Water Quality An Introduction

Abstract

Water is a familiar substance; it is as commonplace as air, soil, and concrete. Like the other three substances—except possibly concrete—water is essential to human and other forms of life. There is a lot of water; two-thirds of the world is covered by the ocean, while roughly 3.5 % of the global land mass is inundated permanently with water. Water exists in the hydrosphere in a continuous cycle—it is evaporated from the surface of the earth but subsequently condenses in the atmosphere and returns as liquid water. The world is not going to run out of water; there is as much as ever or is ever going to be. Despite the rosy scenario expressed above, water can be and often is in short supply—a trend that will intensify as the global population increases. This is because all places on the earth’s land mass are not watered equally. Some places always have little water, while many other localities are water deficient during droughts. The quality of water also varies from place to place and time to time. Most of the world’s water is too saline for most human uses, and pollution from anthropogenic sources degrades the quality of freshwater, lessening its usefulness. As implied above, evaporation is a water purification process, but salts and pollutants left behind on the land and in water bodies remain to contaminate the returning rainwater.