Laserfiche WebLink
<br />drainage fnl;ilitI8s. VVhere land leveling is <br />impractical, or wheu-) crops me not receptive to <br />beill~l irrigatnd by flood or furrow irrigation, <br />rv sprinklers are Installod which also have a high <br />m coefficient of llniforrnity. In hath cases, <br />U' irrigations must he schodulod at more frequent <br />(..-it intervals usill~) :-;maller quantities of water at <br />each irrigatioll to 11l8int[Jin the downward <br />movement of salts as ll)S ill the w3ter reach <br />higher levels of concentrCltions. <br /> <br />These marklgofllt:llt practices require substantial <br />additiollal investment in farm oper8tions. For <br />example, expenditules 0]- $200 to $600 per <br />acre fOI- n srrirlkkn inig8tion setup are not <br />uncommon and ~; bO p{~r r-Jcre for land leveling is <br />a minifllurn. 111 tl1(; c(Jse wh{-:ne fmmers may not <br />have access 10 1hc capital 118cessary for such <br />pri:.lcticcs, they m':lY be forced to change to more <br />salt..toleulnt CI-UPS or discontinue operation <br />alto(Jether. Even ihough the choice to change to <br />mCHe salt-tole!"EHll crops may result from a lack <br />of capital, it i~~ not a costless management <br />prElctice. This is dlle in pmt to necessary changes <br />in equipment and management techniques as <br />well as lost reVfHIl18 frolll the original crop. <br /> <br />In addition, thett~ 1:1iO otlwr direct or variable <br />expenses incur t"Od by irrigators. FOI. example, <br />there are costs of oxtl"a f"arm labor involved in a <br />more pl-eeise irri~latiof1 regime, costs of <br />additional wetm nec8ssmy to leach salts. added <br />fertililer cost~; rcsulling from increased water <br />application, and nthnr similar expenses. <br />Gener-ally stated: As the level of sophistication in <br />farm managelllent mitigation schemes increases, <br />crop production costs generally increase <br />accordingly. Tha~(--'! incrensed costs attributed to <br />salinity adClptcltioll can he considered as <br />economic dohinwnL>. l.ikowlse, the decreased <br />profits due to lower Yields are also considered <br />as economic dehiments. DGtailed enterprise <br />budgets lor the crops reprosontative of <br />conditiol1s in c<-H:h irrigated area were used to <br />formulate much of tile input for tho IP models. <br />Each of these cmpping activities was defined on <br />three or- four soil drainage conditions: very poorly <br />dlained, poc".ly drained. moderately well <br />drained, and well driJineu. The combination of <br />each crop undm each soil condition was then <br />defined for :;ix irrigation activities which <br />included variations ill froquency of water <br />application as well ClS pmtial and full sprinkler <br />and drip irrigation. Available to each of the above <br />combinations were certAin management <br /> <br />activities described earlier. These activities were <br />options open to the manager which might be <br />employed. at a cost, to mitigate the detrimental <br />influence upon net returns. In addition, various <br />combinations of crops were defined to allow <br />more than one crop per year to be produced on <br />Iond suitable to this practice. <br /> <br />Using these parameters as inputs, the IP model <br />projected changes in cropping patterns, physical <br />output by crop, changes in farm niamlgement, '. <br />and dollar impacts in terms of net profit over the <br />TDS ran(Je in question for each area. The details <br />of each program output for correspondin~J <br />salinity levels are found in the report by Ilndersen <br />and Kleinman.~ Table 1 contains a summary of <br />estimated damages for different salinity levels in <br />each of the study areas. <br /> <br />At this juncture. it is important to point out that <br />a single average level of salinity for the Lower <br />Main Stem area may misrepresent the actual <br />situation. Different points along the rrver will not <br />be simultaneously experiencing a common level <br />of TDS, and therefore. damages based on <br />average conditions can be misleading. Table 2 <br />contains prOjections of expected levels of TDS <br />for five diversion points: Hoover Darn, Davis <br />Darn, Parker Dam, Palo Verde Diversion Dam. <br />and Imperial Dam. It is readily observed that <br />while one point. such as Irnperral Darn. may be <br />experiencln(J one level of salinity, Palo Verde is <br />experiencing a different level. Parker still another <br />level. and so on. With this in mind, damage <br />functions were estimated for each individual <br />agricultural area. <br /> <br />Inherent in each damage function are such <br />factors as soils, cropping patterns. mlti(Jation <br />alternatives, etc., which are couplod with the <br />effects of different salinity levels. which, in turn. <br />act as the driver for the function. The result is a <br />singular function for each area with varying rates <br />of impacts. depending on the segment of the <br />function under consideration. Therefore. in order <br />to facilitate the computation of total basin <br />damages. an aggregate damage function has <br />been estimated using the results of the individual <br />damage functions. In the case of agriculture, <br />readings at three diversion points provide salinity <br />information related to water supply for the major <br />areas in the basin and accordingly, total damages <br />(as estimated by the aggregate function) ale <br /> <br />oj Ibid., app. 3, p. 117-252 <br /> <br />7 <br />