Aqua

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Aqua is your ultimate hydration companion, designed to help you stay healthy and hydrated effortlessly. Built with Flutter, Aqua uses Drift for local database management.

Release

Aqua is available on Google Play and GitHub.

Key Features

🧃 Custom Beverages

Log a variety of beverages beyond water—juice, tea, coffee, and more. Easily create, add, and track your intake.

🧑 Personalized Hydration Goals

Aqua calculates your daily water intake by considering age, weight, gender, and weather conditions, ensuring goals tailored to your needs.

⛹️ Physical Activity Tracking

Log physical activities, and Aqua adjusts hydration goals based on water loss during those activities, keeping you optimally hydrated.

🔔 Friendly Reminders

Receive gentle reminders throughout the day to stay on track with your hydration goals, helping you develop healthy hydration habits.

💤 Sleep Schedule Integration

Aqua integrates with your sleep schedule, ensuring reminders are paused during sleep hours, so you can rest without interruptions.

🎨 User-Friendly Interface

Aqua features an intuitive, visually appealing interface that makes tracking water intake simple and effective.

📈 Progress Tracking

Track daily, weekly, and monthly hydration stats to monitor your progress and identify areas for improvement.

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App Screenshots

Developer Notes

Android Release

• To build an app bundle Android, run flutter build appbundle --release

Note: Android SDK is required.

API Keys

OpenWeatherAPI

• Obtain API key here.
• Store the key in lib/api_keys.dart as: String openWeatherKey = <yourAPIkey>.

System Architecture

• Front-end: Files are stored in lib/screens/.
• Navigation: Post-onboarding screens are accessed using lib/nav_bar.dart.
• Utilities: Utilities like colors, fonts, and Firestore can be found in lib/utils/.
• Database Queries: Queries are stored in files named after respective tables in lib/database/queries/.
• SharedPreferences: User data like name, age, sex, etc., are stored here. The onboard boolean determines which widget (OnboardingView() or NavBar()) is displayed.
• Weather Fetching: Done once per day, with last_run stored in SharedPreferences to ensure the task is executed only once daily.
• Notifications: Managed by NotificationsController, which handles creation and deletion of notifications based on an interval (in minutes) and a volume (in mL).
• The interval is obtained using calcReminderGap()
• The volume is obtained using calcMedianDrinkSize()
• A single Drift Database object is instantiated in lib/nav_bar.dart and passed throughout the app to prevent race conditions caused by multiple database instantiation.

Data Storage

Aqua uses Drift and SharedPreferences for local data storage.

Drift

The database includes:

1. Beverages - Stores all beverages.
2. Drinks - Logs all drinks, with a foreign key referencing Beverages.
3. Activities - Stores physical activities and their MET values.
4. Workouts - Logs activities performed by the user, with a foreign key referencing Activities.
5. WaterGoals - Stores daily water volumes like consumed and total.

Default Values

• calcReminderGap() uses a minimum reminderGap value. If calculated gap is below this value, the function returns the predefined value. DEFAULT: minReminderGap = 10.
• calcMedianDrinkSize() uses a positive integer range of last N drinks for median calculation. DEFAULT: drinkRange = 20.
• Both functions mentioned above can be found in lib/database/queries/general_queries.dart
• Pre-defined beverages: Water, Soda, Coffee, Tea, and Milk. All are editable except Water.
• If user's location cannot be determined, the location on Profile Screen defaults to Mumbai, IN, due to its moderate climate and height from sea level.

Reminder Algorithm

• calcReminderGap() determines reminder intervals. It considers sleep hours and adjusts the reminder time accordingly. For the full implementation, refer to lib/database/queries/general_queries.dart.

• PSEUDOCODE (written in Python for simplicity)

def calcReminderGap(consumed, total):
  
  if (sleepTime <= now <= wakeTime):
    return wakeTime - now
  
  timeLeft = sleepTime - now

  toDrink = total - consumed
  drinkSize = calcMedianDrinkSize()
  drinksNeeded = toDrink // drinkSize

  reminderGap = timeLeft // drinksNeeded

  if (reminderGap < 10):
    return 10
  
  return reminderGap

Scientific Research

Aqua’s water intake calculations are based on research detailed in this book.

The book provides a comprehensive water intake estimation model combining findings from multiple research studies.

The primary formula behind Aqua's water intake calculation is: $DailyWaterGoal = AWI + RWL + [SWL]$, where,

• AWI (Adequate Water Intake): Baseline intake based on age.
• RWL (Respiratory Water Loss): Dependent on weather and Metabolic Rate.
• SWL (Sweat Water Loss): Adjusted for physical activity.

A brief about the scientific terms used in the codebase are mentioned below:

AWI (Adequate Water Intake)

• Data used for AWI is based on age and covers minimal water losses in temperate climates for sedentary individuals.
• Here, Beverage AWI (in liters) refers to the amount of water consumed in the form of liquid beverages including water itself.
• Total AWI (in liters) refers to the total amount of water drunk including Beverage AWI and water from foods.

Age	Beverage AWI (M)	Total AWI (M)	Beverage AWI (F)	Total AWI (F)
1-3	0.9	1.3	0.9	1.3
4-8	1.2	1.7	1.2	1.7
9-13	1.8	2.4	1.6	2.1
14-18	2.6	3.3	1.8	2.3
19-30	3.0	3.7	2.2	2.7
31-50	3.0	3.7	2.2	2.7
51-70	3.0	3.7	2.2	2.7
>70	3.0	3.7	2.2	2.7

RWL (Respiratory Water Loss)

• The amount of respiratory water loss, via evaporation within the lungs, is dependent on both the ventilatory volume and water vapor pressure gradient.
• Generally, Physical Activity has a greater effect on respiratory water loss than environmental factors.
• Respiratory water loss (y ml/day) for temperate conditions can be predicted from Metabolic Rate (x kcal/day) using the equation $y= 0.107x + 92.2$
• High altitude exposure (4300 m above sea level, 448 mm Hg) can further increase respiratory loss by approximately 200 mL/day. This will give us the modified equation $y = 0.107x + 292.2$
• The respiratory water losses increase by approximately 340 mL/day when breathing –20°C versus +25°C air.

SWL (Sweat Water Loss)

• For the average adult, loss of water by insensible diffusion is approximately 450 mL/day.
• When a gram of sweat water is evaporated, 2.43 kJ (0.58 kcal) of heat becomes kinetic energy (Latent Heat of Evaporation of Sweat Water). For a given hot weather condition, the required sweating rate for evaporative cooling is dependent upon the physical activity level (metabolic rate).
• To calculate the amount of water excreted in the form of sweat, we can use the formula $V = (1-i)\frac{E}{ΔH}$ where,
  V = volume of sweat excreted per minute (mL)
  i = efficiency of metabolic activity
  E = (MET) * Body Weight * time (kJ)
  ΔH = latent heat of evaporation (2.43 kJ at 30℃)
• The efficiency of humans while performing physical activity is usually 0.2 - 0.25, which means that 25% of the energy is used to do useful work whereas the other part of energy is used up elsewhere (most likely in raising the body's temperature which is what we need).
• $SWL = 1.722 \cdot (1-i) MET \cdot w \cdot t $

BMR (Basal Metabolic Rate)

• Basal metabolic rate is the rate of energy expenditure per unit time by endothermic animals at rest. It is reported in energy units per unit time ranging from watt to ml O₂/min or joule per hour per kg body mass. Proper measurement requires a strict set of criteria to be met.

• We used the Mifflin St Jeor equation to measure basal metabolic rate. It is given as such: $P = (10m + 6.25h - 5a + s)$, where,

  P = total heat production at complete rest (kcal/day)

  m = mass (kg)

  h = height (cm)

  a = age (years)

  s = +5 for males, -161 for females.

MET (Metabolic Equivalent of Task)

• The metabolic equivalent of task (MET) is the objective measure of the ratio of the rate at which a person expends energy, relative to the mass of that person. For more info, check Wikipedia.
• Aqua uses the MET values of 800+ activities mentioned on the Compendium of Physical Activities site here.