governing equation , Neuman was able to reproduce all three parts of the observed unconfined time-drawdown curve and produce parameter estimates (including the ability to estimate $K_z$) very similar to the delayed yield models.

Compared to the delay index models, Neuman’s solution produced similar fits to data (often underestimating $S_y$, though), but [@neuman1975; @neuman1979] questioned the physical nature of Boulton’s delay index. He performed a regression fit between the @boulton1954b and @neuman1972 solutions, resulting in the relationship $$\label{alpha-regression}
  \alpha = \frac{K_z}{S_yb}\left[3.063-0.567
    \log\left( \frac{K_Dr^2}{b^2}\right) \right]$$ demonstrating $\alpha$ decreases linearly with $\log r$ and is therefore not a characteristic aquifer constant. When ignoring the logarithmic term in the relationship $\alpha=3K_z/(S_yb)$ proposed by [@streltsova1972a] is approximately recovered.

After comparative analysis of various methods for determination of specific yield, [@neuman1987] concluded the water table response to pumping is a much faster phenomenon than drainage in the unsaturated zone above it.

@malama2011 recently proposed an alternative linearization of , approximately including the effects of the neglected second-order terms, leading to the alternative water table boundary condition of $$\label{malama}
  S_y \frac{\partial s}{\partial t} =- K_z
  \left( \frac{\partial s}{\partial z} +
    \beta \frac{\partial^2 s}{\partial z^2} \right) \qquad z=h_0$$ where $\beta$ is a linearization coefficient \[L\]. The parameter 