**Answer:**

Water distribution systems typically consist of various components, including pipe mains, which transport water from the source to the reservoir or directly to consumers. The design of these pipe mains is a critical aspect of water distribution system planning and engineering.

The question asks specifically about the design of pipe mains carrying water from the source to the reservoir. In this context, the design objective is to ensure that the pipe mains have sufficient capacity to handle the maximum daily draft of water.

**Maximum Daily Draft:**
The maximum daily draft refers to the highest volume of water that is expected to be withdrawn from the water source and transported to the reservoir in a single day. This volume includes all the water demands from consumers and any additional requirements for system operation and maintenance.

Designing the pipe mains for the maximum daily draft ensures that they can accommodate the peak water demand and prevent any bottlenecks or pressure drops in the system. It ensures that there is sufficient capacity to transport the required volume of water from the source to the reservoir, even during periods of high demand.

**Reasons for Choosing Maximum Daily Draft:**
1. **Peak Demand:** The maximum daily draft represents the peak demand for water in a day. By designing the pipe mains for this peak demand, the system can handle all the water requirements during periods of high consumption.
2. **System Flexibility:** Designing for the maximum daily draft allows for system flexibility. It ensures that the pipe mains have enough capacity to handle variations in demand throughout the day, including peak usage periods.
3. **Reservoir Management:** Designing for the maximum daily draft also considers the capacity of the reservoir. By ensuring that the pipe mains can deliver the maximum daily draft, the reservoir can be effectively managed to meet the demands of consumers and maintain system reliability.
4. **Future Growth:** Designing for the maximum daily draft also takes into account potential future growth in water demand. It provides a buffer for accommodating any increases in demand without requiring major modifications to the pipe mains.

In conclusion, the pipe mains carrying water from the source to the reservoir are designed for the maximum daily draft to ensure that they can handle the peak water demand, provide system flexibility, manage the reservoir effectively, and accommodate future growth in demand.

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