THE production of electric energy has been one of the major problems facing the planners of Europe's economic reconstruction since World War II. The fact that several of the leading industrial nations of Western Europe are importers of coal, dependent on outside supplies for that most important source of thermoelectric power, brought the necessity for new sources of hydroelectric power sharply into focus. France has pushed the development of hydroelectric power more than any other country in Western Europe; for French domestic supplies of coal have been inadequate to cover the needs of both industry and the production of electric energy. In I95 I, France needed a total of 75 million tons of coal a year. At least onethird of this was required for the production of electricity in the great industrial regions of northern and northeastern France and in the Paris metropolitan area. The Monnet Plan, drawn up shortly after World War II (I946) to organize the reconstruction of France's economy, entrusted the task of planning in the field of electric power to Electricite de France, the state agency that now controls the majority of the power plants and the entire high-tension grid. Most of the thermoelectric power is generated in three regions: northern France, eastern France, and the Paris area. Hydroelectric power, on the other hand, is generated in the Pyrenees, the Central Massif, the Alps, and the valleys of the Rhone and the Rhine. Planning and construction of hydroelectric installations are under way in four regions: the Central Massif, the Alps, the Rhone Valley, and the upper valley of the Rhine. In each of these regions dams are being built, powerhouses equipped with turbines and generators, and high-tension lines strung across the countryside to carry power to the industries, railroads, and homes of France. The four regions present different environmental conditions, and thus the problems confronting the planner and the engineer also differ. This study is intended to illustrate the planning and construction techniques cur-