The main objectives were to: (i) evaluate the physical parameters and the concentrations of chemical constituents of groundwater and surface water (Spring Gulch) sources and municipally supplied water in the distributions systems; and (ii) investigate the effects of treatment conditions, distribution arrangements, and seasonal and spatial variations on the quality of drinking water. [...] The physical and chemical properties of the blend of treated waters at the Sandhill reservoir, as well as those of the tap water at the distribution line in the Valley area, typically reflected the compositions of the treated waters, which dominated in the mixture. [...] Nonetheless, the constituents in the mixture of treated waters were slightly diluted, when treated water from the municipality treatment plant dominated in the mixture; the opposite trend was observed when the majority of treated water in the mixture was from the DND treatment plant. [...] Although this blending arrangement has been practiced since the municipal water treatment plant began operation in 2002, systematic investigations have yet to be undertaken concerning the seasonal and spatial changes of the physical and hydrochemical qualities of the water sources, drinking water in the distributions systems and the effects of blending treated waters on the water quality in distri [...] The ultimate purpose is to examine the effects of treatment conditions and blending of treated waters on the quality of tap water Valley and to assist the municipality to provide safe and aesthetically pleasing water at the consumer’ taps.