The average global land subsidence is two centimeters per year, but it is much higher in some parts of Iran, mainly due to the over-extraction of water from groundwater resources, especially in Yazd Province.
“The annual drop in the level of groundwater in Yazd is caused by both over-extraction and reduction in rainfall. Every year, when there is poor rainfall, more water is extracted and as a result, the groundwater level declines. In such years, the land subsides by 50 cm,” the managing director of Yazd Regional Water Company said.
“When the rains increase, we can see a drop of 35 cm in the groundwater level. On average, it can be said that the groundwater level in Yazd Province declines by 45 cm per year,” Mohammad Mehdi Javadianzadeh was quoted as saying by Mehr News Agency.
An average of 1 billion cubic meters of water are extracted from groundwater sources in the arid central province annually, which has caused severe water deficits in most plains.
Groundwater overdraft may lead to the destruction of vegetation, increase the possibility of dust storms, create holes in the plains, higher salt content in groundwater and land subsidence.
To slow down the damaging process, Yazd Regional Water Company has adopted measures, such as installation of smart meters for water wells and sealing of illegal wells that are aplenty in the region.
A smart meter is a modern electricity meter that digitally sends meter readings to energy suppliers and ensures accurate billing. The installation of smart meters helps control groundwater use and prevents overconsumption and waste.
If farmers draw water above the volume(s) specified for them from their own wells, electricity is cut off automatically.
Referring to unauthorized wells as one of the factors worsening subsidence, he said, “Since 2015, 430 illegal wells have been filled, helping save 8 million cubic meters of water.”
Yazd is in the center of Iran where the two deserts of Dasht-e Kavir and Dasht-e Lut meet. Due to the dry and arid climate conditions, as well as near permanent droughts, Yazd needs more proactive management and optimal use of its fast depleting water resources.
National Status
Across the country, 60 billion cubic meters of surface water and 45 bcm of groundwater are used annually. Of the total consumption, the major share is used in the agricultural sector, and the rest in the household and industrial sectors.
Currently, there are 414,000 wells in the agricultural sector, 52,000 wells in the industrial sector and 26,000 wells in the household sector, which constitute a total of 492,000 authorized wells.
Per capita water consumption in Iran is 150 liters for each person, which is much higher than the global average.
Yet the figure is not the same in all provinces. In the provinces where the weather is hotter, the figure is 300 liters and it reaches 350 liters in some metropolises.
Excessive water extraction from agricultural wells has caused land subsidence in about 500 plains out of 609 plains in Iran, leading to the decline in the quality and volume of drinking water and the evacuation of some rural areas.
Land subsidence is defined as a gradual or sudden sinking of the earth's surface owing to the subsurface movement of earth materials.
In addition to injudicious groundwater extraction, other causes of land subsidence are aquifer-system compaction, drainage of organic soils, underground mining, hydro-compaction, earthquake and gas and oil extraction.
Disorganized urbanization, old and obsolete farming practices and the presence of water-intensive industries in different regions are exacerbating the rapidly dwindling water reserves.
The steep decline in groundwater levels is having devastating consequences. Excessive pumping is harming groundwater tables and stopping wells from reaching groundwater. When groundwater is overused, lakes, streams and rivers connected to groundwater also start diminishing.
The problem has evolved over a long time and cannot be addressed overnight, but short-term measures are expected to help improve the current conditions and prevent the expansion of land subsidence.
