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<br />. <br />I <br />. <br />. <br />. <br />. <br />. <br />I <br />I <br />I <br />I <br />I <br />I <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />t <br />~ <br />~ <br />~ <br />~ <br />~ <br />~ <br />. <br />. <br />I <br />I <br />. <br />. <br />I <br /> <br />potential contamination due to its proximity to another historical seeding program over the <br />Grand Mesa. However. we were reluctant to exclude this site entirely. due to its significant <br />contribution to the historical regression equation. and the better target/control correlation which <br />could be obtained by including this S:\OTEL site. Therefore. we decided to sho"..' two different <br />results in both the precipitation and snowpack analyses. corresponding to regression equations <br />which include/exclude this larget site. <br /> <br />Experience has shown that it is virtually impossible to provide a precise assessment of the <br />effectiveness of cloud seeding over one or t\..'o .....inter-spring seasons. However. as the data <br />sample size increases. it becomes possible to provide at least a semi.qualitative ans\""er to the <br />question of. "How effective was the seeding?" Since this past winter season represents the <br />second seeded season. only general indications of the success of the seeding would be expected. <br /> <br />Using the target-control comparison described above. mathematical relationships for the <br />variables (both precipitation and snowpack) were determined between a group of sites in the <br />unseeded (control) areas and the sites in the seeded (target) area. From these data. predictor <br />equations were developed. where the average value of the \'ariable observed in the un seeded <br />(control) areas was used to predict the average value of the variable in the seeded (target) area in <br />the absence of seeding. A positive difference between the obseI"\'ed amount and the predicted <br />amount in the seeded area (target) during seeded periods may indicate a positive result of <br />seeding. A single-season negative difference may theoretically indicate that the seeding <br />decreased the precipitation. a highly unlikely. if not impossible. occurrence. More likely. a <br />negative difference would indicate that the regression equation did not have a high enough <br />correlation to provide an accurale prediction. especialJy for seasons \....ith very lov..- or very high <br />precipitation amounts. <br /> <br />~.1 Precipitation Analysis <br /> <br />Precipitation data used in the analysis were obtained from the :\atural Resources <br />Conservation Service (XRCS) and/or from the ~ational Climatic Data Center. representing the <br />official published records of those organizations. Similar snowpack (water content) records used <br /> <br />30 <br />