WMOD00063

• Applicant: Steven M. Hunter
• Sponsor Name: California Energy Commission
• Project Name: Optimizing Cloud Seeding for Water and Energy in California
• Title: Optimizing Cloud Seeding for Water and Energy in California
• Prepared For: California Energy Commission
• Prepared By: Steven M. Hunter
• Date: 3/31/2006
• State: CA
• Country: United States
• Weather Modification - Doc Type: Report

been increasing from 1922 to 2003 with a commensurate decrcase in the fraction ofthc water
year streamt10w occurring in the April-September period (see Figure 5),

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WaterYear

Figure ~, The avcragc height of thc -5"C level on precipitation days during the October-March
period as a function of water ycar.

It is, therefore, possible that as the hcight of the -5"C level (or the hcight of the activation
tempcrature level for the specific silver iodide chemical complex being used) increased with
time, a criticallcvcl was reachcd in about 1990, give or take a year or two, when less and less of
the silver iodide released from the ground generators activatcd in the quantities, locations and
times intended. thereby decrcasing the efTectiveness of the sceding operation. The situation is
not. of course, as simplc as that. How and \\'hen the incrcasc in height of the _50C level impacts
seeding eficctivcness also depends on the topographical configuration of each \vatershcd and the
strategy employed in seeding each watershed, i,e., the number and height of ground seeding
generators, the aircraft sceding frequcncy, and the silver iodide chemical complex uscd in each
of the operational seeding programs. It is interesting to note that the Group I operational sccding
programs with the most sustained positive rcsults arc in the northern part of thc Sierra Nevada
Mountain range and the Group 2 operational seeding programs where the sceding ctlcctivcness
decayed most rapidly allcr about 1990 are in the southcrn part of the Sicrra Nevada :Vlountain
range. Thc southern end of the Sicrra Nevada Mountain range is the highest and most rugged
with II peaks topping 14.000 ft and. consequently, with more complcx airflow.
As a potcntial remedy for the decreasc in seeding effectiveness; thc seeding procedurcs
might be able to be adjusted to lit the changing meteorology by using silver iodide chemical
complexcs better suited to the changing mcteorological conditions ami/or making greater use of
aircrall sceding. The efTectivencss of the ground generator configurations might also be
improved by increasing their numbcrs and locations.

45