A drought, baptized as “unrepeatable” by the media, is unearthing the corpses. Unrepeatable is the adjective most used by newspapers and TV, in the sense that a human being experiences it only once in a lifetime. But this is not the main concern of the people, because what troubles her is the drying up of the great reservoir that feeds the lives of millions of people. And the disaster occurs on an extraordinarily vast spatial scale, affecting an immense, populous, rich region. The water level is so low that the bodies of the women emerge murder victims of decades ago, once hidden deep inside. Never been this low in the past 85 years, when the river was barred by the dam (see Figure 1).
One of the victims, wounded by a firearm, had been locked in a barrel, perhaps thinking that there, at the bottom of the lake, she would remain invisible forever. The murderer, perhaps, had not read the novel by Raymond Chandler or the murder took place before Raymond published it. If the lake continues to shrink, will soon reach the so-called “dead level”, a water level so low that it will no longer allow gravity discharge. The dead volume could only be exploited with pumping: goodbye to hydroelectric production and goodbye to the downstream reuse of turbinated, irrigation and even civil water. While three quarters of the lake’s regulated waters are indispensable for agriculture, their drinking use is still critical. It is not a European scenario, much less an Italian one.
The basin in crisis is Lake Meadthe largest man-made reservoir in the United States. It is created by the Hoover Dam, which blocks the Colorado River in Black Canyon, Arizona. It was inaugurated on September 30, 1935 by President Roosevelt. This great work, perhaps the most concrete myth of the New Deal, was designed and built in less than five years to cope with the Great Depression, providing low-cost electricity to American industry. Without Colorado’s water, regulated by a dense dam system, the region would be extremely arid. Large cities such as Las Vegas (Nevada) and Phoenix and Tucson (Arizona) could not have developed without the regulation of the waters of the great river. During my first trip to California, in the early 70s of the last century, I realized how, in those parts, drinking water is a limited resource; sometimes in open war with irrigation and industrial demand. And I remember that everywhere one ran into heartfelt appeals to save. The Colorado crisis will strike there too. The Colorado Aqueduct feeds the huge Los Angeles metropolitan area.
And the canal All-American it transports the irrigation waters indispensable to the Imperial valley, also in southern California, from the Atlantic to the Pacific basin: a desert area converted into a very productive agricultural region. If some areas of Los Angeles already suffer from water rationing, at a level of 35 percent, even the richest and most populous state in America could suffer, and a great deal. California is already suffering from a severe and prolonged, recurring drought; and the current situation could bring the 2012 drought closer, which some scholars of the time decreed the worst in the last thousand years. On the water frontthe world is not looking forward to the summer of 2022. The current situation is very critical in much of the globe, as shown by satellite monitoring that allows the mosaic of the Spei index, coarse but significant, since it combines the precipitation data with those of evapotranspiration (see Figure 2).
Droughts are exceptional events, but not really “truly exceptional” as the newspapers like to repeat and you hear dribbling on talk shows. And the fact that we can use the verb “repeat” speaks volumes. The Standardized Precipitation-Evapotranspiration Index, precisely Spei, helps to compare the severity of drought over time and space, with the crucial advantage – compared to other drought indices – of easily identifying and multiscaling the different types of drought and their impact in the context of global warming. . If evaluated over a long time horizon, for example four years, the updated SPEI shows the worrying depth of the crisis that many areas of the planet are experiencing (see Figure 3).
Do we need to remember the biblical lesson, Genesis 41? In 1977, the year of the worst European drought of the 20th century, anyone who had discussed a thesis on flood risk, like your blogger, was forced to publish the first scientific works on the statistical forecast of droughts and lean, as well as on optimal management criteria. of water rationing, on the dynamics between prices and consumption and on the levels of endurance of users. Strengthened by the experience of the heavy Genoese rationing of 1977, I know that mathematical models are not enough to dictate the solutions, although he studied them then with the enthusiasm of a novice. He serves politics. In 1977, choosing between citizens, steel and ships at anchor was not easy, but it was done with courage, combining scientific reasoning with social reasoning, not always quantifiable. In the upcoming summer, if the water emergency also affects Italy, will the technical table be enough?
It is our original and prodigious invention, consolidated in the new millennium: the now traditional table where the national and local administrators sit alongside the regime experts, with their ears set on the contribution of diviners, unscientific pseudo-popularizers, television presenters. In 2007 it was enough, as the table acted as a real sorcerer of the rain, which miraculously fell in abundance In the same day of the first meeting around the beautiful table.