We may never see the likes of Lake Cahuilla again

PGEweather@pge.comSeptember 15, 2012 

Lionel Johnston is a retired ironworker who cares deeply about our environment. He has dedicated the past 20 years of his life to planting trees on the Central Coast. Earlier this year, he visited the Santa Rosa and San Jacinto Mountains National Monument in Southern California. After his visit, he told me a fascinating story of the largest lake in California, and I would like to share it with you.

Once upon a time the Gulf of California extended northward through the Salton Sea toward present-day Palm Springs. Over the ages the raging waters of the Colorado River carved out the Grand Canyon and carried slit, mud and sand into the Gulf of California (Sea of Cortez). At this time the Colorado River intercepted with the Sea of Cortez near present-day Yuma, Ariz.

Over the eons, the river deposited massive amounts of silt and sand into the gulf and created an enormous delta. This delta grew and eventually extended across the entire gulf to the Baja California Peninsula. This delta diverted fresh water from the Colorado River southward into the Gulf of California and created a vast landlocked sea.

Because of the dry and hot climate of this area, this inland sea evaporated and left behind an immense Salton basin. However, the ever changing weather cycles of El Niño and La Niña and the Pacific Decadal Oscillation — that increases or decreases the El Niño and La Niña effect — created prolonged droughts and massive floods.

The debris from these floods diverted the Colorado River from its course. Instead of flowing southward into the Sea of Cortez, the river’s waters were diverted northward into the Salton Trough and created ancient Lake Cahuilla. This freshwater lake covered an area of more than 1,000 square miles, including the present Salton Sea along with parts of the Coachella, Imperial and Mexicali valleys. It was more than six times the size of Lake Tahoe.

But like the ancient landlocked sea, the lake would also eventually evaporate until the next massive flood diverted water back into it.

This cycle of the drying out and filling up continued for thousands of years.

In the 1600s, the lake experienced its last high water mark, about 42 feet above sea level. Because this basin is mostly below sea level, parts of the lake exceeded 300 feet in depth. If Lake Cahuilla formed today, it would flood many towns in the area, including Indio, El Centro and Mexicali.

The Cahuilla people took advantage of these wet cycles for thousands of years.

Chief Francisco Patencio, who lived in the 1800s, said, “The water came standing high with great waves rolling over and over as it came and with the water came the fish.”

The Cahuilla people constructed traps in the rocks on the shoreline to harvest this abundant supply of food. These fish traps can be still be seen along the ancient shoreline.

In the early 1900s, Lake Cahuilla was in a dry cycle. In 1905, a strong El Niño year, the Colorado River flooded and burst through a diversion dam constructed for irrigation canals. The Colorado River flowed into the Salton basin and created the present-day Salton Sea. Since that time, the Salton Sea has receded about 10 feet because of evaporation. During the economic depression years of the 1930s, Hoover Dam was constructed and tamed this part of the Colorado River. The dam now prevents large debris flows required to divert the river. Without these large debris flows, Lake Cahuilla will likely never develop again.

Last week, the Salton Sea made national news. The sea had a fish die-off, and combined with 60 mph winds associated with intense thunderstorms, churned up the water on the bottom of the sea and unleashed bacteria from the sea floor. The smell of rotten eggs, or hydrogen sulfide, spread throughout many parts of Southern California. The smell was reported as far as Lancaster.

Sometimes along the Central Coast, when the winds are blowing from the ocean to the shore and are just at the right speed, not too fast or too slow, they can bring the pungent smell of droppings from pinnipeds and birds from the offshore sea-stack rocks that dot the San Luis Obispo County coastline. Quite a smell indeed.

Today’s forecast

The charts and models are still consistent in leaving the eastern Pacific high quasi-stationary for at least another few weeks. So our weather pattern should change little during this time frame. However, some monsoon moisture from post-tropical Kristy could stream over our area Monday into Tuesday, but rain is not expected.

The marine stratus will clear from the coastal valleys and southwesterly facing beaches (Cayucos, Avila Beach and Shell Beach) by the late morning hours and from the westerly facing beaches (Pismo Beach, Grover Beach and Cambria) by the early afternoon hours. The northwesterly facing areas (Morro Bay, Los Osos, Montaña De Oro and the Nipomo Mesa) will be slower to clear by the late afternoon hours.

Today’s high temperatures will range from the mid-60s along the westerly facing beaches. The southwesterly facing beaches will reach the low 70s, while the northwesterly facing areas will see high temperatures range between the high 50s to low 60s. The North County will reach the high 90s, while the coastal valleys will reach the high 70s.

The high pressure ridge that produced the above-normal North County temperatures will begin to move eastward as an upper-level trough begins to form off the coast. The trough of low pressure will keep locations along the beaches and in coastal valleys at below-normal temperatures while the North County locations will still experience above-normal temperatures.

Temperatures are expected to warm heading into next weekend as the ridge of high pressure will build in from the east; however, extreme heat is not forecasted at this time.

Today’s surf report

Fresh to strong (19- to 31-mph) afternoon northwesterly winds will continue to generate a 2- to 4-foot northwesterly (320-degree deep-water) sea and swell (with a 4- to 9-second period) through Tuesday.

Strong to gale force (25- to 38-mph) afternoon northwesterly winds will generate a 3- to 5-foot northwesterly (320-degree deep-water) sea and swell (with a 4- to 7-second period) starting Wednesday and continuing through Friday.

Arriving from the Southern Hemisphere: A 1- to 2-foot Southern Hemisphere (190-degree deep-water) swell (with an 18- to 20-second period) will arrive along the Pecho Coast on Tuesday, and will peak Wednesday at 1 to 3 feet (with a 16- to 18-second period). This swell will gradually decrease Thursday into Friday.

Seawater temperatures

Seawater temperatures along the immediate shoreline will range between 55 and 58 degrees through Friday.

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PG&E delivers some of the nation’s cleanest electric power. More than half of the electricity the company provides to customers comes from sources that are renewable and/or emit no greenhouse gases.

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If you have any questions or comments about weather or this column, I would love to hear from you. You can also subscribe to my daily weather forecast by emailing me at PGEweather@pge.com.

John Lindsey’s column is special to The Tribune. He is a media relations representative for PG&E and longtime local meteorologist.

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