NowCasting: Our New App to Predict Water Quality

Aug. 2, 2016 — A day at the beach shouldn’t make you sick, writes Ryan Searcy, our new beach water quality modeler. He’s totally stoked about NowCasting — our new method for predicting pollution levels at popular beaches.

Curious what the weather in Big Bear will be like this weekend? Whether there will be good surf at Malibu this evening? How bad traffic will be on the 405 during your morning commute? It’s easy to get answers to these questions, thanks to your trusty mobile device.

Well ocean-lovers, we have some good news to share: you can now add water quality at beaches across the state to the list of on-demand forecasts that are easily accessible from your phone!

Heal the Bay, in partnership with Stanford University and UCLA, has officially rolled out its NowCast tool in California, a new water-quality forecasting system that promises a whole new way of keeping swimmers safe at their favorite beaches. Thinking of hanging out at the beach near Santa Monica Pier this weekend? Now you can find out that same day if it’s safe to swim or not before making the long drive (or Metro trip) out west.

NowCast Excel SpreadsheetNowCasting is a technique that uses predictive statistical models to forecast water quality at a beach based on observed environmental conditions — such as rainfall, waves, tides and past bacteria concentrations. Just as the weatherman on the 11 p.m. news predicts if it will be sunny for your birthday tomorrow, Heal the Bay’s staff scientists are able to predict if it is safe to swim at a given beach on any given morning.

Under the current monitoring protocol, health officials determine if a beach is safe or not by sampling for indicator bacteria (organisms whose presence suggests that other, more harmful bacteria and viruses are also present). Unfortunately, monitoring results do not come back from the lab for 24-48 hours.

In that time, beach conditions may very well have changed from when the sample was taken, potentially exposing ocean users to bacterial pollution. Additionally, most beaches in California are only sampled for bacteria once a week, leaving it to the public to decide whether to recreate or not based on days-old information.

Our new NowCast program fills these gaps.

Using years of environmental and bacteria sampling data, our team has developed complex models to predict the concentration of indicator bacteria on a daily basis. If the bacteria level is predicted by the NowCast system to be above the acceptable standards set by the state, then water quality is assumed to be poor, and a beach posting is recommended. A new prediction will then be made the following day. And the day after that…

Arroyo Burro Beach, courtesy of Damian Gadal, FlickrThese models are also more accurate than the current method of waiting 24 hours for results to come back from the lab. We launched a pilot program last summer as a proof-of-concept test, and the results were very positive. While we don’t (yet) have the telekinetic powers to predict sewage or oil spills, our models still do a pretty good job of notifying the public each day about local beach conditions.

Over the last few decades, water quality in the Santa Monica Bay (and across the state) has improved dramatically. However, there is still much work to be done to clean up our beaches and reduce the number of swimmers, surfers, divers and other ocean users that get sick.

Predictions are made every morning during the summer based on current environmental conditions. Local health agencies can then use these predictions to notify the public of water conditions before most people arrive to the beach. For the remainder of this summer, you can find NowCast predictions for the following five beaches:

  • Arroyo Burro (Hendry’s) in Santa Barbara
  • East Beach (near Mission Creek) in Santa Barbara
  • Santa Monica Pier
  • Belmont Pier in Long Beach
  • Doheny State Beach in Orange County

Arroyo Burro, Santa Monica Pier, and Doheny State Beach were on our radar last year, and all had models that performed well. East Beach and Belmont Pier were added on this year because of good data availability and plenty of willingness from the local health agencies to help implement the program. Over the next three years, we plan to add an additional 15-20 beaches and expand the program across California — from the breezy beaches of San Francisco to the classic surf spots of San Diego.

Ryan Searcy - Beach Water Quality ModelerOur philosophy at Heal the Bay is that no one should get sick from a day at the beach. To make a decision about which beach is best for them and their family, people should be armed with the most accurate and timely water quality information available. Think of the water quality NowCast just as you do sunscreen – protect yourself from poor water conditions before you get in the water. You should be catching waves, not bugs!

Download our beach report card app on your mobile device or head to beachreportcard.org to find daily predictions for all of the NowCast beaches mentioned above. You can also access the lastest grades for our full complement of beaches that we monitor each week statewide — more than 400 beaches up and down the coast!

Download the Beach Report Card App from the App StoreDownload the Beach Report Card App from Google Play