The Downstream Human Consequences of Dams

www.water-alternatives.org Volume 3 | Issue 2 Richter, B.D.; Postel, S.; Revenga, C.; Scudder, T.; Lehner, B.; Churchill, A. and Chow, M. 2010. Lost in development’s shadow: The downstream human consequences of dams. Water Alternatives 3(2): 14-42 Lost in Development’s Shadow: The Downstream Human Consequences of Dams Brian D. Richter Director, Global Freshwater Program, The Nature Conservancy, Charlottesville, Virginia, USA; [email protected] Sandra Postel Director, Global Water Policy Project, Los Lunas, NM, USA; [email protected] Carmen Revenga Senior Freshwater Scientist, The Nature Conservancy, Arlington, VA, USA; [email protected] Thayer Scudder Professor of Anthropology, Emeritus, California Institute of Technology, Pasadena, CA, USA; [email protected] Bernhard Lehner Assistant Professor of Global Hydrology, McGill University, Montreal, Quebec, Canada; [email protected] Allegra Churchill Master’s Candidate, University of Virginia, Dept of Landscape Architecture, Charlottesville, VA; [email protected] Morgan Chow Research Analyst, The Nature Conservancy, Arlington, VA, USA; [email protected] ABSTRACT: The World Commission on Dams (WCD) report documented a number of social and environmental problems observed in dam development projects. The WCD gave particular emphasis to the challenges of properly resettling populations physically displaced by dams, and estimated the total number of people directly displaced at 40-80 million. Less attention has been given, however, to populations living downstream of dams whose livelihoods have been affected by dam-induced alterations of river flows. By substantially changing natural flow patterns and blocking movements of fish and other animals, large dams can severely disrupt natural riverine production systems – especially fisheries, flood-recession agriculture and dry-season grazing. We offer here the first global estimate of the number of river-dependent people potentially affected by dam-induced changes in river flows and other ecosystem conditions. Our conservative estimate of 472 million river-dependent people living downstream of large dams along impacted river reaches lends urgency to the need for more comprehensive assessments of dam costs and benefits, as well as to the social inequities between dam beneficiaries and those potentially disadvantaged by dam projects. We conclude with three key steps in dam development processes that could substantially alleviate the damaging downstream impacts of dams. KEYWORDS: Dams, rivers, dam-affected people, inland fisheries, flood-plain agriculture, food security, poverty alleviation, water resources development, hydropower, environmental flows, ecosystem services Richter et al.: The downstream human consequences of dams Page | 14 Water Alternatives - 2010 Volume 3 | Issue 2 INTRODUCTION Large dams became a prominent instrument for economic development in the past century. Worldwide, the number of large dams stood at 5000 in 1950 (ICOLD, 1998); three quarters of these were in North America, Europe, and other industrial regions. By 2000, the number of large dams had climbed to over 45,000, and these were spread among more than 140 countries (ICOLD, 1998). On average, two large dams were built per day for half a century (WCD, 2000). Today, the number of large dams exceeds 50,000 (Berga et al., 2006). These dams provide water storage that has enabled large cities like Phoenix, Arizona, to grow in desert regions. They supply hydropower that has electrified many rapidly expanding industrial and urban economies, from Seattle to Shanghai. Large dams are also important in agriculture. About half of the world’s large dams were built primarily for irrigation, many of them in Asia as the Green Revolution spread (WCD, 2000). Today large dams are estimated to contribute directly to 12-16% of global food production (WCD, 2000). Undeniably, large dams have played an important role in economic development. However, large dams have also brought serious environmental and social consequences. Whereas the benefits have generally been delivered to urban centres or industrial-scale agricultural developments, river-dependent populations located downstream of dams have commonly experienced a difficult upheaval of their livelihoods, loss of food security, and other impacts to their physical, cultural and spiritual well-being. River flows altered by large dams often disrupt or destroy downstream habitats and life cycle cues for fish and other river species, as well as fishing, cropping and grazing systems that rely on flood-plain ecosystems. While downstream river-dependent communities may benefit from some degree of flood protection and enhanced irrigation opportunities provided by dams, adverse impacts are far more common and usually outweigh the benefits to downstream people, resulting in reduction of their incomes and livelihoods. The nature, duration and severity of these impacts vary from one dammed river to another. In some of the cases documented in this study, the wave of social disruption and human health impacts following dam construction largely passed within a decade, but in other cases dam-induced impacts have persisted through multiple generations. In some cases, impacts may be mitigated by alternative sources of food or employment; in other cases, they may not. And in some cases, the environmental effects of dams are detectable for only a short distance downstream, while in others those effects remain significant through hundreds of river kilometres. What the majority of cases have in common, however, is the failure to account for these impacts and their consequences on downstream populations. In its ground-breaking 2000 report, the World Commission on Dams (WCD) brought much-needed global visibility and media attention to the benefits and costs of large dams. But while the WCD Report documented the downstream impacts of dams for a number of case examples, much of the report’s discussion of social impacts focused on the physical displacement of populations living in the immediate vicinity of dam construction. The WCD estimated that 40-80 million people had been displaced by large dams. However, no estimate was provided of the downstream populations impacted by the alterations in river flows and freshwater ecosystems that accompanied these development projects. Fresh attention to these downstream dam impacts is overdue and urgently needed. The timing of the WCD Report marked the low-point of a decade-long decline in dam financing, driven in large part by effective and persistent protests against large dams by social and environmental NGOs and affected river communities. However, dam construction is again on the rise. Coincident with the WCD Report, the new millennium brought new reports on the dire and worsening condition of the world’s poor, and rapidly accumulating evidence that intense droughts and floods due to climate change could make prospects for poverty alleviation ever-more challenging. Private and state companies and development banks have increased their involvement in financing and building large new dams to provide drinking Richter et al.: The downstream human consequences of dams Page | 15 Water Alternatives - 2010 Volume 3 | Issue 2 water, irrigation, and hydroelectricity supplies (figure 1). Hydropower dams are emphasised as a source not just of electricity but also of funds to finance other development options such as irrigation. Figure 1. Global investment in dams dropped precipitously in the 1990s, but has risen sharply since (adapted from World Bank Group, 2009). 1200 1000 800 600 400 Million US Million dollars 200 0 1992 1993 1994 1995 1996 1997 1998 1999 2000 2001 2002 2003 2004 2005 2006 2007 2008 The majority of the thousands of new large and small dams are under construction or on the drawing boards are in the developing world and in fast-growing economies with rising demands for additional hydroelectricity. In South America, for example, at least 2200 large dams are planned or under construction, including 1700 in Brazil alone, where the potential for additional environmental impacts and social disruption associated with new dams is quite high (figure 2).1 Clearly, a more complete assessment of the downstream impacts of dam development is urgently needed to inform ongoing and future dam development plans. In this paper, we attempt to begin filling this gap. In addition to providing further elaboration of the consequences of dams on downstream populations, we offer the first global estimate of the number of downstream riparian dwellers potentially affected by the largest ~7000 dams built to date. By 'potentially affected' we mean those rural riparian populations that are prone – due to their physical vicinity and likely dependence – to experience negative effects on their livelihoods by altered river flows, such as through reduced food security or the loss of ecosystem goods and services. Our identification of potentially affected people is based upon their proximity to dammed rivers (i.e. within 10 km), the exposure of the landscape (i.e. river deltas and slopes < 1 degree are presumed to sustain fisheries and flood-plain agriculture), and the degree of flow regulation that a river experiences. Our conservative estimate of 472 million suggests that the number of people potentially affected downstream of large dams exceeds by six to 12 times the number directly displaced by these structures (previously estimated at 40-80 million; WCD, 2000). In the process of developing this new global 1 Estimates

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