In several previous meetings of the South Pacific Division of the Union, various reports concerning the San Dimas Experimental Forest were presented but were not subsequently submitted for publication. The present paper is therefore in the nature of a description of the project and a progress report of accomplishments to date. (Data included in this paper were tabulated and summarized by workers on WPA Project 765‐07‐3‐1.)The San Dimas Experimental Forest is situated on the south front of the San Gabriel Mountains northeast of Glendora, California, within the boundaries of the Angeles National Forest. It has a gross area of approximately 17,000 acres, including the drainage‐basins of Big Dalton and San Dimas Creeks tributary to the San Gabriel River. The Experimental Forest was established in 1933 as a branch of the California Forest ana Range Experiment Station of the United States Forest Service and comprises the principal field‐unit of a comprehensive research program in the field of watershed‐management (forest‐influences) in the California region. The objectives of the research program as it applies to the San Dimas Forest are twofold: (1) To study the influence of the chaparral vegetation, soils, geological structure, and other factors upon the yield of usable water; (2) to develop methods of managing or treating the chaparral watersheds to obtain a maximum yield of usable water with a minimum of dam