The limnology of Lake Pleasant, Arizona and its effect on water quality in the Central Arizona Project canal

Abstract

Recent changes in the management strategy of water released from Lake Pleasant into the Central Arizona Project canal have substantially reduced taste and odor complaints among water consumers. Most of the taste and odor complaints were likely caused by 2-methylisobomeol (MIB) and geosmin produced by periphytic cyanobacteria growing on canal surfaces. Most years, Lake Pleasant consists almost exclusively of water brought in via the CAP canal. The location of the inlet towers and the old Waddell dam influence sedimentation of material brought in by the CAP canal. In-coming water was found to contain large amounts of periphyton of the type commonly found growing on the sides of the CAP canal. Withdrawal of hypolimnetic water early in the spring of 1997 decreased the time that sediments were exposed to anoxic conditions, potentially decreasing the amount of nutrients released into the CAP canal and therefore available for periphytic cyanobacteria. Utilizing this management strategy since 1997 has resulted in a substantial reduction (or elimination) of consumer complaints of earthy/musty tastes and odors.