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

• Published in: Journal of geotechnical and geoenvironmental engineering Vol. 134; no. 4; pp. 470 - 486
• Main Authors: Ogorzalek, A. S, Bohnhoff, G. L, Shackelford, C. D, Benson, C. H, Apiwantragoon, P
• Format: Journal Article
• Language: English
• Published: New York, NY American Society of Civil Engineers 01.04.2008
• Subjects: Applied sciences; Buildings. Public works; Computation methods. Tables. Charts; Earth sciences; Earth, ocean, space; Exact sciences and technology; Geotechnics; Hydrology; Hydrology. Hydrogeology; Structural analysis. Stresses; TECHNICAL PAPERS; Water effect, drainage, ground water lowering, filtration; Confinement; Property of soil; Barrier; Coverage; Water balance; Unsaturated flow; Forecast model; Recommendation; Rainfall rate; Measurement in situ; Hydrology; Soil water properties; Coverings; Barriers; Evapotranspiration; Numerical simulation; Unsaturated soil; Comparative study; Hydraulic properties; Containment
• ISSN: 1090-0241; 1943-5606
• DOI: 10.1061/(ASCE)1090-0241(2008)134:4(470)

Predictions of surface runoff (R) , evapotranspiration (ET), soil–water storage (S) , and percolation obtained using three numerical codes (LEACHM, HYDRUS, and UNSAT-H) 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 parameters), 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 mm ) 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∕year ), 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.