The River Great Ouse Part1

The River Great Ouse and Its Tributaries Part 1

The Denver Complex
Arriving at Denver Sluice I was amazed to see a complicated system of sluices, locks and channels, the complex fascinated me and I decided to do a little bit of research to try and understand this important piece of infrastructure.

Map showing the complex

The complex takes its name from the nearby village of Denver, close to its larger neighbour, Downham Market.
At first glance the main sluice seems to just hold back the river, separating the tidal section from the upstream section, whilst this is true, the tidal section continues inland for a further twenty miles or so, to be briefly reunited with the main river at Earith. The river consists of several sections above Denver, the tidal section to Earith is known as the New Bedford river and drains the section above this point.
The non tidal section down to its confluence with the river Cam is know as the Ely Ouse and above here to Earith it becomes the Old West river, this whole section is protected from the tides by Hermitage lock, just below Earith.
There are in fact 3 large sets of sluices at Denver, The tidal barrier, an outlet to the relief channel and the link to the cut off channel.
The relief channel was built in the fifties, following the great floods of 1947, and is used to remove water from the non tidal system in times of flood, it acts as a large reservoir and is wide and deep.
The water in this channel is released out into the tidal river, at low tide, near to Kings Lynn. This was required as the tidal river can be over two meters higher than the main river, so obviously water cannot be released until the tide is lower than the river level.

The lock between the Gt Ouse and the Relief Channel, the difference in
levels can clearly be seen, note that high tides can be over 2 mts above the upper level

The third large sluice holds back the water in the Cut Off channel, this channel serves two purposes, it acts as a further drain from the Ouse and its tributaries, water can then be released into the Relief Channel, its second purpose is to act as a reservoir supplying water to Essex by means of a pipeline and pumps. Water can also be added at Denver when levels allow.
The cut off channel passes beneath the rivers Wissey, Lark and Little Ouse, all main tributaries of the Great Ouse.

The sluice between the Cut Off Chanel and the Relief Channel

The Denver complex thus controls the water levels and protects from flooding a large part of East Anglia and the Fens. During our travels I noticed that a large part the river system in the Fens, is actually at a higher level than the surrounding land and, unsurprisingly, it is contained between two large banks.
Most of this part of the river is man made, being straightened, widened and deepened to provide the required drainage. There are many pumping stations along the length of the system taking water from the surrounding land into the rivers, also there are many pumps drawing water from the system to irrigate the farmland.
The lock keeper informed us that they had not released any water from the river for a number of weeks so water flowing into the system was just keeping up with the demand for irrigation.
So effective is the water management that the water levels at Ely only vary several inches throughout the year.

Looking across the main sluice, this separates the tidal Ouse from the inland river.
The two gates to the left are the lock gates and the New Bedford river is to the far right.

Further info about the Relief Channel

Further info about the Cut Off Channel