The term total dissolved solids is often confused with other types of stream measurement tests. Total dissolved solids is also different than conductivity, which is a measure of the electrical conductance of water. Total dissolved solids measures the amount of ions in water, while conductivity measures those ions' ability to do something - conduct electricity. The more ions in the water, the higher the electron flow. Usually there is a strong correlation between conductivity and TDS, but there is still a difference between the two.
Salinity is also different than total dissolved solids.
Salinity deals only with salts and is defined as the concentration of all ionic constituents that include halides, bicarbonates, and sodium chloride. Total dissolved solids is a complex water quality parameter because it is directly linked to so many chemical and biological processes, and incorporates a number of the other water parameters that we test. Because total dissolved solids are related to so many other chemical parameters and processes, humans can increase TDS levels in a number of ways. Rain will wash additional dissolved solids into a stream. This will occur naturally but we can increase it by encouraging soil erosion through poor farming practices, construction sites, timbering, and removal of riparian zones.