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Water Quality Assessment: Chemical: Hardness
 Image of stream water.Stream water hardness is the total concentration of cations, specifically calcium (Ca2+), magnesium (Mg2+), iron (Fe2+), and manganese (Mn2+), in the water. Water rich in these cations is said to be "hard." Stream water hardness reflects the geology of the catchment area. Sometimes it also provides a measure of the influence of human activity in the area. For instance, acid mine drainage often results in the release of iron into a stream. The iron produces extraordinarily high hardness readings. For these reasons, hardness is a useful water quality indicator. Photo © 1999 -www.arttoday.com

For the most part, however, hardness is a reflection of the amount of calcium and magnesium entering the stream through the weathering of rock such as limestone (CaCO3). When limestone is weathered, it dissolves into calcium (Ca2+) and carbonate (CO32-). Calcium is an important nutrient that is used by plants and animals. Carbonate buffers the stream's pH . Although these two ions are beneficial to a stream, they can cause problems in a home. Foaming agents such as those in soaps and detergents do not work as well in hard water. Also, hard water tends to leave hard, scaly calcium deposits on faucets. This is why many people install water softener systems in their homes.

 

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