Preferential recharge in a reclaimed tailings sand upland: Implications on solute flushing

Eric D Kessel,Owen F Sutton,Jonathan S Price

doi:10.1016/j.ejrh.2021.100953

Eric D Kessel, Owen F Sutton + Show 1 more

Open Access

https://doi.org/10.1016/j.ejrh.2021.100953

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Abstract

Study regionA peatland watershed was constructed on a post-mined oil sands lease in Northern Alberta, Canada, with the intention of replicating the function of natural wetlands removed by surface mining. Study focusGiven the potential for moisture limited conditions due to the sub-humid regional climate, ensuring sufficient water availability in these landscapes is a principal concern. This research demonstrates how small recharge basins can modify the hydrology to promote groundwater recharge critical for sustaining saturated conditions in a downgradient wetland. New hydrological insights for the regionLocation was important in determining the efficacy of recharge basins. Specifically, basins placed at the confluence of two hillslopes detained substantial volumes of runoff due to large upslope areas, contributing ~30% of the groundwater budget to the fen, while only occupying 1% of the upland area. Basins situated near low relief hillslopes or altogether isolated from a hillslope did not detain appreciable runoff and therefore had a minor role in recharging groundwater. Groundwater in the vicinity and downgradient of active recharge basins had considerably lower solute concentrations because of dilution. This suggests that basins can not only enhance recharge within engineered landscapes, providing a consistent and focused supply of water to upland aquifers, but offer relatively fresh groundwater to downgradient ecosystems. This could ameliorate the impact of high salinity present in oil sands process-affected materials.

Highlights

Disturbance associated with surface mining of oil sands has affected over 900 km2 of the Athabasca Oil Sands Region (AOSR) in the Western Boreal Plains (Government of Alberta, 2018)
Following P events that exceeded this intensity, the east recharge basin was observed to fill within 15 min of peak rainfall as a consequence of R from the east-southeast slope confluence (4.9 ha)
Some P events were not received in a single period of continuous rainfall but could span over 24–48-hour periods, resulting in partial re-filling of the east recharge basin, illustrated by the saw-tooth pattern in the ponded water level hydrograph (Fig. 3)

Summary

Introduction

Disturbance associated with surface mining of oil sands has affected over 900 km of the Athabasca Oil Sands Region (AOSR) in the Western Boreal Plains (Government of Alberta, 2018). The oil sands companies are required to reclaim the post-mined landscape to an equivalent capability (OSWWG, 2000), and given the abundance of wetlands in the undisturbed AOSR (Turchenek and Pigot, 1988; Vitt et al, 1996; Zoltai et al, 1988), exploring the viability of fen peatland construction has been deemed a regulatory priority (Daly et al, 2012; Ketcheson et al, 2016; Pollard et al, 2012). In 2012, the Nikanotee Fen Watershed (NFW), a pilot fen reclamation project, was constructed on a post-mined lease from mine waste and salvaged materials to test the feasibility of peatland reclamation (Daly et al, 2012; Ketcheson et al, 2016; Price et al, 2010).

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