Mohammad Khorrami: The fight against groundwater pumping

The following story was written in December 2023 by Isaac Doubek in ENGL 4824: Science Writing as part of a collaboration between the English department and the Center for Communicating Science.

A groundwater pumping crisis endangers the lives of millions of people around the globe, says researcher Mohammad Khorrami. And he wants to do something about that.

    Khorrami is currently in his third year of a Ph.D. program in the Department of Geosciences at Virginia Tech. His academic career began at the Ferdowsi University of Mashhad, Iran, where he received his bachelor’s degree in civil engineering. He then earned a master’s degree from the University of Florida in geotechnical engineering, arming Khorrami to address the critical issues of excessive groundwater extraction, land subsidence, and seismic activity.

    Pumping water from beneath the Earth’s surface is a common practice, but as aquifers empty, land subsidence can occur, Khorrami explains. Materials from underneath the Earth’s surface compact, leading the ground above to collapse. Buildings and other infrastructure are affected by this, as their components tumble with the collapsing land. This poses a significant challenge for countries with limited surface water and high infrastructure density, says Khorrami.

    Aquifers hold water in certain locations and are an essential component of Earth’s water cycle, with water moving to rivers and streams nearby. When the extraction rate exceeds the replenishment rate, the aquifer empties until there is no remaining water. Collapsing ground affects urban areas and prevents humans from accessing water.

    Khorrami has been researching these negative effects in Mexico City. Khorrami and his research group recorded the rate of subsidence – how much the land sinks – and found that it was more than 30 centimeters (cm) per year, with 2 cm per year of uplift, the amount the land rose, across the period for which they recorded data. The city, sitting atop a former lake, is sinking at a massive rate, Khorrami says. To provide its large population with water, city officials will continue to extract water, and the city will continue to sink.

    The formation of sinkholes in Mexico City is a specific form of subsidence. These holes are a direct result of large amounts of water being extracted from the ground. Infrastructures have been collapsing for over a century, Khorrami says, as the population continues to grow. Mexico City is recorded to have one of the largest subsidence rates in the world, with one of the largest amounts of groundwater pumping.

    Khorrami also studies the effect of water removal on fault lines. Earth's crust consists of multiple plates, known as tectonic plates, that constantly move. Fault lines are the cracks in between these plates. The movement of plates along these faults sometimes creates earthquakes. Water within the faults acts as a lubricant and can modify the seismic behavior of faults, Khorrami explains. Groundwater removal can reduce fluid pressure within fault lines, preventing them from creeping and releasing stress gradually. Homes, roads, and railways can be destroyed by earthquakes.

    Khorrami wants to help policymakers understand the increased rate of subsidence, number of sinkholes, and strength of earthquakes compared to the past. He wants to see laws and policies that limit groundwater extraction. While laws and regulations currently exist to prevent excessive groundwater extraction, Khorrami wants stronger limits and stricter laws to reduce land subsidence, sinkhole formation, and earthquake damage.