More Impacts on the Hydrologic Cycle

More Impacts on the Hydrologic Cycle

• Between the Earth's surface and the groundwater beneath is a boundary known as the water table.

• Its shape and height is determined by the land surface it is under.

• When the water table naturally meets the land surface, a spring is formed and will eventually make its way to larger bodies of water like streams, rivers, or lakes.​

​The Water Table

Open Ended

What do you think affects the level of the water table?

• The water table level is affected by changes in precipitation, plants, human interactions, and other factors.

  • When snow melts and precipitation is high, the level rises.

  • When plants take up water from the soil, the level lowers.

  • Humans pumping water from wells also lowers the water table level.

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​The Water Table

Open Ended

After a big rainstorm, Mia notices that the dirt on a small hill in her yard looks different. Some of it has been washed away, and small rocks have moved to a lower spot.

What do you think caused this? How might rain change the shape of land overtime?

• Washing away soil

  • Rain can carry away dirt and small rocks, making hills or slopes smaller

• Creating small channels

  • Water can carve out small paths in the ground that could grow bigger over time

Rain Changing Land Over Time

• Smoothing or breaking rocks

  • Rocks might break apart or wear down over time from water flowing over them

• Building up new land in other places

  • The dirt and rocks that wash away might pile up somewhere else, creating new landforms like small mounds or riverbanks.

• Making sinkholes or changing the ground

  • If water soaks into the ground too much, it could weaken the soil underneath and cause parts of the land to sink

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Rain Changing Land Over Time

• the movement of rock fragments, soil, or dissolved matter by wind, water, ice or gravity

​Erosion

Open Ended

What other factors do you think affect erosion?

• Increasing rates

  • Rain, rivers, wind, flooding, ocean waves, and the movement of ice (glaciers)

  • Deforestation, habitat loss, agricultural activities

    • disruption to roots destabilizes soil, which can decrease soil and water quality

  • Urbanization (ex. paving land with concrete can increase runoff)

• Decreasing rates

  • Human structures (ex. coastal harbors - traps sediments, which increases erosion elsewhere)

  • Damming rivers and extracting water from freshwater ecosystems for human use can decrease erosion, altering habitats and ecosystems.

​Factors Affecting Erosion

• break big rocks into smaller rocks

  • Temperature changes can cause rocks to expand as they warm and contract as they cool (causing cracks).

  • Freezing and expanding of water in rock cracks can split them apart as well.

​Physical Weathering

• Chemical changes in rock OR the rock is dissolved away

  • affected by precipitation and temperature

    (more = faster)

  • plant growth can also change chemistry (ex. increase acidity)

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​Chemical Weathering

Multiple Choice

The Ogallala Aquifer is one of the world's largest underground reservoirs. It stretches across eight states in the United States of America, as shown.

Many farmers in these eight states use water from the Ogallala Aquifer for their livestock and crops. This has caused a dramatic decrease in the water table of the Ogallala Aquifer. If the aquifer is completely emptied, it could take over 6,000 years to for it to refill naturally with precipitation. Which of these would help farmers decrease their impact on the Ogallala aquifer?

• A tool that measures evaporation and transpiration loss to inform farmers how much water the crops need.

• A sensor that predicts precipitation on the farm and then waters the crops before and after the precipitation.

• An automatic watering tool that gives crops the water they need when the Sun is at its highest point in the sky.

• A laser that scans the crops to inform farmers how many insects or birds came near their crops that day.

Multiple Choice

Soil erosion is a natural process that occurs as a result of the hydrologic cycle. When rainwater falls, it flows downhill as runoff toward an accumulation of water. As it flows, the water can carry away the topsoil of a field. Topsoil is the top layer of soil that contains a high concentration of nutrients to support plant growth.

Scientists are designing an investigation to determine changes that occur in a forest that has been cleared. As part of their investigation, they want to collect data about soil erosion. Which investigation best provides data on soil erosion?

• measure the depth of topsoil before and after rainstorms

• determine the amount of nutrients found in the topsoil of other forests

• count the number of trees that grew in the area before it was cleared

• test rainwater to evaluate the amount of acid rain in the area