Due to rising demand, mining operations are facing increasing restrictions regarding freshwater intake. This research develops a general structured methodology to estimate freshwater requirements for a mill plant operation in central Chile. This involves determining water consumption using a general mass-balance algorithm, determination of evaporation and seepage rates, and development of a daily time-step water balance model that accounts for water demand, storage and losses in tailings. The water balance model is applied to estimate water well needs, being accurate in relation to the preceding operational year and thus useful for predicting water requirements.