The marshes and streams between the United States and Mexico, just east of the Pacific Ocean, are often cluttered with trash and clogged with raw sewage after rains. The runoff and jetsam aren't just one country's fault, but represent problems caused by both countries.
But an unprecedented agreement between the United States and Mexico to clean up the Tijuana River Watershed, which extends across the international boundary, may be the beginning of a new era on the western edge of the border.
At least, that's what environmentalists are hoping.
The agreement, called Minute 320, is an addendum to the 1944 US-Mexico water treaty between the United States' International Boundary and Water Commission (IBWC) and Mexico's Comisión Internacional de Límites y Aguas, or CILA. Both agencies govern water rights along the length of the international boundary.
The original treaty covers the Colorado River, the Rio Grande, and the Tijuana River basins. Until now, the Tijuana River has received far less attention than the other two. However, sediment and debris are a huge problem in the river area and along the coast, where international policies create pollution by encouraging border development, and prevent its cleanup by enforcing border security.
Minute 320 provides a long-overdue method by which both countries can work together to address water pollution in the San Diego-Tijuana region, said Sally Spener with the IBWC.
"Because this is a transboundary watershed, we realized that we needed to be cooperating, and looking at solutions so that we could understand upstream and downstream impacts in both countries," Spener said. "I think it enhances our ability to share information and talk about what's going on in both countries."
While Minute 320 does not allocate funds, it does formalize the process of looking at the Tijuana River basin as a whole, rather than a region split down the middle by the international border. Environmentalists say they find that especially encouraging.
"The primary focus of this minute is to look at the Tijuana River watershed as a unit, and to focus on sediments and trash, and water quality in general," said Christopher Peregrin with the Tijuana River National Estuarine Research Reserve.
The Tijuana River Valley is part of a natural flood plain within the 1,700 square miles of watershed, and it is serviced by one tiny pump station on the Mexico side. The station was built to divert water and keep Mexican sewage within Mexico's borders, but whenever heavier than usual rains fall, the pump goes offline to protect and clean its channels, creating an enormous problem on both sides of the border.
"Three hours of rain last Sunday, and south Imperial Beach [in San Diego County] has been closed since, because immediately there was so much water from the Tijuana River that it overflowed," said Fay Crevoshay with Wildcoast and Costasalvaje, a trans-border conservation group that works to preserve biodiversity in California and Baja California. "They didn't turn [the pump] on, so all the water got to the ocean in Tijuana, then the U.S."
She said that those few hours of rain underscore the need for Minute 320 and the importance of an international partnership to fight contamination. The issue of transborder pollution is becoming front and center in the face of a looming El Niño, which climate scientists now say could be one of the largest in recorded history.
"Eighty percent of beach closures have to do with this type of event," said Crevoshay. "Water knows no boundaries."
The minute also establishes the creation of a "Binational Core Group," which would consist of government agencies, nonprofit groups, and local participants to discuss and work together to protect the coastal and marine areas around the international border.
Minute 320's signing comes during Tijuana River Action Month, a series of events held by every year by a coalition of community groups and non-governmental organizations between mid-September and mid-October to advocate for the protection and restoration of the Tijuana River wetlands.