A Hydrogeologic Field Area Encourages Learning of Isotope Hydrology, Geologic Imprint on Water Quality, and Trace Element Hydrochemistry

Abstract:

The Santa Monica Mountains of Southern California affords an excellent opportunity for training students on geologic imprints on stream and groundwater quality. With salinity varying from 500 mg/L TDS in streams fed from groundwater in low solubility sandstones, to 4000 mg/L TDS in streams fed from high solubility and gypsum bearing siltstones and mudstones, the role of geology on natural stream and groundwater chemistry is profound. Use of imported water from Northern California on urban landscapes that is isotopically distinct from locally sourced “native” waters provides an opportunity for students to trace and quantify the percentage of imported versus native water sources in the Santa Monica Mountains streams using stable water isotopes. Furthermore, the presence of natural selenium and uranium in certain types of strata and higher oxidation potential created by anthropogenic nitrate in groundwater provides students with opportunities to learn of trace element hydrochemistry and redox potential in natural and nutrient-contaminated strata. Teams of students have evaluated these processes in this exceptional natural hydrogeological laboratory in our Watershed Analysis, Field Methods, and Water Quality courses. The opportunities for learning hydrogeological processes in this natural field laboratory prepare students for careers in water resources in Southern California and elsewhere.