Soil–atmosphere modelling of an engineered soil cover for acid generating mine waste in a humid, alpine climate

Abstract

A research program studying the performance of soil covers at the Equity Silver Mine was initiated in 1992. This site is situated in the humid, alpine climate of north central British Columbia. A one-dimensional, fully coupled heat and water transport, soil–atmosphere flux model was developed as part of this research program to simulate the movement of liquid water and water vapour within a soil cover in response to rainfall and evapotranspiration. Predicted and measured conditions in the cover showed good agreement for a five-month period from June to November 1993. The modelling exercise showed that vapour flow was the dominant flow mechanism near the surface of the cover within a few days after the start of drying. This points out the necessity of being able to couple heat and water transport in soil cover analyses and design. The numerical modelling demonstrated that input parameters are readily attainable through field and laboratory measurement. Model predictions of extreme and mean climate conditions indicated that percolation through the cover system would be limited to approximately 2% of the annual precipitation and that oxygen flux through the cover would be reduced by approximately 98% from uncovered conditions.Key words: acid rock drainage, soil covers, unsaturated soils, infiltration, evapotranspiration, matric suction.

Spatial analysis of fine root distribution on a recently constructed ecosystem in a water-limited environment

“…At stand scale, it has been shown that high spatial variability and clustered fine root systems reduce root water uptake compared to uniformly distributed root systems (Liedgens and Richner 2001;Pardo et al 2000). While root vertical distribution is a key input in most soil-plant-atmosphere models (Eamus et al 2006;Swanson et al 2003), high lateral variability of fine roots may need to be accounted for in models for systems like the one studied here. For instance, using root data based on a few samples for such a heterogeneous system may entail substantial uncertainties in results of water balance simulations for certain artificial vegetation ecosystems.…”

“…Understanding horizontal and vertical distribution of fine roots is crucial for a number of applications such as spatially distributed modelling of two-dimensional water flow and root water uptake (e.g. Vrugt et al 2001), important for the design and hydrologic performance of vegetated engineered covers (Swanson et al 2003).…”

Spatial analysis of fine root distribution on a recently constructed ecosystem in a water-limited environment

“…A key strategy to minimize the environmental and public health risks associated with hazardous wastes is the use of engineered covers (Scanlon et al 2005;Swanson et al 2003). Covers are designed to serve multiple purposes including: minimizing deep drainage into buried wastes by enhancing soil moisture storage and water loss via evapotranspiration , and supporting a stable vegetation community that closely resembles natural ecosystems.…”

Laboratory and numerical modeling of water balance in a layered sloped soil cover with channel flow pathway over mine waste rock

“…Such combined experimental and modeling approach has been used extensively by many researchers (e.g., Khire et al 1999;Scanlon et al 2002;Swanson et al 2003;Yanful et al 2003;Bussière et al 2003;). Modeling allows hypothetical cases to be run and re-run to check the sensitivity of certain parameters following calibration of the program.…”