The clubtails are a large group of dragonflies, often quite similar to each other.   This is the olive clubtail (I've also photographed the plains clubtail, G. externus, the russet-tipped clubtail, Stylurus plagiatus, the white-belted ringtail, Erpetogomphus compositus, and the gray sanddragon, Progomphus borealis)   The photo was taken near the Black Rock fish hatchery in the Owens Valley in eastern California.