Lysimeters versus Actual Earthen Caps: Numerical Assessment of Soil Water Storage

Lysimeters are commonly used for field-scale assessment of water balance of earthen caps, commonly referred to as evapotranspirative (ET) caps. While lysimeters are the only direct tool to measure percolation through a cap, the lower hydraulic boundary of a lysimeter is significantly different compared to an actual ET cap. In this study, numerical simulations of water balance of lysimeters and ET caps were carried out using Vadose/W for a range of hydraulic properties of the soils and waste. The numerical results suggest that due to the presence of waste below the cap, the soil water storage of an ET cap is greater than an equivalent lysimeter. This greater water storage capacity in an actual ET cap results in lower percolation than for an equivalent lysimeter.