سنجش و ارزیابی کشت برنج و صیفجات بر میزان نشست زمین (مطالعه موردی: آبخوان نورآباد استان فارس- ایران)

The phenomenon of land subsidence depends on many factors of geological phenomena, slow movements of the crust and the outflow of lava, human activities and draining of aquifers, land subsidence in agricultural lands in the plains causes the destruction of irrigation systems and the destruction of fertile soils. It will be accompanied by cracking and making the land unusable. The main problem of land subsidence is the irreversibility of the land. Persistent subsidence in the plains occurs as a result of indiscriminate extraction of groundwater and drainage of aquifers, which leads to compaction of clay layers. Iran is one of the countries that is facing the crisis of underground water resources in recent years, droughts, construction of dams, on the one hand, the increase in population, the need for water resources, excessive drilling of illegal wells, and the cultivation of aquatic species on the other hand. It caused the danger of water crisis in this country. The purpose of this research is to investigate the cultivation pattern and its role on the subsidence of Noorabad aquifer in Fars province.

Currently, extensive cultivation of rice is carried out in this province and consumes water resources. From a long time ago, due to the rich surface water resources of the Bovan, Kati, Doregzan, and Marwarid rivers, as well as the suitable climate, farmers used to dedicate their lands to the cultivation of rice and safijat, and the passage of time and the reduction of surface resources Deep wells have continued the same flooding method as in the past and these species are still used as the dominant species in the region. The conditions have changed, but the cultivation is still in the old way, and this is one of the main problems that has doubled the subsidence crisis in the region as an important issue. Among the objectives of this research is to identify the types of water cultivation in the aquifer area, the areas with maximum subsidence and its relationship with the water types. One of the main innovations in this research is to investigate the relationship between the cultivation pattern and land subsidence for the first time. Is.

Modifying the cultivation pattern is an important solution to prevent the progress of land subsidence by developing the cultivation of medicinal plants and transferring cultivation from open space to greenhouse space and developing planting and changing the time of cultivation from spring to autumn is a way to deal with water shortage. Actions such as pressurized irrigation and laser leveling and the implementation of protective vessels and the development of drought-tolerant gardens and the development of greenhouse cultivation along with training farmers to adapt to water shortages, modifying the cultivation pattern and preventing excessive extraction of underground resources are important measures. in reducing the effects of subsidence phenomenon

The method used in this research is analytical in order to prepare the cultivation pattern in the target area using Centil 2 images in the three months of the summer of 2021 in the GEE environment and it was prepared and then sampled using the support vector machine model in the ENVI software environment. (ROI) of the selected species was done in order to calculate the amount of subsidence using the radar interferometric method in the SNAP software environment.

Investigating the amount of land subsidence in cultivated species shows that all cultivated species in the Noorabad aquifer are considered water-bearing and do not correspond to the conditions of the region. Rice cultivation is one of the most critical species in the Noorabad basin. Due to the high consumption of water and waterlogging and the high use of underground water resources, this species causes the drop of underground water and land subsidence. According to the graph, it shows that the amount of land subsidence in rice species has reached the maximum amount of about 10 centimeters per year. This situation is indicative of excessive wastage of underground water reserves and land subsidence in the Noorabad watershed. Sifijat is ranked second with a 3 cm settlement. These conditions indicate the crisis of subsidence in the region's aquifer.

Land subsidence is a widespread phenomenon in the world, which has had significant quantitative and qualitative manifestations in the last few decades, mainly due to the excessive exploitation of underground water resources and the intensification of its level drop. The results of the study of land subsidence showed that several factors are effective in the occurrence of land subsidence. Therefore, the greatest impact on land subsidence is related to rice cultivation, which has the highest water demand in the summer season. Cultivation in a period of 1 year shows that rice has the highest rate with -10 cm of sediment per year, followed by safijat, with -3 cm. In these areas, due to meeting the water needs of residential communities, including the city of Noorabad and the surrounding areas, as well as meeting the water needs of agricultural activities, there is more water resource exploitation, and the extraction of underground water is very high. The factors with the intervention of the dry climate of this region have caused the high talent of these regions in the discussion of subsidence, and it has been identified as one of the critical areas of the city in the subsidence map. The results of radar interferometry show that the indiscriminate harvesting of underground reserves has caused the subsidence of the central part of the aquifer, including summer rice and corn, at the level of the danger zone of land subsidence, which has increased by 5 cm. The results obtained from the cultivation pattern and its relationship with land subsidence show a positive correlation of R2 coefficient equal to 98% and the lowest error rate is about 0.001