In 1977 the US State Agricultural Experiment Stations (SAES) began a nationwide project to monitor atmospheric deposition and study its effects on the environment.  This project is titled the National Atmospheric Deposition Program (NADP). The NADP precipitation chemistry network, which began in 1978, has the goal of providing data on the amounts, trends, and geographic distributions of acids, nutrients, and base cations in rainfall.  NADP site CA45, located at HREC, has collected some of the cleanest rain water in the nation due to the fact that most moisture in our storms is derived from moisture over the Pacific Ocean (not many industrial plants out there!).