Snapshot Day is quickly approaching! Over the last two decades, thousands of volunteers have participated in this springtime event to capture a health “snapshot” of rivers and streams that flow into the Monterey Bay National Marine Sanctuary. As we prepare for Snapshot Day on May 6, 2023, we wanted to highlight the results of last year’s event, which showed signs of improvement for the San Lorenzo River.
During Snapshot Day 2022, 91 trained volunteers gathered on May 7 to monitor water quality across the four counties that border the Monterey Bay National Marine Sanctuary: San Mateo, Santa Cruz, Monterey, and San Luis Obispo. They measured various water quality conditions in the field, and collected water samples that were analyzed in a laboratory for nutrients and bacteria. Of the 73 sites with flowing water that could be assessed, about one-third (32%) met all of the targets, known as water quality objectives, for clean and healthy streams.
Three sites along the San Lorenzo River were monitored in 2022: the river mouth, Garden of Eden in Henry Cowell Redwood State Park, and Junction Park in Boulder Creek. Happily, samples collected at the river mouth and Garden of Eden met all of the water quality objectives measured, and Junction Park only slightly exceeded one objective (for E. coli bacteria). This is welcome news because in 2021, the San Lorenzo River was labeled an Area of Concern based on the results of Snapshot Day that year.
Areas of Concern are those that do not meet three or more water quality objectives. In 2021, at least one of the sites sampled on the San Lorenzo did not meet targets for dissolved oxygen, pH, E. coli, or Orthophosphate (as P). Since Snapshot Day sampling began in 2000, the San Lorenzo has been flagged as an Area of Concern in two years: 2016 and 2021. The long-term volunteer effort of Snapshot Day makes it possible to understand changes in the conditions of our rivers over time, and this information can be used to protect and improve steam health.
You can read the full report for Snapshot Day 2022 here. Below, you can learn more about the different water quality parameters measured during the event, and see results for the three San Lorenzo River sites. This information is from the Snapshot Day 2022 Final Report compiled by the Monterey Bay National Marine Sanctuary Foundation. We hope you’ll join us to monitor our rivers and streams for Snapshot Day on May 6, 2023!
Click here to read the Snapshot Day 2022 Report in full
Snapshot Day 2022 Results
Field Measurements
Dissolved Oxygen
Aquatic organisms rely on sufficient amounts of dissolved oxygen in the water to perform regular behaviors like feeding, spawning, and incubating. Excessive nutrients in the water can increase plant growth, which uses up dissolved oxygen once plants die and bacteria deplete the oxygen available to aquatic organisms as they decompose plant material. The water quality objectives for dissolved oxygen is a value between 7 mg/L and 12 mg/L, which is considered an optimal range for cold-water fish.
During Snapshot Day 2022, all sites on the San Lorenzo River met the water quality objective for dissolved oxygen. Measurements included 12 mg/L at the river mouth, 8 mg/L at Garden of Eden and 9 mg/L at Junction Park.
pH
pH is a measure of the percent of hydrogen ions in the water. A value of 7 is neutral, above 9 is alkaline (or basic), and below 5 is acidic. Many aquatic organisms require a very specific pH range to carry out necessary chemical and biological reactions; extremely low or high pH levels impede essential functions for survival or damage tissues. The water quality objective for pH is a value between 7 and 8.5.
During Snapshot Day 2022, all sites on the San Lorenzo River met the water quality objective for pH. Measurements included 7.5 at the river mouth, 7 at Garden of Eden, and 7.5 at Junction Park.
Water Temperature
Just as temperature on land impacts terrestrial plants and animals, the temperature of the water can affect the life and health of aquatic organisms. Many fish species and other aquatic life need specific temperature ranges within which to survive and reproduce. Water temperature can also affect the amount of dissolved oxygen, with higher temperatures causing a decrease in dissolved oxygen. Slowing water flow or removing streamside vegetation which provides shade can also cause water temperatures to rise to undesirable levels that may harm aquatic life. The water quality objective for temperature is to not exceed 21 degrees Celsius (oC), which is considered an upper limit for the health of cold-water fish such as salmon and steelhead.
Snapshot Day data is collected during the morning hours, so water temperature measurements do not necessarily reflect the maximum daily temperatures for the water body. During Snapshot Day 2022, all sites on the San Lorenzo River met the water quality objective for temperature. Measurements included 17.3 oC at the river mouth, 14.5 oC at Garden of Eden, and 13.4 oC at Junction Park.
Lab Analysis
E. coli bacteria
Coliform bacteria generally originate from the feces of warm-blooded animals such as humans or wildlife. While coliform bacteria are usually not the cause of sickness, their presence can indicate that other illness-causing pathogens are present. The water quality objective for E. coli 235 MPN/100 mL.
During Snapshot Day 2022, the Junction Park site on the San Lorenzo slightly exceeded the water quality objective for E. coli with a measurement of 268 MPN/100 mL. The river mouth and Garden of Eden met the water quality objective with measurements of 218 MPN/200 mL and 82 MPN/100 mL, respectively.
Nitrate as N
Nitrate (as N) is naturally occurring in streams and rivers; however, other sources that can contribute nitrate to creeks and rivers include fertilizers, pesticides, detergents, animal waste, sewage, or industrial wastes. Heightened levels of nutrients can lead to excessive algal or aquatic plant growth, which ultimately depletes the amount of oxygen available in a waterway when plants die off and bacteria decompose plant material. The water quality objective for Nitrate as N is to not exceed 1.00 mg-N/L.
During Snapshot Day 2022, all sites on the San Lorenzo River met the water quality objective for Nitrate (as N). Measurements included 0.1 mg-N/L at the river mouth, 0.4 mg-N/L at Garden of Eden, and 0.2 mg-N/L at Junction Park.
Orthophosphate as P
Orthophosphate (as P) is also naturally occurring in streams and rivers; however, other sources that can contribute phosphate to creeks and rivers include fertilizers, pesticides, detergents, animal waste, sewage, or industrial wastes. Heightened levels of nutrients can lead to excessive algal or aquatic plant growth, which ultimately depletes the amount of oxygen available in a waterway when plants die off and bacteria decompose plant material. The water quality objective for Orthophosphate (as P) is to not exceed 0.12 mg/L.
During Snapshot Day 2022, all sites on the San Lorenzo River met the water quality objective for Orthophosphate (as P). Measurements included 0.08 mg/L at the river mouth, 0.1 mg/L at Garden of Eden, and 0.04 mg/L at Junction Park.