Continuous stream monitoring reveals diurnal and seasonal variability in water quality parameters of Big Chico Creek, Northern California

Monitoring stream water quality on a continuous basis benefits human and aquatic health by identifying changes in water composition in response to singular events such as storm events or wildfire, and by capturing long-term trends due to land use changes. This study focuses on continuously monitoring Big Chico Creek, a tributary to the Sacramento River in Northern California, to establish a streamflow hydrograph and examine the diurnal and seasonal variability in water quality at an upper watershed location with minimal anthropogenic influence. The monitoring station has been recording stage, electrical conductivity, dissolved oxygen, and water temperature every fifteen minutes since July 2019. Additionally, streamflow measurements were taken periodically using a Teledyne StreamPro Acoustic Doppler Current Profiler (ADCP) to establish a streamflow hydrograph for Big Chico Creek. Electrical conductivity, a proxy for salinity, displayed an inverse relationship with stage, most notably during storm events. This is consistent with the dilution effect of increased streamflow, and the salt concentration effect of increased evaporation under low streamflow conditions. Dissolved oxygen and water temperature were inversely related, with varying amplitude in response to seasonal changes. The dataset generated by the monitoring station has served as an unburned control in a partner study on the impacts of the 2018 Camp Fire on surrounding burned streams, and will be used to evaluate the water quality impacts of downstream urban development. This study contributes a better understanding of the Big Chico Creek behavior by documenting its daily and seasonal variations in water quality, establishing a baseline for water resources management.