A new Black Sluice, including a wide navigation lock, was constructed to the south of the original one, with the cill level lower, which enabled the gradient of the South Forty-Foot Drain to be increased to 3 inches per mile (5 cm/km). Many of the tributary drains were also improved. 1846 also marked the beginning of the use of steam engines for pumping. Ten years later, a map covering of the Black Sluice area showed nine steam-powered and eight wind-powered drainage engines in use. The River Witham Outfall Improvement Act 1880 authorised further improvements to the mouth of the Witham, to which the Black Sluice Commissioners contributed £65,000. This work led to a further drop of in the low water level at the Black Sluice. Oil and paraffin engines began to replace steam and wind engines from 1910, and by 1935 there were 15 such engines pumping water into the South Forty-Foot Drain. The passing of the Land Drainage Act 1930 resulted in the Commissioners being replaced by the Black Sluice Internal Drainage Board, while responsibility for the rivers in the area passed to the Witham and Steeping Rivers Catchment Board. With war imminent, the Rivers Board took over the Black Sluice and the South Forty-Foot Drain in 1939, and although progress was interrupted by the Second World War, a £374,000 scheme to construct the Black Sluice pumping station and to widen of the drain from Boston to Donington Bridge was completed in 1946. The pumping station contained three pumps, each powered by a 5-cylinder vertical diesel engine manufactured by Ruston. Modern era Paraffin and oil engines gave way to electrically powered pumping stations in the 1950s, with the Board constructing six electric and one diesel pumping station to improve drainage to an extra of land. In 1960, the decision was taken to further improve drainage of an area of , as part of a £1.4 million scheme which included the addition of two extra pumps at the Black Sluice, replacement of existing pumps elsewhere, and the widening of of the South Forty-Foot Drain from Donington Bridge to Rippingale Running Dyke. Jurisdiction for the Drain and the sluice passed to the Lincolnshire River Board at this time. The work, which began in 1962 and was completed in 1968, proved successful in preventing flooding during severe wet weather in the winter of 1968/9. With three and two diesel engines, the upgraded