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April 27, 2011

Increase in Dry Weather Tijuana River Flow Causing Increased Beach Closures

By Paloma Aguirre

Increase in dry weather Tijuana River flow cause for water quality concern in south San Diego beaches during spring break.


The Tijuana River a binational seasonal river only flows during or after rainfall. It should not flow during dry weather. Unfortunately there has been an abnormal dry weather flow. It is suspected that this increase in flow may be due to several factors:

1. Treated clean effluent being discharged into the main Tijuana River channel by  the newly constructed Mexican waste water treatment plants Arturo Herrera and La Morita respectively. Daily discharge is 7 Million Gallons per day.

2. High water tables due to unusually high rainfall this year, causing less soil infiltration.

3. The recent channelization of the Alamar creek, a tributary to the Tijuana River. Channelizations prevent water from naturally infiltrating the soil and convey water at a faster and higher rate.

4. Potential spillage from the U.S. Barret Dam due to it being at 100% capacity (because of high rainfall)

These are one of many factors that may be contributing to the increase in Tijuana River flow.

During dry weather a pump station is turned on and redirects this cross-border flow over to Punta Bandera, another treatment plant south of Playas de Tijuana, Mexico and preventing it from coming across the border. The capacity of this diverter system used to be only 12 MGD, but efforts made by different agencies inculding the EPA and the Tijuana State Public Services Comission increased its capacity to 23MGD.

But a lack of clear policy in the binational International Boundary and Water Commission agreement between the U.S. and Mexico to clarify when this diverter system should be turned on or off is of great concern to WiLDCOAST because regardless of where the point source of this pollution is the fact remains that there should be no cross-border flow during dry weather especially is the flow level is less than 25 MGD.

According to data provided by the Department of Environmental Health there has been a significant increase in beach closures during 2010 compared to 2009.

Imperial Beach shoreline closures:

  Total  2009= 18 days   

  Total  2010= 69 days  


Border Field State Park and TJ Estuary closures:


 Total  2009= 127days   

 Total  2010= 224 days

Samples taken yesterday by the Department of Environmental Health showed levels hazardous to human health:


                                                                              PC                           Entero

Imperial Beach   S End of Seacoast.                               >16,000                    453

Imperial Beach   Cortez St.                                             5000                       42

Imperial Beach Pier                                                       2400                       31


Acceptable levels                                                             400                         104


"Entero" short for Enterococci are a type of germ present in the intestines of warm-blooded animals. Their presence in large numbers is a sign that the water they are in may be contaminated by excrement and possibly contain other disease-bearing pathogens.

PC or poly coliform are also a bacteria present in the digestive tract of humans or animals.

Indicator bacteria such as these normally take 24 hrs to produce test results. This is of great concern because beach-goers and ocean users may find out a day later that they had been swimming in contaminated water the day before.

The San Diego County Department of Environmental Health uses additional tools (such as field observations, odor reports and wind/swell/current  direction and river flow to determine whether to issue a beach closure as a preemptive measure while waiting for test results.


Current beach status for April 27, 2011:





Here is a link to real time monitoring of the Tijuana River Flow and ocean-plume direction:


For the latest beach status updates follow: