Big Dams Research Articles

Sharp decline in surface water resources for agriculture and fisheries in the Lower Mekong Basin over 2000-2020

Water resources play a crucial role in the global water cycle and are affected by human activities and climate change. However, the impacts of hydropower infrastructures on the surface water extent and volume cycle are not well known. We used a multi-satellite approach to quantify the surface water storage variations over the 2000–2020 period and relate these variations to climate-induced and anthropogenic factors over the whole basin. Our results highlight that dam operations have strongly modified the water regime of the Mekong River, exhibiting a 55 % decrease in the seasonal cycle amplitude of inundation extent (from 3178 km2 to 1414 km2) and a 70 % decrease in surface water volume (from 1109 km3 to 327 km3) over 2000–2020. In the floodplains of the Lower Mekong Basin, where rice is cultivated, there has been a decline in water residence time by 30 to 50 days. The recent commissioning of big dams (2010 and 2014) has allowed us to choose 2015 as a turning point year. Results show a trend inversion in rice production, from a rise of 40 % between 2000 and 2014 to a decline of 10 % between 2015 and 2020, and a strong reduction in aquaculture growth, from +730 % between 2000 and 2014, to +53 % between 2015 and 2020. All these results show the negative impact of dams on the Mekong basin, causing a 70 % decline in surface water volumes, with major repercussions for agriculture and fisheries over the period 2000–2020. Therefore, new future projects such as the Funan Techo canal in Cambodia, scheduled to start construction at the end of 2024, will particularly affect 1300 km2 of floodplains in the lower Mekong basin, with a reduction in the amount of water received, and other areas will be subjected to flooding. The human, material and economic damage could be catastrophic.

Divinizing Nature for Sustainable Global Growth: The Indian Perspective

The recent catastrophic climate conditions and the spate of wildfires, floods, cyclones, etc. on an unparalleled scale sweeping most parts of the globe has sent mankind in a tizzy. Despite numerous summits and conferences of world leaders and the action plans continue to make headlines even though the real effect on the ground seems suspect. Faultlines flagged include the seemingly unsustainable global market economy, high-level consumerism, widespread deforestation, emissions from ever-burgeoning number of automobiles and fossil-fuel fed industries, use of chemicals, building of big dams, etc. While all this is true, the real change has to come about in human attitude to nature. From the urge to exploit nature, it has to be of an interdependence based on respect for the natural elements and creatures because these maintain balance and provide congenial environment for life. My paper analyses the situation and concludes that for this to happen, we need to involve heart and soul as much as the mind. Our native cultures existing since ages and finding expression in ancient as also contemporary literatures provide an answer to tackle the fearsome scenario facing us, and this is to treat nature not just as a living being, but rather a divine being.

Community Adaptation to Impacts of Big Dams and Water Harvesting at the Red Sea State (Arbaat and Sinkat Areas)

Community Adaptation to Impacts of Big Dams and Water Harvesting at the Red Sea State (Arbaat and Sinkat Areas)

Hydrological regimes and water quality variations in the Yangtze River basin from 1998 to 2018

Understanding the long-term variations in basins that undergo large-scale hydroelectric projects is crucial for effective dam operation and watershed management. In this study, comprehensive analyses were conducted on a dataset spanning over 20 years (1998–2018) of hydrological regime and physicochemical parameters from the Yangtze River basin to evaluate the potential impacts of the Three Gorges Dam. Water level significantly increased from 128.75±58.18 m in 2002 to 136.78±55.05 m in 2005, and the mean flow velocity significantly decreased from 2004 to 2010. However, no significant change in the flow was observed in the basin. Meanwhile, remarkable fluctuations in physicochemical parameters, including dissolved oxygen, chemical oxygen demand, conductivity, hardness, and alkalinity, were mainly observed during impoundment (2003–2009). After that, the above parameters tended to stabilize, and some even returned to their original levels. The dam's retention effect significantly reduced the suspended solids (SS) in both up- and downstream, to only one-third of the pre-operation level. And total phosphorus and chemical oxygen demand also significantly decreased with the decline of SS. Particularly, ammonium also showed a significant downward trend, with the up- and downstream of the dam falling by 36.8 % and 26.1 %, respectively. However, the increasing total nitrogen (7.5 % and 20.0 % up- and downstream of the dam, respectively) still threatened the water quality of the basin, especially in the estuaries. Additionally, the significant decline in dissolved oxygen downstream (from 8.53±1.08 mg/L to 8.11±1.36 mg/L) also exacerbated the hypoxia in the Yangtze River estuary. The results demonstrated the long-term impact of the construction of the Three Gorges Dam on the environmental elements of the Yangtze River basin, which provides reference data and guidance for the construction of big dams in major rivers in the future.

Why does geography matter in big dam removal projects? Lessons from a comparison between the Sélune and Elwha River cases

The dam removal movement is resulting in numerous projects worldwide, especially in Western countries. Whether completed or in progress, these undertakings often trigger conflict. Nearly 30 years after the initiation of the first major projects, this article examines the conditions for the local appropriation of dam removal projects. From the perspective of two pioneering and emblematic projects in France (Sélune River) and the United States (Elwha River), this article highlights the geographic specificities of dam removal projects carried out in European rural areas. The aim is to discuss how to implement ambitious ecological projects without running the risk of local people losing their sensitive relationship (history, experience, landscape) with the areas once they have been restored. In other words, ecological restoration should not result in a loss of meaning and quality in the relationship between local people and newly restored spaces; it should instead enrich it. In fact, the removal of a dam is not just a technical project; it profoundly affects landscapes, disrupting uses and creating new places. We identify the modalities by which a new space is produced and appropriated by local populations based on a comparison of the relevant spaces (national park vs. rural agricultural space), the populations involved (river users, Native American tribes, residents, and NGOs), and, finally, the governance processes and interactions between expertise and politics, all to highlight the need to take geographical context into account. Based on a detailed knowledge of the formation of the Sélune dam removal project, which has been the subject of continuous participant observation since 2011, we examine these projects’ singularities and commonalities to identify the factors that contribute to their success. This study highlights the importance of the spatial scale at which the dam removal project should be framed, the role of government, and the importance of considering people’s attachment to local places. Finally, this comparison makes recommendations for improving the socio-territorial quality of ecological projects, especially in Europe, with the aim of ensuring their sustainability and success.

Western versus Indian Anthropology: A New Discourse

Indian anthropology, though established under the British rule had developed its own tradition of anthropological study. Some of the notable Indian anthropologists however critiqued their own anthropology as being colonial. In this paper, I have argued that quite remarkable anthropological studies were done by outstanding Indian anthropologists after the independence of the country, which encountered the major challenges of nation building, namely, resettlement of refugees after the partition of the country and development caused displacement by big dams and industrialisation.

Arundhati Roy’s Critique of Big Projects: An Eco-critical Perspective

The present article endeavors to analyze Arundhati Roy’s critique of big dams and projects. An attempt is made to bring home various dimensions and commitments that inform her critique of the big dams which cause more damage and devastation than serving the needs of the people at large. The primary focus is on Ms. Roy’s participation in the Narmada Bachao Andolan which is an Indian resistance movement that tries to prevent building of large dams, reservoirs and power plants. As the building of projects may lead to evacuation of villages and to lose immovable properties numerous environmentalists, humanists, activists and other personalities also have condemned the government for the decisions and implementations. Arundhati Roy is one among them who raises awareness of dangers of massive dams, of resulting forced relocation of people and of damage to environment. The present article is going to discuss the tireless and selfless service of Arundhati Roy and the NBA to tens of thousands of farmers, Adivasis and common people who are participating in the protest to oppose the aforementioned large structures constructed by the Narmada Valley Development Authority (NVDA). In conclusion, the article also attempts to bring out the various aspects and convictions that informed Roy’s critique of big projects.

River fragmentation in the northern Sandomierz Basin (SE Poland)

AbstractRiver fragmentation is a process highly detrimental for fish survival by impeding their migrations. Although fragmentation by big dams has been studied, there is still a big deficiency of data related to small barriers. This study was designed as a detailed, local‐scale analysis of several chosen river stretches in the Sandomierz Basin, Poland. It aimed to: (1) map all natural and artificial barriers in the study area, (2) assess the impacts of these barriers on fish migration, (3) compare findings to existing databases, and (4) make recommendations for improved barrier management. Ten lowland rivers covering a total 424 km length were surveyed by river walkovers and kayak surveys, with all the barriers mapped and all the artificial structures assessed for fish migration using the ICE protocol protocol for ecological continuity. There were 67 beaver dams and 89 artificial barriers recorded, with only 24% of the latter being included in national databases. The average artificial barrier density in all the surveyed rivers was 0.2 barriers/km and varied from 0.75 barriers/km in first order streams to 0.01 barriers/km in sixth order river. The findings revealed that 18% of the barriers were passable for all fish species, with 35% totally impassable. The analysis of specific barrier parameters indicated that water depth at the barrier had a greater influence on fish passability than the barrier height. Several barriers were proposed for removal to specifically improve the potential for fish migration.

Impact of Dam Materials and Hydraulic Properties on Developing the Breaching Dimensions

Dam safety is an important issue as it directly influences environmental and life losses. Embankment material and embankment core are important factors that contribute to determining the size and hydraulic characteristics of the breach that occurs due to dam failure. The current topic is to present the analysis of the impact of the dam materials properties and hydraulic characteristics on breach dimensions due to overtopping failure using 2D-HEC-RAS software with the aid of RAS-Mapper. The analysis was made by Digital Elevation Model (DEM) conversed to a Triangular Irregular Network (TIN), then the 2D area of the dam was determined and the storage area boundary was calculated. Mosul dam in Iraq, considered one of the big dams that consist of different materials in the core and body, was selected as a case study to simulate the dam breach development due to overtopping failure. Six scenarios of dam failure were carried out for three types of dam materials (dam with corewall, concrete-face dam, and homogeneous zoned fill dam), each with high and medium erodibility. All scenarios were made for the reservoir elevation of 341 m which is considered the probable elevation for failure occurrence. The results showed that the minimum and maximum values of breach width were found to be 542 m and 1118 m, respectively in both cases of concrete-face dam type with a high erodibility and homogeneous zoned fill dam with medium erodibility rate. It has been illustrated that the medium erodibility in each scenario gives a smaller width for a long time, especially in homogeneous zoned fill dam type which is a good indication in engineering design. The analysis of sensitivity was carried out to examine the impact of pool volume at failure on breaching time and width of the breach. It showed that the breach width is more sensitive to reservoir fill capacity and there is a linear relationship between water volume reduction ratios and the breach width. Finally, tests of the six cases reveal that the proposed model is sensitive to soil conditions.

Complexity in Geophysical Time Series of Strain/Fracture at Laboratory and Large Dam Scales: Review

One of the interesting directions of complexity theory is the investigation of the synchronization of mechanical behavior of large-scale systems by weak forcing, which is one of manifestations of nonlinearity/complexity of a system. The effect of periodic weak mechanical or electromagnetic forcing leading to synchronization was studied on the laboratory load-spring system as well as on a big dam's strain data. Due to synchronization, the phase space structure of the forced system strongly depends on the weak forcing intensity-determinism show itself in the recurrence of definite states of the forced system. The nonlinear dynamics of tilts/strains/seismicity near grand dams reflect both the complexity of the mentioned time series, connected with the natural agents (regional and local geodynamics), which were presented even before dam erection, as well as the effects of the water level (WL) variation in the reservoir, which is a quasi-periodic forcing superimposed on the natural geodynamic background. Both these effects are documented by the almost half-century of observations at the large Enguri Dam. The obtained data on the dynamics of strain/seismicity near a large dam can be used for the assessment of the possible risks, connected with the abrupt change of routine dynamics of construction.

INTEGRATING LIDAR DATA, 2D HEC-RAS MODELING AND REMOTE SENSING TO DEVELOP FLOOD HAZARD MAPS DOWNSTREAM OF A LARGE RESERVOIR IN THE INNER EASTERN CARPATHIANS

The use of 1D, 2D, and 1D/2D modelling techniques to identify flood prone areas is a critical component of any flood hazard management project (e.g., APDF – action plan for dam failure) in the proximity of big dams and reservoirs. In this work, we manage to computed flood hazard models using 2D HEC-RAS module based on Digital Elevation Models (DEM’s) derived from Light Detection and Ranging (LiDAR) data and pre- and post-processed using Geographic Information Systems (GIS)-based software (e.g., ArcGIS, HEC-RAS). Therefore, to produce urban flood hazard (FH) maps downstream of the Strâmtori-Firiza reservoir (S-Fr) in NW Romania, a multi-scenario approach based on LiDAR-derived DEM integration, 2D hydraulic modeling, and remote sensing (RS) data validation is provided. In this context, to assess the flood control capacity (FCC) of the S-Fr hydro-technical system, three flood tests based on S-Fr flow rate with 5% (167 m3/s), 1% (270 m3/s) and 0.1% (447 m3/s) return periods were performed. The flood impact within the urban area of Baia Mare located downstream of S-Fr was achieved for each flood scenarios using four spatial data derived from the RAS Mapper module: flood extent (FE), flood depth (FD), flood velocity (FV) and flood hazard (FH). The results indicate that a large area of Baia Mare city can be affected by a potential flood caused by a dam failure and also contribute to the APDF update of S-Fr dam.

Water Resources and Conservation Strategy of Pakistan

Water is one of the basic necessities of life. God has gifted Pakistan with abundant water resources, with rivers flowing down the Himalayas and Karakoram heights from the world’s largest glaciers and free and unique bounty for this land. Pakistan is basically an agrarian economy. Out of its total geographical area of 79.61 million hectares, cultivated area is 22.05 million hectares. The total area under irrigation is 19.02 million hectares [Agricultural Statistics of Pakistan (2005-06)]. Irrigated land supplies more than 90 percent of agricultural production and most of the country’s food. Agriculture sector is regarded as the backbone of Pakistan’s economy. It contributes 25 percent of the GDP. About more than 50 percent labour force is employed in this sector. Agriculture sector is also the major user of water and its consumption will continue to dominate water requirement. Similarly, for industrial development main source of energy is hydropower which is generated by dint of water stored in big dams and reservoirs. Therefore the importance of the water for the survival of our economy cannot be denied.

Displacement and Livelihoods through the Construction of Small Dams: Legacies of Magunje Dam in Hurungwe District, Mashonaland West Province, Zimbabwe

This article examines the experiences of people in rural areas who are displaced by the construction of small dams. Scholarship on dam construction has generally focused on the impact of big dams on communities. Yet, this study argues, small dam construction projects also impact those living on the site and vicinity of small dams. Using Magunje Dam in Hurungwe District of Zimbabwe as a lens, the study traces the experiences of the changed livelihoods of communities that resisted being moved and those who were relocated to other places. By taking this approach, the study establishes the complex impact of the Magunje Dam project on the evicted people and argues that those who are affected by small dam projects sometimes suffer unwanted consequences and their challenges are difficult to remedy because they occupy the fringes of society. Their challenges go unnoticed, especially after receiving paltry compensation. The study shows that displacement and involuntary resettlement destabilise the family fabric. Through the lenses of the Impoverishment Risks and Reconstruction model (IRR), the effects of dam construction on rural people are unpacked. Data was obtained through qualitative research methodologies.

Potential Assessment and Performance Evaluation of a Floating Solar Photovoltaic on the Great Ethiopian Renaissance Dam

The demand for electricity has increased rapidly in Ethiopia. Renewable energy sources such as solar PV are being used to respond to the power demand and cover a small percentage of the country’s energy need. However, in Ethiopia, where the majority of the land is utilized for agriculture, the land required to generate solar PV power in a large scale is a significant barrier. Big dams, such as Great Ethiopia’s Renaissance Dam, can be used for a solar floating system to eliminate the need for land and transmission infrastructure. Due to its wider area covered by the reservoir, which is about 1,874,000,000 m2, the potential of the renaissance dam needs to be investigated for solar PV floating installation to meet the electricity demand in residential, commercial, and industrial sectors in Ethiopia. In addition, the cooling action of the water on the PV floating allows it to keep its efficiency and increase the power output from the panels. In this study, the performance of grid-connected floating PV systems was evaluated in terms of power generation potential, performance ratio, capacity utilization factor, greenhouse gas emissions, and water conservation. The power consumption of peoples living in the GERD generation site is nearly 1 MW. Though they get electricity through the grid, this study considers performance assessment of a 1 MW solar FPV with the intention of covering the energy need of the hydropower station itself and near rural communities. Modeling and simulation of the proposed FPV plant is done with the help of PVsyst software tool. Finally, the analysis reveals that the GERD has the FPV capability to generate 18,740 MW of maximum power, and its performance was assessed for a 1 MW grid-connected FPV system. The benefits of employing FPV in energy production, water conservation, CO2 emission reduction, and economic benefit are demonstrated in this study. Furthermore, the installation of 1 MW FPV saves 54.4 million liters of GERD water from evaporation per year, which benefits the Blue Nile’s downstream countries to conserve their share of water.

Nehru’s Vision of Swaraj and Socialism

The thought of socialism is an age old phenomenon in the human society. Its traces can be found in the writings of Greek philosophers like Plato and Aristotle. Shades of socialistic thoughts can also be discovered in the Santan Dharma scriptures, Islamic scriptures and the teachings of Jesus Christ. But it was only in the beginning of the 19th century that socialism as a political, social and economic philosophy gained momentum.
 Jawaharlal Nehru believed that no country or individual could develop much without social freedom and a socialist structure of the society and the state. The idea of socialism had been a constant thought in his mind since the pre-independence days. As an economic modernist of his times, Nehru believed in the development of large-scale industries, which he thought was the only key to overcome poverty in the country. Nehru’s concept of socialism was not merely a rigid theoretical doctrine. Theories when put to practice entertain pragmatic difficulties. When Nehru got the opportunity to apply his concept of socialism as the first Prime Minister of India, he had to confront with many complications. His idea of socialism was subjected to many changes looking to the vast population of India. A strict adherence to any doctrine may prove detrimental at times, more so in a country, like, India. Nehru, therefore, envisaged a policy of mixed economy, of course socialist in nature, which would be best suitable to the needs of the country. India has both a rural and an urban economy and what is required is a harmonious blend between the two for the growth and development of the country. The construction of a series of big dams for agricultural irrigation along with the production of hydroelectricity i.e. energy for industrial purposes reflects Nehru’s idea of drawing a balance between the two major sectors of the country. 
 What Nehru meant by Swaraj was not merely political freedom but beside political freedom it should include social and economic justice for the Indian masses. Independence should bring not only a change of the officials but should also bring a change in the fundamentals of the life of a nation.
 The year 1991 will always be remembered in India as a year which is witness to a drastic change in the Indian economy policy. This was the year when the Government of India drifted from Nehru’s policy of mixed economy and announced the new economic policy which consisted of a wide range of reforms. Thirty years have passed under this new economic system and now the time has come when we should evaluate and analyze how far this new approach has been beneficial to the country.
 Today, the country is face to face with innumerable problems; problems related to inflation, unemployment, caste, class and religious activism. The country needs to address these problems in a determined way before it is too late. I understand that the time has come when we need to once again look back to Nehru’s vision of Swaraj and socialism for a pragmatic solution to these problems.

Leveraging machine learning methods to quantify 50 years of dwindling groundwater in India

Global compilations and regional studies, indicative of the unsustainable extraction and subsequent unremittingly depleting groundwater (GW) in India, either provide bulk estimates or are confined to the river basins and therefore conceal inferences from a nationwide policymaking perspective. Here, we provide the state-wise past (2000−2020) and future (2030–2050) assessment of dwindling groundwater in India utilizing in-situ groundwater levels (GWL) from 54,112 wells, remote sensing products, and hydrological simulations. By employing three machine learning methods, we show a decline in GWL of over 80% in North India with a notable shift towards the eastern state of Uttar Pradesh and a cumulative groundwater loss (169.96 ± 19.67 km3) equivalent to the water storage capacity of the world's biggest dam (Kariba Dam, Zimbabwe). Its likely contribution to sea-level rise (0.47 ± 0.06 mm) is about 64% of that from annual global glacier melt. Our results typically contrast the GW recovery paradox in South India (e.g., a declining trend of −84.48 ± 38.81 mm/a (p < 0.05) in Andhra Pradesh during 2000–2020), reveal high seasonal variability (e.g., up to ~6 m in Maharashtra), and illustrate the skewed effect of survivor bias in the traditional assessments. We infer the significant impact of underlying hydrogeology and the implementation of water-related policies and projects on the GWL dynamic and variability in the region. Projected GWL reveals a likely water scarcity situation for about 2.8 million km2 area and one billion residents of the country up to 2050. Our observation-based analysis offers insights into the state-level monthly GW dynamics, which is critical for efficient interstate resource allocation, development plans, and policy interventions with broad methodological implications for the water-scarce countries.

Weather modification, solution and innovation to reservoirs water sustainable management (case study: ZayandeRoud reservoir)

Climate change has had devastating effects on water resources in many countries. Many volumes of Iran’s water resources have declined due to climate change. Meanwhile, the use of weather modification methods, especially cloud seeding, is a practical solution to adapt to the climate change impact. In Iran, consecutive droughts and climate change have reduced water resources of dams behind and in some cases, they have completely dried up. Nowadays, cloud seeding is used as the most costeffective method for water harvesting in the world… The results of the evaluation of cloud seeding projects in most parts of the country indicate an average runoff increase of between 10% and 15% during the seeding periods. Zayanderud Dam is one of the big dams in Iran in the Zagros Mountain range its water resources have been significantly reduced by overdraft and climate change. Cloud seeding operations have been performing for many years in the Charmahal and Bakhtiari catchment, which are located upstream of the ZayandeRoud reservoirs as new method to sustainable water resources management of dams. In this article, the results of runoff production by cloud seeding operation will be noted in the ZayandeRoud Dam for 10 years Non-consecutive (2006 – 2016).

Long term displacement observation of the Atatürk Dam, Turkey by multi-temporal InSAR analysis

Monitoring large infrastructures is vital for determining structural safety over time. Dams are structures that influence agricultural activities and have high economic contributions. The dams' structural safety was mainly addressed using conventional measurement techniques. However, these might not be time-efficient and practical, considering the large surfaces of dams. This paper presents a long-term InSAR analysis of the Atatürk Dam, Turkey's largest and one of the five biggest dams in Europe using ERS, ENVISAT, and Sentinel-1 satellites images. Since only Sentinel-1 data have acquisitions in ascending and descending orbits, we could estimate surface movements also in the vertical and east-west directions using both lines of sight (LOS) displacements. The results showed that the east-west movement is higher than vertical movement. As a result, we observe a maximum of 10 mm/yr displacement in the LOS direction at the dam's crest for period of 2003 and 2010, decreasing down the slope.

The Segmented Zambezi Sedimentary System from Source to Sink: 1. Sand Petrology and Heavy Minerals

The Zambezi River rises at the center of southern Africa, flows across the low-relief Kalahari Plateau, meets Karoo basalt, plunges into Victoria Falls, follows along Karoo rifts, and pierces through Precambrian basement to eventually deliver its load onto the Mozambican passive margin. Reflecting its polyphase evolution, the river is subdivided into segments with different geological and geomorphological character, a subdivision finally fixed by man’s construction of large reservoirs and faithfully testified by sharp changes in sediment composition. Pure quartzose sand recycled from Kalahari desert dunes in the uppermost tract is next progressively enriched in basaltic rock fragments and clinopyroxene. Sediment load is renewed first downstream of Lake Kariba and next downstream of Lake Cahora Bassa, documenting a stepwise decrease in quartz and durable heavy minerals. Composition becomes quartzo-feldspathic in the lower tract, where most sediment is supplied by high-grade basements rejuvenated by the southward propagation of the East African rift. Feldspar abundance in Lower Zambezi sand has no equivalent among big rivers on Earth and far exceeds that in sediments of the northern delta, shelf, and slope, revealing that provenance signals from the upper reaches have ceased to be transmitted across the routing system after closure of the big dams. This high-resolution petrologic study of Zambezi sand allows us to critically reconsider several dogmas, such as the supposed increase of mineralogical “maturity” during long-distance fluvial transport, and forges a key to unlock the rich information stored in sedimentary archives, with the ultimate goal to accurately reconstruct the evolution of this mighty river flowing across changing African landscapes since the late Mesozoic.

Is it safe to remove a dam at the risk of a sprawl by exotic fish species?

The longitudinal dimension of river connectivity has been significantly disrupted by barriers to compensate for water demand in the long periods of water scarcity in the Iberian Peninsula. The scale of this modification is widespread in the Portuguese part of Douro River network where, side to side with agriculture water demand, there is a constant increase in hydropower production. Thus, native species in Iberian freshwater systems, performing reproductive migrations along the rivers, are strongly affected by the amplification of fragmentation caused by the tremendous density of transversal obstacles in this river basin.We aimed to prioritize dam removal in the Portuguese part of Douro River, mainly considering obsolete barriers (small dams, weirs) based on a spatial multicriteria decision analysis (GIS-MCDA) based on a prioritization procedure. A diversity of parameters were used to prioritize (rank) the dam's suitability for removal, considering the losses of connectivity and fish biodiversity, habitat degradation, negative effects on water quality and ecological conditions, and socio-economic factors. Different weights were assigned to the different attributes in each criterion according to their importance. The analysis also included a significant constraint: the potential spreading of exotic invasive fish species if connection was reestablished through dam removal.This procedure started with the georeferencing of 1201 transversal obstacles that were further characterized for their relative permeability to fish migration. In conclusion the model used allowed to identify 158 priority barriers, as well as the 5 most fragmented tributaries, which means the most impacted by river regulation. In 8 cases the barriers were big dams (> 15 m), whereas in the remaining 150 were weirs. From a final rank of 20 most impacting structures, the MCDA results also identified two cases where potential removal could trigger the additional impact to native fish species related to the sprawl of alien populations.