Estimation of Evapotranspiration from Bioretention Areas Using Weighing Lysimeters

In moving toward a water balance approach to storm water management and the modeling tools that can support such an approach, it is clear that there are substantial gaps in our knowledge of the groundwater recharge and evapotranspiration (ET) in urban areas. At a microscale, weighing lysimeters can be used to estimate the ET and may also be designed to also allow drainage (groundwater recharge) to be quantified. A weighing lysimeter has been designed and constructed in Guelph, Ont. to quantify the ET and groundwater recharge from a bioretention area. The results at this scale will vary with the urban surroundings, but will nevertheless contribute to the scant information available. The installation of similar systems in various urban micrometeorological conditions will help to build a database of urban ET and recharge. Other approaches, such as the eddy correlation approach for the ET, are also needed to complement microscale measurements.