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The main challenge facing many of the coal mines in South Africa is the management of mine water following the closure of mining operations. The Sigma Colliery is situated in the Free State Province, adjacent to the town of Sasolburg and bordering the Vaal River, one of the country's largest rivers. The mining includes both opencast and underground operations; however, this paper will only discuss the main underground operations. There are several aquifer systems overlying the deeper mining, which was done by bord and pillar and high extraction mining. Detailed conceptual models of the interactions between several aquifer systems and the rebounding mine voids were constructed using mining and monitoring data. From this, numerical flow models were used to model the complex flow system where rebound of water levels is expected. The results have led to an accurate understanding of the complex flow system and the important controls on the final water levels in the area.