governs the formation of local climate and global climate by converting a large amount of thermal energy into latent heat and then into sensible heat.

The water that runs off the surface and flows through rivers and lakes determin es the amount of renewable freshwater that can be used by terrestrial life and human society. This is a usable resources and at the same time the habitat for aquatic life. It is also an indispensable medium for diffusing and diluting env ironmental contaminants that are discharged by human activities. According to a recent study, a minimum requirement of water is 28.3 Iiters/sec/thousand perso ns. This is referred to as dilution factor. Ac-cording to this, cities with pop ulation of I million and 10 million require 2.44 million m³ and 24.45million m³ of water amount every day only to dilute their contaminants.

5. Use of Water Resources

The amount of water consumption in the world is increasing due to the uncurved increase in the world population and higher standard of living. As shown in Fig ure 6, this trend has become conspicuous particularly after the 1950s. As can b e seen from this diagram, demand for water in agriculture, industry and municip alities has increased dramatically from the 1950s onward. This rapid increase f irst started in the agricultural sector and occurred in the industrial sector d uring the 1970s and has now shifted to the municipality sector. Municipality wa ter consumption increased by about 50% between 1950 and 1990. Among all sectors , water demand for agriculture is far greater than any other use of freshwater resources and accounts for 50% of all water used. This can be understood easily by considering the fact that irrigation plays an important role in improvement of agricultural productivity.

　

　

　

BACK　　　CONTENTS　　　NEXT