2.2 How much water do we use?

Information for Planning & Teaching

Background Knowledge

Understanding both visible and invisible water use is crucial for effective water management and conservation efforts. It helps in identifying opportunities to reduce water consumption, improve efficiency, and promote sustainable practices across various sectors. Water use encompasses both visible and invisible aspects, referring to the various ways in which water is utilized and consumed.

1. The difference between visible and invisible water use lies in the nature of water consumption and its visibility in the context of different activities and processes.
   Visible Water Use:

• Direct Consumption: Visible water use refers to the direct and immediate consumption of water that is easily observable and quantifiable. This includes activities such as drinking, bathing, washing clothes, and watering plants, where water is visibly consumed or utilized.

• Tangible and Measurable: The amount of water used in visible water consumption is typically quantifiable and can be directly measured or estimated. It is often associated with personal or immediate usage and is relatively easier to track and monitor.

2. Invisible Water Use:

• Indirect Consumption: Invisible water use refers to water consumption that is not immediately apparent or observable. It includes water used in the production, manufacturing, or supply chain of goods and services. This water is embedded in products and processes, making it less visible to end consumers.

• Embedded Water: Invisible water use is sometimes referred to as "embedded water" or "virtual water." It represents the amount of water required to produce a particular product or to support a specific activity, including the water used in growing, processing, manufacturing, and transportation.

• Cumulative and Complex: Invisible water use is often cumulative, considering the entire lifecycle of a product or activity. It involves a complex assessment of water consumption throughout multiple stages, making it challenging to measure precisely. Virtual water calculations aim to estimate this hidden water consumption.

3. While visible water use is more immediate and easily identifiable, invisible water use highlights the indirect and often unnoticed water consumption associated with the production and supply chain of goods and services. Both aspects are important to consider in water management and conservation efforts to ensure a comprehensive understanding of water usage and its environmental implications.

Lesson Timing

This lesson is important in establishing that individuals can play a meaningful role in water conservation. It connects the issue to students in a personal way. However, there are many ways to make that connection that can take varying amounts of time.

If students are designing their own experiments to assess their water usage, the teacher may prefer to have students design their experiments in class and get the teacher’s approval. Then as homework, students conduct their experiments and complete a post-lab that is only parts 1 and 4 in class the next day.

Student Ideas & Experiences

Students might have their own ideas about how to asses their visible water use. For example, they might come up with something similar to the below procedures.

Materials Needed:

1. Large container (e.g., a bucket or a gallon-sized container)

2. Stopwatch or timer

3. Measuring cup or scale (optional)

Procedure:

1. Set up the container: Place the container beneath the showerhead, ensuring that it can collect all the water that flows during the shower.

2. Measure the container: If the container doesn't have volume markings, students can measure its capacity by filling it with a known quantity of water using a measuring cup or a scale. This step helps in accurately determining the amount of water collected later.

3. Start the shower: Turn on the shower and adjust the water flow to the desired setting.

4. Begin timing: Start the stopwatch or timer as soon as the shower starts.

5. Shower as usual: Students should take their shower as they normally would, making sure to keep the water flow consistent.

6. Stop timing and measure: When they finish showering, stop the timer and carefully collect all the water from the container. They can use a measuring cup or a scale to determine the precise amount of water collected.

7. Calculate the water usage: Subtract the initial volume of the container (measured in step 2) from the final volume of water collected. This will give the amount of water used during the shower.

8. Analyze and track usage: Students can record their water usage in a journal or spreadsheet and track it over time. They can set goals to reduce their water consumption and compare their usage from shower to shower.

Encourage students to follow their own inquiry using what they know about accuracy and evidence.

Science Practices

Planning and carrying out investigations is an essential science practice for middle school students, aligned with the Next Generation Science Standards (NGSS). By engaging in this practice, students are provided opportunities to develop and refine their inquiry skills. They learn how to ask meaningful questions, make predictions, design procedures, gather data, and draw evidence-based conclusions. These skills foster a scientific mindset and help students think critically and analytically. Additionally, investigations provide opportunities for students to connect scientific concepts to real-world contexts. By planning and conducting investigations related to relevant issues, students can see the practical applications of science and develop a deeper appreciation for its role in addressing societal challenges.

Teaching Cases