Mexico City draws roughly 63% of its water from a massive underground aquifer directly beneath the city, with most of the rest piped in from river systems as far as 127 kilometers away. A small but growing share comes from recycled wastewater. This arrangement, built to support one of the world’s largest metropolitan areas, is under severe strain: the aquifer is being drained far faster than nature can refill it, the imported water requires enormous energy to deliver, and up to 40% of all water entering the distribution network never reaches a tap.
The Aquifer Beneath the City
The single largest source is the Mexico City Aquifer, a vast underground reservoir sitting below the metropolitan area. It supplies about 53 cubic meters of water per second to the region’s roughly 22 million residents. That sounds like a lot, but the aquifer naturally recharges at only about 23 cubic meters per second. The gap means the city pulls out roughly 800 million cubic meters more each year than rain and surface water can replace.
This overdraft has been going on for decades, and its effects are visible at street level. As water is pumped from the clay and sediment layers underground, the ground above compresses. In some parts of the city, the surface sinks by more than 30 centimeters per year. Over a recent ten-year monitoring period, certain areas dropped a total of 3.6 meters. That sinking cracks building foundations, ruptures water and sewer lines, and warps roads. It also makes flooding worse, because areas that used to drain naturally now sit in low bowls.
Water Piped in From Distant Rivers
Because the aquifer alone cannot keep up with demand, Mexico City imports about 27% of its supply from external river basins. The largest of these systems is the Cutzamala, a network of reservoirs and aqueducts west of the city. Water travels 127 kilometers through pipes and tunnels, and because Mexico City sits in a high valley, the system has to pump that water uphill by about 1,200 meters in elevation. That climb makes Cutzamala one of the most energy-intensive water delivery systems in the world.
The Cutzamala system supplies over 5 million people in the Valley of Mexico, but its reservoirs are vulnerable to drought. In June 2024, capacity dropped to just 26%, raising fears of a “Day Zero” scenario where taps would run dry. A strong rainy season brought the system back to 95.5% by October 2025, but the episode illustrated how precarious the supply can be in any given year. The older Lerma system, drawing from rivers to the west, also contributes imported water but has declined in output over the years as those source basins face their own depletion.
Recycled wastewater accounts for about 10% of the city’s total supply. Most of this treated water goes to irrigation, industry, and park maintenance rather than household taps, but expanding reuse is one of the few options for closing the gap between supply and demand.
What Happens Between the Source and the Tap
Even when enough water enters the system, a staggering amount never reaches homes and businesses. Aging, poorly maintained pipes lose up to 40% of the water to leaks. That means nearly half of the water pumped from deep underground or transported over mountain ranges simply seeps into the ground or runs off before anyone can use it. Fixing this infrastructure is expensive and disruptive in a dense urban area, but it represents one of the biggest potential gains in supply without tapping a single new source.
The losses also create equity problems. Wealthier neighborhoods with newer infrastructure tend to receive reliable, pressurized water around the clock. Poorer areas on the city’s outskirts, where pipes are older or where informal settlements lack connections altogether, may receive water only a few hours per day or depend on delivery trucks.
Contamination in the Groundwater
Quality is a concern alongside quantity. Testing of over 100 wells in the metropolitan area has found that fecal bacteria were present in 44 of them, a sign that sewage is leaching into groundwater. Aluminum, ammonia, iron, and manganese regularly exceeded Mexican safety limits. In some areas, more dangerous contaminants like arsenic, lead, mercury, and boron have been detected, and concentrations of several heavy metals are increasing over time rather than improving.
Nitrates and sulfates are also rising in dozens of wells, which points to ongoing contamination from agricultural runoff, leaking sewer lines, and industrial discharge. Because the aquifer is being drawn down so aggressively, the remaining water becomes more concentrated with these dissolved substances. For residents, this means that even when water does arrive, many choose to buy bottled or filtered water for drinking and cooking.
Why the Problem Is So Hard to Solve
Mexico City’s water crisis is a product of geography and history. The Aztecs built their capital, Tenochtitlan, on an island in a shallow lake system. Spanish colonizers drained those lakes over centuries to control flooding, and the modern city expanded across the dried lakebed. What was once a water-rich environment became one that depends almost entirely on pumping from below or importing from far away.
Today, the math is straightforward and grim. Total demand sits at about 84 cubic meters per second. The aquifer provides 53, imported systems provide 23, and recycled water covers 8. But the aquifer can sustainably deliver only about 23 cubic meters per second based on its natural recharge. Closing that 30 cubic meter gap would require some combination of dramatically reducing consumption, repairing the distribution network, expanding water recycling, and finding ways to increase aquifer recharge, such as capturing more rainwater and directing it underground.
Each of those strategies is technically feasible but faces financial, political, and logistical hurdles in a metropolitan area of this size. In the meantime, the aquifer keeps dropping, the ground keeps sinking, and the city’s water future remains one of the most pressing urban challenges on the planet.