What is exactly meant by water quality? It can be identified as a measure of the suitability of water for a particular use based on selected physical, chemical, and biological characteristics. More specifically, water quality is measured against federally passed water quality standards to access its overall safety before reaching the drinking populace. To determine water quality, scientists first measure and analyze characteristics of the water such as temperature, dissolved mineral content, and number of bacteria. Selected characteristics are then compared to said numeric standards and guidelines to decide if the water is suitable for a particular use. Different uses raise different concerns and hence different standards are considered. Natural water bodies will vary in response to environmental conditions. Environmental scientists are working to understand the functioning of these systems, which determines sources and fates of contaminants. Environmental lawyers and policy makers are working to define water laws that designate the fore mentioned uses and natural conditions. The vast majority of surface water on the planet is neither potable nor toxic. This remains true even if sea water in the oceans is not counted. Another general perception of water quality is that of a simple property that tells whether water is polluted or not. In fact, water quality is a very complex subject, in part because water is a complex medium intrinsically tied to the ecology of the Earth. Industrial pollution is a major cause of water pollution, as well as runoff from agricultural areas, urban storm water runoff and discharge of untreated sewage. Aside from the definitions about what water quality actually means, the only way water is determined if it is safe for public consumption is put it through scientific testing. To identify the substances present in a stream or lake, scientists collect samples of the water, of living organisms, and of suspended and bottom sediments. Technicians then analyze these samples in a laboratory with specialized instruments and procedures. Certain measurements such as temperature, dissolved oxygen, turbidity and conductivity can be taken in the field with portable equipment. As the use of technology heightens the quantative analysis of water we will surely improve the drinking water quality. At the same time such discoveries will also reveal new problems and pollutions within our water that will demand new water quality standards and treatment methods to continuously produce a successful drinking water for the population of the world. In the future, water quality will continue to be an enormous issue, partly because of the tremendous growth of the population and urban expansion and development. All this growth puts great stress on the natural water resources, and, if we are not diligent, the quality of our waters will suffer.