  Consider a dam model, $L^{upper}$ and $L^{lower}$ are upper and,
respectively, lower levels, $L = L^{upper}-L^{lower}$ is large and if the level
of water is between these bounds, then the dam is said to be in a normal state.
  Passage across lower or upper levels leads to damage. Let $J_1=j_1L$ and
$J_2=j_2L$ denote the damage costs per time unit of crossing the lower and,
correspondingly, upper level where $j_1$ and $j_2$ are given real constants. It
is assumed that input stream of water is described by a Poisson process, while
the output stream is state dependent. Let $L_t$ denote the level of water in
time $t$, and $c_{L_t}$ denote the water cost at level $L_t$
($L^{lower}<L_t\leq L^{upper}$). Assuming that
$p_1=\lim_{t\to\infty}\mathbf{P}\{L_t=L^{lower}\}$,
$p_2=\lim_{t\to\infty}\mathbf{P}\{L_t>L^{upper}\}$ and
$q_i=\lim_{t\to\infty}\mathbf{P}\{L_t=i\}$ ($L^{lower}<i\leq L^{upper}$) exist,
the aim of the paper is to choose the parameters of an output stream
(specifically defined in the paper) minimizing the long-run expenses
$$J=p_1J_1+p_2J_2+\sum_{i=L^{lower}+1}^{L^{upper}}q_ic_i.$$
