Rain and Rainwater

Abstract

To deal with rainwater harvesting, knowledge of rain, rainfall, and rainwater is necessary. Knowledge of the formation of rain in clouds and its pattern of falling to the Earth’s surface helps one to understand more about quality of rain and the quantity of rain that can be collected for harvesting. To collect rainwater at a particular place, the intensity of rainfall to be measured should be known. A rain gauge is used for this purpose. Installation of a rain gauge and the technique of measuring rain is important. In a particular place, the rainfall pattern and its distribution over a period of time is variable. Therefore, rainfall intensity should be studied and recorded for the planning and design of a rainwater-harvesting system. The nature and quality of the rain, and also of the rainwater, also varies from place to place due to pollution of the air in these areas. As a result, for any place where rainwater harvesting is to be performed, the quality of rainwater must be tested or be known from secondary sources. With a view to enriching the concept of rainwater harvesting in buildings, details about the formation of rain, pattern of rainfall, rainfall intensity, global rainfall scenario, and causes of degrading quality and nature of rainwater are discussed in this chapter.