What are total dissolved solids?
The total dissolved solids test measures the amount of particles that are dissolved in the water. It may include all suspended solids that may or may not pass through a filter.

What factors influence the amount of total dissolved solids in water?
1. Some dissolved solids come from organic sources such as leaves, silt, plankton, and industrial waste and sewage. Other sources come from runoff from urban areas, road salts used on street during the winter, and fertilizers and pesticides used on lawns and farms.
2. Some dissolved solids come from inorganic materials such as rocks and air that may contain calcium bicarbonate, nitrogen, iron phosphorous, sulfur, and other minerals. Many of these materials form salts, which are compounds that contain both a metal and a nonmetal. Salts usually dissolve in water forming ions. Ions are particles that have a positive or negative charge.
3. Since rain water contributes to most of the water in a watershed, it contributes to the amount of TDS in a watershed. Rain water is almost pure with less than 10 mg/L of TDS.

What is the optimal amount of total dissolved solids in water for most aquatic plants and animals?
1. A constant level of minerals in the water is necessary for aquatic life. Changes in the amounts of dissolved solids can be harmful because the density of total dissolved solids determines the flow of water in and out of an organism’s cells. Concentration of total dissolved solids that are too high or too low may limit the growth and may lead to the death of many aquatic organisms.
2. Drinking water may have a TDS reading of 25-250 mg/L. Drinking water should not exceed 500 mg/L TDS.
3. Distilled water will have a TDS reading that will range from 0.5-1.5 mg/L.
4. The amount of TDS ranges from 100-20,000 mg/L in rivers and may be higher in groundwater.
5. Seawater may contain 35,00 mg/L of TDS.
6. Lakes and streams may have a TDS reading of 50-250 mg/L.

What factors are affected by your amount of total dissolved solids in your watershed?
1. A constant level of minerals in the water is necessary for aquatic life. Changes in the amounts of dissolved solids can be harmful because the density of total dissolved solids determines the flow of water in and out of an organism’s cells. Many of these dissolved solids contain chemicals, such as nitrogen, phosphorous, and sulfur, which are the building blocks of molecules for life.
2. Concentration of total dissolved solids that are too high or too low may limit the growth and may lead to the death of many aquatic organisms.
3. High concentrations of total dissolved solids may reduce water clarity, which contributes to a decrease in photosynthesis and lead to an increase in water temperature. Many aquatic organisms cannot survive in high temperatures.
4. It is possible for dissolved ions to affect the pH of the body of water, which in turn may influence the overall health of many aquatic species.
5. If TDS levels are high, especially due to dissolved salts, many forms of aquatic life are affected. The salts act to dehydrate the skin of animals.
6. High TDS concentrations may add a laxative effect to the water or cause the water to have an unpleasant mineral taste.