INTRODUCTIONDuring the 20th century

INTRODUCTION


During the 20th century, humans dammed and regulated most of the world’s rivers for reasons such as hydropower, flood control, domestic water supply, and navigation (Nilsson et al. 2005). Globally, there are now about 50,000 dams exceeding 15 m in height (WCD 2000), and many new dams are planned or under construction (WWF 2004). There is no current record of the global number of small dams, i.e., dams

ผลลัพธ์ (อังกฤษ) 1:

INTRODUCTIONDuring the 20th century, humans dammed and regulated most of the world's rivers for reasons such as hydropower, flood control, domestic water supply, and navigation (Nilsson et al. 2005). Globally, there are now about 50,000 dams exceeding 15 m in height (WCD 2000), and many new dams are planned or under construction (WWF 2004). There is no current record of the global number of small dams, i.e., dams <15 m in height, but in the United States alone there are approximately 2 million such dams (Shuman 1995). Among Sweden's more than 5300 dams, about 5100 (96%) are small (SMHI 1994, 1995, Vattenportalen 2007). Although human control over freshwater flow has increased prosperity for many people, it has also led to serious effects on ecosystems and local human societies (e.g., Nilsson and Berggren 2000, Scudder 2005). Dams increase water retention, modify the hydrograph, eliminate turbulent reaches and riparian wetlands, impede the dispersal and migration of plants and animals, decrease interactions between land and water, and reduce sediment transport (Ward and Stanford 1995, Jansson et al. 2000, Kingsford 2000, Syvitski et al. 2005). Following the creation of dams and reservoirs, many terrestrial ecosystems become permanently inundated. This damages ecological communities, erodes the soil of the inundated land (Dudgeon 1995, Nilsson et al. 1997), and causes emissions of greenhouse gases such as methane and carbon dioxide during the breakdown of organic matter (Fearnside 1997, St. Louis et al. 2000). Even if not directly affected by loss of property, humans are often indirectly affected by hampered ecosystem services such as reduced water availability on farmed floodplains following decreased flooding, lowered aquatic productivity, and reduced control of species invasions (Nilsson et al. 2005).During the Swedish dam-building era after World War II, large, modern hydroelectric power plants were constructed to supply the developing industry and society with electric power. In some cases, small dams, such as hydroelectric dams and splash dams used for timber floating, were removed to make room for larger ones. In this respect, dam removal is not a new concept in Sweden. However, the removal of entire impoundments and dam constructions to restore riverine landscapes is a new practice. Thus, dam removal is becoming a more frequently used management option, especially for old dams in need of renovation and small dams that are no longer used or have lost most of their reservoir capacity. Globally, most dams that have been removed or considered for removal are in the USA. In 2003, Stanley and Doyle (2003) reported that more than 500 dams had been removed in the previous two decades in the United States, although they found no data indicating that any other country had removed more than nine. Dam removal is now becoming a viable option in other regions of the world for several reasons. For the dam owner, removal can be economically preferable to renovation because of the environmental benefits gained from the restoration of turbulent stream reaches and fish migration routes. Safety reasons are also vital, especially in cases in which dams are in bad shape and hold large amounts of water (Stanley and Doyle 2003). Despite such benefits, however, dam removal often gives rise to conflicts. This is the case even when dam owners encourage removal. Conflicts often result in unnecessarily long processing times, and sometimes removals are stalled even in cases in which funding for removal has been provided. In this paper we address incentives for dam removal such as safety issues, law and policies, and economic as well as ecological incentives. We also outline some of the underlying mechanisms of the types of conflict associated with dam removal. Our presentation is based on our own experience with recently debated and implemented dam removals in Sweden (Table 1). We also provide guidance on how conflicts can be prevented or resolved in future dam removals.

ผลลัพธ์ (อังกฤษ) 2:

INTRODUCTION During the 20th Century, Humans dammed and regulated Most of the World's rivers for reasons such as hydropower, Flood Control, Water Supply domestic, and navigation (Nilsson et al. 2005th). Globally, there are now about 50,000 dams exceeding 15 m in height (WCD 2000), and many new dams are planned or under construction (WWF 2004). There is no current record of the global number of small dams, ie, dams <15 m in height, but in the United States alone there are approximately 2 million such dams (Shuman 1995). Among Sweden's more than 5300 dams, about 5100 (96%) are small (SMHI 1994, 1995, Vattenportalen 2007). Although Human Control over freshwater flow has Increased prosperity for many people, it has also LED to Serious effects on ecosystems and local Human Societies (eg, Nilsson and Berggren the 2,000th, Scudder 2,005). Dams increase Water retention, modify the hydrograph, Eliminate turbulent reaches. and riparian wetlands, impede the dispersal and migration of plants and animals, decrease interactions between land and water, and reduce sediment transport (Ward and Stanford 1995, Jansson et al. 2000, Kingsford 2000, Syvitski et al. 2005). Following the creation of dams and reservoirs, many terrestrial ecosystems become permanently inundated. This damages ecological communities, erodes the soil of the inundated land (Dudgeon 1995, Nilsson et al. 1997), and causes emissions of greenhouse gases such as methane and carbon dioxide during the breakdown of organic matter (Fearnside 1997, St. Louis et al. . 2000). Even if not directly affected by Loss of Property, Humans are often Indirectly affected by hampered ecosystem Services such as reduced Water Availability on farmed floodplains following Decreased flooding, lowered Aquatic Productivity, and reduced Control of species invasions (Nilsson et al. 2,005). During. the Swedish dam-building era after World War II, large, modern hydroelectric power plants were constructed to supply the developing industry and society with electric power. In some cases, small dams, such as hydroelectric dams and splash dams used for timber floating, were removed to make room for larger ones. In this respect, dam removal is not a new concept in Sweden. However, the removal of entire impoundments and dam constructions to restore riverine landscapes is a new practice. Thus, dam removal is becoming a more frequently used management option, especially for old dams in need of renovation and small dams that are no longer used or have lost most of their reservoir capacity. Globally, most dams that have been removed or considered for removal are in the USA. In 2003rd, Stanley and Doyle (the 2003rd) reported that more than 500 Dams had been removed in the previous Two decades in the United States, Although they Found no Data Indicating that any Other Country had removed more than Nine. Dam Removal is now becoming a. viable option in other regions of the world for several reasons. For the dam owner, removal can be economically preferable to renovation because of the environmental benefits gained from the restoration of turbulent stream reaches and fish migration routes. Safety reasons are also vital, especially in cases in which dams are in bad shape and hold large amounts of water (Stanley and Doyle 2003). Despite such benefits, however, dam removal often gives rise to conflicts. This is the case even when dam owners encourage removal. Conflicts often result in unnecessarily long processing times, and sometimes removals are stalled even in cases in which funding for removal has been provided. In this paper we address incentives for dam removal such as safety issues, law and policies, and economic as well as ecological incentives. We also outline some of the underlying mechanisms of the types of conflict associated with dam removal. Our presentation is based on our own experience with recently debated and implemented dam removals in Sweden (Table 1). We also provide guidance on how conflicts can be prevented or resolved in future dam removals.

ผลลัพธ์ (อังกฤษ) 3:

INTRODUCTION


During the 20th century humans dammed, and regulated most of the world 's rivers for reasons such, as hydropower. Flood control domestic supply and, water, navigation (Nilsson et al. 2005). Globally there are, now about 50 000 dams, exceeding 15 m. In height (WCD 2000), and many new dams are planned or under construction (WWF 2004).