Groundwater is used all over the world for agriculture and has been a main source of fresh water for irrigation for a very long time. Traditionally accessing the groundwater has been challenging and has been through canal based systems that are expensive to build and maintain. These systems are traditionally managed by local or national governments, depending on the economic state of the country this can either be a good thing for managing groundwater or it can mean that the systems aren't getting the attention they need.
Studies have found that approximately only 2.5% of the earth's water is considered to be freshwater, this means that only 2.5% of earths water is safe for things like freshwater wildlife, drinking and farming. Of the 2.5% about 30% of that is groundwater, that 30% is nearly 100 times the amount of freshwater found above ground. It has also been estimated that of the worlds water 97.5% is salt water Scientists estimate that globally we use 1277 km of water for irrigation each year, groundwater makes up about 43% of that.
The Midwestern region of the USA has a humid continental climate, this means that it gets a decent amount of rain. It is estimated that the Midwest gets about 30-38 inches of rain a year. While this is better than many places the Midwest still relies heavily on groundwater and water from the Great Lakes for agriculture
In places like Middle East and Northern Africa, also known as the MENA region, rainfall is scarce so most of the water used in irrigation comes from groundwater. Due to the heavy reliance on groundwater in this region the groundwater that is available is being overused and overexploited
Places with more Tropical Climates have a much lower reliance on Groundwater for things like agriculture because of the amount of rain. In many Tropical places the groundwater would not be good to use for farming because of the high sodium content from its proximity to oceans or seas.