The primary function of water in bread making is hydration. Without water, the proteins in the flour cannot form gluten. In addition, water plays a role in yeast functionality, enzymatic activity, and starch gelatinization. The amount of water in a formula determines the consistency of the dough (stiff or soft, extensible or elastic) and the quality of the finished product. Water is also the means by which the temperature of the final dough is controlled.
Although water is a substance that has many qualities, in bread making there are only three qualities that will have an impact on dough formation: alkalinity, hardness, and chlorination.