Abstract
Global groundwater assessments rank Iran among countries with the highest groundwater depletion rate using coarse spatial scales that hinder detection of regional imbalances between renewable groundwater supply and human withdrawals. Herein, we use in situ data from 12,230 piezometers, 14,856 observation wells, and groundwater extraction points to provide ground-based evidence about Iran's widespread groundwater depletion and salinity problems. While the number of groundwater extraction points increased by 84.9% from 546,000 in 2002 to over a million in 2015, the annual groundwater withdrawal decreased by 18% (from 74.6 to 61.3 km3/y) primarily due to physical limits to fresh groundwater resources (i.e., depletion and/or salinization). On average, withdrawing 5.4 km3/y of nonrenewable water caused groundwater tables to decline 10 to 100 cm/y in different regions, averaging 49 cm/y across the country. This caused elevated annual average electrical conductivity (EC) of groundwater in vast arid/semiarid areas of central and eastern Iran (16 out of 30 subbasins), indicating "very high salinity hazard" for irrigation water. The annual average EC values were generally lower in the wetter northern and western regions, where groundwater EC improvements were detected in rare cases. Our results based on high-resolution groundwater measurements reveal alarming water security threats associated with declining fresh groundwater quantity and quality due to many years of unsustainable use. Our analysis offers insights into the environmental implications and limitations of water-intensive development plans that other water-scarce countries might adopt.
Highlights
Engineering, Boise State University, Boise, ID; hScience and Research Branch, Islamic Azad University, 1477893855 Tehran, Iran; iThe Whitney and Betty
Iran is grappling with acute water management problems and tensions [9, 10]
Groundwater overdraft has contributed to a host of contemporary socioecological problems, including the drying up of wetlands, desertification, sand and dust storms, deteriorating water quality, and population displacement [10, 11]
Summary
The number of groundwater extraction points has increased rapidly across Iran (Fig. 1A), disrupting the natural groundwater balance in many aquifers. The number of deep wells, semideep wells, qanats, and springs used to meet the increasing water demand rose by 52.4, 81.4, 22.2, and 221.7%, respectively, increasing the total number of withdrawal points by 84.9% from 2002 to 2015. Semideep wells generally outnumber deep wells in most subbasins except those located in the Central Plateau and Qareghom major basins, where groundwater tables are very deep (up to 250 m). This situation may accelerate saltwater intrusion in the vicinity of inland saline lakes (e.g., Salt Lake, Jazmorian Wetland, and Bakhtegan Lake). There are a large number of qanats in the arid subbasins, including Siahkooh Desert, Central Desert, Lut Desert, and Patargan (Fig. 1A)
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