Mexican Drought in Historical Context:
A sign of more extreme heat-driven drought to come

16 April 2024

ISciences has been reporting about widespread drought in Mexico since at least June 2022. The chart below shows the fraction of Mexico’s population exposed to long-term (12 month) surface water surpluses and deficits (droughts). It shows major droughts in 2011-2012, 2020-2021, and 2023-present. The current drought has affected more people longer than either of the prior two droughts.

This chart shows the fraction of Mexico’s population exposed to long-term surface water surpluses and deficits (droughts). Deficits and surpluses are stated in terms of return period – a measure that characterizes the rarity of an event. For example, a return period of 10 years indicates an event that would occur, on average, once every ten years. Higher return periods indicate more extreme and, therefore, more disruptive anomalies. Return period is computed by comparison to location-specific distributions of data from 1981 through 2020. Anomaly levels correspond to return periods: abnormal=3-5 years, moderate=5-10 years, severe=10-20 years, extreme=20-40 years, and exceptional=greater than 40 years. The region outlined in gray depicts 9 months of forecasts (April through December 2024).

The 2011-2012 drought was described at the time as Mexico’s worst drought on record, killing 1.7 million cattle, causing over $1 billion of crop losses, and requiring $2.45 billion in government emergency assistance. At its peak, about 30% of Mexico’s population lived in areas experiencing exceptional long-term drought (>40 year return period.)

Nine years later, NASA described the 2020-2021 drought as “one of the most widespread and intense droughts in decades. Nearly 85 percent of the country [was] facing drought conditions as of April 15, 2021. Large reservoirs across the country [were] standing at exceptionally low levels, straining water resources for drinking, farming, and irrigation. The mayor of Mexico City called it the worst drought in 30 years for the city, which is home to about 9 million people.” Reuters reported that: “Villa Victoria, an important source for Mexico City, was among 77 of 210 principal reservoirs below 25% capacity at the end of June” and that the drought had prompted the government to seed clouds with silver iodide. At its peak, over 20% of Mexico’s population was exposed to exceptional long-term drought for a period of 4 months.

Our analysis estimates that the current 2023-2024 drought has affected more people for a longer period of time than either of the 2011-2012 or 2020-2021 droughts; each of which were previously described as droughts of record. The drought has led to forest fires, damaged the winter corn crop, and affected public water supply in Mexico City to the point where some are expressing concern about “day zero.”

The Global Water Security Center recently reported that the surface area of the largest reservoir that provides water to Mexico City was at its lowest level since 2000, and that three of the four lowest levels on record have occurred in the past three years. While levels have recovered a bit since this summer due to seasonal rains, the January 2024 level was the lowest January level since 2000. Our forecasts indicate that widespread long-term drought (12-month) will persist through at least August 2024 if not longer.

What is driving the recent droughts? Cumulative 12-month rainfall has been lower than normal, particularly from mid 2020 through mid 2021, and again in mid 2023 through early 2024. However, rainfall was actually above normal levels from late 2021 through early 2022. This should have led to improvements in reservoir levels but did not. The big difference has been temperature. High temperatures increase water loss through evaporation and evapotranspiration, while at the same time increasing demand for water for household and industrial use. Average annual temperature has been continuously warmer than expected since 2016 and has been exceptionally hot from 2020 through 2021, 2023 through the present, and forecasts predict the remainder of 2024 to be even hotter. Heat-driven droughts such as the one currently affecting Mexico are a consequence of climate change.

The black line and dots in this chart depict cumulative 12-month average precipitation in Mexico City. The gray line is the forecast for the next nine months, and the dashed gray lines depict the forecast uncertainty using the interquartile range from an ensemble of 28 bias-corrected forecasts issued the last week of March 2024. The background color ribbons show return period ranges based on a 1981-2020 statistical baseline period. The white band in the center is near normal, the blue bands at the top are wetter than normal, and the red bands at the bottom are drier than normal. The darker the color, the more extreme the departure from normal. Sources: *ERA5* *and* *CFSv2*.

The black line and dots in this chart depict cumulative 12-month average temperature in Mexico City. The gray line is the forecast for the next nine months and the dashed gray lines depict the forecast uncertainty using the interquartile range from an ensemble of 28 bias-corrected forecasts issued the last week of March 2024. The background color ribbons show return period ranges based on a 1981-2020 statistical baseline period. The white band in the center is near normal, the red bands at the top are warmer than normal, and the blue bands at the bottom are cooler than normal. The darker the color, the more extreme the departure from normal. Sources: *ERA5* *and* *CFSv2*.

Subscribe to our monthly Water Watch List

Search blog categories

Search blog tags

Mexican Drought in Historical Context: A sign of more extreme heat-driven drought to come

Mexican Drought in Historical Context:
A sign of more extreme heat-driven drought to come