Evaluation of Pyrethroid Toxicity Reduction in the Santa Margarita River Watershed: A Case Study Analysis

Toxicity identification evaluation (TIE) was conducted in the Santa Margarita River watershed by testing water samples collected from Santa Margarita, Temecula and Murrieta Creeks. The biological community of benthic macroinvertebrates which makes up a portion of the ecological composition of Santa Margarita River Watershed was shown to be significantly impacted by both Temecula Creek and Murrieta Creek. The results of the bioassessments further showed that the greatest biological impact on the macroinvertebrate community was in Murrieta Creek. TIE data analysis showed that pyrethroid toxicity fluctuates in the wet weather season in both Temecula Creek and Murrieta Creek from October through March in correlation with storm water runoff. TIE data analysis also showed that the highest average pyrethroid toxicity occurs in Temecula Creek and both agricultural and urban pesticide users are the main factors. Remediation efforts including agricultural drainage ditches, porous pavement, bioswales, and community outreach and education were proposed in order to reduce pyrethroid pollution in the Santa Margarita River Watershed.