During the last weeks the rains they came to south-central Chile with great intensity. A trend that comes from the winter of 2023 where, after almost 15 years, we had a year in the blue with respect to rain.
DGA indicates that 9 of the 25 monitored reservoirs register a volume of less than 20%, but there is more snow than in 2023
However, Thinking that the long megadrought has ended is not very realistic. In this article we will review some data regarding precipitation deficits in recent years.
Monitoring the drought
To monitor the meteorological drought multiple parameters can be used on different time scales. One of them is the index SPEI (Standardized Precipitation-Evapotranspiration Indexin English) that accounts for the drought caused by precipitation deficits and temperature increasessince it considers evapotranspiration.
Using results from the Climate and Resilience Center’s drought monitor, SPEI can be monitored at the national level or at the weather station scale. In this case, we will look at the evolution of the drought in Petorca, Valparaiso Region.
Starting with the precipitation deficits over the last year and so far in 2024it can be seen that although in 2023 the precipitation was above normal in a large part of the central zone (look, for example, in the foothills between the Metropolitan region and the Maule), was not the case in the north of the Valparaíso Region and to the north. In 2024 it has been a different story. And although These data do not contain the rainy June that is being experiencedalready show positive anomalies throughout Chile caused mainly by rains during May.
Another important thing is that in both periods the maximum temperature had positive anomalies. This implies more evaporation and, therefore, loss of water availability that will be considered in the SPEI calculation.
If we look at the SPEI at 6 months, we can see that there are negative values indicative of a drought in the central zone, but if we look further south, the SPEI is at normal or even positive values. If you look at the 12-month SPEI, you can see the signal delivered for the year 2023 and the rainy beginning of 2024 in the central and southern areas. In Petorca, on the other hand, the values remain negative.
The worst thing about the megadrought in Chile is that in addition to its impressive territorial extension, affecting practically the entire country, it is its temporal extension; since approximately 2010. For this reason we must look at broader indicators.
As values of The larger the SPEI, the worse the situation is.. In Petorca, for example, with the SPEI-24 a value corresponding to Droughtwith the SPEI-36 a value of Strong droughtwhile with the SPEI-48 a value of Extreme Drought.
What was observed in Petorca can be extrapolated to a good part of the central and southern area of Chile. In the following figure it is possible to see how Drought values range from Strong to Extreme Drought in much of the country..
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With this the idea is to emphasize the importance of continue fighting the drought despite the intense rainfall in recent weeks. In addition, it also highlights the fact that, in the context of a drought as great as the megadrought, episodes of extreme rainfall can occur.
The values presented here will change after June precipitation values are computed, however, will not alter the conclusions obtained in a significant way.
