The materials in this subseries primarily relate to the Colorado portion of the 1979-1981 six-state High Plains-Ogallala Aquifer Study. The $6 million study administered by the U.S. Department of Commerce, with the Colorado portion conducted by Colorado State University and three state agencies, investigated the aquifer's depletion and generated suggestions for mitigation and management. Documents focus on Robert Longenbaugh's examination of economic sustainability and energy and water consumption by irrigation pumps on Colorado's Northern and Southern High Plains. This study is a later but similar study to that found in Series 5. Materials include raw data, reference material, correspondence, research notes, conference materials, and reports and publications. Files are grouped by material type and follow a general timeline from the beginning to the end of the study.