Long-term reliability of the Athabasca River (Alberta, Canada) as the water source for oil sands mining

Abstract

Exploitation of the Alberta oil sands, the world's third-largest crude oil reserve, requires fresh water from the Athabasca River, an allocation of 4.4% of the mean annual flow. This allocation takes into account seasonal fluctuations but not long-term climatic variability and change. This paper examines the decadal-scale variability in river discharge in the Athabasca River Basin (ARB) with (i) a generalized least-squares (GLS) regression analysis of the trend and variability in gauged flow and (ii) a 900-y tree-ring reconstruction of the water-year flow of the Athabasca River at Athabasca, Alberta. The GLS analysis removes confounding transient trends related to the Pacific Decadal Oscillation (PDO) and Pacific North American mode (PNA). It shows long-term declining flows throughout the ARB. The tree-ring record reveals a larger range of flows and severity of hydrologic deficits than those captured by the instrumental records that are the basis for surface water allocation. It includes periods of sustained low flow of multiple decades in duration, suggesting the influence of the PDO and PNA teleconnections. These results together demonstrate that low-frequency variability must be considered in ARB water allocation, which has not been the case. We show that the current and projected surface water allocations from the Athabasca River for the exploitation of the Alberta oil sands are based on an untenable assumption of the representativeness of the short instrumental record.

Keywords: Alberta; climate variability; oil sands; paleohydrology; statistical hydrology.

Fig. 1.

Alberta’s seven major drainage basins. The numbers refer to hydrometric gauges identified in Table 1. The Alberta oil sands development is in the vicinity of Fort McMurray (6). Reproduced with permission from the Government of Alberta.

Fig. 2.

Licensed water allocations by sector and decades to 2000 and selected subsequent years in the Athabasca River Basin, 1900–2010. Reproduced with permission from the Government of Alberta.

Fig. 3.

Mean annual flow of the Athabasca River at Athabasca (gauge 07BE001, Water Survey of Canada) for the water year (October 1 to September 30, 1913–2013).

Fig. S1.

The tree-ring sampling sites within and near the Athabasca River Basin in north-central Alberta. The colored triangles represent four coniferous tree species.

Fig. 4.

Observed versus modeled flow of the Athabasca River at Athabasca over the calibration period (1952−2010) for the five tree-ring models described in Table 2 and Table S4.

Fig. S2.

Tree-ring series sample depth in the Athabasca River at Athabasca water-year flow reconstruction. Sample depth is 16–18 series throughout the 1100s and at least 20 series throughout the 1400–1500s.

Fig. 5.

The full AD 1111–2010 tree-ring reconstruction of the water-year (October−September) flow (cubic meters per second) of the Athabasca River at Athabasca. Also plotted is the mean annual flow for the entire record (418 m³⋅s⁻¹) and a 15-y running mean.

Fig. S3.

An ensemble of 200 tree-ring reconstructions of the water-year flow of the Athabasca River at Athabasca for AD 1599–2010. The red curve represents the best single reconstruction presented in the paper.

Fig. 6.

Wavelet evolutionary spectrum of the Athabasca River tree-ring reconstruction for AD 1111–2010. Significant (P < 0.05) power exists at the frequencies and time intervals depicted in red and enclosed by a black line.

Fig. S4.

MTM spectral analysis of the Athabasca River at Athabasca tree-ring reconstruction for (A) the Medieval Climate Anomaly (AD 1111–1550) and (B) the Little Ice Age (AD 1551–1850). Significant (P < 0.05) power exists at the frequencies where the spectra project above the magenta line. Analysis was performed with the software described in refs. and . “Harmonic” (black) denotes the clear distinct periodic components associated with a coherent phase spectrum; “reshaped” (red) denotes the remaining narrowband quasi-periodic components of the spectra.