WSP00978 - Laserfiche WebLink

Home Browse Search

~ \ - ';. '.' " ~ .' i ~ ;;j I \ . :\ ! " 'it " li] i ! " i i I. .",.., , ~. .N,': ~ ~ 'the degraclation of water quality associated with the irrigation of agri- cultural lands is usually most economically controllecl on. the .croplands where the water is applied. The preventative structU1:al measures, which were included in this analysis were limited to concre'tecanal and lateral linings and five broad categories ofon-fam irrigationeystem improvements. Desali- nation of agricultural return flo"Ws by reVerse osmosis procedura "as inclucled .QS. the final measure to be implemented in theinoet cos.t-effective.salinity control strategy. However, it was as"umed that the on-farm pro.gcralll would include long-term and capable technical assistanee in order to maximize the benefUs of the respect:tve syatems. The critarion of minimum cost wa" utilized in this analysis faT two main reasons. One, the salinity problem and the associatecl c1amages ere a clessic . . example of a true eeonomic externality, and purely economic forces are una'ble to cause remedial measures. Second, the goal of maint:eining the 1972 salinity leve1sinthe'Coloreclo River Basin is a mandated raquiramant, an<l also no.t an economic consideration. Thus, the control must: be accomplished via govern- mental action and minimum costs are an accept:able criterion fOT determining salinity controlstratag1es. PRESENTATION OF RESULTS Figure 22 illustrates the graphical presentation of enawicle salinity control programs. The heavy clark line represents the aggngate eoet~ effectiveness funct:ton for the area in terms of annual coets and salt load recluction. The area above the cost-effectiveness curve represents .the salt load i:ecluctionwhichean 'be 'obtain<!d from each alternative for anyleve;L of sslinity control. Correspond:tngly ,the area'belo"W. t:he coat-effectiveness function defines the costs associated with each alternative. For example, the dashad lines. in Figure 22 represent the optinialstraeegy for a given area to. remove a total of 750,000 Mgmper year at a e'ost'of$30 'million annually. The ,;alues of salt ancl .dollatS "Which are listed on tha "policy. spaces" of Figure 20 correspond to this level of salinity control. The. total. salinity impact .is achieved by investments of $10 million!yrin on-farmilllprovements, $7'05 million!yr inlateul linings,. $6.5 million/Yr in cBnallinings;and $6.0 million!yr in a c1esalination program. Each of these systems could be improved sufficiently if totally constructed to reduce salinity 'by 350,000 Mgm!yr, 180,000 Mgm!yr, 120,OOOMgm, and 100,000 Mgm/yr. respeotively. A similar saUt\1ty control stutagy can be identified in .such.diagcrams aa, the delineation of thecoordinetas of the oost:-effectivenass, function. ,,", , ' , " . , .' . '. .'Thelinear:l:t.ias"1ntroclIiCecl by desalination in the'i-anges whe....c1..sl\l,.Ung . ... wQ.uld be implemented were betterrepreSSll1;$d by a cubic re~at;ion than Equa- -, "tion,.'8,i' "This . equation hils the form:. ., .,' AS + BS2 + cs3 a Annual Cost (29) whera A, B, C aTe regression coefficients and S is the selt loecl recluction. OtheTWise, the e~act proceduras and methoclology ara followecl ae ware outlinecl in tha previous chapter. Although it is not shown on the gcraphs, it shoulcl be mentioned that the very top of thedesal.ting region is nonlinear ancl turns very sharply upwerd. This rapid change is due to the typicall.y high costs of 72 .,.." "';" . '. ".,"