Chapter 6 Sustainabilty and Engineering: Sustainable Water

Chapter 6 Sustainabilty and Engineering: Sustainable Water#

  1. Introduction: Sustainable Water

  2. Simulation: Sustainable Water

  3. Self-Assessment

1. Introduction#

💧 Sustainable Water: Overview#

Sustainable water refers to the responsible management of water resources to meet current needs without compromising future availability. It emphasizes:

  • Equitable Access: Ensuring all individuals have access to 20–50 liters/day of clean water for basic needs

  • Holistic Management: Balancing ecological, economic, and social demands across agriculture, industry, and domestic use

  • Resilience: Adapting to climate change, droughts, and floods while maintaining water quality and supply

📊 Water Footprint: Definition and Calculation#

The water footprint measures the total volume of freshwater used directly and indirectly by an individual, product, or process. It includes:

Type

Description

Blue Water

Surface and groundwater used in production or consumption

Green Water

Rainwater stored in soil and used by plants

Grey Water

Freshwater required to dilute pollutants to meet water quality standards

🔢 Calculation Tools#

🏡 Household-Scale Sustainable Water Upgrades#

Sustainable water upgrades at the household level can reduce water use by 30–50%, lower utility bills, and cut greenhouse gas emissions from water treatment and heating.

🛠️ Key Strategies#

  • Low-Flow Fixtures
    Faucets, toilets, and showerheads reduce indoor water use by up to 700 gallons/year

  • Rainwater Harvesting
    Covers up to 34% of annual water needs for toilets and irrigation

  • Greywater Recycling
    Reuses water from sinks and showers for landscaping or flushing

  • Smart Irrigation
    Uses weather and soil data to optimize outdoor watering

🌍 Environmental Benefits#

  • Reduces energy demand for water heating and pumping

  • Cuts carbon emissions from municipal water treatment

  • Preserves local ecosystems and groundwater reserves

📘 Summary Insight#

Sustainable water management at the household scale is a powerful lever for climate action. By combining efficient technologies, behavioral changes, and reuse systems, homes can dramatically reduce their water footprint while enhancing resilience and comfort.

2. Simulation#

💧 Sustainable Water Savings Simulation#

📘 Overview#

This interactive model estimates daily and monthly water savings for a household based on the adoption of efficient appliances and fixtures. It simulates how upgrades like low-flow toilets, efficient showers, and eco-friendly dishwashers can reduce water consumption over time.

🧮 Model Assumptions#

🔹 Base Water Usage (per person/day)#

Activity

Default Usage (L/day)

Toilet

18

Shower

50

Faucet

12

Laundry

60

Dishwasher

15

These values reflect typical modern usage patterns.

🔹 Efficiency Upgrades#

Upgrade

Default Savings (%)

Low-flow toilet

40%

Efficient shower

30%

Aerated faucet

30%

High-efficiency laundry

40%

Eco dishwasher

50%

Each slider allows users to adjust the efficiency level of these upgrades.

📊 Simulation Output#

  • Daily water saved: based on the difference between baseline and adjusted usage

  • Cumulative savings: plotted over a 30-day period

  • Interactive controls: adjust household size and efficiency levels

📈 Visualization#

The plot shows:

  • X-axis: Day of the month (1–30)

  • Y-axis: Cumulative water saved in liters

  • Line: Total savings over time for the selected household and upgrade settings

🧠 How It Works#

  1. Calculates total daily water use for the household

  2. Applies efficiency reductions to each category

  3. Computes daily and cumulative savings

  4. Displays results interactively with sliders

📚 Use Cases#

  • Estimating impact of sustainable upgrades

  • Educational tool for water conservation awareness

  • Planning household retrofits or green building design

import numpy as np
import matplotlib.pyplot as plt
from ipywidgets import FloatSlider, IntSlider, interact

# 💦 Base water usage estimates (per person/day)
usage_defaults = {
    'toilet': 18,     # liters/day (modern low-flush ≈ 6L/use × 3 uses)
    'shower': 50,     # liters/day
    'faucet': 12,     # liters/day
    'laundry': 60,    # liters/day
    'dishwasher': 15  # liters/day
}

# 🧠 Water savings % for sustainable upgrades
savings_defaults = {
    'low_flow_toilet': 0.4,
    'efficient_shower': 0.3,
    'aerated_faucet': 0.3,
    'HE_laundry': 0.4,
    'eco_dishwasher': 0.5
}

# 💧 Main function to calculate and plot results
def simulate_water_savings(people, toilet_eff, shower_eff, faucet_eff, laundry_eff, dish_eff):
    days = np.arange(1, 31)
    
    # Base consumption (L/day)
    daily_base = people * sum(usage_defaults.values())
    
    # Adjusted usage with efficiencies
    adjusted = {
        'toilet': usage_defaults['toilet'] * (1 - toilet_eff),
        'shower': usage_defaults['shower'] * (1 - shower_eff),
        'faucet': usage_defaults['faucet'] * (1 - faucet_eff),
        'laundry': usage_defaults['laundry'] * (1 - laundry_eff),
        'dishwasher': usage_defaults['dishwasher'] * (1 - dish_eff),
    }
    
    daily_saving = people * (sum(usage_defaults.values()) - sum(adjusted.values()))
    cumulative_saving = daily_saving * days

    # 📊 Plot
    plt.figure(figsize=(10, 4))
    plt.plot(days, cumulative_saving, label="Cumulative Water Saved (L)", color="royalblue")
    plt.title(f"Sustainable Water Savings Simulation — {people} People")
    plt.xlabel("Day of Month")
    plt.ylabel("Water Saved (Liters)")
    plt.grid(True)
    plt.legend()
    plt.tight_layout()
    plt.show()
    
    print(f"💧 Estimated Daily Water Saved: {daily_saving:.0f} L")
    print(f"📆 Estimated Monthly Savings: {cumulative_saving[-1]:.0f} L")

# 🎛️ Interactive sliders
interact(simulate_water_savings,
         people=IntSlider(value=3, min=1, max=10, step=1, description='Household Size'),
         toilet_eff=FloatSlider(value=savings_defaults['low_flow_toilet'], min=0.0, max=0.6, step=0.05, description='Toilet Efficiency'),
         shower_eff=FloatSlider(value=savings_defaults['efficient_shower'], min=0.0, max=0.5, step=0.05, description='Shower Efficiency'),
         faucet_eff=FloatSlider(value=savings_defaults['aerated_faucet'], min=0.0, max=0.5, step=0.05, description='Faucet Efficiency'),
         laundry_eff=FloatSlider(value=savings_defaults['HE_laundry'], min=0.0, max=0.6, step=0.05, description='Laundry Efficiency'),
         dish_eff=FloatSlider(value=savings_defaults['eco_dishwasher'], min=0.0, max=0.6, step=0.05, description='Dishwasher Efficiency'));

3. Self-Assessment#

Conceptual Questions#

These questions explore the physical meaning and modeling assumptions behind the simulation.

Household Water Use#

  • What are the primary contributors to daily household water consumption?

  • How does household size affect total water usage and potential savings?

  • Why is water usage modeled as a linear function of time in this simulation?

Efficiency Modeling#

  • How do efficiency percentages translate into reduced water usage for each appliance?

  • Why is the adjusted usage calculated as ( \text{usage} \times (1 - \text{efficiency}) )?

  • What assumptions are made about the consistency of daily water use and behavior?

Cumulative Savings#

  • Why is cumulative savings modeled as a linear accumulation over days?

  • How would the results change if usage patterns varied by day (e.g., weekends vs weekdays)?

  • What are the limitations of using fixed default values for water usage across households?

🔍 Reflective Questions#

These questions encourage critical thinking and application to real-world sustainability decisions.

  • Which efficiency upgrade offers the greatest potential savings in your household context?

  • How would the model change if you included outdoor water use (e.g., irrigation)?

  • What behavioral changes could complement technological upgrades to further reduce water use?

  • How could this simulation be adapted for seasonal or regional differences in water availability?

  • What are the trade-offs between cost, convenience, and water savings when choosing efficient appliances?

Quiz Questions#

Multiple Choice#

  1. Which appliance has the highest default daily water usage per person?
    A. Toilet
    B. Shower
    C. Laundry
    D. Dishwasher
    Answer: C

  2. If a faucet has 30% efficiency, how much of its default usage is saved?
    A. 3.6 liters
    B. 8.4 liters
    C. 12 liters
    D. 30 liters
    Answer: A

  3. What does the cumulative savings curve represent?
    A. Total water used over time
    B. Water saved each day
    C. Accumulated water savings over the month
    D. Efficiency of each appliance
    Answer: C

True/False#

  1. Increasing household size increases both total usage and total savings.
    Answer: True

  2. The model assumes water usage is constant every day.
    Answer: True

  3. A 50% efficient shower reduces its water usage by half.
    Answer: True

Short Answer#

  1. Explain how the model calculates daily water savings.
    Answer: It subtracts the adjusted usage (based on efficiency) from the default usage for each appliance, multiplies by the number of people, and sums the result.

  2. Why might the actual water savings differ from the model’s estimates?
    Answer: Variability in user behavior, appliance performance, maintenance issues, and seasonal factors can all affect real-world outcomes.

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