چکیده:
منابع آب زیرزمینی پس از یخچالهای قطبی، دومین منبع آب شیرین موجود در جهان به شمار میروند. بررسی تغییرات سطح آب زیرزمینی در برنامهریزی و مدیریت پایدار هر منطقه از اهمیت فراوانی برخوردار است. هدف از این مطالعه بررسی تغییرات مکانی و زمانی سطح آب زیرزمینی حوضه آبخیز دامغان در ارتباط با تغییرات کاربری اراضی با استفاده از روشهای زمینآمار، سنجشازدور و روندیابی تغییرات با استفاده از نرمافزار R در دوره آماری ۱۳۷۲-۱۳۹۸ است. دادههای سطح ایستابی بهصورت میانگین برای هر دوره اطلاعات ۱۷۶۰ حلقه چاه عمیق، نیمهعمیق، مادرچاه قنوات جمعآوری گردید. پس از کنترل کیفیت، صحت و بررسی نرمال بودن دادهها با استفاده از روش کریجینگ و IDW میانیابی گردید و با استفاده از نرمافزار R روندیابی تغییرات صورت گرفت و در نهایت تغییرات کاربری اراضی برای سالهای ۱۹۹۳، ۲۰۰۰، ۲۰۱۰، ۲۰۱۵ و ۲۰۲۰ با استفاده از تصاویر ماهواره لندست و سنجشازدور مورد بررسی قرار گرفت و رابطه آن با تغییرات سطح منابع آب زیرزمینی با استفاده از روش زمینآمار مورد تجزیهوتحلیل قرار گرفت. نتایج نشان داد که سطح ایستابی آب زیرزمینی در بیشتر قسمتهای حوضه ازجمله قسمت شرق، شمال، جنوب غرب کاهش داشته در این مناطق که سالانه به طور میانگین ۵۶ سانتیمتری و در طی ۲۶ سال ۷/۱۴ متر افت سطح آب زیرزمینی رخداده است، بیشترین تغییرات کاربری اراضی نیز در این مناطق اتفاق افتاده است بهگونهای که مساحت اراضی باغی ۳۷/۱۰۰۱۶ هکتار افزایش، مناطق شهری ۰۲/۶۳۷ هکتار افزایش، اراضی بدون پوشش (بایر) ۴/۷۶۹۰۷ هکتار افزایش، منابع آب سطح ناشی از احداث سد ۱۵/۴۵۳ هکتار افزایش، مراتع ۵۸/۳۰۳۳۷ هکتار کاهش، جنگل ۸۶/۴۸۳۲۵ هکتار کاهش و اراضی کشاورزی ۴۷/۹۳۵۰ کاهش از سال ۱۹۹۳ تا ۲۰۲۰ داشته است.
Groundwater resources are the second largest freshwater source in the world after the polar glaciers. The study of groundwater fluctuations has significant importance in the planning and sustainable management of each region. The purpose of this study is to investigate the spatial and temporal changes in groundwater levels in Damghan watershed concerning land-use changes. This study is conducted using geostatistical methods and remote sensing and routing of changes using R software in the statistical period of 1994-2020. Groundwater table data were collected for 1760 wells including deep wells, semi-deep wells, and main wells of qanats. After controlling the accuracy and quality of data and checking the data normality, interpolation was performed. The Kriging method was used for interpolation and Inverse Distance Weighting, and changes were routed using R software. Land-use changes for 2000, 2010, 2015, and 2020 were studied using remote sensing and their relationship with groundwater level changes was analyzed. The results show that the groundwater level has decreased in most parts of the basin, including the east, north, and southwest. In these areas, the groundwater level has decreased by 14.7 m, over 26 years, which means an average of 56 cm per year. Also, the most land-use changes have occurred in these areas in that the area of gardens has increased by 10016.37 hectares, urban areas have increased by 637.02 hectares, barren lands have increased by 76907.4 hectares, and surface water resources -due to the construction of the dam - have increased by 453.15 hectares, and rangelands have increased by 30337.58 hectares, forests have decreased by 48325.86 hectares and agricultural lands have decreased by 90350.47 hectares for the time interval between 2000 to 2020. Extended Abstract 1-Introduction Land use changes affect a wide range of environmental and natural resource characteristics such as the quantity and quality of surface water and groundwater resources, climate systems, and so on. Groundwater resources are the second largest source of fresh water in the world after polar glaciers. The growing population, improvement of living standards and the consequent necessity to meet the growing needs of human societies have intensified the pressure and have increased the use of these resources. Timely and accurate detection of these types of changes is the basis for a better understanding of the relationships and interactions between humans and natural phenomena, thereby allowing for better management and better use of natural resources. In this regard, this study examines land use changes and its effect on groundwater changes. 2-Materials and Methods The main purpose of this study is to reveal land use changes related to the level of groundwater resources during the last 27 years (1993-2020) in Damghan Basin (Damghan city), for understanding the main causes that lead to changes in the environment and changes in the level of groundwater resources. The purpose of this study is to investigate the spatial and temporal changes of groundwater level in Damghan watershed in relation to land use changes using geostatistical methods and remote sensing and routing of changes using R software in the statistical period of 1994-2020. Groundwater table data were collected for 1760 deep wells, semi-deep wells and main wells of qanats. After controlling the accuracy and quality of data and checking the data normality, interpolation was performed using Kriging method and Inverse Distance Weighting, and changes were routed using R software. Land-use changes for 2000, 2010, 2015 and 2020 were studied using remote sensing and its relationship with groundwater level changes was analyzed. The results showed that the groundwater level has decreased in most parts of the basin, including the east, north and southwest. 3- Results and Discussion The main purpose of this study is to reveal land-use changes related to the level of groundwater resources during the last 27 years (1993-2020) in Damghan Basin (Damghan city) for understanding the main causes that lead to changes in the environment and changes in the level of groundwater resources. The study of land-use changes in Damghan watershed shows a decrease in the level of forest lands, pastures, agriculture and an increase in garden lands, barren lands without vegetation, urban areas and water resources (dams). The study of land-use change shows that the decrease in rangeland, forest, and agricultural land by 30337.58, 48325.86 and 9350.47 hectares from 1993 to 2020, respectively, is associated with a downward trend, but the increase in the use of garden lands, surface water resources (due to the construction of the dam), uncovered lands and urban areas by 10016.37, 453.15, 76907.4 and 637.02 hectares, respectively, in the mentioned period and has an upward trend. The study of groundwater level changes in the planning and sustainable management of water resources in each region is of great importance. A steady decline in groundwater levels has been observed in many parts of the world in the second half of the last century. This has led to a reduction in large-scale groundwater reserves in the region. This reduction in reserves is due to two factors: over-exploitation or reduction of nutrition in the region. In recent years, in Damghan watershed, the use of groundwater has been continuous to meet the needs of agriculture, drinking, and industry. By examining the information of 26 deep wells in the basin, it was revealed that the average groundwater level in Damghan watershed has decreased by about 14.7 per year for 27 years and the average annual groundwater level in this area has decreased by 0.56 cm. in the basin (Table 7). On average, in the assessment of 1760 wells studied in the province, during this period, an average of 12.34 meters of groundwater level has decreased, and this shows that the drop in groundwater level in this area is 2.36 meters, which is more than the average of 27 years in Semnan province. Overall, The results of the research show that the changes in the level of each land-use -regardless of whether they are increasing or decreasing with the increase in the utilization of groundwater resources - has had a negative effect on reducing its level with a certain trend. The change of groundwater resources can be mainly affected by climate change, the type, and the intensity of exploitation of these resources in the form of different land uses. Since groundwater resources are not immediately - and in a short period of time - affected by climate change, and especially by rainfall fluctuations, land use changes in Damghan watershed have a negative impact on the level of groundwater resources over 28 years. The study conducted by Samadi et. al. (2015) in Urmia plain showed a similar result in relation to reducing groundwater levels by changing land use and thus the intensity of exploitation of these resources. Also, Asghari Sarkanrood et al. (1400) showed that the decrease in pastures and the increase in the area, followed by the intensity of groundwater abstraction in agricultural lands during the years 1396-1396 has led to a significant drop in groundwater levels. 4- Conclusion According to the results of this study, the trend of groundwater level changes in the study area is in relation to land-use changes. If the exploitation of groundwater resources in the study area continues in its current form, social and economic crises can form in the region. In addition, they can have negative effects on the environment and natural resources of the region and may increase the risks and damages caused by natural disasters such as floods.
خلاصه ماشینی:
نتـايج نشـان داد کـه سـطح ايسـتابي آب زيرزميني در بيشتر قسمت هاي حوضه ازجمله قسمت شرق ، شمال ، جنوب غرب کـاهش داشـته در ايـن منـاطق که سالانه به طور ميانگين ٥٦ سانتيمتري و در طي ٢٦ سال ١٤/٧ متر افت سطح آب زيرزمينـي رخ داده اسـت ، بيشترين تغييرات کاربري اراضي نيز در اين منـاطق اتفـاق افتـاده اسـت بـه گونـه اي کـه مسـاحت اراضـي بـاغي ١٠٠١٦/٣٧ هکتار افزايش ، مناطق شهري ٦٣٧/٠٢ هکتار افزايش ، اراضي بدون پوشـش (بـاير) ٧٦٩٠٧/٤ هکتـار افزايش ، منابع آب سطح ناشي از احداث سد ٤٥٣/١٥ هکتار افزايش ، مراتـع ٣٠٣٣٧/٥٨ هکتـار کـاهش ، جنگـل ٤٨٣٢٥/٨٦ هکتار کاهش و اراضي کشاورزي ٩٣٥٠/٤٧ کاهش از سال ١٩٩٣ تا ٢٠٢٠ داشته است .
تحقيقات نيکزاد و همکاران (١٣٩٧) در بازه زماني ١٣٧٠- ١٣٩٤ در دشت بيستون کرمانشاه نيـز نشـان از کـاهش ٢٢ متري افت سطح آب زيرزميني در اين منطقه است (٢٠١٥( Kumar &Mishra نيز در تحقيقي اثر تغيير کاربري اراضي را بر منابع آب زيرزميني در منطقه Haridwar در هند مورد بررسي قرارداد نتايج تحقيق نشان داد کـه افـزايش وقوع سيل ، افزايش بي رويه جمعيت ، فعاليت هاي صنعتي به همراه تقاضاي سوخت هاي فسيلي و گياهي موجب افـزايش سرعت تغيير در الگوهاي کاربري اراضي گرديده و به تبع آن افزايش مناطق مسکوني و کاهش سطح پوشش گيـاهي بـه طور مستقيم بر کاهش سطح منابع آب زيرزميني اثـر گذاشـته اسـت .