UC San Diego

The nearshore environment is an extremely dynamic seascape that is difficult to characterize with high spatial and temporal resolution. Here, I utilize a novel sensor package, the WavepHOx, to spatially depict the signature of the seawater reverse osmosis (SRWO) byproduct plume emanating from the outfall of the Carlsbad Desalination plant (CDP) over the course of 60 days and 10 different surveys with a human powered watercraft equipped with a global positioning system (GPS). Subsurface and surface measurements detected areas of seawater at the mouth of the desalination plant’s outlet into the ocean with properties 1.5% higher salinity (RMS = ±0.17%) and 7.7% (±0.20%) higher temperature than nearby ambient values (~33.4 on the Practical Salinity scale and ~14 ⁰C respectively) and similar surface values as far as 600 m from the outfall. This brine-induced gravity current tended to propagate latitudinally southward parallel to shore, consistent with the encompassing Oceanside Littoral Cell. Possible explanations for vertical distributions of the plume are also discussed. These observations provide a pathway for a new method to map the nearshore environment’s physical and biogeochemical processes.