Thus the edge $(4,5)$ will change its source from $4$ to $5$ and the time parameter has to be restored to the old value $7$.

The same happens with the edge $(5,9)$. The edge $(5,6)$ will not be active any more. The reason is that the old flow of water from $6$ to $5$ will not be able to increase the label of the vertex $5$. Also, the new flow of water from $5$ to $6$ would not be able to change the label of vertex $6$.

![\[fi:figure 3\] The configurations after the seconds 5 and 6.](graph03.png "fig:") ![\[fi:figure 3\] The configurations after the seconds 5 and 6.](graph04.png "fig:")

A special care has to be taken when a water flow reaches a vertex that is already active. In this example such situation happens after the $11$th second. The edge $(7,11)$ has the smallest time parameter. Hence each edge gets their time parameter decreased by $2$. In the $13$th second the water from the edge $(7,11)$ reaches the vertex $11$. The label of vertex $7$ is $L(7)=11$, while $L(11)=6$. The weight of the flow over the edge between these two vertices is $2$, hence this new water is of higher quality 