Watershed liming is one method used to increase the alkalinity and reduce the aluminum content of surface waters. To increase the understanding of the processes involved in soil liming and develop a tool for planning and evaluating terrestrial liming operations, a mathematical model was developed. The model includes key soil processes such as limestone dissolution, cation exchange, and the leaching and accumulation of dissolved components. The model’s ability to describe short-term and long-term improvement of watershed liming upon stream water chemistry is demonstrated by comparing model calculations with data from Swedish full-scale experiments. Watershed liming as a management method is discussed in relation to watershed characteristics. The influence of temporal, hydrological, and hydrochemical variations, as well as liming design parameters is demonstrated as well. The model is used to assess the applicability of watershed liming as a tool for neutralizing acid lakes. Simulations of the responses of different lakes suggest that watershed liming may provide interesting advantages when compared to traditional lake liming methods, although a higher annual treatment cost must be expected.