GEF

Unit 2  |  Water Science and the Water Cycle 46 lot of heat before its temperature changes. Consider the con- trast between the warm air and a cold swimming pool on a summer day. Both the air and the water absorb the sun’s warm rays, but the air heats up much more rapidly. Water’s high specific heat capacity plays a critical role in moderating the Earth’s climate , because the oceans and other water bodies absorb heat from the surrounding air. Specific heat capacity also makes water a vital cooling agent in industrial applica- tions such as power plants. The near-transparency of water is a valuable but often over- looked characteristic for maintaining life on Earth. Water’s transparency enables sunlight to penetrate relatively far into a deep body of water. This light allows photosynthesis to occur, and therefore life can thrive in oceans, lakes, and rivers. Conversely, the loss of water clarity in polluted water is a seri- ous problem. For example, in the Chesapeake Bay on the East Coast of the U.S., reduction in water clarity due to pollution and algae growth harms the aquatic grasses which form the base of the food chain. 2.2  Water Resources and the Water Cycle In addition to being extremely scarce, accessible fresh water is also distributed unevenly. Tropical rain forests receive very high amounts of precipitation , even though they are home to relatively few people. In contrast, many arid regions, such as the Middle East, North Africa, and the western U.S., are experiencing water stress due to low precipitation and grow- ing populations. Even within countries, there is high variation in available water between regions. Southern China receives much higher precipitation than the arid north, prompting the Chinese government to initiate massive infrastructure projects in order to redistribute water. CLIMATE Regional weather patterns over an extended period of time. PRECIPITATION Water falling from the atmo- sphere as rain, snow, or hail. WATER STRESS When insufficient water is available in a given region to meet human needs.