Abstract:
Abstract: Understanding unsaturated water movement in closed tailing storage facilities (TSFs) is challenging due to limited subsurface characterization and dynamic (transient) monitoring of responses to hydraulic stresses. This study demonstrates the calibration of a one-dimensional infiltration model of a closed TSF covered with 2 feet of soil, using data obtained from an eddy covariance tower. Hydraulic properties of the soil cover were indirectly estimated from precipitation, potential evapotranspiration (PET) and actual evapotranspiration (AET) data.
For this work, capabilities of the PHYDRUS Python framework [1], an advanced module for HYDRUS-1D [2], were enhanced. Improvements included integration of parallel computing techniques, recompilation of the HYDRUS-1D source code to expanded temporal output capacity, and expansion of automated pre- and post-processing workflows. In addition, a systematic calibration of saturated and unsaturated hydraulic parameters using the Iterative Ensemble Smoother (IES) algorithm [3, 4] was integrated into PHYDRUS.
In the present study, the model was calibrated using six months of data from an eddy covariance tower, providing measurements of actual evapotranspiration, estimates of potential evapotranspiration and shallow soil water content (WC) data. Despite the short monitoring period and limited subsurface data, calibration achieved reasonable agreement between simulated and observed cumulative AET. This measure reflects the overall precipitated amount that did not remain in the soil and did not lead to infiltration deeper into the TSF. Calibration to cumulative AET improved when WC data were omitted from calibration and only AET data were considered. Given uncertainty in PET estimates, a 20% reduction in input PET resulted in improvement of AET calibration as well.
The findings indicate that effective model calibration remains feasible when subsurface data are limited, when incorporating direct above-ground measurements of PET and AET. The augmented PHYDRUS and IES framework delivers a robust foundation for quick evaluation of various conceptual models for infiltration into reclaimed tailing facilities.
Presenter:
- Aya Mohamed | Consultant | SRK USA (Denver)
Co-Authors:
- Assaf Wunsch | Consultant | SRK USA (Denver)
- Philine Tullius | Consultant | SRK USA (Denver)
- Kyle Williams | Consultant | SRK Canada (Vancouver)
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