This seems like an obvious question. We need to understand water quality in order to protect our health, and also the health of ecosystems. Those, of course, are the main reasons we are interested in water quality, so that we make sure our drinking water is safe and we are not damaging the environment.

But there are other important reasons to study water quality. Water quality helps us understand what is going on in the subsurface, where and how fast water is moving, what geochemical reactions are occurring, identifying different sources of water, etc.

Water quality also affects, for want of a better term, civilization’s plumbing. The dissolved minerals in water can cause corrosion of pipes, staining of bathroom fixtures, and influence how well washing machines clean our clothes. Groundwater in Illinois is typically “hard” (high levels of calcium and magnesium), which can cause the formation of scale and limits lathering of soap, and has significant amounts of dissolved iron, which causes staining. To take care of these nuisance problems, softeners and iron removal systems often need to be used.

One problem I’ve been researching lately is the role of increased chloride in the waters of Illinois, especially in the Chicago region. We add a lot of chloride to our roads in the winter with road salt. Chloride aggressively corrodes steel reinforcement in concrete, such as in road beds and bridge decks, causing millions of dollars in damage. And increasing chloride levels in rivers and canals in the Chicago may lead to increased corrosion in industrial plants and utilities. I recently corresponded with someone in the Joliet area who was seeing increased corrosion in a power generation plant, and wondered if the increasing chloride in the Des Plaines River was the cause.