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<br />002'193 <br /> <br />Reclamation's reservoir operations staff, who will make <br />all decisions with respect to flood potential. <br /> <br />"Avalanche Conditions: Whenever the existing snowpack <br />condition is such that additional snow added to the pack <br />would lead to an unstable condition, producing an <br />avalanche potential. This condition would be evaluated <br />with the cooperation of the U.S. Forest Service Pacific <br />Southwest Forest and Range Experiment Station. <br /> <br />"Total Precipitation: The average snowpack accumulation <br />level in the American River Basin exceeds 1.8 times the <br />preceding 20-year average snowpack anytime subsequent to <br />December. This defines a 'wet' year in which additional <br />augmentati.on is not recommended. <br /> <br />"Locally Severe Storm Occurrences: Whenever the forecast <br />or observation of severe storms as defined by radar <br />reflectivities of individual cells within the project <br />area or immediately upwind are strong enough to suggest <br />the possibility of hail or severe rain, or when forecast <br />by the National Weather Service, it is recommended that <br />seeding activities be suspended. <br /> <br />"The third condition could result in cessation of opera- <br />tions for most of a year, since there would be little or <br />no advantage gained from further augmentation. Under the <br />other conditions, program operations will be suspended <br />until the conditions are no longer present." <br /> <br />Instrumentation and Extended Area Effects <br /> <br />MBA used climatology combined with trajectory of seeding materials <br />to determine anticipated areas of effect. <br /> <br />Based on expected seeding material diffusion and resulting plume <br />width, MBA recommended a total of 45 gages, located as uniformly <br />as possible above 1220 m (4000 ft) within the primary area of effect <br />show in figure 3. The network will increase the likelihood of <br />sampling precipitation influenced by any particular seeding plume. <br /> <br />The maximum area of effect (based on silver iodide activity duration), <br />intermediate level flow fields, and diffusion calculations were used <br />to establish boundaries for the extended area of pOSSible effect <br />beyond the primary area. Figure 3 shows the regions that may be <br />affected and have been recommended for monitoring. Region 1 is the <br />primary area of effect as previously defined. Region 2 is the down- <br />wind area recommended for monitoring and was defined by MBA as follows: <br /> <br />24 <br />