Four main rivers, the Welland, Nene, Ouse and Witham drain 10% of England into the Wash. For most of their journey across the Fens the rivers have been straightened, to improve the speed of the water carried away to the sea.
The drainage of the land has caused it shrink over the centuries and now most of the Fens sits below sea level some by as much as 4 or 5 metres. You can see just how much the land has shrunk by looking at the Holme Post.
As a result many of the main rivers and other key waterways - variously known as rivers, leams, lodes, drains, eaus, ditches and dykes sit above the surrounding land. This in turn means that water has to be pumped against gravity from in-field networks of drainage ditches into the main rivers to keep the land dry.
Even this extensive system of pumped drainage is not enough on its own and two extensive washlands are needed, on the rivers Ouse and Nene to hold back and temporarily store water at times of extensive rainfall. Without them the system would be overwhelmed. It is this network of drainage ditches, pumping stations, high level water carriers and washlands that define the landscape and land use of the Fens.
The drainage of Fens is thought to have started from Roman times. In the 7th Century Christianity came to the Fens. Abbeys were founded at Thorney, Peterborough, Ely, Crowland, Ramsey and were able invest their wealth into small scale drainage works to improve surrounding pasturelands. The Fens remained far from tamed however providing a safe haven for invaders such as the Danes and outlaws like Hereward the Wake.
It wasn’t until the 17th Century that land drainage really began to gather pace. The 4th Earl of Bedford employed a young drainage engineer from Netherlands called Cornelius Vermuyden. He straightened the River Ouse into two channels (the Old and New Bedford Rivers), so that water could get away more quickly to the sea. In between them he created a washland, the Ouse Washes that could contain flood water when the channels couldn’t. It is still in operation today.
Unfortunately drainage caused the land to shrink which meant that the rivers now sat above the land and water could no longer drain away. Wind pumps had to be introduced lift water up from the marshes and into the rivers. These were eventually replaced by steam engines, diesel pumps and finally modern electric pumps. As pumping efficiency and capacity increased more and more parts of the Fens could be drained. In 1851, Whittlesey Mere, the largest of the Fen meres was drained. The Fens had finally been tamed.