تحليل آسيب پذيري فرونشست آبخوان دشت مرند با استفاده از روش ALPRIFT بر اثر بهره برداري بيش از حد از منابع آب زيرزميني

VULNERABILITY ANALYSIS TO AQUIFER SUBSIDENCE BY ALPRIFT METHOD DUE TO OVER-EXPLOITATION FROM GROUNDWATER RESOURCES

در پژوهش حاضر با استفاده از روش ALPRIFT به ارزيابي آسيب پذيري فرونشست زمين در دشت مرند پرداخته شده است. در اين روش، از هفت لايه شامل محيط آبخوان، كاربري اراضي، پمپاژ، تغذيه، ضخامت آبخوان، فاصله از گسل و افت تراز ايستابي استفاده شد. با توجه به اهميت افت تراز ايستابي، براي تهيه ي اين لايه از دو راهكار استفاده شد. در راهكار اول از اختلاف ماهانه ي تراز آب طي سال هاي 1397−1390 استفاده و لايه هاي مختلفي تهيه شد. در راهكار دوم از روند افت تراز ايستابي طي همان دوره زماني بهره گرفته شد. نتايج نشان داد آسيب پذيري در راهكار اول براي سال هاي مختلف متفاوت بوده ولي در راهكار دوم، آسيب پذيري فارغ از تغييرات ساليانه ارايه شده است. بر اساس نتايج به دست آمده،مناطق جنوب شرقي و جنوب غربي دشت، شهر مرند و مناطق يامچي و كوشك سراي در برابر فرونشست آسيب پذيرند و متوسط فرونشست دشت برابر 2 سانتي متر طي سال هاي 1396−1397 است.

Land subsidence due to groundwater over-exploitation is a man-made hazard, and identifying those areas vulnerable to subsidence is of undeniable significance. The present study applies the ALPRIFT method to assess the vulnerability of land subsidence in the Marand plain located in East Azerbaijan province in Iran, which has been at the risk of subsidence in recent years. In the framework of this method that has been developed recently, seven incorporated data layers comprise aquifer media, land use, groundwater pumping, net recharge, aquifer thickness, distance from fault, and water table decline. The data layers were prepared by GIS processing, and the prescribed rates were assigned to the data layers. Then, the data layers were prioritized based on the recommended weights, and the vulnerability map of the region was delineated. In this paper, with respect to the significance of water table decline, two strategies were used in the process of preparing this data layer. In the first strategy, the difference in water levels was used in the first and the last months of a specific year. Based on this strategy, the decline of water table was prepared during 2011-2018. In the second strategy, the trend or slope of water table decline during the same period was used to prepare this data layer. The goodness-of-fit for the vulnerability map and InSAR processing were evaluated by ROC curve. The comparison of the results showed that the estimation of subsidence vulnerability by the first strategy varied for different years; however, the second strategy provided the vulnerability to subsidence regardless of seasonal and temporal fluctuations. Moreover, the result revealed that the southeast and southwest parts of the plain, the Marand city and the Yamchi and Kushksaray residential areas were located in the vulnerable area to subsidence. Moreover, the average subsidence in this plain is 2 cm based on the results of InSAR processing during 2017-2018. The results of this research can be utilized in the planning and management of groundwater abstraction to control subsidence.