It will be used to protect the dike during the time of floods or high water by automatically allowing water to flow from the pond directly to the river when the pond water reaches the height of the overflow tube.
(It; will be used; to protect the dike during the time of floods or high water by automatically allowing water to flow from the pond directly to the river) (the pond water; reaches; the height of the overflow tube)
It the pond water
will be used reaches
to protect the dike during the time of floods or high water by automatically allowing water to flow from the pond directly to the river
the height of the overflow tube