Lake Dunstan is a man-made lake and reservoir in the South Island of New Zealand. The lake was formed on the Clutha River as a result of the construction of the Clyde Dam, filling in four controlled stages beginning in April 1992 and completed the next year. Parts of the town of Cromwell were relocated to a new area above the new lake. Between the town of Cromwell and the Clyde Dam the lake passes through what is called the Cromwell Gorge. Because of the expense of stabilising the gorge walls and the changing economic climate, this was also the last of Rob Muldoon's Think Big projects.