The image of the San Rafael waterfall is ubiquitous in Ecuador's Amazon region, appearing on everything from tourist brochures to the backs of buses, alongside the Virgin Mary meant to protect drivers.
The waterfall, the country's largest, is in the Sumaco Biosphere Reserve, a lush site protected by the United Nations for its unique flora and fauna, a result of the wet climate that originates from the meeting of the Andean and Amazon regions.
But environmentalists say this natural wonder and its delicate ecosystem will be destroyed by what is set to be the country's largest hydroelectric power plant, which is being built on the river that feeds the San Rafael Falls.
The state-owned company that is managing the Coca Codo Sinclair project says such worries are unfounded.
They say hydrological studies have established the optimal ecological flow needed for the waterfall to keep flowing with the same intensity, and the project is designed to ensure that this flow is met.
Once complete, Coca Codo Sinclair would double Ecuador´s hydroelectric production and some say, make the country energy independent for years to come. Currently, the country´s largest hydro plants, located east of Cuenca in the southern part of the country, provide about 40% of the country´s needs.
Promoters and critics agree that Ecuador needs to renew its energy model, and that hydroelectric power will play an important role; where they disagree is over how sustainable Coca Codo Sinclair will be.
The idea for the project was born in the 1970s, but it was not until President Rafael Correa came to power in 2007 that Coca Codo Sinclair became a priority. The project was stalled for a few years while the government looked for funds to finance its construction. Last June, after long negotiations the government secured a $1.7bn loan from the Export-Import Bank of China.
Chinese contractor Sinohydro officially started operations soon after but, several months on, the construction site seems eerily empty — hardly what one would expect from the government's flagship project. Signs in Chinese and bright lights — which locals say have forced away the area's endemic butterflies — are the main indications of the changes to come.
The dam will be built some 20km (12 miles) upstream of the fall to divert the Coca river, one of the main watercourses in Ecuador's Amazon region. The project is supposed to generate 1,500 MW of electricity using 222 cubic metres (7,840 cu ft) of water per second from the river.
According to Matt Terry, director of the Ecuadorian Rivers Institute, a non-governmental organisation, the hydrological studies are out of date. He believes that the river now typically maintains a flow of only 80-100 cubic metres per second, which means that a project of this size is not sustainable.
"We're very concerned that when they build the project for this very large capacity, they'll take every drop of water in the river and leave this waterfall dry," says Mr Terry. He points to Ecuador's second largest waterfall, Agoyan Falls, further south than San Rafael, which he says has been heavily affected by a similar hydroelectric project.
Moreover, says Mr Terry, Coca Codo could result in long-term debts for the country if the plant is not able to generate enough energy to repay the loan – with its 6.9% interest rate – to China.
During a recent visit, the Coca river appeared rather dry. But experts at Coca Codo Sinclair say that even if the river were drier, the project will leave 22 cubic metres per second of water in the river, which they believe is the minimum necessary to keep the river and the waterfall alive. They say that the plant is expected to work at full capacity only 57% of the time, because the flow of the river can vary.
"It would be criminal to waste diesel (to fuel thermal power plants) when there are some months during which we can use the river to generate energy. Even if we can only operate at full capacity five or six months a year, it's still very important," says Luciano Cepeda, technical manager at Coca Codo Sinclair.
According to the latest available data, Ecuador depends on thermal power plants for 50% of its electricity generation, and only 38% on hydroelectric power. The thermal plants are fuelled by costly imported diesel.
In 2009, a period of drought partially halted electricity production at the country's largest hydroelectric plant in the south of the country. There were rolling blackouts for over two months, with a financial impact for the country that some have put as high as $1bn (£620m).
Eduardo Aguilera, an engineer who worked on the Coca Codo Sinclair project in the past and is now an alternative energy consultant, says hydroelectric power is the lesser of two evils.
But he also believes that large projects such as Coca Codo are not as financially feasible or environmentally sustainable as smaller ones. "This is a government that focuses on giant public works," says Mr Aguilera. "This has an impact on the public."
He says that the government could use the same amount of money to work on small and medium-scale hydroelectric plants.
Mr Aguilera believes these could be complemented by geothermal plants, a sustainable source of energy in a country like Ecuador, which has dozens of active volcanoes. This way, diesel-fuelled plants could be used to cover just peaks in demand, according to Mr Aguilera. "The conclusion is that Ecuador is not using any of the sources of energy that are considered most economically feasible and environmentally friendly," he says.
Officials at Ecuador's Ministry of Electricity and Renewable Energy have been approached several times since January but they have declined to comment on the issues raised by this report.
In 2008, Ecuador became the first country in the world to grant constitutional rights to Pacha Mama, or Mother Nature, and President Correa has declared his strong commitment to the environment.
The government also has a pilot project to keep oil underground to avoid exploiting one of the most biodiverse areas in the world. But critics such as Mr Terry worry that, despite the green rhetoric, the government has not shown enough commitment to preserving the San Rafael waterfall and similar sites.
The plant is expected to be fully functional in 2016, so it will not be for another few years until its full impact, if any, on the Coca River and the San Rafael waterfall can be assessed.
Credit: By Irene Caselli, BBC; photo caption: San Rafael waterfall