983 1. BACKGROUND Copper is a critical mineral for the global energy transition, supporting electrification, renewable generation, and grid infrastructure. Meeting projected demand requires unlocking deposits that are deeper, wetter, and structurally more complex than those previously developed. The Mingomba copper deposit in northern Zambia, located within the Copperbelt just south of the Democratic Republic of Congo (DRC) border, is one such deposit. Mingomba lies between two active mining sites, the Lubambe Mine to the northwest and the Konkola Mine to the southeast, and one historical site, the Musoshi Mine in the DRC. Historical dewatering rates at the Lubambe Mine have ranged from 50,000 to 125,000 m³/day. Konkola is one of the wettest mines in the world, with current inflow rates between 300,000 and 350,000 m³/day and reported dewatering costs of approximately US$5 million per month. A hydraulic connection between the mines has been documented; historically, dewatering at Konkola resulted in dewatering of Lubambe Shaft 2 due to subsurface communication. Anecdotal evidence indicates that during operations in the 1990s, the dewatering of Lubambe and Musoshi also influenced one another. The proposed Mingomba workings are deeper than both Lubambe and Konkola. They will pass through the entire geological sequence to the deepest part of the stratigraphic basin, making the site a potential hydraulic sink and increasing the importance of regional groundwater interactions in dewatering design. The Mingomba site lies within the Kafue River catchment. The hydrogeology comprises an upper weathered profile of residual soils and saprolite underlain by unweathered fractured bedrock, and includes the Lower and Upper Roan Groups, shales, and basement rock. Mean annual precipitation at the nearby KCM weather station (1954 to 2016 record) is 1,279 mm/year, with rainfall concentrated between December and March. Recharge has been estimated at approximately 10 to 20 percent of rainfall, depending on soil conditions. Regional-scale faults cut across the mining areas and are inferred to be in hydraulic connection with the aquifer system. Two previous numerical groundwater flow models have been developed for the area: an initial Lubambe model in MINEDW (2017, updated 2018) and a subsequent FEFLOW model (2018). Both models share important limitations: each was originally focused on a single mine site with limited representation of others, both relied on the 2018 Leapfrog geologic model, and both reported limited model calibration data. Predictive simulations from these models indicate that pumping (or absence of pumping) at Konkola alone may change Mingomba dewatering requirements by 30 to 40 percent, illustrating both the importance of regional connectivity and the substantial uncertainty in any single deterministic forecast. Effective dewatering planning at Mingomba therefore requires a methodology that explicitly quantifies pre-operational uncertainty rather than relying on a single calibrated base case, and that can be applied at a stage when sitespecific dewatering data does not yet exist. 2. OBJECTIVES This study has three linked objectives: 1. To quantify pre-operational uncertainty in pore pressure evolution at Mingomba under a defined fiveyear dewatering scenario, by sampling probabilistic prior distributions over different stratigraphic units, vertical permeability anisotropy in confining layers, a bulk fracture permeability multiplier, and regional aquifer recharge boundaries. 2. To identify, through global sensitivity analysis, which uncertain hydrogeological parameters most strongly control predicted pressure evolution and therefore which parameters represent the highestpriority targets for further data acquisition.
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