The New River (Spanish: Río Nuevo) flows north from near Cerro Prieto, through the city of Mexicali, Baja California, Mexico, into the United States through the city of Calexico, California, towards the Salton Sea. The river channel has existed since pre-historic times. The river as known today formed from a levee failure and massive flooding that filled the Salton Sea. The river flow mostly consists of agricultural runoff, municipal discharge and industrial wastewater. The river has been called the most severely polluted river of its size in the United States. Several projects have begun to reduce and mitigate the levels of pollution in the river, including upgrades to sewage treatment infrastructure and enclosure of the river channel.
Flow The New River channel begins at a volcanic lake near Cerro Prieto. Today this lake feeds the Cerro Prieto Geothermal Power Station. The river flows north 15 miles (24 km) through Baja California, and another 66 miles (106 km) through California into the Salton Sea, the largest lake in California. Flow at the border is approximately 200 cu ft/s (5.7 m3/s), and about three times more at the Salton Sea because of agricultural runoff collected along the way. The New River's flow is composed of agricultural and chemical runoff waste from farm industry irrigation in the U.S. (18.4%) and Mexico (51.2%), sewage from Mexicali (29%), and manufacturing plants operating in Mexico (1.4%). Where New River crosses the Mexico–U.S. border near Calexico, California, its channel contains a stew of about a hundred contaminants: volatile organic compounds, heavy metals including selenium, uranium, arsenic and mercury, pesticides (including DDT), and PCBs. The waterway also contains pathogens that cause tuberculosis, encephalitis, polio, cholera, hepatitis and typhoid; levels for many of these contaminants violate United States Environmental Protection Agency (EPA) and Cal/EPA standards by several hundredfold. Fecal coliform bacteria have reached 100,000 to 16 million colonies per milliliter at the border checkpoint (possibly more, as this is the measuring capacity threshold), far above the U.S.–Mexico treaty limit of 240 colonies. In 2017 monthly samples from the New River ranged from 12,000 to more than 160,000 per 100 milliliters. California considers water safe for swimming at 400. Highly polluted inflow to the New River and agricultural runoff has resulted in elevated bacterial levels and large algal blooms in the Salton Sea. Lacking an outlet for its water, the Salton Sea's salinity has increased by approximately 1% per year. Increasing water temperature, salinity and bacterial levels led to massive fish die-offs in 1992, 1994, 1996, 1999, 2006, and 2008, and created ideal breeding grounds for avian botulism, cholera and Newcastle disease, leading to massive avian epizootics 1992–2019. The Salton Sea has a salinity of 4.4% (4.4 parts per 100), making it saltier than ocean water (3.5% for Pacific). Many fish species can no longer reproduce or survive in the Salton Sea. Tilapia may be the only fish species able to persist there for a limited time. Without restoration, the Salton Sea will likely increase in toxicity and remain an ecological trap for avian species. Toxic levels of PCBs, DDT, and DDT byproduct DDE regularly appear in sediment samples taken between 2002 and 2012.
History The modern courses of the New River and the Alamo River, and the creation of the Salton Sea, date from the autumn of 1904 when heavy rainfall and snowmelt caused the swollen Colorado River to overrun a set of headgates for the Alamo Canal. The resulting flood poured down the canal and breached an Imperial Valley dyke. The sudden influx of water and the lack of drainage from the basin formed the Salton Sea; the rivers had re-created a great inland sea in the Salton Sink, which had frequently flooded. Nearly two years passed before workers could control the Colorado River's flow and stop the flooding, but the river was effectively dammed in the early part of 1907 and returned to its normal course. The flood significantly enlarged the channels of the New and Alamo Rivers. Some water still flowed after the dyke was repaired, as the larger channels collected and carried agricultural runoff to the Salton Sea.
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