Construction and calibration of a groundwater-flow model to assess groundwater availability in the uppermost principal aquifer systems of the Williston Basin, United States and Canada

Groundwater availability of the Williston Basin, United States and Canada

“…An example of the use of this model to help determine high-value locations to establish new hydrologic-monitoring stations also is presented. The study described in this report has benefitted from numerous studies and publications dating from the 1960s until present, most of which were summarized by Long and others (2014), Thamke and others (2014), and Davis and Long (2018a). A brief summary of the key findings from this report is in Thamke and others (2018).…”

“…Specifically, this report describes (1) the current groundwater availability of the three uppermost principal aquifer systems-the glacial, lower Tertiary, and the Upper Cretaceous-in the Williston Basin, (2) how these resources have changed over time, and (3) tools to assess system response to anthropogenic stresses and climate variability. The scope of this report is focused on the Williston Basin and summarizes previous publications that resulted from this study describing a hydrogeologic framework, a conceptual model and groundwater-flow budget, and a numerical model of groundwater flow (Long and others, 2014;Thamke and others, 2014;Davis and Long, 2018a). This report presents hydrologic forecasts simulated with this numerical model to assess the potential for drought, pumped groundwater, and free-flowing artesian wells to affect future groundwater availability.…”

“…Thamke and others (2014) constructed a three-dimensional hydrogeologic framework that defined and described these three aquifer systems in the Williston Basin for the United States and Canada, with emphasis on the lower Tertiary and Upper Cretaceous bedrock aquifer systems. Davis and Long (2018a) further developed the hydrogeologic framework for the glacial aquifer system by spatially defining five glacial-material zones and extending this analysis to the edges of the active model area ( fig. 1).…”

“…1). This section summarizes the hydrogeologic framework described by Thamke and others (2014) and Davis and Long (2018a), which include greater detail of the lithostratigraphic and hydrogeologic units.…”

“…Hydraulic conductivity values estimated by Thamke and others (2014) for the glacial aquifer system range from 0.01 to 25 feet per day, varying more than for the lower Tertiary and Upper Cretaceous aquifer systems. Davis and Long (2018a) separated the glacial aquifer system into two layers and subdivided these layers horizontally to represent different materials present in the glacial drift on the basis of geologic maps, aquifer maps, borehole logs, and locations of buried pre-glacial valleys. The upper layer was subdivided into three material zones:…”