Rogerio,

Thank you for voicing your criticisms, which I see through the eyes of a social and environmental scientist.

As far as the number of fish species, these estimates are based on more than a dozen surveys in different rivers of the Amazon system and are available online.

I appreciate you informing me about the hydrological differences between Tucurui and Belo Monte. My broad comparison focused on the ecological and socioeconomic impacts of large impoundments in the tropical environment of the Amazon Basin and on evidence that they also occurred at Tucurui.

On the indigenous people issue I am less convinced than you about the country's interest in safeguarding their culture and lives. My visits to the reservations of the Mexacali and Xacrioba Indians in Minas Gerais, discussions with functionarios of FUNAI and mainstream Brazilians, a visit to Manaus and surroundings, and reading of reports on the deteriorating livelihoods of tribes coming into contact with outsiders reveals a situation similar to the occupation of Indian lands and the ruthless subversion of their occupants in the USA.

Clearly, the persistence of largely clean rivers and extensive tropical rain forest of the Amazon Basin are attributable to the fact that the indigenous peoples pursued extensive, rather than intensive, hunting/fishing/gathering/shifting cultivation economies. Today, while the booming population and economy of Brazil require that the country must develop its resources, including hydroelectric power and irrigation agriculture, there is also a need for development agencies to respect the Brazilian constitution, which requires that local people be consulted during the planning and implementation phases of water development projects. This has not happened in practically all projects because indigenous populations oppose them. Instead of seeing the relatively small Indian population as occupying an unjustifiably large part of Brazil, these people should be cherished as the stewards of the land and waters the national economy is increasingly benefiting from.

I gave you an idealized, pre-development scenario of the Amazon forest ecosystem acting as the lungs of the world. The extensive burning of forest for agriculture in recent years has reduced this service and possible made the basin a greater producer than sequester of carbon.

Question: Do you agree that there is need for environmental water/environmental flows to protect biodiversity where dams have been built or to be built?

Answer: I agree; for this reason is important to develop damless machines to extract energy from water flows; as always any time we introduce something artificial into enviroment we create an impact; impact 0 is not possible as it would require no activity at all but we can work to minimize;

Question: If so, how can we achieve a balance between water usages for consumptive purposes (drinking water, industry and irrigated agriculture) and meeting the demand for environmental flows for smooth functioning of river ecosystems and river biodiversity?

Answer: it is a mass balance at all so if we take away from environment we have to give back the same quantity as water and its dissolved compounds, so we have to make a water return in the same conditions in a point not far from those where we collect the water. It is obvious that if we give back less water the water course then thends to dry and if we give more it tends to flood.

In few words: collect water - use for human activities - depuration - add (or remove water to fit the balance) - add (or remove dissolved compounds) to fit the balance

What can be done to mitigate the problem is: to have a series of small check dams right up to its opening to sea,with adequate height,so that the length of each of the stretches in between can be filled up with water,thereby trying to sustain biodiversity.This has been tried to a small extent in a tropical city,but not right up to its end.Here the idea was not to sustain biodiversity,but to have those stretches to remain always filled with water, so as to bring down the air temperature in the vicinity of the city.Another advantage of the system was during monsoon floods,the speed of run off was lessened,thereby not inundating the banks to a great extent,at the same time the system brought up the ground water table.Earlier tapping underground water in the city was banned,now it is allowed.

Dear Luca Patauner

Thank for you inputs and agreeing that environmental water is required for biodiversity protection

Dear Chandravadan Trivedi

Thank you for your inputs and ideas. The other way I feel that perhaps by dividing the total volume of water in a dam/storage into (a) consumptive water (drinking and irrigation and other) and (b) environmental water. Then allocating/ or holding a portion of dam water for the specific purpose of the environment via specific government rules and regulation. The allocated water (reserved water for the environment) can then be released when it is considered to be essential or environmentally beneficial for the biodiversity such as during droughts, low flow seasons

Dear Golam.

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Your question seems disconnected from engineering that is being practiced today. The dams that were built before the 60's and 70 did not take into account problems such as those written in your text. These problems were ignored until the time mentioned in the construction of large dams especially in developed countries.

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Currently the need for an environmental flow (or sanitary flow or minimum flow, ...) is already a consensus, the current discussions are focused on the quantification and qualification in countries that still have water potential being used. It is because Europe and the USA is not intense discussion (simply because no more dams to be built!) that the issue is not discussed. If you look on the internet with the local languages of these countries still have ability to build dams for multiple purposes, you will see that the discussion is intense on quantification and how to obtain this flow (to the right name for your appointment is purpose of discussion).

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The period to dispute the validity of whether there is a flow that satisfies the environmental parameters has already passed, which is now discusses how to maximize the usages and minimize damages.

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I'm surprised with this type of question because it seems that any scientific discussion must necessarily pass by developed countries, simply ignoring the efforts being made in developing countries to preserve biodiversity.

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The concern of environmental damage is present even in the current legislation in several developing countries, ie, is no longer an academic issue, is a real problem.

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Thank you Rogerio for your inputs and agreeing that 'this is a real problem'

By now it's clear that (especially large) dams can have many adverse effects on biodiversity and ecosystem functioning, many of which you already mention. So yes, the problem is real, and yes, actions should be taken to avoid these negative affects.

However before considering environmental flows I'd like to state that often the dam itself should be reconsidered, since many other more sustainable ways exist to produce energy (e.g. floating turbines, wind-energy, energy from biomass, etc.) or to improve availability of water for irrigation and consumption (or reduce the water needed). Several options should be evaluated regarding the local conditions and needs.

If the dam is really the best option (mostly it isn't) serious actions should be taken to reduce the negative environmental impacts. Environmental flows can be a way to do so, but again, whether this would be the best option depends on the local conditions and needs. Therefor most countries have rather strict regulatory frameworks that require serious analysis of the potential environmental impacts and demand technically viable solutions (especially for large dams). This implies two things: 1) the technical question is turned into a legal one, often distracting the discussion from the underlying technical/scientific questions, 2) research is needed to fundament the solutions offered... and often legal requirements exceed technical/scientific possibilities, as in the case of the lack of scientific proof that passages for fish really facilitate the migration of the fish species thy were intended for.

Hi Vincent,

Many thanks for your good inputs and agreeing that actions should be taken to avoid these negative effects. I do agree that we need to evaluate some other means of producing energy since some reports highlight that dams are also a source of greenhouse gases such as methane. Further, perhaps for old dams allocating water for environmental flows may still be an option.

A major case should be made regarding the Hoover Dam and it´s negative long-term effects upon the Mar de Cortes or Gulf of California, given that the reduced inflow has gradually increased salinity in the northern basin, endangering a unique ecosystem and endemic species, particularly the vaquita marina porpoise.

Dear Franciso,

Many thanks. Hoover Dam (the largest reservoir in the United States by volume) stopped natural flooding affecting many species adapted to the flooding, including both plants and animal and native fish. Four native fish of Colorado River, the Bonytail chub, Colorado pikeminnow, Humpback chub, and Razorback sucker, are currently listed as endangered.

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Dear friends.

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Hoover Dam was a work built between 1931 and 1936 (design 1922), where environmental care did not exist in any large or small works, but the Bureau of Reclamation who administered the construction of the dam, was one of the first state agencies to begin studying environmental damage exploitations hydropower.

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It's easy to say that something built 90 years ago and due to a process of filling the reservoir that nowadays does not run over caused serious environmental damage, but this is a thing of the past.

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If we should not build something that does not happen we dream, we should be in the Neolithic.

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Dear Friends:

We are not speaking of the dams themselves but about actions to diminish their negative effects on ecosystems. Hoover dam was an engineering prowess, and in many aspects still can be seen, as a historical engineering landmark. Yet, environmentally it has gradually had significant effects not only upon the Colorado River and its wildlife, but also upon one of the world´s unique ecosystems, i.e., the Mar de Cortes or Gulf of California, where it has generated an imbalance in local sea water that used to be and is no longer mixed with fresh water.

If pointing to this and the desirability of restoring environmental flows is Neolithic and saying that this is a case being a 90 year old process is correct then why worry about, say, climate change or polluted land, as the first will take place, if it does, in 80 to 90 years, and the later may be due to actions generated in the 19th century.

Only recently have the environmental effects upon the sea of Cortes, located in Mexico, begun to be considered, and they have proven to be significant, despite the proportionately small volumes of water involved. The case pointed to is not the dam itself, but the need for environmental restoration of what still is a unique ecosystem worldwide.

Dear Francisco,

Many thanks for your insights. What you said I do agree with you as in case of Australia there are a number of very old dams but actions are being taken to diminish the environmental impacts via allocating environmental flows or buying water from irrigators to restore the environment flows. The need for such actions have been realised in recent time and accepted. Goods and services provided by the ecosystems are invaluable and we cannot ignore it!

@Francisco

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In no time I said the construction of Hoover Dam was something perfectly calculated in accordance with good engineering of the late twentieth century or early twenty-first century, only said a dam designed in 1922 could not have design parameters that were only established from the 60s!

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To give an example, the name and definition of Environmental Flow appears only in the technical literature around 1990, before there was the concept of minimum flow (only after 60s), ie, it is kind of hard in 1922 to adopt a criterion based on scaling a technical support 1990!

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This all does not imply that it is not necessary to adopt the same works or operations of dams to mitigate the damage of the past made more due to unawareness than by design error.

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It is interesting that the current review of dams, such as Hoover Dam, are only marked the evils of the same, as the extinction of certain species of fish, leaving aside the benefits accrue in terms of social and industrial progress. If there were abundant energy in California probably would not have Silicon Valley!

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@Rogerio

Excuse me for my persistence. I am not arguing about Hoover Dam itself. I am arguing about its environmental effect across borders, and the need for action to at least partially recover the delta of the Colorado River in Mexican territory, not for Mexicans but for the sake of restoring a part of the Gulf of California as it is of significant environmental value not only for Mexico but for migratory species.

Whereas previously this had not been properly addressed I believe that it is worth pointing to now that we are aware of the effects it has had, regardless of when it was built!

Dear Francisco,

Thank you. Perhaps more awareness and education would be needed about ecosystems sustainability for the present as well for our future generations. We always learn from earlier mistakes, it does not mean we should not do anything and remain silent and blame others. We have to work together with all professions such as engineers, environmental scientists, and social scientists to tackle the problems (a holistic approach). In Australia, both engineers and environmental professions work very closely so that impacts from earlier projects or new projects on ecosystems can be minimized. As you cited climate change has recently been identified as a major environmental problem affecting all the sectors (water, agriculture, fisheries, biodiversity, ecosystems, human health, assets and infrastructure, livelihoods) but countries and their government departments and international organizations are now trying to reduce climate change impacts (for the current and future generations) via climate change adaptation and mitigation measures. One of the measures suggested is the ecosystems based adaptation (integrating land-water-biodiversity) since the healthier the ecosystems the more resilience it is to climate change and a healthy biodiverse ecosystems is capable of resisting shocks and stress. Furthermore, we have to remember that worlds most poor are dependent on ecosystems for food, water and their livelihoods but they are most vulnerable to climate change!

Dear all

It may be helpful to remember that most use of water from impoundments is ultimately non-consumptive, the water returning (often in an altered or polluted state) to the catchment, or nearby. The main consumptive use is for irrigation, powering transpiration by crops and plantations. Also, no reservoir is truly multi-purpose, even the new ones; they are constructed for one or a few prime reasons, and other uses are subsidiary. As a reservoir ages and infills, these uses may change.

Regards, Julian

Dear Julian, Thank you for your inputs. I do agree that no reservoir is truly multipurpose

Dear all, I agree that most man-made lakes serve single or dual purposes but that One of my greatest concerns is the impending construction of more than 50 large dams by Brazil and neighboring countries in the Amazon Basin over the next three decades. Not only will reduced flooding destroy the habitats of many of the estimated 2000-5000 species of fish in the Amazon Basin, damage the ecology of the tropical rain forest-often referred to as "the lungs of the world"- but also threaten the livelihoods and survival of many Indian tribes depending on fishing. Now would be the time for environmental impact studies by governments constructing or planning to construct dams in the Basin to begin to model post-dam river flow regimes and the need for environmental flows on a regional basis, which need to be considered in the planning process but are all too often neglected. The currently rising Belo Monte Dam in Brazil promises to result in similar hydrological changes and biotic and disease ecological upsets as the existing Tucurui Dam, and the risk of schistosomiasis, traditionally non-existent or absent or negligible in the Amazon river system, is being reported from increasing numbers of impoundments.

Dear Helmut, Many thanks for your inputs highlighting the facts and figures of the future dams (to be built in Brazil and neighbouring countries), which will threaten the habitat of 2000-5000 fish species as well as livelihoods of Indian tribes. The increasing risk of Schistosomiasis (bilharzia) disease (that may infect urinary tract or intestines) is of much concern

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@Helmut

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Dear Sir, wish you quoting me the source from where this number came out 2000-5000 endangered species of fish, after all we are writing in RechearchGate and not in any Blog Internet. I think you are extremely misinformed, for example, the Belo Monte reservoir is a reservoir-river, the capacity of the reservoir was decreased much, just to generate an instream flow. To give a concrete fact the detention time of the Belo Monte reservoir is LESS THAN 20 DAYS.

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Making an equivalence between hydroelectric Tucuruí and Belo Monte, is an absurd mistake. I note that in addition to the characteristics of the facilities are completely different (depth, detention time, operating system and other) building Tucuruí (1974-1985) was conducted during the military governments that no democratic participation was allowed, since Belo Monte (2011-2016) the participation and discussion were taken both nationally and internationally.

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As for the livelihoods of indigenous tribes learn that 428 indigenous lands already regularized comprise an area of 104 616 529 ha (2013 data) comprise 12.2% of the national territory. On the other hand the indigenous population in Brazil is 817,963 (2010 census), ie 0.47% of the population. I note that there are further 196 indigenous areas (115 in study, 30 defined, 51 declared and approved 12) covering an area of more than 5.2 million hectares.

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In short, say a country that reserves 12.2% of its territory to 0.47% of its population shows the country's interest in safeguarding the culture of these people and life.

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PS.

As the reference of the Amazon be "the lungs of the world", something that would make me extremely happy if it were true, remember that in recent research this concept has been abandoned, because it found that the balance of atmospheric exchanges in the Amazon is almost a closed system.

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Rogerio,

Thank you for voicing your criticisms, which I see through the eyes of a social and environmental scientist.

As far as the number of fish species, these estimates are based on more than a dozen surveys in different rivers of the Amazon system and are available online.

I appreciate you informing me about the hydrological differences between Tucurui and Belo Monte. My broad comparison focused on the ecological and socioeconomic impacts of large impoundments in the tropical environment of the Amazon Basin and on evidence that they also occurred at Tucurui.

On the indigenous people issue I am less convinced than you about the country's interest in safeguarding their culture and lives. My visits to the reservations of the Mexacali and Xacrioba Indians in Minas Gerais, discussions with functionarios of FUNAI and mainstream Brazilians, a visit to Manaus and surroundings, and reading of reports on the deteriorating livelihoods of tribes coming into contact with outsiders reveals a situation similar to the occupation of Indian lands and the ruthless subversion of their occupants in the USA.

Clearly, the persistence of largely clean rivers and extensive tropical rain forest of the Amazon Basin are attributable to the fact that the indigenous peoples pursued extensive, rather than intensive, hunting/fishing/gathering/shifting cultivation economies. Today, while the booming population and economy of Brazil require that the country must develop its resources, including hydroelectric power and irrigation agriculture, there is also a need for development agencies to respect the Brazilian constitution, which requires that local people be consulted during the planning and implementation phases of water development projects. This has not happened in practically all projects because indigenous populations oppose them. Instead of seeing the relatively small Indian population as occupying an unjustifiably large part of Brazil, these people should be cherished as the stewards of the land and waters the national economy is increasingly benefiting from.

I gave you an idealized, pre-development scenario of the Amazon forest ecosystem acting as the lungs of the world. The extensive burning of forest for agriculture in recent years has reduced this service and possible made the basin a greater producer than sequester of carbon.

See a report entitled: Projects in Amazonia-A geopolitical and socio-environmental primer (published in April 2014)

www.dar.org.pe/archivos/.../145_megaproyectos_ingles_final.pdf

The report identified the following socio-environmental impacts from new mega-development projects in the Amazon Basin:

• Amazonian indigenous peoples and local Amazonian communities will bear the greatest negative impact of these projects, even though they have little say

• The blockage of long-distance fish migrations and the destruction of spawning habitats by dams could produce major biodiversity loss, as well as harm riverine fishing communities that depend upon the river for their sustenance.

• The hydroelectric dams in the headwaters region of the Amazon basin would disrupt of flooding cycles and sediment deposits and could cause the drying up, either temporarily or permanently, large areas of flooded forests. This could cause the death of the forest, not through deforestation, but rather through dehydration.

• The most directly impacted communities are those forcibly relocated to other lands due to the flooding of their homes and fertile floodplains by reservoirs.

Summary of impacts: The hydroelectric dams can cause downriver impacts, such as drying out of portions of the river, reduction in fisheries and interruption of seasonal floods which fertilize the floodplain; upriver impacts, such as flooding, disruption of fish migrations and sediment flows; and reservoir impacts, such as changes to water quality, and an increase in the release of climate-damaging methane gases

Dear Golam.

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For those who know geography is easy to identify the manipulation that is being made in this report, there is much talk of the Amazon, but when you show where the "Mega-works" are in the Amazon basin there is a complete disconnect between the presented facts and reality .Table 1

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(http://www.dar.org.pe/archivos/publicacion/145_megaproyectos_ingles_final.pdf)

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lists the planned investments of UNASUR, this framework does not call the attention of all 31 investment provided only 3 of them are in the Amazon. For more unsuspecting reader is not clear for example that border Brazil Uruguay is about 3000 km away from Amazon, but the author did not care to write a bridge between Brazil and Uruguay in the city of Jaguarão has nothing to do with Amazon. For anyone who is European give an example, if a bridge is built on the border of Italy with France I think not cause ecological damage in the Siberian Tundra!

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Also the author does not state that the roads forth in the Brazilian Amazon are existing roads, or will simply be paved and improved.

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Another manipulation of the article lies in hydropower as repercussions in the international press

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(http://www.theguardian.com/environment/andes-to-the-amazon/2014/may/06/more-400-dams-amazon-headwaters )

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according to the cited work (Mega-Development Projects in Amazonia:. socioenvironmental The geopolitical and primer), will be made 412 hydropower plants in the Amazon. New in the cited work are presented with more than 17 hydroelectric 1500MW, and of these 17 are not usually notice that 10 of these are plants that are in operation for over 36 years (the Guri Dam in Venezuela). Geography is not too the fort, as this is a hydroelectric river that empties into the Caribbean Sea (near Trinidad Tobago), soon does not belong to the Amazon Basin!

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In summary, if you install a media manipulation with vested objectives releasing data that ordinary people will not check.

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Now has a personal interpretation of such manipulation on my part.

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South America is the only place in the world where states are at peace with each other, and differently than it did the last 500 years is seeking to link the countries of this continent by promoting exchanges between countries and nations and not getting involved in aggressions against other countries. This change in direction, leaving only communicate via seaports with industrialized first world countries and integrating the South American countries must be annoying to many people, and how they can not sow war and hate among the countries use the Amazon as a pretext for intervention.

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@ Helmut.

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I'm surprised when you do not consider as relevant reserve 12.2% of the surface of a country (104,616,529 ha) to 0.47% of its population, and this value with the new demarcations should reach over 13%, around 1,200,000 km ² (areas of France, Spain and the UK added) to 817 963 people (approximately the population of Cyprus).

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Thank you Golam for summarizing the major upstream and downstream impacts of dams. I wish that my currently tight schedule would allow me to spend more time to discuss with all of you in greater depth the important issue of supplemental flow needs and practices in dam environments. Here I like to direct attention to semi-arid and arid environments, where inadequate and poorly timed supplemental flow or dam releases can cause problems in addition to those you summarized for the Amazon Basin. They include destruction of downstream flood plain crop production and animal husbandry and reduction of the size and biodiversity of downstream lakes to the point where they can no longer support viable fisheries, as seen in the case of Lake Chad, the Ural Sea and now predicted for Lake Turkana in Kenya. We described flood plain effects of reduced river flow in the Awash and lower Omo valleys of Ethiopia in our book Water Resources Management in Ethiopia: Implications for the Nile Basin (H. Kloos and Worku Legesse eds, 2010, and Sean Avery carried out an environmental and hydrological study of the impending ecological impacts of the construction of the 240 meter tall Gibe III Dam and reduced river discharge on the lower Omo Valley and Lake Turkana.

First Dear Golam,

I forgot to write out the reference to Sean Avery's monograph. It is Sean Avery, What Future for Lake Turkana? African Sudies Centre, Oxford, 2013.

Second Dear Rogerio,

I have been worried for some time that the boundaries of many of the Indian reservations in this huge area have not been clearly demarcated as Indian land and where they have been deliniated, the government has been unable to protect the Indians from loggers, gold miners, and farmers illegally invading and settling on their land. One exception was the recent removal of intruding settlers from the forests of the shrinking Awa Tribe by the Brazilian armed forces, but only after after world-wide outrage over the killing of numerous Awa by these outsiders. If you are interested in following the fate of various Indian Tribes I would recommend Survival International.com as a reliable site.

Thank you Helmut for sharing your life experience with all of us!

Benefits of environmental water

In Australia, there is a sustainable diversion limits (SDL) of water use/water offtake from reservoirs/dams/regulated rivers aims to maintain a balance between the water needs of communities, industries and the environment. The SDL reflect an environmentally sustainable level of water (ESLT) use. ESLT is the amount of water that can be taken for town water supplies, industry, agriculture and other human or 'consumptive' uses, while ensuring that there is enough water to achieve/improve/maintain the health of rivers, lakes, major wetlands and floodplains and habitats for animals and plants that rely on the river or water.

The life cycles of many aquatic plants, riparian forests and woodlands, aquatic animals (invertebrates, waterbirds, amphibians, reptiles and fish) are dependent on various flow regimes, therefore acquiring of water (environmental water) with the goals/objectives to increase water flows in rivers and wetland would be essential to protect and/or restore the environmental assets.

The environmental water/environmental flows will help aquatic ecosystems and water dependent biodiversity in many ways: (a) maintaining and improving wetlands, creeks, riparian habitat; (b) supporting habitat for water birds, native fish and native frogs; (c) making connectivity between rivers and billabongs/anabranch, wetlands, river channel etc to maintain populations; (d) supporting ecosystems functions such as dispersal of biota, and transfer of nutrients and energy; (e) protecting and/or restoring environmental assets in RAMSAR listed wetlands; (f) improving water quality (flush out of salt from rivers, reducing problem of dissolved oxygen or algal blooms); (g) providing an additional river flows for localised refuge habitat for fish and aquatic biota during adverse water quality events such as black water or low dissolved oxygen.

Thanks Golam for summarizing the SDL provision in Australia, a much needed measure in environmental justice that needs to be applied not only in many developing countries but also in the North, including in drought-plagued California, where different interest groups are far from reaching an equitable and sustainable solution to rapidly decreasing groundwater and surface water resources. Unfortunately I will have to exit this interesting discussion at this point and 'change hats' to prepare for my trip to Ethiopia to undertake a survey of medicinal plants by market vendors (a follow-up of a survey I carried out 41 years ago) and to evaluate two doctoral dissertations, on malaria distribution and traffic accidents. I hope that I can join your group again in a future discussion.

Dear Helmut,

many thanks, will update as new information are available!

Summary of some pros and cons of dams based on International Rivers News (Tuesday, May 27, 2014)

Pros

Generate 16% of the world's electricity (about 80% of the water stored in dams are used for hydropower), dams facilitate food production via irrigation, supplies water, protect against flood, helps navigation and tourism etc.

Cons

Block/prevent fish migration, causes depletion of oxygen in rivers, interfere with the biological triggers/cue of fish; the freshwater population has declined by 37% between 1970-2008 (due to dam building and other factors); rotting of organic matter causes to emits methane; dams displaced 80 million people, negatively impacted about 500 million people living downstream

See more: http://www.internationalrivers.org/resources/8326

Dear Helmut,

An article is available in RG as follows:

Worlds Rivers in Crisis: Water Quality and Water Dependent Biodiversity at Risk

https://www.researchgate.net/publication/263852254_Worlds_Rivers_in_Crisis_Water_Quality_and_Water_Dependent_Biodiversity_at_Risk?ev=prf_pub

Hope you are having a good time in Africa

Technical Report World Rivers in Crisis: Water Quality and Water Dependent Bi...

Hello

 I think the environmental water is not enough because the dams interrupt lifecycle for several species. An example of that is in Paramillo National Park in Colombia, where the "bocachico" fishes (Prochilodus sp) had cut their migration in the Sinú River, and their natural population has disapeared above the Urrá dam located near the limit of the Park

I know about the work of Cordoba University Professor Victor Atencio, who has a publication in ResearchGate (but I don't ask him for it):" Impactos de la Hidroeléctrica Urrá en los peces migratorios del río Sinú"... ask him in the link.

Article Impactos de la Hidroeléctrica Urrá en los peces migratorios ...

Hi Rebeca,

Yes, some species requires frequent flooding and environmental water may not be sufficient. For example, many other prochilodontids, P. magdalenae has high fecundity and spawns all eggs at once in the open waters of the main river channel. Larvae drift passively towards flooded areas where they feed and remain until maturation. Their life cycle is reliant on the hydrological patterns of the Magdalena River basin, where the fish migrate to the main river in twice-yearly hydrological periods. In the first one when water levels begin to decrease (December-February), spawning migration to the upstream starts and fishes remain there during the dry season. Spawning begins with the onset of the first high-water period (March-June). The second one takes place when water levels start to decrease (July-September) and a second spawning migration occurs.

Berdugo, Gilberto Orozco ; Narváez Barandica, Juan C. 2014. Genetic diversity and population structure of bocachico Prochilodus magdalenae (Pisces, Prochilodontidae) in the Magdalena River basin and its tributaries, Colombia. Genetics and molecular biology. Vol.37(1), pp.37-45

http://dx.doi.org.ezproxy.lib.rmit.edu.au/10.1590/S1415-47572014000100008 

Hi

Article An Update on the Global Stressors and Constraints Affecting ...

This is a very important question and a serious problem has been posed. Till recently the concept of environmental flow was not considered in the water management field. However now a days the concept of environmental flow has gained importance. Even while assessing the water potential and water utilization in a given river basin, the amount of water required for maintaining the environmental flow in the downstream portion and to maintain the ecological balance is calculated and accounted. Now a days the water release from reservoirs do consider the amount of water required to maintain the environmental flow.

This type of debate is often reduced to highlighting the needs of a few species (particularly commercially important and/or sport fish species) where these have been overtly disturbed by dam construction. This is because a reductionist approach of this nature is easier for civil engineers and hydrologists to model and 'engineer' mitigation measures (e.g. the building block approach). We need to talk less about particular species (except as examples) and more about impacts on the riverine (and floodplain) ecosystem, which affect whole species assemblages at large scales. The need for the protection of the natural flow regime in all its variability is far more evident from this holistic perspective. Many attempts at defining environmental flows are deeply flawed because of a lack of holistic ecosystem perspective, but at the same time the measures needed to truly protect ecosystem integrity run up against huge socio-political barriers associated with the critical need for water, particularly in rapidly developing countries. We need a frank debate about what river ecosystems really need to safeguard them, and an open discussion about the extent to which that can realistically be delivered under any particular circumstance. Environmental flows are critical to this debate, generically and locally, but the manner of evaluating and defining environmental flows needs to be right. Greater ecological and biodiversity compromises are needed in some circumstances compared to others. You might be interested in some UK papers relating to this subject:

Technical Report An Evidence Base for Setting Flow Targets to Protect River Habitat

Article The role of the UK conservation agencies in protecting river flows

Article Developing a coherent narrative for conserving freshwater an...