The US, India, Libya and Saudi Arabia all rely on groundwater for irrigating large areas, and all are overpumping many of their aquifers. One famous example is the Ogallala Aquifer in the central US . It runs from northwest Texas to southern S. Dakota, and contains about as much water as Lake Michigan . This is essentially fossil water that is being mined , as it is recharged only very slowly. Rain-watered crops can still be grown in some of this area, but at lower yields.
Surface water is also problematic.
Excessive diversion of rivers for irrigation has adverse effects on the rivers and on the seas into which they flow.