Focusing on Our Delta: Diked, Dredged, and Diverted - April 3, Berkeley
The Sacramento-San Joaquin River Delta is an expansive inland river delta and estuary, formed by the convergence of five major rivers, including the Sacramento and San Joaquin rivers (see map). Water from the western side of the Sierra Nevadas, the southern reaches of the Cascades, and the coast range are funneled through this river system forming a watershed that covers thousands of square miles. The delta is unusual in its shape in that the fan converges (rather than diverges) as the waters exit the Central Valley via the narrow channel of the Carquinez Strait and then empty into the San Francisco Bay, through the Golden Gate and ultimately the Pacific Ocean.
For thousands of years, huge areas of the Delta flooded with each spring melt. However, starting in the late 19th century, hundreds of miles of levees were constructed by Chinese workers in an effort to control flooding and to preserve the land for farming. These laborers were replaced by steam-powered dredges in the late 1870s, and by the 1920s nearly all the marshland had been reclaimed and many waterways were expanded for navigation.
The Delta today:
As a natural system:
Californians rely on the Delta as a primary source of our drinking water and our major highways, railways, gas and electricity lines cross over and through the region. But as important as the Delta is, it is also at extraordinary risk. Much of the land in the region has subsided and now rests below sea level. It is protected only by a complex and aging system of levees threatened by earthquakes, river floods, climate and sea level change. Following the disaster that struck New Orleans, there is a renewed focus on how to strengthen the levee system and to protect the Delta region that is so vital to the entire state.
Delta - a fan-shaped area at the lower end or mouth of a river, formed by eroded material that has been carried downstream and deposited
Estuary - A semi-enclosed body of water with one or more rivers flowing into it and what connects to the open sea. The water is brackish as seawater is diluted by fresh water and there is usually a high rate of biological productivity.