Numerical modeling of a regional groundwater flow system to assess groundwater storage loss, capture and sustainable exploitation of the transboundary Milk River Aquifer (Canada – USA)

Abstract

Groundwater capture and storage loss play a major role in the sustainable exploitation of a regional aquifer. This study aimed to identify the impact of major and long-term groundwater exploitation on a regional aquifer system to understand the processes controlling the sustainable exploitation of the transboundary Milk River Aquifer (MRA). The MRA extends over 26,300 km 2 , being a major water resource across southern Alberta (Canada) and northern Montana (USA). Concerns about the sustainability of the MRA were raised as the century-old exploitation has led to important drawdowns and the local loss of historical artesian conditions. A steady-state numerical model of the regional flow system was developed and calibrated against hydraulic heads, groundwater fluxes, and the area with flowing artesian wells. Four groundwater abstraction scenarios were simulated: 1) natural flow conditions without exploitation; 2) the mean abstraction rate over the last 108 years; 3) the historical maximum global abstraction rate of the 2 MRA; and 4) a theoretical high abstraction rate based on the maximum rate estimated for each MRA exploitation zone. The numerical model agrees with the previously formulated conceptual model and supports its hydraulic plausibility. Results show that MRA exploitation has led to a major change in flow patterns to sustain groundwater abstraction. The MRA water balance under exploitation indicates that more recharge and reduced seepage to bedrock valleys compensate groundwater withdrawals. Based on its impact on regional discharge and the reduction in MRA storage, the mean historical level of exploitation of the MRA appears sustainable. Larger exploitation rates would significantly reduce groundwater discharge to surface seepage locations and lead to a larger reduction in groundwater storage in the MRA. Modeling also illustrates that the MRA is an internationally shared resource. This situation would justify a joint management of the aquifer system between Canada and USA; especially in the area comprised between the recharge area in Montana and the Canadian reach of the Milk River.

Stochastic analysis of the variability of groundwater flow fields in heterogeneous confined aquifers of variable thickness

“…There is an increasing demand for science-based approaches to the management and use of groundwater resources at regional scale (e. g., Zhou and Li 2011;Barthel and Banzhaf 2015;Sishodia et al 2017;Pétré et al 2019). Hydrologists are therefore often interested in the solutions of regional groundwater flow models.…”

Glacial Melt in the Canadian Rockies and Potential Effects on Groundwater in the Plains Region

“…The partition of the study area into sub-flow regions helps to target the major groundwater flow systems (GWFS) and compare one model to another. The division of flow systems has been performed by other authors [45][46][47] using field data and modelling. Nevertheless, this approach has yet to be tested with numerical data alone.…”

The importance of transboundary aquifer management between Poland and Ukraine for the protection of common water

“…When dis cuss ing transboundary ground wa ter, it is worth dis tin guish ing sev eral ini tia tives where TBA as sess ment was car ried out in a com pre hen sive man ner, com bin ing in ter pre tation of mon i tor ing se ries and spatio-tem po ral nu mer i cal sim u lation (Voss and Soliman, 2014;Tóth et al, 2016;Pétré et al, 2019;Vaquero et al, 2021). Of par tic u lar im por tance is the use of nu mer i cal mod els that are not re quired by the Wa ter Framework Di rec tive (WFD) (EU, 2000 Di rec tive 2000/60/EC), but should nev er the less be taken into ac count when iden ti fy ing ground wa ter bod ies (GWBs) and de vel op ing wa ter man agement plans.…”