《Water Cycle 英语思维导图》

Central Idea: Water Cycle

I. Processes (主要过程)

A. Evaporation (蒸发)

• Definition: Liquid water changes into water vapor (Water molecules gain enough energy to break free from the liquid surface)
• Factors Affecting:
  • Temperature: Higher temperatures increase evaporation rates. (Heat provides the energy needed for water molecules to escape)
  • Surface Area: Larger surface areas increase evaporation. (More water is exposed to the air)
  • Humidity: Higher humidity decreases evaporation. (Air is already saturated with water vapor)
  • Wind Speed: Higher wind speeds increase evaporation. (Removes saturated air and replaces it with drier air)
• Sources:
  • Oceans: Main source of evaporation. (Vast surface area)
  • Lakes & Rivers: Contribute significantly. (Freshwater sources)
  • Soil: Moisture evaporates from the ground. (Especially after rainfall)
  • Vegetation: Through transpiration (植物蒸腾作用)
• Significance: Essential for transferring water from the Earth's surface to the atmosphere. (Drives the water cycle)

B. Transpiration (蒸腾作用)

• Definition: The process by which plants release water vapor into the atmosphere. (Water moves from roots to leaves and then evaporates through stomata)
• Mechanism:
  • Water Uptake: Roots absorb water from the soil. (Water moves up the plant through xylem)
  • Water Transport: Water travels through the plant's vascular system. (Xylem vessels transport water upwards)
  • Evaporation: Water evaporates from the leaves through stomata. (Stomata are small pores on the leaf surface)
• Factors Affecting:
  • Temperature: Higher temperatures increase transpiration rates. (Increases evaporation)
  • Humidity: Higher humidity decreases transpiration rates. (Reduces the concentration gradient)
  • Wind Speed: Higher wind speeds increase transpiration rates. (Removes humid air from around the leaves)
  • Light Intensity: Higher light intensity increases transpiration rates. (Stimulates stomatal opening)
  • Soil Moisture: Adequate soil moisture is essential for transpiration. (Water must be available for uptake)
• Significance: Plays a vital role in the water cycle and plant cooling. (Cools plants and releases water into the atmosphere)

C. Condensation (凝结)

• Definition: Water vapor changes into liquid water. (Water molecules lose energy and come together)
• Process:
  • Cooling: Air cools, causing water vapor to lose energy. (Cooling reduces the kinetic energy of water molecules)
  • Saturation: Air becomes saturated with water vapor. (Air can hold no more water vapor)
  • Nucleation: Water vapor condenses onto condensation nuclei. (Dust, pollen, salt particles)
• Formation:
  • Clouds: Water vapor condenses to form clouds. (Tiny water droplets or ice crystals)
  • Fog: Water vapor condenses near the ground. (Similar to clouds, but at ground level)
  • Dew: Water vapor condenses on surfaces. (When surfaces cool below the dew point)
  • Frost: Water vapor freezes directly onto surfaces. (When surfaces are below freezing)
• Significance: Forms clouds, fog, dew, and frost, which are essential for precipitation. (Prepares water for return to the Earth's surface)

D. Precipitation (降水)

• Definition: Water falls from the atmosphere to the Earth's surface. (In the form of rain, snow, sleet, or hail)
• Types:
  • Rain: Liquid water falling from clouds. (Most common form of precipitation)
  • Snow: Frozen water crystals falling from clouds. (Occurs when temperatures are below freezing)
  • Sleet: Rain that freezes as it falls through a layer of cold air. (Forms ice pellets)
  • Hail: Balls of ice that form in thunderstorms. (Updrafts carry water droplets high into the atmosphere where they freeze)
• Formation:
  • Cloud Formation: Condensation forms clouds. (Water droplets or ice crystals grow in size)
  • Collision & Coalescence: Water droplets collide and combine in clouds. (Larger droplets become heavy enough to fall)
  • Ice Crystal Growth: Ice crystals grow by attracting water vapor. (In colder clouds)
• Significance: Returns water to the Earth's surface, replenishing water sources. (Provides water for plants, animals, and human use)

E. Runoff (径流)

• Definition: Water that flows over the Earth's surface. (From precipitation, snowmelt, or other sources)
• Flow Paths:
  • Surface Runoff: Water flows over the land surface. (Occurs when the ground is saturated or impermeable)
  • Streamflow: Water flows in streams and rivers. (Channels concentrate runoff)
  • Groundwater Flow: Water infiltrates into the ground and flows underground. (Slowest flow path)
• Factors Affecting:
  • Precipitation Intensity: Higher intensity leads to more runoff. (Excess water cannot infiltrate quickly enough)
  • Slope: Steeper slopes increase runoff. (Water flows faster)
  • Vegetation: Vegetation reduces runoff. (Intercepts rainfall and slows flow)
  • Soil Type: Impermeable soils increase runoff. (Water cannot infiltrate)
  • Land Use: Urban areas increase runoff. (Impermeable surfaces like roads and buildings)
• Significance: Transports water and sediments to rivers, lakes, and oceans. (Contributes to erosion and water quality)

F. Infiltration (渗透)

• Definition: Water seeps into the ground. (Water moves from the surface into the soil)
• Factors Affecting:
  • Soil Type: Sandy soils have higher infiltration rates than clay soils. (Larger pores allow water to move more easily)
  • Soil Moisture: Dry soils have higher infiltration rates than wet soils. (Soil pores are not already filled with water)
  • Vegetation: Vegetation increases infiltration rates. (Root systems create pathways for water to enter the soil)
  • Land Use: Compacted soils reduce infiltration rates. (Reduces pore space)
• Groundwater Recharge:
  • Percolation: Water moves downward through the soil profile. (Driven by gravity)
  • Aquifers: Water replenishes underground aquifers. (Underground layers of permeable rock or sediment)
• Significance: Replenishes groundwater supplies and reduces runoff. (Important for water storage and availability)

II. Reservoirs (水库/蓄水池)

A. Oceans (海洋)

• Largest Reservoir: Holds the vast majority of Earth's water. (About 97% of all water)
• Evaporation Source: Main source of water vapor for the atmosphere. (Constant evaporation occurs)
• Water Movement: Ocean currents distribute water around the globe. (Influence climate patterns)

B. Ice Caps and Glaciers (冰盖和冰川)

• Freshwater Storage: Second largest reservoir, storing significant amounts of freshwater. (Frozen water)
• Melting: Contribute to sea level rise and freshwater runoff. (Climate change is accelerating melting)
• Seasonal Variation: Melt and refreeze seasonally, affecting water availability. (Important water source in some regions)

C. Groundwater (地下水)

• Underground Storage: Water stored in aquifers beneath the Earth's surface. (Replenished by infiltration)
• Drinking Water Source: Important source of drinking water for many communities. (Pumped from wells)
• Slow Movement: Moves slowly through the ground. (Can take years or centuries to recharge)

D. Lakes and Rivers (湖泊和河流)

• Surface Water: Easily accessible freshwater sources. (Used for drinking, irrigation, and industry)
• Runoff Collection: Collect runoff from surrounding land areas. (Channels and storage areas)
• Ecosystem Support: Provide habitat for many aquatic organisms. (Essential for biodiversity)

E. Atmosphere (大气)

• Water Vapor: Contains a relatively small amount of water compared to other reservoirs. (Crucial for precipitation)
• Water Transport: Transports water vapor around the globe. (Influenced by wind patterns)
• Rapid Turnover: Water vapor cycles through the atmosphere quickly. (Constantly evaporating and precipitating)

III. Human Impact (人类影响)

A. Deforestation (森林砍伐)

• Reduced Transpiration: Decreases the amount of water vapor released into the atmosphere. (Fewer trees to transpire)
• Increased Runoff: Increases surface runoff and erosion. (Loss of vegetation cover)
• Altered Local Climate: Can lead to drier conditions and altered precipitation patterns. (Disrupts the water cycle)

B. Urbanization (城市化)

• Increased Runoff: Increases surface runoff due to impermeable surfaces. (More paved areas, less infiltration)
• Reduced Infiltration: Decreases groundwater recharge. (Less water seeps into the ground)
• Pollution: Can lead to water pollution from urban runoff. (Contaminants washed into waterways)

C. Climate Change (气候变化)

• Increased Evaporation: Higher temperatures lead to increased evaporation. (More water vapor in the atmosphere)
• Altered Precipitation Patterns: Changes in precipitation patterns, leading to droughts and floods. (Shifts in weather systems)
• Melting Glaciers: Accelerated melting of glaciers, contributing to sea level rise. (Loss of freshwater storage)
• Sea Level Rise: Rising sea levels can contaminate freshwater sources and coastal ecosystems. (Saltwater intrusion)

D. Water Diversion (水资源转移)

• Reduced Streamflow: Diverting water for irrigation or other uses can reduce streamflow. (Affects downstream ecosystems)
• Altered Ecosystems: Can disrupt aquatic ecosystems and affect water quality. (Changes in water availability and temperature)
• Water Scarcity: Can exacerbate water scarcity in already arid regions. (Competition for limited water resources)

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