The volume of groundwater is much greater than that of all fresh water lakes and streams combined. Underground water plays an important role in the water balance of the earth. It is a primary source of fresh water in several urban and rural areas. The quality of ground water in some parts of the country, particularly shallow ground water is changing as a result of human activity. It is less susceptible to bacterial pollution than surface water, as the soil and rocks through which it percolates screen out most of the bacteria. But freedom from bacterial pollution alone does not mean that the water is fit to drink. Many dissolved mineral and organic constituent are present in ground water in various concentrations. Most are harmless or even beneficial; though occurring in frequently, others are harmful, and a few may be highly toxic. Ground water quality comprises the physical, chemical, and biological qualities of water. Naturally it contains mineral ions which slowly dissolve from sediments and rocks as the water travel along mineral surfaces in the pores or fractures of the unsaturated zone and the aquifer. These are referred to as Total Dissolve Solid. A list of dissolved solids in any water is long, but it can be classified into major constituents, minor constituents, and trace constituent. In water all of the dissolved solids are either positively charged ions or negatively charged ions. In recent years the growth of industry and technology has increased the stress upon both our land and water resources. Locally the quality of ground water has been degraded. Municipal and industrial waste entered the soil, infiltrated some aquifers, and degraded the ground water quality. In recognition of the potential for pollution, physical and chemical analyses are made routinely on water supplies. State and local agencies are taking steps to increase water quality monitoring. Analytical techniques have been refined so that early warning can be given, and plans can be implemented to mitigate water pollution.