Determine the estimated total volumes ofwater used in 24 h for “essential” tasks andfor “optional” tasks.

To determine the estimated total volumes of water used in 24 hours for "essential" and "optional" tasks, you would need to follow these steps:

1. Identify Essential Tasks: Essential tasks are those that are necessary for survival and basic hygiene. This could include drinking, cooking, bathing, and toilet flushing.

2. Estimate Water Usage for Essential Tasks: Research or estimate the average amount of water used for each of these tasks. For example, a person might drink 2 liters of water per day, use 10 liters for cooking, 50 liters for bathing, and 30 liters for toilet flushing.

3. Calculate Total Essential Water Usage: Add up the estimated water usage for all essential tasks to get the total volume of water used in 24 hours for essential tasks.

4. Identify Optional Tasks: Optional tasks are those that are not necessary for survival or basic hygiene. This could include watering plants, washing cars, filling swimming pools, etc.

5. Estimate Water Usage for Optional Tasks: Again, research or estimate the average amount of water used for each of these tasks. For example, watering plants might use 20 liters of water per day, washing a car might use 100 liters, and filling a swimming pool might use 1000 liters.

6. Calculate Total Optional Water Usage: Add up the estimated water usage for all optional tasks to get the total volume of water used in 24 hours for optional tasks.

Remember, these are just estimates and the actual amount of water used can vary greatly depending on individual habits, lifestyle, location, and many other factors.