  Prabhu (1958) obtained the stationary distribution of storage level $Z_{t}$
in a reservoir of finite volume $v$, given an inflow $X_{t}$ and an outflow
$Y_{t}$. Time $t$ is assumed to be discrete, $X_{t} \sim$ Gamma$(p,\mu)$ are
independent and $p$ is a positive integer. The mean inflow is $p/\mu$; the
target outflow is $m$ (constant). We attempt to clarify intricate details,
often omitted in the literature, by working through several examples. Of
special interest are the probabilities of depletion ($Z_{t}=0$) and spillage
($Z_{t}=v$). For prescribed {$v,p,\mu$}, what value of $m$ minimizes both of
these?
