HYDROLOGIC PROCESSES IN A SOUTHERN ONTARIO WETLAND

A 12 month investigation on the hydrology of a southern Ontario wetland was completed. The mass flux of water and concentrations of total phosphates, ortho-phosphates, and chlorides were measured in all components of the hydrologic budget; over 800 grab samples were analyzed. The study showed that both groundwater recharge and discharge could occur within a wetland; data on these opposing flows must be quantified in order to develop effective long-term wetland management strategies and to accurately determine nutrient budgets. The study concluded that theoretical formulae may greatly underestimate summer evapotranspiration rates for hydrophyte dominated marshes. Storm inputs of physio-chemical parameters were found to be very significant, accounting for 32 to 51 percent of the total surface water loadings; failure to measure and/or model these inputs would have greatly distorted the study findings. Finally, since flow rates and concentrations of the chemical parameters were less variable at the wetland outflow, it was concluded that the wetland moderates event response inputs into stable response outputs. Over the study period total phosphate imports were double that of total phosphate exports while the ortho-phosphate discharge from the wetland was 22 percent more than the inputs. This indicates that the wetland is transforming sediment-bound phosphate to plant available ortho-phosphate, thus contributing to downstream eutrophication problems.