Effect of Soil Type and Vegetation on the Performance of Evapotranspirative Landfill Biocovers: Field Investigations and Water Balance Modeling

The water balance performance of evapotranspirative landfill biocovers (ET-LBCs) under Canadian cold climate conditions is evaluated by constructing seven lysimeters at a field site in Alberta, Canada, and monitoring water balance for 1 year. Two granular media types (topsoil and compost mixture) and three types of vegetation (native grass species, alfalfa, and Japanese millet) were used. The results suggested that as plants became established, the average percolation as a percentage of water input [percolation ratio (PR)] decreased in all lysimeters. Between the lysimeters subjected to rainfall simulation events, the lysimeters with Japanese millet transmitted the lowest amount of percolation (10%-17%), followed by native grass species (23%-28%), and alfalfa (25%). Under the same vegetation coverage, lysimeters with a compost mixture transmitted lower or equal percolation compared with lysimeters with topsoil. Water balance predictions made using Hydrus-1D and commercial model SEEP/W were compared with water balance data from lysimeters over the growing season. The predictive capabilities of the models decreased under high intensity rainfall events and with the occurrence of preferential pathways associated with plant roots. (c) 2020 American Society of Civil Engineers.