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'tf OJ.. e. "I' .... i ! "j i 1 ~" \: . .'1 .'<.. obtaining the last increment of control. However, it was found that c1esalting would very selclom be implemented to that extent, and further co~rection of the equation was not warranted in this analysis. ~ N c.11 ..... Tables presenting the c1ata for the opti....l a~..awicle salinity cont~ol program are:tncludecl in this ohapter. The first: column is the percentage of .the total salt load "Which hae been treated, ancl the sacond columni.. the estimated total combinecl annual. cost. The thii'd column is .thees.timated ..verage coet per mg/l at Imperial Dam fo.r these improvements; howeve~, this is not marginal cost and should not b.. oompareclasainst th.. $450,OOO/mg/l damages which are a tTue marginal value. The columns uncler th.. various ..lternativ..s repres..nt th.. amount of the ..ttainabl.. salt loadr..duction attributed to that alternativa. Due to the lineaT relationship b:eew..en the. degr....of salt load- ing anel the level of control, th.. columns for ~anal .ancl.lat..ral linings can be almost c1irectly translated into peroent of Hning length tob.. implemented at each level of control. The aotual percentag.. .of salt reduction in the can..l lining oolumn in the areawide program corr..sponds direotly to the pe'l.'oent:age of. total salt reduct:ion column in the speoific area canal lining strat:egy. .tablea presented in A.ppenelix D. . Tables hev.. not bean. presentecl for laterl1l.1iningbecause they correspond very closely to canal lining. The. same seepage rates and groundwater quality fortheaggregat.. laterals uncler a canal wereaesumeclto b... the eame as the canal. Thus, the perc..ntageof lateral lining in the ar..a"Wid.. anelysis "Will corresponll direotly. to thei~ respective oanalin orde~ of priodty. Tables lieting the optimizat:ion parameters and the characteristics of each9fthemajor .canalsanclla1."gelllt$rals iii..each .of ~1:\"lemain ag1;icultura:l:c . areas ,can be found in Appendix B. These tables represent the best estimate of'. representative oonditions for each of the areas,and indicate the results of the hyllro-salinity analysis which "Wa... performed for.....ch area. . ^ AREAWIDE ANALYSIS OF SALINITY CONTROL. PROGRAMS Th.. sre..wicle analysas of the ind:tvidualsal1ii.ity conti:-ol proj ectsindi- cate a fllirly high c1..gree of uniformity in t1:!e optimal order of implement a- tion,' In every agricultural area, axcept th~ G~andVal1..y, th..on-farm improvem..nts was the first programs to b.. implemented followed by lateral ~ lining, canal lining and desalination. Tabl.. 7 presents the aggregate cost- . ,.effec.tiveness function. .for eanli11 'l::tning:,lateralliningancl on-fa.;;m.imp.roy..- mentsand their astimatecl.max:tmum salinity reduction potential. .., , ,':."" " ... The on-farm' improvements are probably. the most: diff:ioult comj:>onents,t,o' quantify. ancl to char..cterize in ..n optimization context. In this analysis it .was.ne.cessarytoassume a higher'level of on-fllrmlilSter management and long- term, teohnical assistanoe by the implementing agency anel/or extenaionper- sonnel to the gro"Wers. The smount of salinity control is much easier to establish for fix..d structural measures .such as canal snel lateral linings. Howeyer, there will also be an inherent amount of salinity recluction on the fsrmers' fielcls as a re..ult of the improved "Water application ancl the easier water deliveries clue to a conveyance liningprogrsm, even if the farmars revert as much as possible to pa..t practices. Analysis of the areawicle pro- grams under lower irrigation efficiencies still indicatecl that on-farm . 74 ;:.