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<br />..' <br /> <br />1.0 INTRODUCTION <br /> <br />1.1 General <br /> <br />The Denver Water Board (DWB), in cooperation with other interested parties, sponsored <br />an operational cloud seeding program during t..he 2002/03 winter season. The goal was to <br />augment the mountain snowpack and, thereby, subsequent spring and early summer runoff in <br />drainages important to the DWB and its many customers throughout the Denver metropolitan <br />area. The DWB contracted with a private company, Western Weather Consultants, to conduct <br />the seeding. Western Weather Consultants operated many manually operated, ground-based <br />silver iodide (AgI) generators in the region of interest. Generdtors were typically at relatively <br />low-elevation valley locations where local residents could readily operate them when contacted <br />by telephone. Seeding commenced in early November 2002 and continued until April 7,2003. <br /> <br />This final report describes the work and results of a measurement and evaluation program <br />done by Woodley Weather Consultants for the DWB. The program's primary goal was to <br />provide an economical physical evaluation of the effectiveness of its 2002/03 winter operational <br />cloud seeding program. This physical evaluation analyzed trace silver concentrations for <br />evidence of the silver iodide seeding agent in the target area's seasonal snowpack. Samples were <br />collected near the end of the seeding program, and analyzed by a well-known independent <br />laboratory to determine whether silver was present in above background levels. Trace silver <br />analyses are crucial because the absence of enhanced silver would indicate that little of the <br />released seeding agent actually reached the clouds, which produced the target area snowfall. <br />Such a result would make highly dubious any statistical suggestions or other claims of seeding- <br />induced snowfall increases. <br /> <br />The task involved sampling of the seasonal snowpack from ten target area sites and three <br />control sites, the latter chosen in upwind, nonseeded, mountain areas. The number of sampling <br />sites was somewhat limited, given the large target area, but was expected to provide enough point <br />measurements to detect "seeding silver" (silver from AgI releases) within that target. The <br />number of control samples was limited by budget considerations, but was expected to verify <br />numerous past observations of natural background levels of silver in nonseeded mountain <br />snowfalls. <br /> <br />This limited physical assessment is important for both scientific and political reasons. <br />From a scientific standpoint it is important to know whether the seeding may have worked as <br />intended. Silver-in-snow analysis cannot demonstrate that seeding was successful. This would <br />require a major physical measurement program far beyond the scope of the DWB project. <br />However, failure to demonstrate enhanced silver levels in the target area snowpack provides <br />strong evidence of inadequate transport and dispersion (T &D) of the seeding agent, which must <br />result in failure of the seeding project to produce meaningful snowfall augmentation. <br /> <br />The political reasons for the assessment are just as persuasive as the scientific reasons. <br />Water consumer funds were used to fund the operational seeding program. Such a program, <br />without credible evaluation by parties with no vested interest in the outcome, would eventually <br /> <br />4 <br /> <br />