The exact amount of water underground, also known as groundwater, is not known with precision. However, groundwater is estimated to be the largest freshwater reservoir on Earth, holding significantly more water than all the lakes, rivers, and swamps combined. According to the United States Geological Survey (USGS), it is estimated that about 30% of the world’s freshwater is stored underground in aquifers, which are porous rock formations or sediment layers capable of storing and transmitting water.
Estimates of total global groundwater volume vary, with different studies and models providing different figures. The volume of groundwater is influenced by various factors such as geological formations, climate, hydrological cycles, and human activities. It is estimated that the total volume of groundwater on Earth is roughly in the range of 22 to 30 million cubic kilometers (km^3), or 5,500 to 7,200 cubic miles (mi^3).
It’s important to note that not all groundwater is easily accessible or usable due to factors such as depth, quality, and sustainability. Some groundwater reserves are not economically viable or technologically feasible to extract, while others may be limited by concerns about over-pumping and depletion, or contamination from human activities. Proper management and sustainable use of groundwater resources are critical to ensure their availability and sustainability for present and future generations.
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