Sanctuary Integrated Monitoring Network
Monitoring Project

Snapshot Day

Principal Investigator(s)

  • Lisa Emanuelson
    Monterey Bay National Marine Sanctuary
Start Date: April 24, 2000

Started on Earth Day in 2000, Snapshot Day is the largest, one-day water quality monitoring event of its kind in California. Snapshot Day utilizes citizen volunteers to collect and analyze water samples from streams that enter the Monterey Bay National Marine Sanctuary (MBNMS) from the four counties at border it- San Mateo, Santa Cruz, Monterey and San Luis Obispo. Snapshot Day is designed to increase public awareness by providing a “snapshot” of regional water quality conditions and to provide resource managers with valuable information for reducing pollution. Waterbodies as diverse as drainages, brackish sloughs, and major river systems are monitored. Trained volunteers measure dissolved oxygen, pH, conductivity, air and water temperature, transparency/ turbidity, and collect water samples to be lab tested for nutrients (nitrates and orthophosphate) and bacteria. All tested analytes measure the health of a waterbody and its’ ability to support cold water fish and other aquatic organisms (the standard against which Snapshot Day data is compared).

Summary to Date

In 2009, Snapshot Day celebrated its’ 10th Anniversary. On May 2nd, 2009, 224 volunteers monitored 185 sites in the four counties bordering the sanctuary- San Mateo, Santa Cruz, Monterey, and San Luis Obispo. The majority of sites did not show water quality impairments; however, 39 sites, from 25 water bodies, were identified as impacted by human activities. Results from the water bodies along the San Mateo Coast and Big Sur Coast continue to demonstrate healthy conditions.

Every year Snapshot Day data are compiled to determine Areas of Concern. Areas of Concern are waterbodies with sites that have exceeded the water quality objective for at least three of the nine analytes measured- air temperature, water temperature, pH, turbidity/transparency, conductivity, dissolved oxygen, orthophosphates, nitrates, and bacteria. Throughout the nine years of Snapshot Day data, recurring Areas of Concern are noted for some specific watersheds.

Snapshot Day data are used by the State of California in conjunction with other data to list water bodies as impaired under the Clean Water Act’s 303 (d) listing. Other resource managers use Snapshot Day data to further engage citizenry and agencies to address problems of pollution in waterways.

Monitoring Trends

  • E. coli concentrations exceeded the water quality objective in 24 percent of the sites monitored.
  • 18 sites (11%) tested above the Central Coast Ambient Monitoring Program Action Level for orthophosphate (as P) set at 0.12 mg/l.
  • 34 sites (20%) exceeded the Central Coast Ambient Monitoring Program Action Level for nitrate (as N) of 2.25 mg/l.
  • The average dissolved oxygen level for central coast sites was 9.2 mg/l.


Past results (2005):
The results from Snapshot Day 2005 were encouraging. Based on the data from the event, the number of exceedances for water temperature, dissolved oxygen, turbidity, E.Coli, nitrate and orthophosphate were down as compared to 2004. Eighty-six of the sites (53%) did not have a single exceedance for any of the water quality objectives, which is almost identical to 2004 data. Many of the water bodies along the San Mateo Coast and Big Sur Coast were, overall, in very good condition. In contrast, the water bodies in urban and agricultural areas seem to be more impacted by the surrounding land use. Dissolved oxygen was the most common field measurement that did not meet the water quality objective (between 6.5 and 12 mg/l) at twenty-one sites (13%), but this is still a significant decrease from thirty-seven sites in 2004. Seventeen sites (11%) had pH values that fell outside of the General Basin Plan Objective for pH (6.5-8.5), and eighteen sites (11%) did not meet the water quality objective for turbidity. As for the laboratory analyses, the E.Coli bacteria water quality objective of 400 MPN/100 ml was exceeded at twenty-six sites (16%), which is down from forty sites in 2004, and forty-one sites in 2003. The highest concentrations were found in Corcoran Lagoon, Watsonville Slough, and Graves Creek in San Luis Obispo. Nitrate as N and orthophosphate as P were the two nutrients measured. Eighteen sites (11%) exceeded the CCAMP action level for nitrate as N of 2.25 mg/l, but this is down from twenty-three exceedances in 2004, and is the same as in 2003. All nitrate exceedances were found between the Watsonville Slough and the Lower Salinas Valley, except for one site in Morro Bay on Los Osos Creek. Twenty-eight sites (18%) reported concentrations above the Central Coast Ambient Monitoring Program Action Level for orthophosphate set at 0.12mg-P/l. Most were found in the lower Salinas Valley and Watsonville Slough watersheds, but there were also two sites in San Mateo County, one site in Santa Cruz County, and five sites in San Luis Obispo County. The total number of exceedances is down from thirty-nine sites in 2004, and thirty-three sites in 2003. Stations that exceed three or more of the seven parameters are identified as “Areas of Concern”. This directs attention to a subset of water bodies that may require additional monitoring or follow up. In 2005, eighteen Areas of Concern were identified on the Central Coast. There were also eighteen areas in 2004, but this is up from fourteen in 2003, and eleven in 2002. Twelve of this year’s Areas of Concern were listed in both 2004 and 2005, and those twelve are all located between the Watsonville Slough and the Lower Salinas River.

The volunteers collecting the data were well trained, and the rigorous quality assurances implemented for this event give us confidence that the results presented are accurate. This was the sixth annual Snapshot Day on the Central Coast, and the one day event continues to demonstrate the value of citizens collecting important water quality information. Volunteer data supplement year round monitoring data and help guide management decisions and other water quality efforts.

Study Parameters

  • Total coliform
  • Nitrates
  • Ortho-phosphate
  • Dissolved oxygen
  • pH
  • Conductivity
  • Turbidity
  • E. coli.
  • Air temperature
  • Water temperature

Study Methods

All Snapshot Day results are compared with water quality objectives recommended by the Central Coast Ambient Monitoring Program (CCAMP), the Basin Plan, or the US Environmental Protection Agency. All collection methods and lab analyses follow the requirements set forth in a state approved Quality Assurance Project Plan (QAPP) and Monitoring Plan ensuring all data is of known quality.

Prior to Snapshot Day, a volunteer training is conducted in each of the four counties that drain into the Monterey Bay Sanctuary- San Mateo, Santa Cruz, Monterey, and San Luis Obispo. Volunteers learn about the history of the program, specific monitoring protocols, field safety and event logistics. Practice with the monitoring equipment is conducted to ensure that all volunteers are comfortable with and safely use all equipment.

On the morning of the Snapshot Day, volunteers converge at their local “hub”, meet other team members, get their final team assignments and check their bucket of equipment. Monitoring kits include a conductivity meter, dissolved oxygen kit, pH strips, transparency tube, a thermometer, distilled water, gloves, paper towels, a trash bag, pens/pencils, sample bottles, a clipboard with data sheets, instructions, and site maps. Teams all head out to their sites at the same time and then return to the hub with data sheets and sample containers of water to be lab tested.

Figures and Images

Figure 1. Volunteers gather at REI in Marina for Snapshot Day's 10th Anniversary, May 2nd, 2010.

Figure 2. Meagan Maughan, Sacha Lozano and Jason Williams at the Salinas Reclamation Ditch.

Figure 3. MBNMS staff, Erica Burton, measures conductivity with two volunteers.

Figure 4. Areas of Concern identified using Snapshot Day data.

Figure 5. Map of Snapshot Day sampling locations.

Figure 6. E. coli concentrations for Snapshot Day 2009.

Figure 7. Nitrate-N concentrations for Snapshot Day 2009.

Figure 8. Orthophosphate-P concentrations for Snapshot Day 2009.


  • 2010 Big Sur Fire Study
    Final report comparing concentrations of nitrate-N, orthophosphate-P, total suspended solids and transparency following the 2008 Big Sur wildfires vs. historical Snapshot Day measurements collected before the fires.
    440 KB PDF