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, ~ N W ~ ':' ~ , Not all irrigating costs are incluclecl in this analysis because many are incident to the farming enterprise and c10 not affect the choice of syatem improvements for sslinity control. Th~s assumption is basecl on the fact that a farmer is committecl by choice to the contribution of a certain level of labor, energy, capital, and water resources for continuecl irrigated agricul- ture. For example, seed, fertilizer, pesticides, taxes, and insurance are costs only minimally affected by system improvements and are not considered. Actually, many of these costs are often compensatecl for by higher yielcls and greater land valuas. It is obvious that the coats on which a specific on-farm salinity control measure shoulcl be comparecl with others are the differences between the total annual cost of the improvecl system minus the pre- implementation total annual costs and minus increases in net farm profit incurrecl as the result of better irrigation practices. The pre-implementatioll. of "bS:se" conditiOrts in the salinity affectecl ,'."', ".'ra:g10ns of the ITeRB is most likely to be the furTow irrigatecl fielcl having .' . moderate slopes less than 1,5pe'teent ancl r.e:Lative.J:y.low intake soUs. The .0': water supply is c1elivered to the field in unlinecl ditches from river c1iver- si~ns or at the farm from wells. Water supply costs are already being paid and therefore "WOuld not affect the choice of the on-farm improvement. The exception is the case of the water supply being grounclwater requiring a pump and a well. If the system improvement was to be a sprinkle or trickle system, the new pumping plant and higher energy costs must be includecl in the evalu- ation regardless of water source because these facilities woulcl require sub- stantial modification. Ii'} . ~ .,'i.. ,.W' The base topological condition one might also expect, woulclbe relatively well gradecl fielcls, thereby eliminating large land a:haping costs for most improved systeme except for possibly wide borcler and basin irrigation. Water c1istribution on the farm itself would typicslly be with unlined ditches ancl appliestion to the fields would be accomplisheclwith cuts in the earthen c1itch bank, siphon tubes, spiles, or small check structures. New systems ancl improvements woulcl replace sll of these facilities except siphon tubes. Rebuilt or new structures for flow measurement ancl regulation woulcl be aclded. . Costs were c1eveloped for pressurized anc\ gravity irrigation systems obtaining water from surface ancl grounclwater sources.. The results of aver- aging the scale distributecl capital ancl construction costs are shown in Table 5. Depencling on the type of improvement selectecl, annualizecl capital costs range from below $30/ha to more than $600/ha. Systems currentlyutiliz- ing a groundwater resource and converting to a pressurized system, involve substantial upgracling of the pumping systems thus such changes would not be necessary for the gravity or surface irrigation methocls. . Appenclix C presents suggested annual maintenance costs for various pres- surizecl and surface irrigation systems, data on labor requirements per irri- gation for selected types of systems, and listing of expectell equipment life of various irrigation system components with a goocl maintenance program. Replacement costs of short-lived components are includecl in 0 & M cost esti- mates. 57 :!." / j ", ,'; <