Hydrological inputs and outputs determine water depth, flow patterns, and duration and frequency of flooding. The seasonal pattern of changes in a wetland’s water level is called the hydroperiod. Year-to-year variability of hydroperiod is related to climate and site specific conditions. Hydrologic conditions primarily affect abiotic factors such as nutrient availability, soil chemistry, and water chemistry which all, in turn, determine the biotic components (species composition, species richness, primary productivity) of wetland ecosystems. Wetland hydrology (water level) at PEI National Park is sampled in four basin marsh ponds using in-situ Onset HOBO U20 water level loggers. Five informative parameters pertaining to fundamental hydrological characteristics are measured: mean daily water level, magnitude of annual min/max water level difference, Julian date of annual minimum water level, Julian date of annual maximum water level and Richards-Baker Index (RBI) – standardized daily fluctuations are calculated annually (based on May 1 – April 30 water year) for each site.