Alkalinity and Hardness
WHAT IS ALKALINITY?
Alkalinity is water's capacity to resist acidic changes in pH, essentially alkalinity is water's ability to neutralize acid. This ability is referred to as a buffering capacity. A water body with a high level of alkalinity (which is different than an alkaline water body) has higher levels of calcium carbonate, CaCO3, which can decrease the water's acidity. Therefore, alkalinity measures how much acid can be added to a water body before a large pH change occurs.
ALKALINITY VS WATER HARDNESS
Alkalinity and water hardness are fairly similar--essentially they both come from sources in nature. Water moves through rocks (and picks up minerals as it does so) on its way to rivers and lakes. When limestone and dolomite dissolve in water, one half of the molecule is calcium or magnesium (the "hardness") and the other half is the carbonate (the "alkalinity"). This means that the level of water hardness and alkalinity in a place will be very similar. However, they are very separate measurements, and have very different importance.
WHY CARE ABOUT ALKALINITY?
Fish and other aquatic life require a pH range of 6.0 to 9.0, and because alkalinity buffers against rapid pH changes, it protects the living organisms who require a specific pH range. Higher alkalinity levels in surface water will buffer acid rain and other acid wastes, preventing pH changes that are harmful to aquatic life. Alkalinity is also in important considering the treatment of wastewater and drinking water because it influences cleaning processes such as anaerobic digestion. Water may also be unsuitable for use in irrigation if the alkalinity level in the water is higher than the natural level of alkalinity in the soil.
NATURAL FACTORS INFLUENCING ALKALINITY
- Geology - the types of rocks surrounding the stream affects alkalinty. Phosphates, limestone, and borates give the water a higher alkalinity and buffering capacity.
- Seasonal weather - spring snow melt and rain can increase runoff which generally also increases acidity, in turn decreasing alkalinity.
HUMAN FACTORS INFLUENCING ALKALINITY
- Acid Mining Waste- Acids from mines can wash into rivers and streams and increase the acidity, which requires more alkalinity.
- Urbanization- The particles from cement and other urban construction materials can wash into streams and affect alkalinity.
- Learn more about limiting human impacts: Protect Your Water.
HOW DO WE MEASURE ALKALINITY?
Utah Water Watch- Learn how volunteers across the state monitor water quality.
Stream Side Science- Explore different lesson plans relating to water quality and see how they line up with the core curriculums for grades k-12.
Utah DEQ- Learn how the state water quality department monitors surface water.