An ongoing severe drought in California highlights the importance of understanding and predicting multi-year swings in moisture availability on the scale of large watersheds. The 20th and early 21st centuries have seen large oscillations with an average period of about 15 years in annual flows of the Sacramento and San Joaquin Rivers, two major sources of water supply for the state of California. A meeting sponsored by the California Department of Water Resources (CADWR) was held in La Jolla, California, this past May specifically to address hydrologic and climatological aspects of the rh