The drain was upgraded during the Second World War, to provide a backup water supply for an armaments factory at Puriton, and again in 1972, when the Sowy River flood relief channel was built.

Cornelius Vermuyden was active in the region in the mid 17th century, building small-scale drainage schemes at Cossington, Catcott, Huntspill and Puriton, but despite the devastation caused by extensive flooding in 1607, was unable to convince the communities of Sedgemoor of the benefits that a drainage scheme would bring, as they feared that improved pastures would prejudice their common rights.

[3] The five commissioners who were appointed under the act proposed a new drainage channel from the area to an existing sluice called Dunball Clyse, and asked William White, a surveyor from Wedmore near Wells, to carry out a survey.

White found a suitable route, but there were some misgivings, as the area is separated from the coast by a slightly higher ridge of clay, and the scheme involved cutting nearly 2.5 miles (4.0 km) of drain to a depth of 15 feet (4.6 m) through this ridge, in order to provide the necessary gradient for the water to flow.

He was supported in this by John Billingsley, one of the commissioners who farmed near Sutton Mallet,[4] but who had written a book on the agriculture of Somerset,[5] and the drainage of the levels.

White's plans had proposed running the channel further downstream to Nine Streams Reach, but this had been opposed by landowners, and so the clyse was built at Dunball.

The unsuitable conditions at Dunball resulted in the clyse being built about 4 feet (1.2 m) too high, and the shallower gradient caused sedimentation in the channels.

A timber floor in the drain was built to restrict this, but the recurrent problem of the peat rising up was not finally solved until the banks were moved further back and in many cases, spread over the adjoining fields.

£15,000 of the total had been spent on engineering work, and the scheme resulted in improvements to the drainage of an area of 11,000 acres (4,500 ha).

Ten years later, they commissioned another report, but the local landowners took matters into their own hands and asked Josiah Easton to inspect the drain.

A special commission, which was only responsible for King's Sedgemoor, was created, but like their predecessors, they found that their powers were limited, and their ability to raise funds by rates was inadequate.

The Catchment Board needed to be able to guarantee that 4.5 million gallons (20.5 Megalitres) of process water would be available to the factory every day.

To this end, the Huntspill River was constructed, a little further to the north, which was essentially a revival of a plan by J. Aubrey Clark in 1853, to provide better drainage for the Brue valley.

[14] Greylake sluice was built by the Somerset Rivers Catchment Board in 1942, and used guillotine gates to control water levels.

[15] The drain was upgraded in 1972, as part of a £1.4 million scheme to construct a flood relief channel for the River Parrett.

The 7.5-mile (12.1 km) embanked channel, called the Sowy River, runs from Monks Leaze Clyse below Langport to the King's Sedgemoor Drain near Westonzoyland Airfield.

Consideration was given to replacing Dunball clyse with a pumping station in 2002, which would have allowed water to be discharged into the estuary at all states of the tide, but this course of action was not followed.

The installation, together with a similar one at Oath lock on the River Parrett, has provided valuable information on the migration and decline of eels.

Like most rivers in the UK, the chemical status changed from good to fail in 2019, due to the presence of polybrominated diphenyl ethers (PBDE) and mercury compounds, neither of which had previously been included in the assessment.

It followed part of the route of the present day King's Sedgemoor Drain, forming almost a great loop along the southern flank of the Polden Hills.

To the south, the parallel courses of the Langacre Rhyne and Sowy River also cross under the road, as they approach and run beside the Drain.

Greylake Sluice is situated immediately after the bridge, and the three drains join about 1 mile (1.6 km) further on near Westonzoyland Airfield, which was formerly RAF Weston Zoyland.