How is the discharge rate from a subsoil drainage system calculated for sandy and clay soils, respectively?

The correct answer specifies that the discharge rate for sandy soils is calculated at 2 gallons per minute (gpm) per 100 square feet, while for clay soils, the discharge rate is set at 1 gpm per 100 square feet. This reflects the inherent differences in permeability and drainage characteristics between sandy and clay soils.

Sandy soils have larger soil particles and more space between them, allowing water to flow through more readily. Therefore, a higher discharge rate is typical to accommodate the more efficient drainage capacity of these soils. The value of 2 gpm per 100 square feet for sandy soil effectively represents this higher permeability, ensuring that the system can adequately manage the water that drains through this type of soil.

On the other hand, clay soils consist of much finer particles that are densely packed, resulting in low permeability. Water moves slowly through clay, so the discharge rate is lower, with the figure of 1 gpm per 100 square feet appropriately reflecting this.

This understanding of discharge rates is crucial for effective drainage design in different soil types, ensuring that systems are designed to handle the expected inflow of water efficiently based on the soil characteristics.