Statewide assessments began in 1978, and have occurred every year since 1989. During this time over 150 reservoirs have been monitored. This has resulted in what may be the most complete, long-term study of reservoirs within an individual state. Through this effort we have gained a better understanding of reservoir water quality and the factors that influence it, as well as how water quality varies in the short (within summer) and long terms (year to year). The data generated through the Statewide Assessment helps the state meet Clean Water Act requirements for monitoring water quality, but more importantly, the knowledge helps agencies (DNR, MDC, local governments, etc.) identify problems and manage our lakes.