Ponds vs Wetlands - Performance Considerations in Stormwater Quality Management

Ponds and wetlands are commonly used in urban design to meet a number of urban planning objectives including the management of urban stormwater for water quality improvement. Ponds and wetlands are detention systems with their differences typically being reflected in their surface area to volume ratio and water level fluctuation. These differences influence a number of hydrologic, hydraulic and botanic factors of the detention system, which affect their performance in stormwater treatment. The detention periods of stormwater inflow into these systems are often used as a measure of the performance of these facilities as pollution control systems. However, it is widely recognised that other factors such as the flow hydrodynamics within the detention system and vegetation density and layout can have a significant influence on the performance of these facilities. The appropriate selection of ponds and wetlands for stormwater treatment requires a balance of the advantages and disadvantages of these systems as stormwater quality treatment facilities. This is dependent on the type and priority of pollutants to be removed and the association of these pollutants to the particle size fractions of stormwater sediments. This paper discussed the various issues and performance considerations associated with the comparison of ponds and wetlands for stormwater pollution control.