UCLA Special Collections has extensive holdings related to water, as well as materials documenting agriculture, real estate development, and oil in Southern California.
Finding aids for collections related to natural resources can be found in the Online Archive of California.
The collections listed below are among the most important ones documenting water resources, but materials related to water can be found in many other collections as well. Prominent among these are the Mayor Tom Bradley Administration Papers (Collection 293) and the John Randolph Haynes Papers (Collection 1241).