Prediction of the water balance of two soil cover systems

Abstract

Soil cover systems are widely used for containment of municipal solid waste, hazardous and mine waste, with the objective of limiting the ingress of precipitation and oxygen. The ability to predict their long-term performance is crucial, as their failure would result in the release of contaminants to the environment. However, monitoring covers over the long term to derive the information needed to aid in design is impractical and there are no large-scale covers that have been in use for a long enough period to generate the data needed. Numerical models have been particularly useful as design tools. To improve their reliability these models may be calibrated to field data and then used to make long-term predictions of cover performance. The field performance of two resistive test soil covers on a 20% sloping waste rock platform is predicted using the two-dimensional soil-atmosphere model Vadose/W. Input data for the model included soil, climate and vegetation data obtained either in the field or laboratory. Model results were compared to field data to assess the validity of the program. The model reasonably simulated field response patterns for soil water storage and suction. Divergence between field performance data and model predictions were significantly influenced by snowmelt, interflow and flow through preferential pathways.

Stochastic Analysis of Hydraulic Hysteresis in Multi-Layer Unsaturated Soil Covers Under Random Flux Boundary Conditions

“…However, for the traditional non-hysteretic model (NHM), only one branch of the major hysteresis SWCC loop is used, generally the main drying branch due to its relatively easy measurement (Adu-Wusu et al 2007;Yanful et al 2006). There are also cases where both main drying and main wetting SWCC branches are used to simulate the drying and wetting boundary conditions respectively, while ignoring the transition process in between and artificially switching the hydraulic state in the whole soils from drying to wetting, or vice versa (Tami et al 2004;Indrawan et al 2007).…”

Modellierung des Wasserhaushalts von Straßenböschungen in Lysimetern

“…Berechnungen von Khire et al zum Wasserhaushalt von mineralischen Deponieoberflächenabdichtungen ergaben eine tendenzielle Überschätzung des Sickerwassers durch die abdichtende Schicht, obgleich zu den Materialien labortechnisch ermittelte hydraulische Kennwerte vorlagen. Adu‐Wusu et al belegten mit Berechnungen von Lysimetern in einer Deponieoberflächenabdichtung die Bedeutung einer zutreffenden Abbildung der hydraulischen Eigenschaften der Böden. So zeigten sie die Notwendigkeit einer Kalibrierung der Saugspannungs‐Wassergehalts‐Beziehungen und der ungesättigten hydraulischen Leitfähigkeit der betrachteten Böden anhand gemessener Sickerwassermengen, um realistische Prognoseergebnisse mittels numerischer Berechnungen erzielen zu können.…”

“…Untersuchungen von Adu‐Wusu et al , Schweller et al und Barbour et al belegen daneben, dass die Prozesse an der Oberfläche wie Evaporation und Transpiration sowie die oberflächennahen Schichten, z. B. Oberboden und Bankettmaterial , einen großen Einfluss auf den Wasserhaushalt von Straßendämmen haben.…”

Development of dual capillary barrier system using recycled materials

“…Despite its shortcomings, Fayer and Gee (1997) Benson et al (2004) showed that VADOSE/W can predict water balance in a landfill cover system more accurately than UNSAT-H. Similar results were reported by Adu-wusu et al (2007) in their prediction of the water balance in Whistle Mine, Ontario. Another study by Song and Yanful (2008)…”

“…Capillary barrier has also been used in the mining industry (Woyshner and Yanful 1995;Yanful and Choo 1997;Cabral et al 2000;Adu-Wusu and Yanful 2006;Adu-Wusu et al 2007). The contrast between fine and coarse-grained layers of capillary barrier restricts water infiltration through the interface between fine and coarsegrained layers.…”