The South Saskatchewan River Project, of which Lake Diefenbaker is one the most significant features, is a multi-purpose water resource project of considerable importance to the people of Saskatchewan. It has provided a stable source of water to a province which has historically suffered from water shortages, the most notable of which resulted in a period known as the “dirty thirties”. Although the project was primarily intended to provide a water supply for irrigation, it has also resulted in many other benefits. These benefits include hydropower production (now the most significant benefit in economic terms), municipal and industrial water supply, recreation, flood damage mitigation, and several smaller benefits.This paper presents an overview of the South Saskatchewan River Project, including some historical notes, and its benefits to the people of Saskatchewan. To the extent possible, the benefits have been expressed in economic terms. A brief discussion is also included with respect to the negative impacts which necessarily result from a project of this magnitude.