The rivers, the threatened arteries of Gea

In 1895, a French traveler found in a courtyard of the Palermo museum two stone stelae with hieroglyphic inscriptions that no one had paid much attention to. Over the years it was discovered that they were part of the ancient system for measuring the fluctuations of the Nile levels described by Pliny the Elder in his Naturalis Historia (79 AD). For this reason they are considered one of the greatest archaeological finds of ancient Egypt.

The stelae were carved during the 5th Dynasty, in the 25th century BC, to record the ebb and flow of the Nile, with data dating back to 1st Dynasty times (3100 BC). The Nilometers they allowed the pharaohs to improve the yield of crops and, with it, the collection of tributes. Those on Roda Island in Cairo were used between 861 and 1887, illustrating the close relationship between hydraulic systems and great kingdoms and empires.

Around 7,000-6,000 BC, the sedentary peoples of ancient Mesopotamia began to build irrigation canals along the Tigris and Euphrates, the cradle of Sumerian culture. This civilization was the first to record, through its cuneiform writing, its political affairs, literature, philosophy, laws, agriculture, medicine, and family life.

rivers of power

The growth of the global population, which went from 6.7 billion to 7.7 billion between 2008 and 2020, will make large rivers and their tributaries even more important. By 2050, 70% of the population will be urban, up from 55% today, a growth rate equivalent to adding three Shanghais a year for 30 years.

To feed nearly 10 billion people, food production will have to double under adverse conditions. According to the UN biodiversity agency, 75% of crops depend on pollination processes that are currently in danger due to the intensive use of pesticides by agribusiness.

Water is the only scarce resource for which there is no substitute and also the least internationally regulated despite the fact that, among many other conflicting cases, Israel, Jordan, Palestine, Syria and Lebanon share the Jordan, today almost a stream when it reaches the sea Dead.

«According to the demographic projections of the UN between now and 2035, megacities will double to fifty from 28 in 2015»

In 1950, China annexed Tibet, giving it control of the headwaters of rivers that flow to India, Bangladesh, Myanmar, Laos, Cambodia, Thailand, and Vietnam. In rivers of power (2020) Laurence Smith points out that 63% of the global population lives an average of 20 kilometers from a large river. 84% of cities with between one million and 10 million inhabitants –which will be 759 in 2035– are on the banks of rivers.

The large coastal cities –where 20% of the population lives– are actually riverside cities of large deltas. Among the megacities –with more than 10 million inhabitants– they are 93%. According to UN demographic projections by 2035, megacities will double to fifty from 28 in 2015. New Delhi will be the largest, followed by Shanghai, Tokyo, Dhaka and Cairo. New York will be the thirteenth.

Open veins (and arteries)

Threats from population growth, pollution, and climate change loom over the veins and arteries of the planetary circulatory system. Using images captured by satellites from NASA, the European Copernicus program and the University of North Carolina, it has been discovered that rivers and lakes cover 773,000 square kilometers, 44% more than previous estimates. But they only make up 0.58% of the non-glacial land surface.

Some 4 billion people experience acute water scarcity for at least one month of the year. Some 900 million live in China and 1 billion in India. Chennai in India, Sao Paulo in Brazil and Cape Town in South Africa have suffered persistent power cuts in recent years due to drought and overconsumption.

The UN predicts that the global demand for drinking water will double between now and 2050, an increase of six trillion cubic meters per year. Agricultural crops currently cover some 5 billion hectares, twice the size of North America. If the agricultural frontier continues to advance at this rate, by 2050 an area similar to that of one and a half India will have been deforested.

To feed so many people will require an additional 7.4 trillion calories a year. And many will want them to be animal protein. Livestock –bovine, bovine…– consume more water and pasture per calorie than any agricultural crop. In Brazil, producing beef is 100 times more land-intensive than soybeans, which, on the other hand, are almost always used as fodder. Livestock represents 80% of the agricultural land although it only produces 20% of its calories. Under these conditions, if the Global South wants to eat the average American’s three hamburgers a week, the Amazon rainforest will not survive for long.

kill zones

Another problem is chemical. Due to the use of nitrogenous fertilizers and pesticides, which almost always end up in rivers and then in the sea, there are more and more marine areas with low oxygen levels, the feared hypoxia (less than two milligrams of oxygen per liter) that extinguishes almost all Lifestyle.

“Death zones” began to appear in the 1960s and 1970s. The more than 400 that exist today cover about 245,000 square kilometers. The largest are around the Mississippi Delta, where nitrate concentrations are eight times higher than in the pre-industrial era. Others are in the Elbe estuary and the Bay of Kiel in Germany, the Loire and Seine estuaries in France, the Thames in the United Kingdom, and the Yangtze in China.

In November, the low level of the Mississippi, the main waterway of the United States, prevented almost 3,000 boats with a load equivalent to that of 210,000 trucks from sailing. Through its channels and those of its tributaries, 17,000 million dollars of grain, meat and agricultural products are transported each year. In Germany, this summer droughts made long stretches of the Rhine unnavigable, along which 80% of the country’s shipped cargo is transported.

ancient wisdom

The solutions are as diverse as the threats. In June, the US Congress passed a wildlife conservation law that will direct $1.3 billion to protected areas. The 574 indigenous peoples of the country, who already manage natural reserves that cover 40.5 million hectares, will receive an important part of these funds. Since 2000, the 7.2 million-hectare Navajo Nation reserve has multiplied some endangered species – trout, beavers, badgers… – preserving springs, streams and other sources of water.

«Pre-Columbian irrigation techniques can cost up to 100 times less per cubic foot of water than conventional dams»

In Peru, Andean populations are recovering pre-Hispanic stone channels (amunas in Quechua) to harness rainwater and replenish underground aquifers with help from brewing companies and European development aid agencies and Imperial College London.

Pre-Columbian irrigation techniques can cost up to 100 times less per cubic foot of water than conventional dams. Lima, which has a water deficit of 100 cubic feet of water per second, is after Cairo and Karachi the third largest city built on a desert, in its case on a foothill of the Atacama. 98% of the rains occur to the east of the Andean mountain range. The problem is that two thirds of the 33 million Peruvians live on the arid coast.

cutting edge technologies

Other solutions are technological. In the coming years and decades, the largest river transfers in history will take place, among other things due to the gradual collapse of the Himalayan glaciers, which is already reducing the flows of the Indus, the Ganges, the Brahmaputra and the Yangtze between 5% and 20%.

Transfers from the humid south to the arid north of China are already well advanced. The State Council approved the final plan in 2002 with a budget of 77,000 million dollars to interconnect the Yangtze, Huai, Hai and Yellow River basins and transfer 45,000 million cubic meters (mmc) of water per year. The largest transfers in California move 14,000 mmc. The first stage was completed in 2013. The 1,300-kilometre canal between the Han River and Beijing, which now carries 70% of the Chinese capital’s water supply.

The African Transaqua plan, which will require an investment of 50,000 million dollars, plans to transfer water from the Congo basin to the Chari, which flows into Lake Chad, almost 2,500 kilometers to the north, through a 1,500-kilometre canal that it will carry 50,000 million cubic meters of water per year to irrigate 70,000 square kilometers in Cameroon, Chad, Niger and Nigeria. In the last half century, Lake Chad has lost 90% of its surface, from 22,000 square kilometers to less than a thousand.

Both projects pale, however, next to Indian megaprojects that will reconfigure the river systems of the Hindustani peninsula to bring water from the northeast, which receives 50 times more rainfall than the rest of India, to the arid parts of the country. The investments of the National River Linking Project will exceed 168,000 million dollars to build 15,000 kilometers of canals and tunnels that will transfer 174,000 million cubic meters of water per year. This will mean a 30% increase in cultivated areas in the country.

eyes in the sky

Another promising field is hydraulic micromills that can be retrofitted to existing or obsolete dams to generate clean electricity. Rivers recover their old channels and natural characteristics very quickly once they are freed from barriers and artificial obstacles. Following the demolition of dams and levees on the Elwha River in Oregon, in Washington State, salmon recolonized its former waterways in a short time.

Other solutions will come from outer space. On December 16, NASA, France’s CNES, Canada’s CSA and Britain’s UKSA launched the SWOT (water surface and ocean topography) satellite, which will use laser technology to make three-dimensional measurements of sea levels. of millions of rivers and lakes. Artificial intelligence programs will analyze the millions of petabytes of images (the entire US Library of Congress contains 0.01 petabytes of data) to detect vital information for its conservation in changes of color or temperature.