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Earth Sciences



The Earth Sciences Department welcomes your comments and questions.
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Judd Curran

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 Natural History

San Diego is rich with natural history.  Below are images of the flooding which occurred in 1916.  This was  prior to the Mission Bay Development plan to redirect the San Diego River.

Image of a bridge washed out during a flood.

Image is the property of: Journal of San Diego History (San Diego Historical Society),  San Diego River 1916.

1916 flood, San Diego, CA.

Above: The 1916 flood wiped out the Old Town bridge that crossed the San Diego River at the western end of Mission Valley.  Image is the property of:

The plan was drawn up and work began in May of 1948 on the project to redirect the San Diego River through Mission Bay.

Illustration of the plan to redirect the San Diego River through Mission Bay.

Below, 50 years later in 1999, Mission Bay reflects the success of the redirect project.

View of Mission Bay 1999 

Image: California Coastal Records Report
View the complete presentation online (*warning: Be Patient: 9MB page-load time to view this presentation)

Below: Images of the damage to Sweetwater Dam (left),  and Otay Dam (right), San Diego, CA.  1916.

Sweetwater Dam, 1916  The flooding resulted in complete failure of both structures.  Otay Dam, 1916.

Images are the property of: Journal of San Diego History (San Diego Historical Society)

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Water resources have historically been an important part of San Diego History.  Earth Sciences explores the relationships between water, land, climate, and people. Below is a timeline of events related to water resources in San Diego.

Timeline: San Diego

Modified from:


Hoping to improve agriculture yields, the Franciscan missionaries organize construction of the first water engineering project on the west coast of the United States. The first dam to cross the San Diego River is located in present day Mission Trails Regional Park.

San Diego River is diverted from San Diego Harbor into False Bay (Mission Bay) under the harbor improvement plan of Lt. George Derby. The "Derby Dike" failed after two years and the river returned to depositing sediment into San Diego Bay until another levee was constructed in 1876.

Mission Dam falls into disrepair. San Diego's population is clustered around wells at the mouth of Mission Valley.

Storms dump 30 inches of rain on San Diego. Statewide the storms destroy 25% of California's taxable property.

Successive years of light rains bring severe drought to San Diego.

The first wells are sunk in downtown (new town) San Diego.

H.M. Covert and Jacob Gruendike initiate the first major waterworks since mission days forming the city's first water company (San Diego Water Company) on January 20th. Wells drilled in Pound Canyon near site of the present Cabrillo Bridge provide the first reliable water supply for the city. Two reservoirs are constructed on mesas bordering the canyon with a total capacity of 170,000 gallons.

Increasing demands for water lead San Diego Water Company to tap water from Mission Valley. The first pumps raise water to a reservoir in University Heights. Construction soon begins on a more energy efficient route across a lower portion of San Diego Mesa. The new pipeline runs from wells near the mouth of Mission Valley through tunnels driven in the hills below the present site of the UCSD Medical Center. Pumps lift water to the crest of the mesa near the core of present-day Hillcrest. From there an aqueduct carries the water downhill to a reservoir at Fifth and Hawthorn.

Severe drought. A dike across the San Diego River is completed allowing some of the run-off of the river to be diverted into the city's water system.

San Diego Reservoir is constructed in what is now Presidio Park. Water pumped from Mission Valley supplies the reservoir which has a four million gallon capacity. It remains in use until 1912, and in 1927 it's filled forming the "Picnic Bowl"  bounded by Cosoy Way.


Sweetwater Reservoir is completed.

The 35.6-mile San Diego Flume is completed at a cost of about one million dollars. The flume, a series of five tunnels and 315 redwood trestles, carries water from Cuyamaca Mountain to the University Heights reservoir.

City covers over the abandoned Pound Canyon well citing danger of the deep well..

La Mesa Dam is completed. In 1918 it is superseded by a larger dam which forms Lake Murray.


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Lake Murray
Lake Murray 2007
George Chaffey begins irrigation of the Colorado Desert.      

The first water runs into Imperial Valley canals. San Diego purchases all water systems within the city limits.

Floods on the Colorado River bring disaster to Imperial Valley farmers creating the Salton Sea.  
Pumping plant in Mission Valley closes, and the city enters into a contract with Southern California Mountain Water Company to buy water (4 cents per 1000 gallons) from mountain reservoirs.
1912 After 17 years of construction Morena Reservoir on cottonwood creek, a tributary of the Tijuana River, is completed.
Southern California Mountain Water Company is purchased by city.
After four dry years in a row, former sewing machine salesman and fabled rainmaker Charles M. Hatfield offers to aid the city. San Diego City Council accepts his offer, and Hatfield erects a tower containing a secret chemical concoction near Morena Reservoir.

The worst floods in county history.

Jan.14 Heavy rains start falling in the county -- we know now this was a strong El Nino year. A total of 7.56 inches falls before the end of the month. (A normal January rainfall is 2.2 inches.))
Jan.17 Flooding washes away the bridges along San Diego River.
Jan.26 Fearing a break due to rising waters behind the old Switzer Canyon reservoir (in southeast Balboa Park) the city dynamites the dam creating a flood down 16th Street to the bay.   
 Jan.27 The dam at Sweetwater Reservoir fails releasing 13 billion gallons of water..
Feb.04  Charles Hatfield bills city $10,000 for filling Morena Reservoir.

 The city offers to settle tab if Hatfield accepts responsibility for $3,500,000 of damages caused by the flooding. Hatfield forgoes payment from San Diego, but continues to ply his rainmaking abilities in California and Central America for many years..

1918 Hodges Reservoir is completed across the San Dieguito River. The first dams were completed on Alvarado Creek to form the Lake Murray.
1924 Wohlford Dam is constructed on top of the 1895 dike on Escondido Creek. Combined capacity of the all counties reservoirs nears half a million acre-feet.
1935 El Capitan Reservoir is completed across the headwaters of the San Diego River. Hoover Dam is completed bringing control to the Colorado River. 
1938  Parker Dam is completed across the Colorado River forming Lake Havasu. Three years later, the Colorado River Aqueduct is completed. The aqueduct conveys Colorado river water from Lake Havasu to Lake Matthews in Riverside County.
1943 In anticipation of receiving Colorado River water, San Vicente Reservoir is built to significantly increasing storage capacity in San Diego County
1960 First pipeline of the San Diego Aqueduct is completed. The aqueduct taps into the Colorado River Aqueduct and delivers water from the Colorado to San Diego for the first time. In seven years another pipeline is added parallel to the original aqueduct. The combined capacity of the San Diego Aqueduct is 196 cubic feet per second (about 140,000 acre feet a year))