Winter Orographic Cloud Seeding over the Kern River Basin in California

An operational cloud seeding program using solely airborne treatment to augment precipitation over the full watershed of the Kern River in the southern Sierra Nevada of California has been conducted for eight of the past ten water years. A target-control regression analysis of the non-randomized program indicates a 15% increase in average annual streamflow during the seeded period to date, significant at better than the .01 level. Support for the regression results is found in double mass analysis of target-control streamflow, as well as in comparisons of radar characteristics between seeded and not-seeded precipitation echoes. The program design, operations and evaluations are described.