By Amy Irani, director of Nevada County Environmental Health
Nevada County is home to an abundance of beautiful natural areas perfect for outdoor recreation, many of which feature seasonal streams, creeks, lakes, and rivers. As summer temperatures rise and rainfall decreases, water levels in these bodies naturally decline. These changes can alter the aquatic environment, increasing nutrient concentrations that support the growth of bacteria—including Escherichia coli (E. coli).
Lower water levels often lead to the accumulation of organic matter, creating ideal conditions for microbial activity. While this is a natural ecological process, it’s important to take simple precautions to protect your health while enjoying these waters.
Tips for Safe Recreation:
• Always wash your hands after swimming, especially before eating or drinking.
• Avoid swallowing water while swimming whenever possible.
The Sierra Streams Institute plays a vital role in monitoring the health of Nevada County’s waterways. It maintains a comprehensive database and regularly conducts water quality testing. Its recent article highlights important updates regarding bacteria in Little Deer Creek and related public notices.
The State Water Resources Control Board, Region 5 Central Valley, also recently completed the Wolf Creek Bacteria Study Report, conducted by their environmental scientists.
Key findings from the study revealed only trace amounts of human DNA—levels that were either below the detection limit or not quantifiable, which is great news. In contrast, the quantifiable sources of bacteria were linked to ruminant animals such as sheep, goats, and cattle, as well as domestic dogs, which are much less likely to make people sick.
This is a significant finding, as Wolf Creek has been identified by the Water Board as an impacted water body within Nevada County with elevated levels of nitrates that are presumed to be associated with residential onsite wastewater treatment systems or septic systems. The results suggest that, during the summer dry-season sampling, there was no evidence connecting contamination in the creek to the wastewater treatment systems or septic systems.
These insights help guide future efforts to protect and improve water quality in our local waterways.