How does a dam generate electricity, and what happens when a dam is removed?

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1. 1

   Classification of US Hydropower Dams by their Modes of Operation

   River Research and Applications (McManamay et al.)Published Feb 19, 2016Checked Oct 18, 2026

   “After reviewing information for 721 dams and 597 power plants, we developed a two-tier hierarchical classification based on (i) the storage and control of flows to powerplants, and (ii) the presence of a diversion around the natural stream bed. This resulted in nine tier-1 MOPs representing a continuum of operations from strictly peaking, to reregulating, to run-of-river, and two tier-2 MOPs, representing diversion and integral dam-powerhouse configurations. Although MOPs differed in physical characteristics and energy production, classification trees had low accuracies (≤62%), which suggested that accurate evaluations of MOPs may require individual attention. MOPs and dam storage explained 20% of the variation in downstream subdaily flow characteristics and showed consistent alterations in subdaily flow patterns from reference streams. This standardized classification scheme is important for future research including estimating reservoir operations for large-scale hydrologic models and evaluating project economics, environmental impacts, and mitigation. Copyright © 2016 John Wiley & Sons, Ltd.”

2. 2

   Dam removal: Listening in

   Water Resources Research (Foley et al.)Published Jul 1, 2017Checked Oct 18, 2026

   “me general conclusions have emerged: (1) physical responses are typically fast, with the rate of sediment erosion largely dependent on sediment characteristics and dam‐removal strategy; (2) ecological responses to dam removal differ among the affected upstream, downstream, and reservoir reaches; (3) dam removal tends to quickly reestablish connectivity, restoring the movement of material and organisms between upstream and downstream river reaches; (4) geographic context, river history, and land use significantly influence river restoration trajectories and recovery potential because they control broader physical and ecological processes and conditions; and (5) quantitative modeling capability is improving, particularly for physical and broad‐scale ecological effects, and gives managers information needed to understand and predict long‐term effects of dam removal on riverine ecosystems. Although these studies collectively enhance our understanding of how riverine ecosystems respond to dam removal, knowledge gaps remain because most studies have been short (< 5 years) and do not adequately represent the diversity of dam types, watershed conditions, and dam‐removal methods in the U.S.”

3. 3

   Rewilding the upper Klamath River Basin: rapid recolonization of Chinook salmon following the world's largest dam removal.

   Scientific reports (Goodman et al.)Published Aug 27, 2026Checked Oct 18, 2026

   “We used a stationary high-resolution multi-beam imaging SONAR to quantify adult Chinook salmon (Oncorhynchus tshawytscha) passage into newly reopened reaches during the first two migratory seasons following dam removal. An estimated 7,742 (95% CI: 7,702-7,778) Chinook salmon migrated upstream in 2024 and 13,310 (95% CI: 12,876-13,733) in 2025, representing 18-19% of fish returning to the Klamath River Basin. Within this period, Chinook salmon recolonized 88% of their documented historical distribution, expanding into 345 km of reconnected habitats and reaching elevations of up to 1,250 m. Recolonization required fish to swim through dam removal sites, complex hydraulic corridors and engineered fishways, demonstrating the propensity for rapid recolonization at basin scale despite these challenges. These findings provide the first quantitative assessment of salmon response to the world's largest dam removal and demonstrate how reconnection can catalyze large-scale recolonization in historically fragmented river networks.”

4. 4

   The Impacts of Hydropower Dams in the Mekong River Basin: A Review

   Water (Soukhaphon et al.)Published Jan 22, 2021Checked Oct 18, 2026

   “This paper explores the social and environmental impacts of several Mekong basin hydropower dams and groupings of dams and the geographies of their impacts. Specifically, we examined the 3S (Sesan, Sekong Srepok) river system in northeastern Cambodia, the Central Highlands of Vietnam, and southern Laos; the Khone Falls area in southern Laos; the lower Mun River Basin in northeastern Thailand; and the upper Mekong River in Yunnan Province, China, northeastern Myanmar, northern Laos, and northern Thailand. Evidence shows that these dams and groupings of dams are affecting fish migrations, river hydrology, and sediment transfers. Such changes are negatively impacting riparian communities up to 1000 km away. Because many communities depend on the river and its resources for their food and livelihood, changes to the river have impacted, and will continue to negatively impact, food and economic security. While social and environmental impact assessments have been carried out for these projects, greater consideration of the scale and cumulative impacts of dams is necessary.”

5. 5

   Trading off: the ecological effects of dam removal

   Frontiers in Ecology and the Environment (Stanley & Doyle)Published Feb 1, 2003Checked Oct 18, 2026

   “Dam removal is gaining credibility as a viable management option for dams that have deteriorated physically and are no longer economically practical. However, the decision to remove or repair a dam is often contentious and emotionally charged. Part of the acrimony arises from our limited scientific knowledge of the effects of dam removal. We believe that the ecological consequences are best understood by viewing the removal process as a disturbance. Ecological outcomes will include changes that are both environmentally costly, such as invasion of exotic species, and environmentally beneficial, such as increasing access to spawning habitats for migratory fish. It has also become apparent that the wholesale aging of the US dam infrastructure will make dam removal even more common in the future. The challenge ahead is to better understand and manage the consequences of these removals.”

6. 6

   Study on the effects of hydrological connectivity on the dispersal and driving factors of macroinvertebrate communities.

   Scientific reports (Zhang et al.)Published Mar 2, 2026Checked Oct 18, 2026

   “After dam removal, strong dispersers increased, whereas weak dispersers decreased. Additionally, at most sites, the dispersal capacity metric (DCMc) of the impaired sites was higher than before dam removal. Temporal variation patterns showed significant changes before and after dam removal, and in the initial stage after removal, the DCMc at each site increased with the increase in the number of “fugitive species,” those with strong dispersal capacity but weak competition capacity in the initial stage. Piecewise structural equation models revealed that Flow-Velocity and Flow-CPOM (coarse particulate organic matter) were positive feedback paths that affected DCMc, whereas Flow-Width and Flow-FPOM (fine particulate organic matter) were negative feedback paths. Our findings provide foundational support for the study of future freshwater ecosystem communities and biodiversity maintenance mechanisms as well as a scientific basis for the protection and management of cascade dams.”