Short answers, pulled from the story.
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. It exists below the water table within aquifers, which are units of rock or unconsolidated deposits that can yield a usable quantity of water.
About 30 percent of all readily available fresh water in the world is groundwater. Groundwater accounts for about half of the world's drinking water, 40% of its irrigation water, and a third of water for industrial purposes.
The rate of increase was especially high during the period from 1950 to 1980 due to higher population growth rates and rapidly increasing groundwater development. Global freshwater withdrawal increased from around 600 km3 per year in 1900 to 3,880 km3 per year in 2017.
Groundwater depletion occurs mainly through the expansion of irrigated agriculture in drylands such as the Punjab region of India where levels have dropped 10 meters since 1979. Cities on river deltas including Venice in Italy, Bangkok in Thailand, and Mexico City have experienced significant surface subsidence.
Climate change causes changes to the water cycle which lead to declines in groundwater storage and reduction in groundwater recharge alongside water quality deterioration. Direct redistribution of water by human activities amounting to approximately 24,000 km3 per year is about double the global groundwater recharge each year.