Sanctuary Integrated Monitoring Network
Monitoring Project

Snapshot Day

Principal Investigator(s)

  • Lisa Emanuelson
    Monterey Bay National Marine Sanctuary
  • Debie Chicro-MacDonald
    Coastal Watershed Council
Start Date: April 24, 2000

The first Snapshot Day began on Earth Day in 2000, and is the largest, one-day water quality monitoring event of its kind in central California. Snapshot Day utilizes citizen volunteers to collect and analyze water samples from streams that enter Monterey Bay National Marine Sanctuary (MBNMS) from the four counties that 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. Water bodies as diverse as small creeks, brackish sloughs, and major river systems are monitored. All of the analytes measure the health of a water body and its ability to support cold water fish and other aquatic organisms, the standard against which Snapshot Day data is compared.

Summary to Date

On May 2nd 2015, Snapshot Day celebrated its 16th anniversary. On that day 154 volunteers monitored 113 sites. Due to the prolonged drought, some sites where flowing water was expected were dry. Of the 113 sites monitored, only 102 had flowing water.

Results are compared to Water Quality Objectives (WQO) set by either the Environmental Protection Agency (EPA), the Central Coast Ambient Monitoring Program (CCAMP), or the State Water Resources Control Board. All WQO and Action Levels and their source, see Table 1.

Annual Snapshot Day data are compiled to determine Areas of Concern (Figure 4). Areas of Concern are water bodies with sites that have exceeded water quality objectives for at least three of the seven analytes measured- water temperature, pH, turbidity/transparency, dissolved oxygen, orthophosphate, nitrate and fecal indicator bacteria. Throughout the sixteen years of Snapshot Day data collection, Areas of Concern are commonly identified at sites at the bottom of larger watersheds, especially those with heavy urban or agricultural use. In 2015, 30 of the 113 sites did not any show water quality impairments; however, 13 sites on 7 water bodies, were identified as Areas of Concern due to high concentrations of nutrients and bacteria; low dissolved oxygen; high water temperatures; pH, or low transparency. Two sites are located in San Mateo County on one water body, 9 sites on 4 water bodies in Monterey County and the remaining 2 sites on two water bodies are in San Luis Obispo County. There were no Areas of Concern in Santa Cruz County in 2015.

Monitoring Trends

  • * 34 monitored sites (30%) monitored, had E. coli concentrations that exceeded the water quality objective set by the EPA Ambient Water Quality Criteria at 235 MPN/ 100 ml.
    * 20 of the monitored sites (18%), had orthophosphate (as P) concentrations above the CCAMP Action Level of 0.12 mg/l.
  • * 13 of the sites monitored (12%), had nitrate (as N) concentrations that exceeded the CCAMP Action Level of 2.25 mg/l.
    * Dissolved oxygen at 28 of the monitored sites (25%), exceed the Water Quality Objective set by the SWRCB�s California Basin Plan.
  • * Water temperature at 3 monitored sites (3%), was above the Action Level set by the CCAMP.
    * Transparency was above the Action Level suggested by CCAMP of no less than 25cm in 12 of the monitored sites (11%).
  • * Turbidity was above the Action Level set by CCAMP of no greater than 50 NTU in 1 of the sites where turbidity was monitored (50%).
    * pH at twelve sites (11%) did not meet the criteria for pH as set by the SWRCB�s Basin Plan objective (between 6.5 and 8.5).


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. Resource managers also use Snapshot Day data to further engage citizenry and agencies to address problems of pollution in waterways.

Throughout the past 16 years, Snapshot Day has been conducted on the first Saturday of May with the help of numerous volunteers that have taken field measurements and collected samples. The basic water quality parameters tested for allow a �snapshot� of overall water quality at sites for a specific date and time. Many of the water bodies along the San Mateo County and Big Sur coastlines are, overall, in very good condition with low water temperatures, good dissolved oxygen, low bacteria and low nutrient concentrations. In fact the water quality in these watersheds is so good they have been used as Reference Sites for the Areas of Special Biological Significance (ASBS) program. In contrast, the water bodies in urban and agricultural areas have impacted water quality and seem to be more affected by the surrounding land use of agriculture and urban areas. High levels of bacteria, nutrients and even water temperature all point to land uses that impact water quality.

By identifying Areas of Concern focused efforts can be initiated to address water quality objective exceedances and improve water quality flowing into Monterey Bay National Marine Sanctuary can be initiated.

In 2015 a multi-year Snapshot Day report was produced and included analysis of 14 years worth of Snapshot Day data focused on three questions: 1. Characterization of the deviation of analyte concentrations from water quality objectives (exceedances). 2. Assessment of trends over time of three water quality constituents: nitrate, orthophosphate and E. coli. 3. Representativeness of Snapshot Day data to more frequent sampling efforts conducted by the Central Coast Ambient Monitoring Program (CCAMP).

Study Parameters

  • Nitrates
  • Ortho-phosphate
  • Dissolved oxygen
  • pH
  • Transparency
  • Turbidity
  • E. coli
  • Water temperature

Study Methods

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.

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.

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 by waterbody. Waterbodies are listed from north to south San Mateo County to San Luis Obispo County).

Figure 5. Map showing Areas of Concern identified using Snapshot Day data.

Figure 6. Map of Snapshot Day sites 2015.

Figure 7. Map of E. coli concentrations for Snapshot Day 2015.

Figure 8. Nitrate-N concentrations for Snapshot Day 2015.

Figure 9. Orthophosphate-P concentrations for Snapshot Day 2015.


  • Snapshot Day report for 2000-2013
    Krone-Davis, Emanuelson, and Hoover (2015)
    2.4 MB PDF
  • 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