| چکیده انگلیسی مقاله |
Land subsidence is one of the major geomorphological hazards in arid and semi-arid regions. It is primarily caused by excessive groundwater extraction. In such areas, a decline in groundwater levels can lead to the irreversible compaction of fine-grained layers, a reduction in storage capacity, and damage to critical infrastructure. This study aims to monitor the rate of land subsidence in the Damghan aquifer and analyse its relationship with groundwater decline, using satellite data, piezometric information and field evidence. The study area covers part of the Damghan aquifer in Semnan Province, spanning approximately 1,522 km². It contains an unconfined aquifer within heterogeneous alluvial deposits. The dataset includes Sentinel-1A images from 2017 to 2021, records from 38 observation wells from 2017 to 2022, and drilling logs from 13 exploitation boreholes. The results indicated that the decline in groundwater levels in the central and south-eastern parts of the aquifer reached 5 metres, with an average annual rate of approximately 0.33 metres. Radar interferometry maps confirmed an average Analysis of soil texture and saturated thickness revealed that zones with higher percentages of clay and silt are more sensitive to groundwater decline. Even small drawdowns in boreholes containing fine-grained sediments resulted in noticeable subsidence, whereas boreholes containing coarse-grained sediments showed limited deformation. Field evidence, including casing protrusion in piezometer wells of up to 27 cm, the formation of initial sinkholes and changes in natural drainage patterns, highlights the practical implications of this phenomenon. The findings of this study demonstrate that, in interaction with geological characteristics and soil texture, groundwater decline is the main driver of subsidence in the Damghan aquifer. Therefore, continuous groundwater monitoring and targeted management of exploitation are essential to mitigate risks and ensure the region's environmental and economic sustainability. |
