Comparison of Field Data and Water-Balance Predictions for a Capillary Barrier Cover

Abstract

Predictions of surface runoff ͑R͒, evapotranspiration ͑ET͒, soil-water storage ͑S͒, and percolation obtained using three numerical codes ͑LEACHM, HYDRUS, and UNSAT-H͒ employed to simulate the hydrology of water-balance covers are compared to measured water-balance data from a lysimeter used to monitor a capillary barrier cover profile in a subhumid climate. All of the codes captured the seasonal variations in water-balance quantities observed in the field. LEACHM and HYDRUS predicted total R during the monitoring period with reasonable accuracy ͑within 18 mm using general mean parameters͒, but the timing of predicted and observed R events was different. In contrast, UNSAT-H consistently overpredicted R by at least 239 mm. Evapotranspiration was predicted reliably ͑within 60 mm͒ with all three codes when data from the first year were excluded. However, all three codes overpredicted ET in late winter and early spring, when snowmelt was occurring and S was accumulating in the field. Consequently, S generally was underpredicted by all three codes. Predicted and measured percolation were in good agreement ͑within 1 mm/ year͒, except during the first year. Results of the comparison indicate that cover modelers should scrutinize runoff predictions for reasonableness and carefully account for snow accumulation, snow melt, and ET during snow cover.

Field-scale spatial variability of saturated hydraulic conductivity on a recently constructed artificial ecosystem

“…A key strategy to minimize the migration of pollutants is the use of engineered covers (Albright et al, 2006;Bohnhoff et al, 2009;Ogorzalek et al, 2008). Covers are designed to serve multiple purposes, which include supporting a stable vegetation community that closely resembles natural ecosystems and minimizing deep drainage into buried wastes, both by enhancing soil moisture storage in the top layers, and increasing transpiration and evaporation (Ogorzalek et al, 2008).…”

“…Most of the existing water balance modeling studies for engineered covers rely on K s estimated from pedotransfer functions (PTFs) derived for natural soils or few point measurements which fail to characterize the spatial heterogeneity of the site (e.g. Bohnhoff et al, 2009;Ogorzalek et al, 2008). Comparative hydrological prediction of the artificial Chicken Creek using ten different models clearly demonstrated the impact of hydraulic properties and their estimation on water balance components (Holländer et al, 2009).…”

Sustainable Reuse of Mine Tailings and Waste Rock as Water-Balance Covers

“…Water-balance modeling was completed in this study using the code WinUNSAT-H, which simulates variably saturated flow, root water uptake, and climatic interaction [24][25][26][27]. WinUNSAT-H is an implementation of the variably-saturated flow code UNSAT-H [28] used for near surface hydrology.…”

“…WinUNSAT-H is an implementation of the variably-saturated flow code UNSAT-H [28] used for near surface hydrology. When properly parameterized, WinUNSAT-H provides a reliable prediction of hydrology for WBCs, and modestly overpredicts percolation [26,27,29]. Water-balance modeling is typically completed for climate conditions representative of the wettest years or wettest periods (i.e., 5 to 10 sequential years) on record [2].…”

Steady-state analytical model for vapour-phase volatile organic compound (VOC) diffusion in layered landfill composite cover systems

“…The volumetric water content θ w of the sandy layer ranges from 0.04 to 0.36 (Ogorzalek et al 2008;Abdolahzadehamir et al 2011;Vachon et al 2015;Ng et al 2015c). For CCL and protective layer, the ranges of volumetric water content are 0.1-0.58 (Ng et al 2015a (Kim et al 2001a(Kim et al , 2005.…”