Which of the following factors contributes to water hardness?

Water hardness primarily arises from the presence of dissolved minerals in the water, specifically bivalent metal ions. The correct answer details how dissolved bicarbonates, sulfates, and/or chlorides of magnesium and calcium in groundwater contribute to this phenomenon. These ions are naturally occurring in water sources, particularly in groundwater where water percolates through limestone and other mineral deposits, leading to higher concentrations of calcium and magnesium. As these minerals dissolve, they impart hardness to the water, affecting properties such as scale formation in pipes, soap efficacy, and laundry quality.

The other options do not address the primary components that define hardness. High concentrations of iron can influence water quality but do not directly correlate with hardness levels. Surface water, such as that from ponds or creeks, may have variation in mineral concentration but is not a consistent contributor to hardness unlike the minerals found in groundwater. Similarly, while poorly constructed or protected well-water supplies can lead to contamination or safety issues, the construction or placement of a well does not inherently affect the hardness of the water it supplies.