Groundwater Quality in the Klamath Mountains, California

The Klamath Mountains study unit covers more than 8,800 square miles and consists primarily of hard rock terranes characterized by high peaks and deep river gorges with relatively few groundwater basins (Bennett and others, 2014). Most of the study unit consists of metamorphic, ultramafic, and granitic rocks. The primary aquifer system sampled in the study unit, in contrast to most other study units evaluated by the GAMA Priority Basin Project, consisted of localized areas of fractured bedrock. The fracture systems may be interconnected or isolated, resulting in variability in water levels, well yields, and water quality on local and regional scales (California Department of Water Resources, 2003). The primary aquifer system in the study unit is defined as those parts of the aquifer corresponding to the open or perforated intervals of wells listed in the California Department of Public Health (CDPH) database.