About the Symposium


The purpose of the California Extreme Precipitation Symposium (CEPSYM) is:

  1. To attract professionals from diverse disciplines interested in the impacts of extreme precipitation upon society and the environment,
  2. To focus attention on precipitation extremes in California,
  3. To share technical and scientific information and knowledge about the various factors responsible for producing extreme precipitation and the hydrologic processes responsible for generating runoff,
  4. To advance our understanding of the causes of extreme precipitation with the hope of increasing the planning and warning time in advance of extreme precipitation ranging from droughts to floods, and
  5. To exchange information on engineering, water resource management, flood risk management, agricultural, and other needs for information on the impacts of extreme precipitation.

The purpose of CEPSYM has evolved since its beginning in 1994. Our scientific understanding of what causes extreme precipitation events in California and along the western coast of North America has advanced over these years. Now we understand the importance of atmospheric rivers (ARs) for producing extreme precipitation events which cause flooding and without ARs we experience droughts.

The Symposium is designed to be an informal setting for an interesting day of scientific and technical presentations with time for questions and answers. The cost is kept low to encourage participation by a diverse audience.


The first Symposium was convened in 1994, and held annually thereafter (except for 2000). From 1994 to 2003, the Symposium was known as the California Weather Symposium. The name was changed in 2004 to California Extreme Precipitation Symposium to acknowledge our emphasis on extreme precipitation. From the initial gathering of 55 weather aficionados, participation has grown to over 200.

Over the years our primary focus has been on precipitation responsible for floods. Flooding is of primary concern to government agencies responsible for protecting life and property located in California's floodplains and the private sector professionals assisting them.

In 2003, the Symposium was invited to be part of the larger Lower American River Science Conference and in 2005 and 2007 the American River Watershed Conference, each organized by the College of Natural Sciences and Mathematics, California State University, Sacramento.

2015 International Symposium on California Extreme Precipitation

Part of poster for the event; click to see full poster

Gary Estes, the Founding Coordinator of the California Extreme Precipitation Symposium, and Matt Fleming, a speaker from the 2014 Symposium, with the Hydrologic Engineering Center of the U.S. Army Corps of Engineers, were invited as speakers for the International Symposium on California Extreme Precipitation. The event, sponsored by the Japan Society of Hydrology and Water Resources, Disaster Prevention Research Institute, Kyoto University, and the Japan Civil Engineers Consultants Association, was held in Tokyo, Japan, on February 7, 2015.

The purpose of this International Symposium was to increase efforts to share scientific knowledge among private, government, and academic sectors in order to prepare against atmospheric river-induced disasters.

The English version of each of the presentations is available here: