Effective porosity is equal to the sum of which two components?

• A. Specific yield and specific retention
• B. Porosity and permeability
• C. Specific retention and hydraulic conductivity
• D. Water content and porosity

Answer: (A)

Effective porosity represents the portion of pore space that actually participates in groundwater flow through interconnected pathways. It combines two aspects: water that can be drained from the pore space by gravity (specific yield) and water that remains in the interconnected pores due to capillary forces (specific retention). Together, these two components account for the part of the porosity that can transmit water under a hydraulic gradient. In other words, effective porosity ≈ the sum of specific yield and specific retention.