Water - The difficulty in computing the volume of conserved <br />water is fIguring out what number you subtract from to compute the volume of conserved water? <br />For example, assume that the canal improvements have been completed and GVWUA is able <br />to reduce diversion requirements during the late irrigation season. It is not difficult to fIgure <br />out how much is diverted in anyone year, but how would you fIgure out whether that volume <br />represented any conservation. The question is, "What would they have diverted had they not <br />had the improvements?" Would the baseline condition be the average annual diversions within <br />the project? Variables such as cropping patterns, rain and wind have a large effect on annual <br />diversion requirements. Would it be the diversion based upon a dry, average, and above <br />average water years? .df ~ ~ J.j.. <br />aa-.,~tJ"- r~. .~:: ~ .' ''l. t~. c...!c"t.. <br />- [).~._/J, ~~ ~~-ce<l'''' j}r <br />The pipe laterals which have been mstalled as part of the salinity control program have increased 1~.? <br />the flexibility for on-farm water management. This additional flexibility is usually benefIcial . "'jJ <br />to salinity control because it allows water users to apply water at higher flow rates and with ~......~ <br />more control over the timing of application. Historically, GVWUA needed to know how much ~~l..o...-II; <br />water farmers wanted so that a lateral headgate could be adjusted to the lateral demand. But the ;~ i.$.....J. <br />canal headgates for the pipelines are now left in the full open position throughout the irrigation ~tl';'" <br />season. Flow adjustment along a pipe lateral is therefore adjusted by individual fIeld turnouts. Je,.,.~tt> <br />Flow control has moved from lateral headgate to fIeld delivery. ~~~\..., <br />~,~~ <br />~{ ~~k.\c:s, <br /> <br />As on-farm flexibility increases, off-farm flexibility decreases. The flow in the canal needs to <br />be able to meet anticipated demands, but since the demands can change quickly and without <br />notice, the only option is to keep the supply in the canal above anticipated demand and <br />administratively spill the water at canal spillways if the demand falls. Demand is hard to <br />anticipate because of the variables. It may be possible to project some of the variables, such as <br />cropping pattern and the amount of crop water requirements, but others such, as rainstorms, <br />wind and heat are not. These variables can change canal demand by up to 100 to 150 cfs over <br />the period of a day. With the pipelines, if the on-farm demand exceeds the canal's capacity, all <br />users are asked to decrease their fIeld turnouts by an equal percentage. With all of the <br />unpredictable variables, it is doubtful that it will be possible to compute the quantity of <br />conserved water. It does appear to be both possible and reasonable to estimate this quantity <br />based upon experience. ...J <br />"- ~+~)) . fl r J <br />P/ f!'"eJ'~' ! ~ \,JP -f},.e; ,*~j' 23 / ' <br />,1:JcJl ~ . ~/C ,~f4 .,v <br />~~QI!i(.i._l. i)4",#jfJA D, I ilY'v,,1JI0qt"~;v <br />ft~~~ CO dO J f vJl . j)tj<Y} ~ ~( <br />r 1 (Jo5 1'" {u r <br /> <br />l~ <br />j~~X <br />