Sacramento Valley Growers Work to Protect Aquatic Life

Thursday, Feb 13th, 2020

Recent water quality monitoring testing conducted for the Sacramento Valley Water Quality Coalition (Coalition) shows that water quality in the Sacramento Valley is good and particularly healthy for the aquatic ecosystem. Aquatic health and the biological condition of waterbodies is generally measured by toxicity testing using sensitive algae, invertebrates, and fish that are intended to be protective of resident species. Toxicity tests performed by certified laboratories are used in the Central Valley Regional Water Quality Control Board’s regulatory programs as a tool to evaluate potential effects on aquatic life beneficial uses under the Porter-Cologne Water Quality Control Act.

This figure above shows more than 1170 water column and sediment samples collected and analyzed from 22 waterbodies (see map for monitoring locations) throughout the Sacramento Valley over the period 2012-2019. In summary, the figure shows:

  • Rare toxicity (<1% of all samples) to Selenastrum (algae) and Ceriodaphnia (water flea) have shown these species to be doing well, suggesting protection of algae (phytoplankton) and invertebrates (zooplankton) that are important food for fish and wildlife;
  • No toxicity to Pimephales (fathead minnow), suggesting the protection of a sensitive fish species;
  • Low frequency of toxicity to Hyalella, a shrimp-like invertebrate that feeds on algae and diatoms and is a major food source for waterfowl along the Pacific Flyway.

Starting in 2011, Hyalella testing was linked to pyrethroids in sediments when toxicity to Hyalella is observed to be significant and shows an effect greater than (>) 80% of the control sample (red portion of bar graph in figure below). The observance of such an effect requires the Coalition to analyze sediment samples for pyrethroid pesticides. Since 2011, 173 sediment samples have been tested with Hyalella and only eleven (11) have triggered the analysis of pyrethroids. A toxicity effect less than or equal to (£) 80% of the control sample (gold portion of bar graph) does not trigger sediment analysis. Since the requirement for pyrethroids testing of sediment, the proportion of Hyalella samples with statistically significant toxicity requiring such analysis has averaged about 7% annually with no such analysis required during several years.

Water leaders in the Sacramento Valley watch the results from this testing closely as part of their sustainability objective to manage water and land uses for multiple beneficial uses (i.e., farms, fish, birds, cities and rural communities and recreation). In this case, the focus is on assuring that agronomic practices are protective of aquatic life beneficial uses of water that support fish, birds, and wildlife. Here, the results suggest that the management practices used by the 8300 owners and operators of irrigated agriculture are generally working and continue to protect aquatic ecosystems that are important to fish, birds, and other wildlife. The results also indicate a healthy biological condition for these waterbodies, which should generally support a wide variety and high number of macroinvertebrate taxa, including many that are critical for supporting fish and wildlife.

In areas where there are notable detections, the local leaders will analyze the results with the Coalition’s scientists, try to identify the source of toxicity and then determine what actions upstream can rectify any problems. These actions include targeted outreach and education efforts directed to landowners, farm operators, pest control advisors, and pesticide applicators that emphasize pesticide application and runoff management practices that minimize the potential for impacts to surface waters. The implementation of these practices is documented through the Coalition’s Farm Evaluations and targeted surveys, and the principles of adaptive management are employed to focus management practices and heighten the awareness of water quality issues in support of the protection of beneficial uses.

For more information on this data and the program for improving water quality in the Sacramento Valley, please visit the Coalition’s website at

Stephen Clark is Vice President at Pacific EcoRisk and has conducted extensive research for over 30 years in aquatic ecotoxicology with an emphasis on the effects of contaminants on aquatic organisms at the whole organism/cellular/biochemical level (e.g., “biomarkers”). Mike Trouchon is an Associate Scientist at Larry Walker Associates with 25 years of experience in the water quality and water resources field, with recent assignments focused on management and coordination of a regional agricultural water quality monitoring program in the Sacramento Valley; wastewater NPDES permit and waste discharge requirements (WDR) compliance.

Leave a Reply

Your email address will not be published. Required fields are marked *