Volume Twelve - Pre-Victorian to the Present Day - further aspects - Report upon Penarth Dock - 1984 . . .

More complicated gate arrangements are possible including a lock between the sea and the basin and in rare cases a lock at the entrance formed by reverse gates and allowing vessels to enter when the water level outside is higher than that in the basin.

It is perhaps also worth pointing out that a problem arises in that by continually sluicing the main dock into the basin the level of water in the main dock can become seriously reduced.

At Cardiff this was not a problem since water for the docks was continually supplied from the River Taff and the level maintained at a constant depth. However, Penarth Dock had no such supply and instead huge pumps were used to raise the water level within the dock whenever necessary. These pumps were capable of raising the water level over the entire 23 acres at a rate of 1 foot per hour.

	Stages in the use of a Half-tide Basin.