Comparison of ion-activity products and equilibrium constants for solution of CaCO3, CaMg(CO3)2, and CaSO4 indicates that water from Fairmont Hot Springs and Banff Hot Springs, and from thermal springs in British Columbia, on Lussier River, Ram Creek and near Fording Mountain, are super-saturated with respect to CaCO3 and, to a lesser extent, with respect to CaMg(CO3)2. At other springs saturation occurs after water is discharged from the springs. In the case of hot springs this is caused by the rise in pH that accompanies loss of excess CO2 and, to a lesser degree, by evaporation; cooling of the water tends to lower the degree of saturation somewhat. At cold springs, increase in water temperature after discharge increases the degree of saturation. Only near-saturation with respect to CaSO4 is indicated for Miette Hot Springs, Fairmont Hot Springs, and Fording Mountain Springs; precipitation of CaSO4 may occur here owing to evaporation of part of the water; the effect of temperature on the degree of saturation is small.