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FAQ (Frequently Asked Questions)

WATER QUALITY NOWCAST

What is the Beach Report Card?

Heal the Bay’s Beach Report Card is the only comprehensive analysis of coastline water quality in California. We monitor more than 350 beaches weekly from Oregon to the Mexico border, assigning an A to F grade based on the health risks of swimming or surfing at that location. On our website, you can find out which beaches are safe and unsafe, check recent water quality history and look up details of current and past beach closures.

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Why should I care about water quality?

Numerous studies have shown that swimming in water with high levels of bacteria can make you seriously ill. The water may look fine, but it could be teeming with microorganisms that can cause severe stomach flu, respiratory illness and debilitating ear, nose and throat infections.

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Will I definitely get sick if I swim at an D or F beach?

No one can say for sure, but you definitely raise your risk. One in 25 beachgoers will get sick swimming or surfing in polluted water near a flowing storm drain. Many D and F beaches are near these outfalls. Other poorly performing beaches are frequently near piers or in enclosed marinas and harbors with poor circulation. Simply put, the lower the grade, the greater the risk of getting sick.

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How are the grades determined?

All county health departments are required to test beach water quality samples for three types of indicator bacteria at least once a week. Heal the Bay compiles the complex shoreline data, analyzes it and assigns an easy-to-understand letter grade. Learn more about the Grading Methodology.

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How often are the grades updated?

We publish new grades based on the latest data each week. These are available on this website. We also publish annual reports that provide detailed summary analysis for each coastal county, as well as a summer report card that analyzes sites during the traditional beachgoing season between Memorial Day and Labor Day. You can find PDFs of these reports here.

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What do the indicator bacteria mean?

Indicator bacteria are not necessarily pathogenic, i.e. their presence will not definitely make you sick. However, numerous epidemiological studies have shown that these bacteria are usually found near microorganisms that do cause human illness. Unfortunately, there are no reliable water quality tests that can identify with certainty the pathogens themselves.

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How is the bacteria getting into the water?

Determining the exact cause of bacterial pollution at a particular site can be a challenge. Sometimes the bacteria is the result of a leaky septic system nearby or a cracked sewer pipe. Othertimes, urban runoff carries animal droppings directly into the ocean via the storm drain system. Some unscrupulous boat owners discharge raw waste into the open ocean as well.

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Why are their dry grades and wet grades?

The Beach Report Card provides grades for both dry and wet weather to allow a clear analysis of the water quality at any given monitoring location. Water quality significantly drops during and immediately after a rainstorm, but often rebounds to previous levels within few days. Grades for dry weather are calculated for days of no rain and at least 3 days after it stops raining. Grades for wet weather pertain to data from samples collected on days that experience rain, including the following three days.

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What’s being done to clean up polluted beaches?

Due in large part to Heal the Bay’s Beach Report Card program and advocacy efforts, the state of California has committed over $100 million to clean up its most polluted beaches. The Clean Beach Initiative, a series of funding measures passed earlier this decade, has already paid for numerous runoff diversions and other infrastructure enhancements throughout the state. More than 70 sites are targeted.

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How can I and my family stay healthy at the beach?

  • Water quality is generally very good during the dry summer months (April to October)
  • Wait 72 hours after rainfall before you go swimming
  • Swim 100 yards away from flowing storm drain outlets. (Imagine a football field.)
  • Do not let children play in storm drains or puddles nearby
  • Access the Beach Report Card to find out if your beach is safe


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What is a Water Quality Nowcast?

The California Water Quality NowCast (NowCast) system is a tool that provides information similar to a daily weather forecasts except the NowCast system predicts good or poor water quality for the day at specific beaches across the California. NowCast predictions are based on the results of statistical computer models that estimate fecal bacteria levels in the surf zone. Predictions are made using up to date environmental information, and are released by 10AM every morning. Local agencies can compare the model results to the State’s bacteria health standards for contact with ocean waters to determine if the water is safe for recreational uses (such as swimming and surfing). If a model estimates bacteria levels at a beach to comply with the health standards, the NowCast result is shown as “Good”; however, if a model estimates bacteria levels to exceed the health standards, the NowCast result is shown as “Poor”.

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How many beaches are involved in the California NowCast program?

As of 2017, ten beaches across southern California have summertime NowCast models making daily predictions:
  • Cowell Beach [west of the wharf] (Santa Cruz)
  • Arroyo Burro/‘Hendry’s’ (Santa Barbara)
  • East Beach at Mission Creek (Santa Barbara)
  • Santa Monica Pier
  • Redondo Beach Pier
  • Long Beach City Beach [near 5th Place]
  • Belmont Pier (Long Beach)
  • Huntington State Beach [near Brookhurst Ave.]
  • Doheny State Beach (Orange County)
  • Moonlight Beach (Encinitas)
Our short-term goal is to have summertime models for up to 20 beaches and wintertime models for 5 beaches across the state by 2019.

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Where and when will I be able to find the Water Quality Nowcasts?

Beach-goers can access NowCast predictions on Heal the Bay’s Beach Report Card website (beachreportcard.org) or on the Beach Report Card app, now available for download (LINKS). Information and links to the predictions may also be available on the participating city and county health agencies webpages. Daily predictions are currently being made for the duration of the State AB 411 summer season (April 1st through October 31st), though eventually models will be created to make wintertime predictions.

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Who developed the predictive models?

The predictive beach water quality models were developed as part of a study completed by Heal the Bay, Stanford University and UCLA, and funded by the California State Water Resources Control Board. Experts in beach water quality developed and tested over 700 different beach models using many years of historical data on environmental conditions and bacteria levels from 25 beaches in California. This study represents the most comprehensive study completed to date on using predictive models at marine beaches. Following the study, a successful pilot test was performed at three California beaches during the summer of 2015 to determine if a nowcasting program in the state could effectively provide water quality information to the public.

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How are the daily NowCast predictions from the models different from Heal the Bay’s Beach Report Card grades?

The NowCast models for a given beach take into account current environmental conditions and historic bacteria levels to predict fecal indicator bacteria levels on a daily basis. The Beach Report Card provides weekly grades every Friday throughout the year based on the last 30 day of sample data, including the current week. The grades take into consideration the magnitude and frequency of exceedances above allowed bacterial levels over the course of the specified time period. So, while the NowCast models predict current conditions at the beach every morning, the Beach Report Card grades take a longer look back in time to look at the average conditions. Both pieces of information are important to a beach-goer assessing beach water quality because fecal bacteria levels can vary considerably over short time periods. The NowCast system and Heal the Bay‘s Beach Report Card are valuable tools to help people protect themselves and their family and friends.

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Why do we need predictive models for beach water quality?

Currently, local health agencies use laboratory analyses of water samples collected at the beach to determine if it is safe for recreational use. Unfortunately, there is a long delay in this approach: it typically takes 24-48 hours to collect the samples, transport them to the lab, and analyze the beach water samples. Meanwhile, water quality can change with environmental conditions. Additionally, most California beaches are sampled on a weekly basis (although there are some beaches that are monitored more frequently). As a result, health agencies currently rely on data that is days old to make health protection decisions. Predictive models can quickly provide daily water quality information based on the most recent environmental conditions at the beach. Local health agencies can then make public notifications of poor water quality in the morning before most people arrive at the beach.

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What factors affect beach water quality?

Fecal bacteria levels can be affected by many environmental factors such as rainfall, tide levels, solar radiation, wind, and wave action. Water quality can even be affected by human-made factors such storm drain flow and the presence of piers or jetties. Because the effect of these factors on water quality varies from beach to beach, site-specific NowCast models are developed for individual beaches.

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How accurate are the NowCast models?

Models are created and calibrated to be more accurate than the current method of using days-old sample data to make a decision on whether to ‘post’ the beach or not. In practice, the predictive models have generally performed as well as – or better than – the current method. For example, for the years 2011-2012, the models accurately predicted 25% more of the days when beach water quality failed to meet the health standards than the current method.

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Are there shortcomings to using NowCast models to make beach management decisions?

Predictive models are developed using the best available environmental data to capture variations in beach water quality. However, not all factors that affect water quality have available data to use in modeling. For example, the presence of seagulls at a beach has been linked to increased indicator bacteria level, yet accurate seagull counts at the time of water sampling are typically unavailable. The models are also unable to predict acute pollution events like sewage and oil spills.

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Are predictive models being used at other beaches

Yes. In the U.S., predictive nowcasts are implemented in the summertime at several beaches on the Great Lakes, including beaches in Ohio, New York, Wisconsin and Illinois. At these beaches, local beach agencies successfully use predictive models to determine when the public should be notified of bacteria levels that exceed health standards. Predictive models are also used at Hong Kong coastal beaches where the predictive models accurately predict 30-70% of water quality standard exceedances, and have been shown to reduce 27% of illnesses caused by swimming in contaminated beach waters.

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What does 'NP* - No Prediction’ mean on the Heal the Bay homepage widget?

This means that a water quality prediction has not yet been made today for this beach. There are a couple of reasons for this outcome. Models decisions are typically posted by 10AM every morning, and a ‘NP’ status may mean that predictions have simply not been made yet. However, if the ‘NP’ status is present later in the day, models runs may have been postponed due to insufficient environmental or bacterial data or technical difficulties with our server. Please check back tomorrow for an updated water quality prediction. In the meantime, please refer to the weekly letter grade for water quality information.

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While every effort will be made to ensure accurate information dissemination, the project team (Stanford University, Heal the Bay) and any involved health agencies and departments make no representation about the content for any purpose, and assume no responsibility for anyone’s use of the information.



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2008-05-13 02:05:16.467 2010-05-24 11:06:18.823 NULL

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