Did you observe that the contaminants, represented by the sugar mixture, followed the water into the reservoirs of water on the surface of the plate but also seeped into the water that was in the bowl? While this isn't a perfect model and certainly wouldn't be the most accurate way for scientists in the real world to study the human impacts on water supplies, it does provide a starting point for us to discuss how humans can impact a watershed.
- A watershed is the area of land where all the water that is under it or drains off of it goes to the same place.
- Surface water is any liquid water on Earth's surface such as that found in ponds, lakes, rivers, streams, and oceans.
- Groundwater is liquid water that is under Earth's surface, in the ground.
You already know about the water cycle. Water evaporates to form clouds, falls as precipitation, drains into rivers as runoff, and flows to larger bodies of surface water. Due to the force of gravity, precipitation can also seep through soil into aquifers, which are areas of permeable rock that contain and transmit groundwater. On Earth, water is a finite resource. This means that there is a given amount of clean water. Once our water is contaminated, it is extremely difficult to restore its purity.
Let's examine the Explore investigation and see what each material models.
You observed how the colored sugar mixture dissolved into and flowed with the water. Some of the contaminants followed the precipitation as runoff and flowed directly into the surface water. The rest of the water seeped through the soil due to the force of gravity. This caused contamination of the groundwater as evidenced by the clean water turning a green color. The contamination could have been from fertilizers or pesticides, among others things you will discover in the Elaborate.
While models are useful for scientific study, they are not always 100% accurate. Our model certainly has its limitations, such as the following:
- Gravel is not soil.
- The model does not represent all the ways humans impact a watershed.
- There are often places where groundwater feeds back into bodies of surface water.
- Real contaminants were not used.
It should be pointed out that human activity does not automatically have a negative impact on groundwater and surface water. As the most intelligent mammal on the planet, humans have the ability to make choices and correct their own behavior to avoid contamination of the watershed.
Great work so far! Now it's time to check your understanding and make sure you are on track. Test your knowledge by trying the interactive activity below.