Water Quality - Nutrient Management and Cropping Systems - Lesson 3 The Water Cycle

Water Quality - Nutrient Management and Cropping Systems - Lesson 3 The Water Cycle

Target Grade Level / Age Range:

Grades 9-12


90 minutes


The water cycle describes the movement of water on, above, and below the surface of the Earth. Students will learn the process of the water cycle and how it contributes to the environment and agriculture. Students will also learn how water from precipitation contributes to groundwater and creates runoff into our streams, lakes, and oceans.       


  • Computer or tablet with internet access
  • Pencil and paper
  • RainfallThroughTheSeasonsWS.doc

Suggested Companion Resources (books and websites)

Vocabulary (with definitions)

  • Climate: the weather of a particular region over a series of years
  • Condensation: the process in which water is changed from vapor to liquid. It takes place when water collects as droplets on a cold surface when humid air is in contact with it and is part of the formation of clouds.
  • Evaporation: the process of which water changes from a liquid into a gas or vapor
  • Evapotranspiration: water that transpires from plants and evaporates from the soil to the atmosphere.
  • Infiltration: to pass through a substance by filtering or permeating
  • Permeability: the ability of the ground surface to absorb water.
  • Precipitation: moisture in the form of rain, snow, sleet, or hail that falls to the ground
  • Relative humidity: the amount of water vapor present in air expressed as a percentage of the amount needed for saturation at the same temperature.
  • Runoff: the draining away of water from the surface of an area of land
  • Saturation: the state of process that occurs when no more of something can be absorbed, combined with, or added
  • Transpiration: the process where plants absorb water through the roots and give off water vapor through pores in their leaves
  • Watershed: the land which drains water to a particular body of water or outlet

Background – Agricultural Connections (what would a teacher need to know to be able to teach this content)

Knowing how water moves around the Earth is important in connecting the ocean, land, and atmosphere together. Understanding the water cycle allows scientist to better understand and analyze precipitation’s impact on rivers, streams, landforms, surface runoff and groundwater. It helps us understand geography and a regions climate, along with environmental impacts and agriculture’s importance in a certain area. When we understand the water cycle, we then can understand how the water cycle contributes to water erosion, the hypoxia in the Gulf of Mexico, and other environmental issues and how to go about working towards a solution.

Interest Approach or Motivator

  1. Have students pair up and have access to a computer or tablet with internet access.
  2. To begin this lesson, use the RainfallThroughTheSeasonsWS.doc and have students research the amount of rainfall that falls in the state of Iowa during the 4 seasons (fall, winter, spring, summer)
  3. After each pair of students find their results have them report on the white board their results.
  4. Discuss the results students found and discuss with them factors that influence rainfall in a certain season and region.


Using the WaterCycle.pptx, walk through the content of this lesson provided below and have students take notes on the water cycle.

The Water Cycle—How It Works
  • The water cycle describes the existence and movement of water on, in, and above the Earth.
  • It is important to note that the water cycle is powered by the Sun.
  • There is no starting point of the water cycle because it is a continuous cycle, but for explanation purposes we will begin with evaporation.






  • Evaporation: the process of which water changes from a liquid into a gas or vapor
    • The sun drives the water cycle process. It begins by heating earth’s surface along with heating the water in lakes, rivers, streams, and the ocean.
    • Energy from the heat of the sun is used to break the bonds that hold water molecules together.
      • Heat is necessary to evaporate water. Water easily evaporates at the boiling point (212° F, 100° C) but evaporates much more slowly at the freezing point (32° F, 0° C).
    • When water is heated, it begins to turn from the liquid state into the gaseous state (water vapor) and evaporates into the air.
    • Water vapor is all around us and is known as relative humidity: the amount of water vapor present in air expressed as a percentage of the amount needed for saturation at the same temperature.
    • Evaporation is the primary pathway that water moves from the liquid state back into the water cycle as atmospheric water vapor.
    • Evapotranspiration: water that transpires from plants and evaporates from the soil to the atmosphere.
      • Plants put down roots into the soil to draw water and nutrients up into the stems and leaves. Some of this water is returned to the air by transpiration.
      • Transpiration rates vary widely depending on weather conditions, such as temperature, humidity, sunlight availability and intensity, precipitation, soil type and saturation, wind, and land slope.
      • To learn more about evapotranspiration, follow this link https://water.usgs.gov/edu/watercycleevapotranspiration.html
    • Condensation: the process in which water is changed from vapor to liquid
      • Condensation is responsible for the formation of clouds.
      • The atmosphere high above land is cooler, and as the water vapor rises, it cools.
      • Cooler temperatures cause it to condense and thus creates the formation of clouds.
      • Clouds are made up of water vapor and cloud droplets (small drops of condensed water) These droplets are too small to fall as precipitation, but they are large enough to form visible clouds.
      • When clouds form the process of precipitation can occur.
    • Precipitation: water that falls to the Earth in various states such as hail, mist, rain, sleet, snow.
      • In this process, small water droplets attach to small dust, salt, or smoke particles (this acts as the nucleus that holds the water particles together. Water droplets can then grow in size by colliding with other water particles. If enough collision occurs to the water droplets become heavy enough to fall from the ground to the sky.
    • Factors That Influence Precipitation
      • Different areas of the Earth’s surface receive different amounts of precipitation
        • Altitude: Rains more in high areas than in low areas.
        • Latitude: Rains more in the areas near the equator than in the temperature zones and polar regions. Temperature is higher near the Equator so more evaporation takes place
        • Level of Humidity: Rains more on the coast than inland. Large bodies of water are a source of humidity.
    • Infiltration: the action of a liquid entering or permeating the ground by filtration. (Water from precipitation soaking into the ground)
      • Permeability: the ability of the ground surface to absorb water.
        • The less water the ground can absorb, the more runoff on the surface there will be
        • A surface with high absorption ability has high permeability
        • A surface with low absorption ability has low permeability
      • When infiltration of water reaches the max holding capacity it is known as saturated ground.
        • Saturation: the state of process that occurs when no more of something can be absorbed, combined with, or added (Ex. Soil becomes saturated when it can no longer hold any more water and runoff or flooding can be a result.)
    • Runoff: when rain hits saturated or impervious ground and flows overland downhill to a stream, lake, or watershed.
      • Watershed: the area of land where all of the water that falls in it and drains off of it goes into the same place.
        • Water will flow along channels as it moves into larger creeks, streams, and rivers.
      • The interaction between precipitation and surface runoff varies according to time and geography.
      • Surface runoff is affected by both meteorological factors and the physical geology and topography of the land.
      • https://water.usgs.gov/edu/watercyclesummary.html 
    • Factors Influencing Runoff
      • Meteorological factors affecting runoff:
        • Types of precipitation (rain, snow, sleet, etc.)
        • Rainfall intensity
        • Rainfall amount
        • Rainfall duration
        • Distribution of rainfall over the drainage basin
        • Direction of storm movement
        • Precipitation that occurred earlier and resulting soil moisture
        • Other meteorological and climatic condition that affect evapotranspiration, such as temperature, wind, relative humidity, and season
      • Physical characteristics affecting runoff:
        • Land use
        • Vegetation
        • Soil type
        • Drainage area
        • Basin shape
        • Elevation
        • Topography, especially the slope of the land
        • Drainage network patterns
        • Ponds, lakes, reservoirs, sinks, etc. in the basin, which prevent or delay runoff from continuing downstream
    • Human changes to these landscape features can greatly influence runoff
      • As more and more people inhabit the Earth, and as more development and urbanization occur, more of the natural landscape is replaced by impervious surfaces, such as roads, houses, parking lots, and buildings that reduce infiltration of water into the ground and accelerate runoff to ditches and streams.









Meteorologist Moment


  • Based off the information presented in the PowerPoint and the data collected in the first activity have students create a meteorologist report for a season in Iowa.
  • Have the students pair up and assign each group a season (Fall, Winter, Spring, Summer)
  • Lead a short brainstorming session eliciting the terminology of a weather report: highs, lows, fronts, low pressure, high pressure, winds, temperature, humidity and what terminology would be appropriate for each Iowa season.
  • Direct students to create a thirty-second “weather report” on what to expect to see in the Iowa season. Have the weather reporter answer the question: “Has human activity had an affect (positive or negative) on the water cycle? Has human activity changed the water cycle at all? If so, how?”
  • Have students use information from the water cycle and plug into their report and explain why this weather occurs during specific seasons.
  • Students can present their weather reports in pairs or present their weather reports in front of the whole class.




Essential Files (maps, charts, pictures, or documents)



Did you know? (Ag facts)


  • Over 70 percent of the Earth's surface is covered by the oceans
  • Once evaporated, a water molecule spends about 10 days in the air.
  • Studies have shown that the oceans, seas, lakes, and rivers provide nearly 90 percent of the moisture in our atmosphere via evaporation, with the remaining 10 percent being contributed by plant transpiration.
  • Only about a third of the precipitation that falls over land runs off into streams and rivers and is returned to the oceans. The other two-thirds is evaporated, transpired, or soaks into groundwater.


Extension Activities (how students can carry this beyond the classroom)


  • Have students draw up a weather cycle diagram based off of the geography around their hometown. Have them label each step in the cycle and write a report about how the cycle works for their location.
  • Have students measure the amount of rainfall for a week or two and calculate the amount of rainfall they capture correlates with the average estimates of that month.




Lesson plan development was funded by the Resource Enhancement and Protection Conservation Education Program (REAP CEP). Resource Enhancement and Protection Program (REAP): Invest in Iowa our outdoors, our heritage, our people. REAP is supported by the state of Iowa, providing funding to public and private partners for natural and cultural resources projects, including water quality, wildlife habitat, soil conservation, parks, trails, historic preservation and more.








Author(s) (your name)


Hannah Pagel


Organization Affiliation (your organization)


Iowa Agriculture Literacy Foundation


National Agriculture Literacy Outcomes


  • T1.9-12.f. Evaluate the various definitions of “sustainable agriculture,” considering population growth, carbon footprint, environmental systems, land and water resources, and economics
  • T1.9-12.h. Understand the natural cycles that govern the flow of nutrients as well as the way various nutrients (organic and inorganic) move through and affect farming and natural systems
  • T2.9-12.d. Evaluate evidence for differing points of view on topics related to agricultural production, processing, and marketing (e.g., grazing; genetic variation and crop production; use of fertilizers and pesticides; open space; farmland preservation; animal welfare practices; world hunger)


Iowa Core Standards


  • HS-LS2-6. Evaluate the claims, evidence, and reasoning that the complex interactions in ecosystems maintain relatively consistent numbers and types of organisms in stable conditions, but changing conditions may result in a new ecosystem. (soil structure, water cycle, nitrogen cycle)
  • HS-ESS2-2. Analyze geoscience data to make the claim that one change to Earth’s surface can create feedbacks that cause changes to other Earth systems. (water cycle, nitrogen cycle)
  • HS-ESS2-5. Plan and conduct an investigation of the properties of water and its effects on Earth materials and surface processes. (water cycle, tiling, terracing, bioreactors, riparian areas)
  • HS-ESS3-6. Use a computational representation to illustrate the relationships among Earth systems and how those relationships are being modified due to human activity. (water cycle, nitrogen cycle)