The Future of Dams: Developing Nations
The Future of Dams: Developing Nations azs2As may be evident from a re-examination of Figure 1 above, the era of major dam building is winding down, at least in the U.S. This is primarily because the best sites for large dams are now already being used; and because the impacts are more widely understood and, as a result, proposed dam construction projects face major challenges from environmental groups. Construction of large dams (defined as those higher than four stories) in North America and Europe peaked in the 1970’s - and the average age of the worlds large dams is 35 years. Nonetheless, in parts of the world, mainly in developing nations in Africa, Asia, and South America, there is substantial untapped potential for hydroelectric power.
During the 1900s, in the so-called “golden age” of dam building, one large dam was commissioned somewhere on Earth every day (World Commission on Dams, 2000). On the one hand, dams are effective and powerful tools for water distribution and management, power generation, and flood control - and thus indirectly facilitate economic development, food production, and industrialization. Indeed, major dams are often viewed as symbols of modernization and progress - although a work of fiction, you may recall this quote from the movie “O Brother Where Art Thou”, as the protagonist, Ulysses Everett McGill, and his sidekicks are saved by the onset of a flood:
“Out with the old spiritual mumbo jumbo, the superstitions, and the backward ways. We're gonna see a brave new world where they run everybody a wire and hook us all up to a grid. Yes, sir, a veritable age of reason.”
Human Intervention in the Global Water Cycle
Human Intervention in the Global Water Cycle azs2On the other hand, as discussed above in Ponding the Waters: Impacts of Dams, the effects of large-scale alteration of river systems and the hydrologic cycle have become increasingly clear in the past few decades. The scale of human intervention in the global water cycle is also becoming apparent, including restriction of river flows such that they no longer reach the ocean in many years, associated two- or three-fold increases in the residence time of runoff, decreased sediment delivery to the oceans, and a long-term measurable effect on global sea level caused by the impoundment of thousands of cubic km of water (Vörösmarty et al., 2004). As a result, new large dam projects have been heavily scrutinized and faced political and environmental opposition. At the same time, the efficiency and economics of energy production, and the net offset of greenhouse gas emissions from increased hydropower generation have been increasingly questioned (World Commission on Dams, 2000). One way to minimize environmental impacts is to design “run of the river” systems, in which no reservoir is created and instead the natural flow of the river in its channel is harnessed to generate power. However, these systems have several drawbacks: they rely on natural flows, so the power generating capacity fluctuates dramatically as a function of seasonal rainfall patterns and climate change; and there are no added benefits of flood control or water supply.
Dams and Economic Development
Dams and Economic Development azs2Despite the controversy, in many developing nations, major dam projects remain important engines for economic development and hold substantial potential for renewable energy generation. As of 2020, hydroelectric power constituted as much as 17% of global electricity production (and 50% of estimated renewable energy production). Of this, ~23% is in China, ~12% in Brazil, ~10% in Canada, and ~7.5% in the United States; combined, these four nations generate over half of the world's hydropower!
Moreover, globally, estimates suggest that up to two-thirds of economically viable dam sites have yet to be exploited. Undeveloped sites are especially abundant in Latin and South America (79% of renewable water remains unused), Africa (96%), India and China (48% is unused in Asia) (UNEP, 2013). Rapidly growing energy demand in India, China, and the Amazon Basin have driven the construction of hundreds of large dams as of 2002 (Figures 10-11; Table 1). This development may be a harbinger of things to come on the African continent. Africa has the second-highest population (after Asia), and the fastest-growing (See Module 1.3); it also has the lowest per capita energy use (UNEP, 2013). Looking to the future as demand for energy, water, and food in developing nations continue to grow – both per capita and in total as populations swell - it seems inevitable that demand for large dams will persist well into the 21st century. Hydroelectric power provides 50% of electricity for 28 emerging and developing nations reaching over 800 million people.
Figure 16. Number of large dams by geographic region, as of 1998 (World Commission on Dams, 2000).
| Region | Number of dams |
|---|---|
| China | 22000 |
| Asia | 9000 |
| North and Central America | 8000 |
| Western Europe | 4000 |
| Africa | 1000 |
| Eastern Europe | 1000 |
| South America | 800 |
| Austral-Asia | 500 |
| Country | Number of Dams | Purpose |
|---|---|---|
| India | 695-960 | Irrigation, multipurpose |
| China | 280 | Flood control, irrigation, power |
| Turkey | 209 | Water supply, hydropower |
| South Korea | 132 | Irrigation, hydropower, flood control |
| Japan | 90 | Flood control |
| Iran | 48 | Irrigation, multipurpose |
| Country | Number |
|---|---|
| China | 24,089 |
| United States | 10,158 |
| India | 4,540 |
| Japan | 3,135 |
| Canada | 1,440 |
| South Africa | 1,428 |
| Repbulic of Korea | 1,359 |
| Brazil | 1,280 |
| Mexico | 1,107 |
| Spain | 1,066 |
Data taken from CIG ICOLD
