Main Street, Prickwillow, Ely, Cambridgeshire, CB7 4UN
Most areas of the UK are comfortably higher than sea level. When heavy rain occurs, water can run downhill into streams and small rivers, leading to bigger rivers that eventually run into the sea. In a lot of the Fenland area, this is not possible because the land is lower than the sea. Here at Prickwillow for example, the fields behind the museum are between 1 metre and 3 metres below average sea level and up to 4.5 metres (14 feet) below high tide level.
Fenland pumping stations like the one here at Prickwillow exist to pump excess water from the low lying land up into the river - in this case, the River Lark which flows into the River Great Ouse just to the North of Ely.
The main ditches (drains) carrying water from farms and villages down to the pumping stations and the pumping stations themselves are in the control of local Internal Drainage Boards.
This work is paid for by a Drainage Rate or tax that is levied annually on every hectare of land and house (via council tax) within the area of the particular Drainage Board.
Drainage Boards can also let water back into the drains from the river during the summer to provide water for crop irrigation.
Most of the rain falling within the district is used by the growing crops but on average, about 25% of the total rainfall has to be pumped into the rivers each year.
This means that without pumping stations such as this one, rain would accumulate on the land at a rate of about 125mm (5 inches) per year. Nowadays, pumping is mainly carried out using automatic electric pumps. These can be switched to operate over night and at weekends when the power is cheaper. There are still some diesel engine pumps, to back up the electric pumps at times of heavy rain or mains power failure.
The level of the main rivers also has to be controlled to prevent flooding. The River Lark at this point is normally controlled at a level about 1.6 metres above average sea level.
The level can rise a little at times of heavy rainfall but not by very much.
The main control is by the use of the Denver Sluice. The gates of the sluice are closed when the tide is high so that sea water cannot travel inland up the river. When the tide has fallen below the river level, the gates are opened by a controlled amount to release excess water without reducing the river level too much so that boating can continue.
There is also a channel called the "cut off channel" running around the Eastern edge of the fens from Mildenhall to Denver.
This can intercept water from the upper reaches of the Rivers Lark, Little Ouse and Wissey so reducing the strain on the fenland water levels at times of heavy rainfall.
This channel was built in the 1950s and before that time, river levels were much more difficult to control and major incidents like the great flood of 1947 were impossible to avoid.
