Springs, or points of natural, concentrated groundwater discharge, may be located in river or lake beds, or below mean sea level along the coast, but many are found some distance from surface-water bodies. Spring water commonly represents rain or snow-melt that has entered the ground at a higher elevation a number of years earlier.Measured springwater temperatures in Canada range from very cold (−2.9 °C) to hot (82.2 °C). Thermal spring waters, with temperatures above the local mean-annual air temperature, have undergone geothermal heating during deep subsurface circulation in areas of high topographic relief. Hot springs (>37 °C) are therefore found only in mountainous areas, in Alberta, British Columbia, Yukon, and the Northwest Territories. Spring locations are commonly controlled by major folding or faulting, or both, in the bedrock strata.Reported pH values in Canadian spring waters range from strongly acidic to alkaline (2.8 to >10.0). Low pH values (<4.0) are associated with high contents of dissolved Fe (up to 2600 mg·L−1) and other heavy metals (e.g. Zn up to 177 mg·L−1), resulting from the oxidation of metal sulfides. Measured redox potentials (Eh) range from −252 to +683 mV. Negative Eh values are found in spring waters that contain dissolved H2S and S2−, produced by bacterial reduction of dissolved sulfate.Total-dissolved-solids contents of Canadian spring waters are reported to range from as little as 32 to over 75 000 mg·L−1. Chemical composition also varies widely. Major anions include bicarbonate (up to 5960 mg·L−1), sulfate (up to 17 520 mg·L−1), and chloride (up to 44 300 mg·L−1). Major cations include calcium (up to 1823 mg·L−1), magnesium (up to 1190 mg·L−1), sodium (up to 27 100 mg·L−1, and potassium (up to 1568 mg·L−1). The chemical composition of each spring water reflects the mineral composition of the rock types with which the water has been in contact, as well as its subsurface residence time. In simplified terms, Ca–Mg/HCO3 waters come from carbonate rock (limestone, dolomite), Ca/SO4 waters from gypsum or anhydrite, and Na/Cl waters from salt beds.Springwater temperature and composition can both show gradual (seasonal) and sudden (incidental) variations. In springs that show seasonal variations, maximum temperature and mineralization occur near the end of winter; minimum values commonly occur during snowmelt. Sudden variations in temperature, mineralization, and discharge rate can occur during periods of heavy rain, if cold, non-mineralized rainwater enters spring conduits. Earthquakes may cause sudden changes in discharge rates and suspended-solids contents, without affecting water temperature or chemical composition.Information on Canadian spring locations, and on their physical and chemical character, is still spotty. As detailed knowledge about springs can be useful in both ecological and water-supply studies, an effort should be made to expand and refine the existing database.