Because the Grevelingen dam had already enclosed the Grevelingen on the east side, the Grevelingen Lake was created by the construction of the Brouwers dam. The Brouwers dam was not an easy dam to build. The construction of the Brouwers dam was a good exercise for the even more complex Oosterschelde barrier, because the gap that needed to be closed between Goerree-Overflakkee and Schouwen-Duiveland was as much as 6.5 kilometres in width. Both caissons and a cableway were used for the construction for the Brouwers dam, as was the case with the Grevelingen dam. Firstly, two sandbars were raised in the lake of Brouwershaven (‘Brouwershavense Gat’). Consequently, the northern gap was closed by caissons. Finally, the southern gap was closed by cradles that plunged concrete to the bottom of the sea. At the end of 1971 the dam was finished. Ten years later, however, a change was made in the dam: a lock was built to let salt sea water pass through. Because of this, the flora and fauna gradually changed.