Leggi in italiano

Italy is facing the worst drought of the last 70 years. For weeks, the water level of the river Po, the country’s main river system, has been so low in some areas that old shipwrecks are resurfacing. Several regions have declared a state of emergency, and drinking water is being rationed in hundreds of municipalities across northern Italy. The drought is threatening crops in the Po Valley, where around 40% of the country’s food is produced. Nature Italy spoke to Stefano Fenoglio, professor of zoology and hydrobiology at the University of Turin, and founder of Alpstream, a research centre for the study of Alpine rivers.

“We are coming from a particularly dry and warm winter,” Fenoglio says. “Almost 100 days with no precipitation, no snow and no rain, plus we had higher-than-average temperatures”. A temperature of nearly two degrees above average between December and January was an “anomaly” and, to make things worse, the water normally retained in glaciers evaporated, he explains. “The result is that the rivers did not receive any water input and, by the end of February, their state was very similar to that of a river in August”.

Fenoglio says the river regime in Northern Italy is now undergoing a process of ‘mediterranization’ due to higher temperatures. This means increasingly intermittent rivers, where water can disappear from the riverbed for many months at a time.

One consequence is a depletion of the river biodiversity which, in turn, leads to a collapse in functionality. Many organisms do not have the time to adapt and get through the drier periods. “The water heats up, the oxygen diminishes, and it’s a huge environmental stress,” Fenoglio explains.

“The first to disappear are animals with a very long lifecycle. If there is a drought every six months and the water disappears, these animals won’t make it because they need more time to develop in water they don’t have. In their place, many opportunistic organisms spawn and quickly develop a colony. Warmer, slower and less abundant waters also favour species such as filamentous algae and common bacteria usually found in polluted, stagnant or contaminated ponds. These species are no longer able to metabolize organic matter, which moves downstream and creates problems.”

Drought is also leading to an increase in pathogens. “These past few weeks we are finding worrisome concentrations of salmonella, fecal coliform, and a number of other potentially dangerous pathogens,” says Fenoglio. “What’s flowing into our rivers is often what’s coming out of the treatment plants”. He explains that while treatment plants purify wastewater, rivers also help by diluting the water through their flow rate. “If too much water is missing from the rivers, the treatment plants are no longer helped in this process”.

The bridge between Viadana and Boretto, with an almost dry Po river underneath. The Po in Boretto reached a historic low level in June 2022. Credit: Michele Lapini

In order to study how water decline correlates with water quality change, the Alpstream centre, which has its headquarters in the Po valley, has developed a microcosm of artificial rivers that will allow “manipulative experiments”. “We can recreate a river environment and then vary certain characteristics, for example water permanence, velocity, temperature and transparency, and figure out what happens,” Fenoglio explains.

Scientists in Italy have been sounding the alarm on the impact of climate change on river ecosystems for decades, but political action is lacking. “Italy is very exposed to climate change, especially the Alpine region and facing this crisis should be a priority,” says Fenoglio. “Drought is treated like an acute episode, but it’s becoming a chronic one now.

Some of the proposed solutions, such as creating more reservoirs, will only work so far. “It’s not like we can create a series of reservoirs and then continue to use water the way we are using it.” Another proposed solution is to open dams to send water to crops, but this means taking water away from hydroelectric plants, at a time when energy supply is also in crisis.

Fenoglio says Italy should rather adopt long-term water planning. “We can no longer have very demanding crops, inefficient distribution and irrigation systems” he says. “We have to think about a system that uses water more sparingly.”