#SummerScienceFriday | Testing the Waters of the LA River


One of the five questions addressed by the Los Angeles River Watershed Monitoring Program (LARWMP) is “Is it Safe to Swim?”  Prior to LARWMP, we knew very little about bacteria concentrations at sites thousands of visitors swim in every year. This question looks at bacterial contamination at recreational swimming and kayaking sites along the LA River and assesses the concentration of bacteria, comparing them to California recreational standards. In order to tease out at the relationship between heavy recreational use and E. coli concentrations, we sample at sites not only on weekdays but also on weekends and holidays, when we see a higher number of visitors.  In addition to collecting river samples for E. coli analysis, Council for Watershed field staff also measure water quality parameters such as pH, conductivity, and dissolved oxygen to get a more holistic understanding of water quality and the relationship between water chemistry and bacteria.  


Below is a summary of the measurements we take and what they mean for the health of the river.

  • pH:  measured with a multi-parameter meter. We place the probe in the water and jot down the number on the meter (picture).  pH is a measure of how acidic a solution is.  The pH of a waterbody is important because all organisms have a pH range in which they can survive, and for river inhabitants, an extremely low or extremely high pH can be deadly.  For example, a relatively low pH, indicating acidic water, can hinder fish eggs from hatching and damage the membranes of macroinvertebrates (water bugs that are food for fish).  Amphibians like frogs are also very sensitive to low pH levels.</