Subsurface water terminology – relating yield, specific yield, and specific retention to porosity Which statements correctly define yield, specific yield, and specific retention, and relate their sum to porosity for a saturated soil mass draining by gravity?

Introduction / Context:
This question checks foundational hydrogeology terms used in well hydraulics and groundwater storage calculations. Understanding how the pore space partitions into drainable water and retained water is essential for aquifer yield estimation.

Given Data / Assumptions:

• Saturated soil or aquifer material undergoing gravity drainage.
• Porosity n is the total void fraction.
• Some water drains (specific yield), some remains due to capillary and adsorptive forces (specific retention).

Concept / Approach:
Specific yield (Sy) = V_drained / V_total.Specific retention (Sr) = V_retained / V_total.Porosity (n) = Sy + Sr (neglecting entrapped air). The total void volume splits into drainable and retained portions under gravity drainage, hence the additive relation.

Step-by-Step Solution:
Map each statement to standard definitions → all match accepted terminology.Conclude that the combined statement “All the above” is correct.

Verification / Alternative check:
Textbook water-balance in a representative elemental volume shows V_void = V_drained + V_retained → n = Sy + Sr.

Why Other Options Are Wrong:
Any single option alone is incomplete; the comprehensive, correct choice is the collection.

Common Pitfalls:
Confusing “yield” (a volume) with “specific yield” (a ratio); the latter is dimensionless and is what appears in groundwater storage equations.

Final Answer:
All the above