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Groundwater Hydraulics: Leaky Confined Aquifers and De Glee’s Steady State Theory

 When a confined aquifer is bounded above or below by a semi-pervious aquitard, pumping causes vertical leakage into the main aquifer. Under steady-state flow conditions toward a fully penetrating well, De Glee’s Formula governs drawdown (s) at a radial distance $r$:

$s = \frac{Q}{2 \pi \cdot T} \cdot K_0\left(\frac{r}{B}\right)$

​Where $Q$ is pumping rate, $T$ is aquifer transmissivity, $K_0$ is the modified Bessel function of the second kind of zero order, and $B$ is the leakage factor:

$B = \sqrt{\frac{T \cdot b'}{K'}}$

​Here $b'$ and $K'$ represent the thickness and vertical hydraulic conductivity of the aquitard, respectively. The leakage factor $B$ measures the resistance of the aquitard to vertical leakage; larger values of $B$ indicate negligible leakage.

​In multi-layered alluvial plains across the Indo-Gangetic basin, multi-aquifer systems interact complexly through semi-confining clay layers during intensive agricultural pumping.

​Modern hydrogeological investigations replace simplified analytical leakage estimates with multi-layer finite-difference groundwater models (such as MODFLOW-NWT). Hydrogeologists utilize nested piezometers and automated pressure transducers to continuously monitor vertical head differentials, accurately mapping aquitard leakage rates to prevent regional land subsidence and aquifer cross-contamination.

​Note: This technical content was curated and structured with AI assistance to support technical education.

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