Steam Assisted Gravity Drainage (SAGD) is the in-situ method of choice to recover bitumen from reservoirs in the Athabasca basin. In SAGD, steam is injected into an upper horizontal injection well, while emulsified bitumen and condensed water are produced from the lower horizontal production well. Produced water is treated and recycled to generate steam. Water management is a key factor in the operation of the whole process. Reservoir water losses are an essential part of the physics of the subsurface process with enormous implications for the water management. Prediction of reservoir water losses is critical to the design and operation of SAGD wells and facilities. For the purpose of forecasting water losses, three different approaches have been taken. The obvious inherent assumption in these methods is the ability of cold water to move through cold reservoir from higher pressure to lower pressure areas. This paper presents three methods to forecast reservoir water losses: the empirical, the analytical and the numerical simulation methods. These different approaches are complementary and incrementally complex allowing for flexibility (depending on time demand to create the forecast and required precision of the results). Ability to forecast water losses assists in planning the most efficient and reliable strategy to maximize future value of a SAGD operation.