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w co <=> ...... The CRSS model a:nd data base have been significantly refined to instill ,a higher level of confidence in the simulation model and its representations. One of the concl'usions from the CRSS analysis is that, as portrayed on figure 13, level~ of hydrologic uncertainty remain that cannot be reduced or simplified to reduce management risk. On the same extended time scale, figure 12, the range of future depletion rate assumptions in the basin shows the re 1 at i ve 1y mi nor effect that present dep 1 et ion schedu 1 es have on sa 1 i nity projections. It is important to remember, however, that uncertainty in deple- tion rates remains significant due to basic unknowns of future project fund- ing, ?olitical climate, economic growth, and energy development activities. To meet specific objectives, minimize a conservative bias, and avoid any unnecessary commitment of program resources, the salinity control program management strat~gy must consider an incremental decisionmaking process, setting priorities for the short term (1984-1993) and providing for deliberative decision cycles in the long term (beyond 1993). Moreover, to deal effectively with the identified uncertainty, management must regularly review all relevant information, be it measurable, intangible, judgmental. or intuitive, and use it to address the salinity program budget and policy. 1 .j i c, ! .' ":i '1 "Ii ,Uncertainty Analysis of Implementation There is another general category of program uncertainty related to imple- mentation that is unique to salinity control. Most of the control units deal with complex ground-water situations that make on-site specific salt load reductions qncertain. The risk of successful installation and long- term operation is magnified by the difficulties in site monitoring and the lag time and reservoir effects in projecting impacts to Imperial Dam. Due to the changing nature of the relationship between the mg/L impact at Imperial Dam and'the tons removed at the site of a salinity control unit, Reclamation is now Usi ng $/ton removed at the site as the basis for project formulation. This will provide a'c05t-effectiveness figure independent of depletions or hy<!rology assumptions. In addition to the technical risks involved, the externally imposed requirements for water rights and permits, coupled with resolving the concerns of local au~horities and entities, impose administrative constraints to timely implementation of program units. Management strategy in addressing this uncertainty is focused on verification of selected control technology or process and staged construction to minimize risk. Early act~on is important in verification of staged construction activities to allow time for innovation and monitoring results. Continuing analysis is needed to identify control tradeoffs and contingencies. Finally, to deal directly with the uncertainty in the overall program implementation, an attempt should be made to identify or quantify the consequences of failing to reduce sal i,ni ty to meet the standards. J , -.1 :i ,! .~ J t~ ;A -~ ,-A Evaluation Results Figure 14 shows the resulting salinity at ImpeMal Dam assuming scenarios 2, 3, 4, and 5 are implemented under Reclamation's depletion schedul,e. Note that the standards will be exceeded if scenario 2 projects are not imple- mented by about 1993. 38 ;L~ ,<",,' ,.i"Oi;,., ~_, -,it:"".-""o:'," .c,