Which of the following must be included in the working plans for water supply requirements?

The inclusion of the density and area of water application in working plans for water supply requirements is crucial because it directly impacts the effectiveness of the fire protection system. This information determines how much water is needed and over what area it must be distributed to meet the performance criteria for fire suppression. Accurately detailing the required density facilitates proper hydraulic calculations, ensuring that the system can deliver the requisite volume of water within the appropriate time frame during a fire event.

Understanding the density (typically measured in gallons per minute per square foot) and the area (usually indicated in square footage) allows engineers and designers to assess the water supply needs for different types of occupancy and fire scenarios. This ensures that the water supply is adequate to handle potential fire situations based on the layout and usage of the building, reflecting the system's intended efficacy and compliance with relevant codes.

The other options, while important to the overall fire protection system, do not specifically address the fundamental requirement of water supply for effective sprinkler operation. The type of sprinkler head, total building area, and control panel location pertain to different aspects of the fire protection system design but do not directly influence the water supply requirements as critical as density and area.