Subtopic: Overview of groundwater recharge estimation and artificial recharge techniques
Question Statement:
In the Water Table Fluctuation (WTF) method for estimating annual net groundwater recharge ($R = S_y \cdot A \cdot \Delta h + \text{Draft} - \text{Inflow}$), the most critical and sensitive hydrogeological parameter that must be accurately determined is:
Options:
(A) Specific yield ($S_y$) of the zone of water table fluctuation
(B) Dynamic viscosity of water at freezing point
(C) Barometric pressure at mean sea level
(D) Acoustic wave impedance of upper topsoil
Answer Key:
A
Step-by-Step Solution & Explanation
The Water Table Fluctuation method directly multiplies the water table rise $\Delta h$ by the specific yield $S_y$ of the fluctuating phreatic zone. Because specific yield varies strongly with soil texture and drainage time, errors in $S_y$ propagate directly and linearly into recharge estimates. Option A is correct.