Groundwater is one of the most important water resources, making it fundamental to human life and economic development in arid and semi-arid regions such as Iran. The mean annual precipitation of Iran is about 240 mm, roughly a third of the global average. Until the 1940s groundwater was extracted by means of the indigenous Qanats system. Currently, the existence of 41000 of Qanats is recorded in Iran. However, in the period of 1971-2013 the number of wells increased from just over 47000 to almost 789000. Today about 196000 deep and 593000 shallow wells have been dug all over the country with a mean discharge of about 0.17×10^-3 million cubic meters (MCM) and 0.02×10^-3 MCM respectively. Based on our results, the volume of groundwater exploitation (through wells, Qanats and springs) has risen from less than 18 MCM annually in the early 1970s to over 79 MCM in 2005. However, groundwater exploitation has reduced since 2005, and reached about 61 MCM in 2015. The results also show that agriculture is the sector  with the highest water demand. Over 90 percent of the extracted ground water resources are consumed in agriculture. Finally, in recent years annual average water table drawdown rate has been about 0.51 m/yr and the total overexploitation of groundwater has been calculated at 5.086 MCM/yr. Of a total 609 areas studied, 347 are prohibited areas.