Secchi disk measurements have been an integral component of Minnesota's and Wisconsin's lake water quality assessment programs for some time; lake residents make periodic measurements and submit their readings to state and local agencies. The aggregated longitudinal data are used to reveal general trends in water quality. Similarly, the Indiana Clean Lakes Program trains and relies on volunteers to monitor turbidity in over 80 Indiana lakes using secchi disks, and uses data submitted by volunteers to monitor lake quality in the state.