During the 20th century large dams emerged as symbols of modernity. Hailed for being an effective way to harness water
resources for food production, energy generation, flood control and domestic use, dams became synonymous with progress and economic development. Construction peaked during the 1970s when an average of two or three large dams
were commissioned per day throughout the world. An estimated $2 trillion has been invested in large dams since the early 1900s,5 justified by a range of projected outcomes from poverty reduction to increased local water supply. However, in recent decades dam projects have become mired in controversy. Opponents charge that benefits have been grossly overstated while the social and environmental costs have been largely ignored.