Lakes, Ponds & Pools Master Page: Dams

For thousands of years mankind (and beavers) have been blocking streams and rivers to control flooding, or to store water in lakes and ponds. According to Wikipedia's article on dams, the earliest-known is the Jawa Dam in Jordan, dating to around 3,000 BC. The first written record of the word dam in English was in the 12th century.

San Diego's oldest dam, the Mission Dam, was built between 1809-1816. It sits across the San Diego River in Mission Gorge, and was originally 244-feet long, 13-feet thick, and 13-feet high. Like many dams, it's been rebuilt several times.

The newest dam project in the county was the raising of San Vicente in 2014. Here's a link to the project which raised the 220 foot dam by 117 feet, nearly doubled the reservoir's capacity and added about 500 acres to its area. Images from San Diego Water Authority.

View of the raised and completed dam (images thanks to the Water Authority)

DAM LOCATIONS

Dams originally were placed across running streams or rivers, and water backed up behind them. However, in Southern California we have almost no rivers, so dams are now used to create reservoirs (water holding places) wherever we can put them, including at the top of a mountain, such as the new Olivehain Reservoir. I have not yet visited this location so I am using a PR photo by P Konstantin:

Dixon Lake is another reservoir at the top of a steep climb into the mountains.

WATER LEVELS

Many of the San Diego lakes are intended to store water, and have substantial dams. People often think that a storm will fill up the reservoirs quickly, but when we compare the water levels over a few months surrounding our rainy December 2019, there's not THAT MUCH difference.

However, when you check the levels for San Vicente, it's picked up 13,000 acre feet which is (quick math) 4.2 billion gallons, or about 1200 gallons per person. Our per-capita water consumption in the City of San Diego is about 100 gallons a day. So we have added only 12 days of water use per person at San Vicente over the last 3 months.

Click here to see the current report.

Last updated Dec 2, 2019

Last updated March 11, 2020

Water levels vary for reasons you wouldn't suspect. At Morena the water is low because its only source is rainfall, and thus it is "free" to the city. At Hodges the water is kept relatively low because the dam is very old and in questionable condition.

DAM MANAGEMENT & REGULATION

I found a National Inventory of Dams website, operated by the Army Corps of Engineers.

This online resource supplies a great deal of data: dam owner, watercourse being blocked, surface area, capacity, length, height and age of a dam, etc. Here is a summary of San Diego dams: