As the demand for freshwater resources increases due to increasing human populations, degradation of available resources, and climatic changes it will become increasingly important to understand the factors that impact the physicochemical characteristics of surface water resources over space and time. This study assessed a headwater stream over the course of a year in the San Bernardino National Forest that serves as both surface and groundwater resources for the Santa Ana River Watershed region, the largest and most populated watershed in Southern California. Streams were monitored bi-weekly during dry periods and weekly during wet periods from April 2018 through April 2019 for dissolved oxygen (DO), flow rate, temperature, conductivity, turbidity, pH, nitrate (NO3-), and ammonium (NH4+) with additional lab assessments for total dissolved solids (TDS), E. Coli (EC), and total coliform (TC). Findings illustrated that across the study sites NO3-, NH4+, and TDS exceeded federal and regional water quality standards for a majority of the sampling events (>60 percent). Additionally, NO3-, DO, and flow rates were elevated in the wet season, while conductivity, NH4+, TDS, pH, TC, and EC were elevated during the dry season.