Water Cycle — Reading Comprehension Lesson

Reading Passage

Water Cycle

The water cycle, also called the hydrological cycle, is the continuous movement of water through Earth’s atmosphere, land, and oceans. Water has been cycling through this system for billions of years — the water you drink today may have once been part of a prehistoric ocean, a glacier, or even a dinosaur’s bloodstream. The total amount of water on Earth never changes; it simply moves between different reservoirs in different forms. The sun provides the energy that drives the water cycle, and gravity pulls water back down to Earth’s surface.

Evaporation is the process by which liquid water at the surface is converted into water vapor by solar energy. The ocean is the largest source of evaporation, supplying about 86 percent of the water vapor in the atmosphere. Evaporation also occurs from lakes, rivers, soil, and wet surfaces. Transpiration is the release of water vapor through the pores of plant leaves — a large tree can transpire hundreds of gallons of water per day. Together, evaporation and transpiration are called evapotranspiration. Water vapor rises into the atmosphere, cools, and condenses around tiny dust particles to form cloud droplets — a process called condensation.

As cloud droplets combine and grow heavy enough, they fall to Earth as precipitation — rain, snow, sleet, or hail, depending on atmospheric temperatures. Global precipitation is not evenly distributed: tropical regions receive far more than desert regions, and mountain ranges force moist air to rise and cool on their windward sides, producing heavy precipitation while leaving their leeward sides in a “rain shadow.” When precipitation reaches the surface, it follows several pathways. Some runs off directly into streams and rivers, which eventually flow to the ocean. Some infiltrates into the soil, replenishing groundwater in underground aquifers.

Some precipitation is intercepted by vegetation and evaporates before reaching the ground. In cold regions, precipitation accumulates as snowpack or glaciers, storing water for months or years before it melts and flows into streams. Plants take up water through their roots and use it in photosynthesis or release it through transpiration, returning it to the atmosphere. The water cycle plays a critical role in distributing heat around the planet — the energy absorbed during evaporation is released when water vapor condenses, transferring heat from warm tropical oceans to cooler regions. Understanding the water cycle is fundamental to managing water resources, predicting floods and droughts, and understanding climate change.

Printable Worksheet

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