For most of his years in Egypt, MacDonald's principal work was with the Aswan Low Dam and its first heightening. The initial dam provided storage capacity above the Nile's natural flow, for Egyptian agriculture requirements, and was capable of holding a summer water supply for lands reasonably expected to be converted to summer irrigation in the immediate future. By 1905 however, it appeared that Egypt was experiencing a cycle of low years in regard to the volume of water passing down the river during the summer. The Government was thus very soon faced with the problem of finding additional storage room to meet possible demands for the existing area, as well as making adequate provision for future extension. A scheme for thickening and heightening the existing Aswan Dam was prepared by Benjamin Baker, and a great deal of the work involved was undertaken by MacDonald. The project was brought to fulfillment principally under his direction, with the "first heightening" completed in 1912.