How does water circulate?---**Title:**
B The water (hydrological) cycle
**Text Descriptions:**
* **A Evaporation:** water is stored in the sea as a liquid. High temperature and warm winds change the liquid water into gas (water vapour), which rises into the atmosphere.
* **B Evapotranspiration:** vegetation not only intercepts rainfall but also takes it up through roots from the soil. This water is eventually returned to the atmosphere by transpiration from leaves. Surface water is also evaporated from leaves.
* **C Condensation:** as water vapour is blown towards mountains by the prevailing winds it is forced to rise, cools and condenses back into water droplets. These form clouds and relief (orographic) rainfall or snow.
* **D Interception:** some rainfall is intercepted by plants and trees before reaching the ground. Some falls on land and infiltrates the ground or flows on the surface as small fast-flowing streams.
* **E Overland flow:** upland streams flow downhill and join at confluences to form slower-moving, wider, deeper rivers which eventually discharge the water into lakes or the sea.
**Diagram Description:**
* **Type:** Cross-section diagram illustrating the hydrological cycle and the long profile of a river from source to mouth.
* **Main Elements:**
* Depicts a landscape showing mountains on the left, sloping downwards to the sea on the right.
* **River Profile:** Divided into Upper course (near source, steep slope), Middle course, and Lower course (near mouth, gentle slope). Labeled as "Long profile of river's fall".
* **River Source:** Labeled box "RIVER SOURCE Where river begins in the uplands". Located in the mountainous upper course.
* **River Mouth:** Labeled box "RIVER MOUTH Where the river meets the sea". Located where the river enters the Sea.
* **Sea:** Depicted on the right side.
* **Mountains/Hills:** Shown in the upper course, green and sloped.
* **Valleys:** Labeled as "V-shaped valleys" in the upper course.
* **Waterfalls:** Depicted in the upper course.
* **Trees:** Shown in the upper and middle courses. Label 4 points to arrows rising from trees/land, suggesting evapotranspiration. Label 5 points to trees with arrows suggesting water flow or interception.
* **Meanders:** Curved river path shown in the lower course.
* **Floodplain:** Flat area next to the river in the lower course.
* **Oxbow lake:** Crescent-shaped lake shown near the meanders in the lower course.
* **Delta:** Fan-shaped landform at the river mouth.
* **Clouds:** Depicted above the mountains.
* **Wind:** Labeled as "Prevailing wind" blowing from the sea towards the mountains, indicated by arrows.
* **Processes/Flows (with labels):**
* Label 1: Arrows rising from the Sea/water surface upwards towards clouds, representing Evaporation.
* Label 2: Arrows downwards from clouds over the mountains, showing raindrops and snowflakes, labeled as "Precipitation = rain and snow".
* Label 3: Points to the river flowing downwards in the upper/middle course.
* Label 4: Arrows rising upwards from trees/land surface, likely related to evapotranspiration or evaporation from land.
* Label 5: Arrows pointing downwards and horizontally near trees, suggesting processes like interception, infiltration, or overland flow near vegetation.
* **Overall Flow:** The diagram illustrates the movement of water through evaporation from the sea, transport by wind, condensation in clouds over mountains, precipitation onto land, flow through rivers (from source in uplands through V-shaped valleys, waterfalls, meanders, floodplain, delta) to the sea at the mouth, and processes like evapotranspiration and interception on land.
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Water circulates through a continuous process called the hydrological cycle. This involves the movement of water between the sea, atmosphere, and land. The cycle includes evaporation from water bodies, condensation in the atmosphere forming clouds, and precipitation returning water to the land and sea.
The water cycle begins with evaporation and evapotranspiration. Solar energy heats water in seas, lakes, and rivers, causing it to evaporate and rise as water vapor. Meanwhile, plants absorb water through their roots and release it through their leaves in a process called transpiration. Together, these processes add moisture to the atmosphere, forming the first step of the hydrological cycle.
As water vapor rises into the atmosphere, it is carried by prevailing winds toward higher elevations like mountains. As the air rises and cools, the water vapor condenses around tiny particles to form water droplets, creating clouds. When these droplets grow large and heavy enough, they fall back to Earth as precipitation in the form of rain, snow, or hail, completing the atmospheric phase of the water cycle.
When precipitation reaches the land, several processes occur. Some rainfall is intercepted by vegetation such as trees and plants before it can reach the ground. Water that does reach the surface either infiltrates into the soil, where it may become groundwater, or flows over the surface as overland flow. This surface water collects in small streams and channels that flow downhill, eventually joining larger water bodies.
Rivers play the crucial final role in the water cycle. Small streams join together at confluences to form larger rivers. These rivers flow from their source in the uplands, through valleys and across floodplains, eventually reaching the sea at their mouth. Here, rivers discharge the collected water back into the ocean, completing the hydrological cycle. The water can then begin the process again through evaporation, ensuring the continuous circulation of water on Earth.