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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?

A water quality nowcast provides information similar to a daily weather forecast except the nowcast predicts good or poor water quality for the day at specific beaches. The nowcasts are based on the results of predictive computer models that estimate fecal bacteria levels in the surfzone. Local agencies can compare the computer 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 the model estimates bacteria levels that exceed the health standards, the water quality nowcast is “Good”, however, if the model estimates exceed the health standard, the water quality nowcast is “Poor”.

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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 and Stanford University, 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.

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How are the daily nowcast from the models different from the Heal the Bay Beach Report Card Grades?

The water quality nowcast of fecal bacteria levels at a beach takes into account current environmental conditions and historic bacteria levels to estimate fecal bacteria levels at the beach. The Beach Report Card provides weekly grades every Friday throughout the year based on the last 30-days worth 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 takes into account current conditions at the beach (usually each morning), the Heal the Bay grades take a longer look back in time to look at the average conditions. Both pieces of information are important to the beach-goer assessing beach water quality because fecal bacteria levels can vary considerably over short-time periods. Water quality nowcasts 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 Water Quality 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 provide daily water quality nowcasts 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 factors such as rainfall, tide levels, solar radiation, wind, storm drain flows, and swell conditions. Because the effect of these factors on water quality varies from beach to beach, site-specific models are developed for individual beaches.

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How Accurate are the Models?

The predictive models generally perform as well as, or better than, the current method that relies on waiting for laboratory analysis of water quality samples to determine if the water is safe for swimming. 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 compared to the current method of collecting a water sample and then waiting for the laboratory analyses.

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Are there Shortcomings to Using Nowcasts based on Predictive Models?

Predictive models are developed to capture variations in beach water quality caused by changes in environmental conditions but are not able to predict unusual events such as a sewage spills.

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Are Predictive Models being used at other Beaches?

Yes, in the U.S. predictive models are used for daily nowcasts in the summertime at several beaches on the Great Lakes including beaches in Ohio, 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 at Hong Kong coastal beaches where the predictive models accurately predict 30-70% of water quality standard exceedances, and can reduce 27% of illnesses caused by swimming in contaminated beach waters.

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What does 'NP*' - No Prediction mean on the Home Page Slider?

A water quality prediction has not been made today for this beach. There are a couple of reasons for this outcome, such as 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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Why do a Pilot Test? What Beaches are Involved?

The goal of the pilot test is to determine how well nowcasts based on predictive models can be integrated into existing programs run by local beach health agencies in California. Also the models will be assessed to see how accurately they predict water quality on a day-to-day basis. The pilot test will run from Memorial Day weekend to Labor Day at three California beaches: Arroyo Burro Beach in Santa Barbara County, Santa Monica Pier Beach in Los Angeles County, and Doheny State Beach in Orange County. These three beaches were chosen because they have a history of variable water quality, and researchers developed and tested models for the three beaches based on historic water quality data. The pilot will test the performance of the models and determine if models can be run everyday before 10 a.m. to provide a timely prediction of beach water quality.

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Who is doing the Pilot Project?

Heal the Bay has been funded by the California State Water Resources Control Board to facilitate the development of predictive models at beaches and to pilot test the models. Heal the Bay has partnered with researchers at Stanford University to develop the models and test them. Santa Barbara County Public Health, Orange County Environmental Healthcare Agency, and the Los Angeles Department of Public Health have volunteered to participate in the pilot test.

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

Beach-goers will have easy access to predictive forecasts on Heal the Bay’s beach report card website starting on July 6th 2015 for the pilot project beaches: Santa Monica Beach, Doheny State Beach, and Arroyo Burro Beach. Information and links to the forecasts are also on the participating health agencies webpages: Orange County Health Care Agency, Los Angeles County Department of Public Health, and County of Santa Barbara Department of Public Health

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The Beach Water Quality Predictive Modeling Project is a pilot study to investigate the suitability and operational feasibility of using the predictive system to inform beach management decisions. 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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