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Groundwater depletion

Polina Schapova / UNU-EHS

Groundwater is an essential freshwater resource stored in underground reservoirs called “aquifers”. These aquifers supply drinking water to over 2 billion people and around 70 per cent of withdrawals are used for agriculture. However, 21 out of 37 of the world’s major aquifers are being depleted faster than they can be replenished. The water stored in aquifers often has accumulated over thousands of years and would equally take thousands of years to fully recharge, making it essentially a non-renewable resource. In these at-risk aquifers, lives and livelihoods are put on the line as the water level drops further and further out of reach.

Some places in the world have already extracted significant amounts of their groundwater resources. For example, Saudi Arabia once sat atop one of the world’s largest aquifer systems and, in the 1970s, used it to make the desert a productive oasis. By the mid-1990s, farmers were pumping around 19 trillion litres per year, and Saudi Arabia became the world’s sixth-largest wheat exporter. This vast overextraction is estimated to have depleted over 80 per cent of the aquifer, prompting the Saudi government to announce the 2016 wheat harvest as its last. Now, to feed the country’s 30+ million people, Saudi Arabia must rely on crops imported from other countries.

Key Numbers

21 of 37

world's largest aquifers being depleted faster than they can be replenished

70%

global groundwater withdrawals used for agricultural production

2 billion

people relying on groundwater as a primary source of freshwater

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Polina Schapova / UNU-EHS

A strong relationship between groundwater and global food production means that local problems can quickly have far-reaching consequences. For example, the High Plains aquifer in the United States supplies one third of all groundwater for irrigation used in the country and supports over $35 billion worth of crops such as wheat and soy. However, as unsustainable groundwater extraction continues, around 40 per cent of the aquifer’s area will not support irrigation by the year 2100. Since the United States exports almost half of its groundwater-dependent crops to other countries, places like Mexico, China and Japan will also suffer the impacts. Additionally, India is the world’s largest user of groundwater, exceeding the use of the United States and China combined. The north-western region of India serves as the breadbasket for the nation’s growing 1.4 billion people, with the states of Punjab and Haryana producing 50 per cent of the country’s rice supply and 85 per cent of its wheat stocks. However, 78 per cent of wells in Punjab are considered overexploited, and the north-western region as a whole is predicted to experience critically low groundwater availability by 2025.

Agricultural intensification combined with new technologies and policies that make groundwater cheaper to use has accelerated extraction rates, leading to alarming levels of aquifer depletion. We can no longer consider groundwater as a boundless source of easily-accessible freshwater. Instead, we can now see that it has limits and is becoming increasingly inaccessible, with worrying implications for its use as a coping mechanism when rains fail. We need drastic changes in our global agricultural system to be mindful of the limits of groundwater systems and our ability to access this water. We need regulations and technologies to ensure the sustainable use of groundwater and preserve this resource for when we need it most.

Tipping point: When the water table in a given aquifer drops consistently below the well depth, access to groundwater will become problematic, increasing the risk for farmers to be unable to irrigate their crops.

Justin Sullivan / Getty Images / AFP