Dam removal continues to garner attention as a potential river restoration tool. The increasing possibility of dam removal through the FERC relicensing process, as well as through federal and state agency actions, makes a critical examination of the ecological benefits and costs essential. This paper reviews the possible ecological impacts of dam removal using various case studies. Restoration of an unregulated flow regime has resulted in increased biotic diversity through the enhancement of preferred spawning grounds or other habitat. By returning riverine conditions and sediment transport to formerly impounded areas, riffle/pool sequences, gravel, and cobble have reappeared, along with increases in biotic diversity. Fish passage has been another benefit of dam removal. However, the disappearance of the reservoir may also affect certain publicly desirable fisheries. Short-term ecological impacts of dam removal include an increased sediment load that may cause suffocation and abrasion to various biota and habitats. However, several recorded dam removals have suggested that the increased sediment load caused by removal should be a short-term effect. Pre-removal studies for contaminated sediment may be effective at controlling toxic release problems. Although monitoring and dam removal studies are limited, a continued examination of the possible ecological impacts is important for quantifying the resistance and resilience of aquatic ecosystems. Dam removal, although controversial, is an important alternative for river restoration.

Broad-scale studies of climate change effects on freshwater
species have focused mainly on temperature, ignoring critical
drivers such as flow regime and biotic interactions. We use
downscaled outputs from general circulation models coupled with a hydrologic model to forecast the effects of altered flows andincreased temperatures on four interacting species of trout across the interior western United States (1.01 million km2), based onempirical statistical models built from fish surveys at 9,890 sites. Projections under the 2080s A1B emissions scenario forecast amean 47% decline in total suitable habitat for all trout, a groupof fishes of major socioeconomic and ecological significance. We project that native cutthroat trout Oncorhynchus clarkii, already excluded from much of its potential range by nonnative species, will lose a further 58% of habitat due to an increase in temperatures beyond the species’ physiological optima and continuednegative biotic interactions. Habitat for nonnative brook troutSalvelinus fontinalis and brown trout Salmo trutta is predictedto decline by 77% and 48%, respectively, driven by increases in temperature and winter flood frequency caused by warmer, rainier winters. Habitat for rainbow trout, Oncorhynchus mykiss, isprojected to decline the least (35%) because negative temperature effects are partly offset by flow regime shifts that benefit the species. These results illustrate how drivers other than temperature influence species response to climate change. Despite some uncertainty, large declines in trout habitat are likely, but our findings point to opportunities for strategic targeting of mitigation efforts to appropriate stressors and locations.

Hydropower represents approximately 20% of the world’s energy supply, is viewed as both vulnerable to global climate warming and an asset to reduce climate altering emissions, and is increasingly the target of improved regulation to meet multiple ecosystem service benefits. It is within this context that the recent decision by the United States Federal Energy Regulatory Commission to reject studies of climate change in its consideration of reoperation of the Yuba-Bear Drum-Spaulding hydroelectric facilities in northern California is shown to be poorly reasoned and risky. Given the rapidity of climate warming, and its anticipated impacts to natural and human communities, future long-term fixed licenses of hydropower operation will be ill prepared to adapt if science-based approaches to incorporating reasonable and foreseeable hydrologic changes into study plans are not included. The licensing of hydroelectricity generation can no longer be issued in isolation due to downstream contingencies such as domestic water use, irrigated agricultural production, ecosystem maintenance, and general socioeconomic well-being. At minimum, if the Federal Energy Regulatory Commission is to establish conditions of operation for 30-50 years, licensees should be required to anticipate changing climatic and hydrologic conditions for a similar period of time.

This report is to develop a list of likely candidate dams for removal within the Muskegon River Watershed based on a number factors. The report ranks 15 dams as the most favorable for removal, at minimal cost and with minimal public and private opposition based on available information.

Damming a river may bring electric power, but it often comes at the price of high-quality food fisheries, experts say. When dams are proposed for power, flood control or irrigation, the often devastating impacts on fisheries in rivers and lakes are ignored or discounted.

This report by the UN Environment Programme (UNEP) and the World Fish Centre warns that despite over 40 years of steady production globally, rapid environmental changes are occurring which challenge the viability of future fish stocks and a range of internationally- agreed development targets including the Millennium Development Goals.

The report is available online at http://www.unep.org/pdf/Blue_Harvest.pdf

Over the past two decades, watershed restoration has dramatically increased internationally. California has been at the forefront, allocating billions of dollars to restoration activities through legislation and voter-approved bonds. Yet, the implications of restoration remain ambiguous because there has been little examination of restoration accomplishments and almost no analysis of the political context of restoration. This article addresses these gaps, utilizing a case study of the Russian River basin in Northern California. We identify trends that shed light on both the ecological and the political implications of restoration at a basin scale by examining a database of 787 restoration projects implemented in the Russian River basin since the early 1980s. Although a total of over $47 million has been spent on restoration in the basin, dominant forms of restoration are limited in scope to small-scale projects that focus on technical solutions to site-specific problems. The majority of restoration efforts are devoted to road repair, riparian stabilization, and in-stream structures, accounting for 62% of all projects. These types of projects do not address the broader social drivers of watershed change such as land and water uses. We suggest that restoration can become more effective by addressing the entire watershed as a combination of social and ecological forces that interact to produce watershed conditions.

1. Despite escalating conflict over fresh water, recent years have witnessed a growing realisation that human society must modify its behaviour to ensure long-term ecological vitality of riverine ecosystems. In response, ecologists have been increasingly asked to guide instream flow management by providing ‘environmental flow’ prescriptions for sustaining the ecological integrity of riverine systems.
2. Environmental flows are typically discussed in the context of water releases from dams and water allocation for extraction (such as for urban use or irrigation), where there is general agreement that rivers need to exhibit some resemblance of natural flow variability necessary to support a functioning ecosystem. Although productive dialogue continues on how best to define environmental flows, these discussions have been focused primarily on water quantity without explicit consideration of many components of water quality, including water temperature – a fundamental ecological variable.
3. Many human activities on the landscape have modified riverine thermal regimes. In particular, many dams have modified thermal regimes by selectively releasing hypolimnetic (cold) or epilimnetic (warm) water from thermally stratified reservoirs to the detriment of entire assemblages of native organisms. Despite the global scope of thermal alteration by dams, the prevention or mitigation of thermal degradation has not entered the conversation when environmental flows are discussed.
4. Here, we propose that a river’s thermal regime is a key, yet poorly acknowledged, component of environmental flows. This study explores the concept of the natural thermal regime, reviews how dam operations modify thermal regimes, and discusses the ecological implications of thermal alteration for freshwater ecosystems. We identify five majorchallenges for incorporating water temperatures into environmental flow assessments, and describe future research opportunities and some alternative approaches for confronting those challenges.
5. We encourage ecologists and water managers to broaden their perspective on environmental flows to include both water quantity and quality with respect to restoring natural thermal regimes. We suggest that scientific research should focus on the comprehensive characterisation of seasonality and variability in stream temperatures, quantification of the temporal and spatial impacts of dam operations on thermal regimes and clearer elucidation of the relative roles of altered flow and temperature in shaping ecological patterns and processes in riverine ecosystems. Future investigations should also concentrate on using this acquired knowledge to identify the ‘manageable’ components of the thermal regime, and develop optimisation models that evaluate management trade-offs and provide a range of optimal environmental flows that meet both ecosystem and human needs for fresh water.

Over the past two decades, watershed restoration has dramatically increased internationally. California has been atthe forefront, allocating billions of dollars to restoration activities through legislation and voter-approved bonds. Yet, the implications of restoration remain ambiguous because there has been little examination of restoration accomplishments and almost no analysis of the political context of restoration. This article addresses these gaps, utilizing a case study of the Russian River basin in Northern California. We identify trends that shed light on both the ecological and the political implications of restoration at a basin scale by examining a database of 787 restoration projects implemented in the Russian River basin since the early 1980s. Although a total of over $47 million has been spent on restoration in the basin, dominant forms of restoration are limited in scope to small-scale projects that focus on technical solutions to site-specific problems. The majority of restoration efforts are devoted to road repair,riparian stabilization, and in-stream structures, accounting for 62% of all projects. These types of projects do not address the broader social drivers of watershed change such as land and water uses. We suggest that restoration can become more effective by addressing the entire watershed as a combination of social and ecological forces that interact to produce watershed conditions.