مکانیابی سد زیرزمینی با استفاده از روش تحلیل سلسله مراتبی مطالعه موردی: حوضه آبخیز دشت کویر

با توجه به فصلی بودن آبراهه‌ها در مناطق خشک و نیمه‌خشک و انتقال آب سطحی به زیر سطح زمین استفاده از سازه‌هایی که کنترل و ذخیره کننده جریان برای فصول کم باران سال باشد ضروری است. به دلیل پرهزینه و زمانبر بودن مکانیابی سد زیرزمینی، استفاده از تکنیک‌های سیستم‌های اطلاعات جغرافیایی همراه با فرایندهای تصمیم‌گیری به‌عنوان یکی از ابزارهای کاربردی در این مطالعات محسوب می‌گردد. سدهای زیرزمینی سازه‌هایی هستند که در مسیر جریان آب زیرزمینی ساخته شده و باعث بالا آمدن و ذخیره آب در مخزن خود می‌شوند. منطقه مورد مطالعه بخشی از حوضه آبخیز دشت کویر است که در شمال‌غرب استان سمنان واقع شده است. هدف از این مطالعه تعیین محل مناسب احداث سد زیرزمینی با استفاده از تلفیق و امتیازدهی به لایه‌ها در محیط نرم افزارسیستم اطلاعات جغرافیایی به منظورتغذیه و کنترل آب‌های زیرزمینی در بخشی از حوضه آبخیز دشت کویر برای حفظ منابع آب در فصول کم باران می‌باشد. دراینتحقیقبه منظور اولویت‌بندی مکان‌های مناسب جهت احداث سدهای زیرزمینی، از روش تحلیل سلسله مراتبی استفاده گردید که با در نظرگرفتن معیارهای ارزیابی، شش مکان مناسب جهت احداث سد زیرزمینی در مرحله دوم مکانیابی مشخص شد. در مرحله پایانی به علت نظرات و عقاید مختلف کارشناسان و برای تامین نظرات و خواسته‌های تمامی گروه‌های دخیل در این امر 5 سناریو برای وزن دهی و ارزش‌گذاری معیارهای اصلی تعریف شد که طی این پنج سناریو وزن نهایی برای هر یک از 6 محور محاسبه شد. نتایج بدست آمده، نشان داد که مناطق جنوبی دشت دارای پتانسیل خوبی برای احداث سدهای زیرزمینی می‌باشد.

Suitable site selection for groundwater dams construction using analytical hierarchy process Case study: Dasht e Kavir Watershed

1. IntroductionProblem related to water scarcity has always been one of the most important issues to be considered in arid and semiarid regions. Due to the seasonality of surface water drainages and subsurface structures in these regions, it is necessary to use structures which control and store the water flow in order to use during arid seasons. One of these types of structures is underground dam to control the flow of water in the subsurface.In semiarid and arid areas in which desert are progressing, exploitation of water has been focused on underground surface water resources having the trouble of stability. In semiarid and arid areas in which desert are progressing, exploitation of water has been focused on underground surface water resources having the trouble of stability (Ouerdachi, L., et al., 2012). These conditions require the use of surface and underground short dams for exploiting water in developing countries with arid weather situations. At present, these kinds of structures have been desirably featured in terms of both implication and efficacy in performance (Nilsson 1986, Cavalcanti, N.B., 2001). 2. Materials and methodsThe area studied being part of Semnan province and its surroundings are 216467 hectare in width which geographically have the coordinates of 53D 81M to 53D 15M eastern length and 35D 13M to 35D 85M northern width. Evaluation of station climes studied by both Domarten and Amberje indicates that the studied span has a semi drycold climate at heights reaching coldarid climate where lowerheight areas exist. The situation of considered area is shown by Figure 1. With respect to climatic conditions, there are many syllabic flows throughout side hills of the area where underground dam’s establishment is a proper way to control aridity problem in arid seasons of this area. The most significant data of this study are related to topography, geology, underground water, and aqueduct resources. Software's used in this research are both expert choice to prioritize and Geography information systems to combine data.In this research, basic criteria of evaluation including water, pedestals, fountain, economicsocial criteria have been targeted at the highest range placing indicators and incidentals criteria at other categories of AHP. Then, proper locations for underground dam establishment have been prioritized.3.  Results and discussionBased on Gorry and Morton method, decisionmaking supportive systems are either the systems capable of transporting data or computerized systems which can be used to solve our problems clearly or partly clearly known or unknown respectively (Gorry, G. A., and Morton, M.S., 1971). Decisionmaking supportive systems are models which receive vast majority of data and deliver many solutions specifically designed to overcome the existing problem (Klosterman, R.E., 1997). Decision support system (DSs) used in identifying proper location to underground dam establishment possess AHP mode and are used in three stages. 4. ConclusionConsidering climatic conditions over the area studied and existing stream, Underground dam establishment highly affects both performance revising and balancing act in underground water removal. Using new methods instead of traditional and timeconsuming ones can highly help with saving time and cost to underground dam locationfinding. In the first step of this research, presented DSs considering eliminating criteria in the area 216467 hectare in width assign suitable pedestal in each limit which is capable of potential underground dam establishment. Then, in second step, the most suitable strait in each limit is assigned to the underground dam establishment. In the latest step after weighting each main criterion at its related map and as well adding total values of map pixels together in a software called GIS, 8 locations to underground dam establishment at the second step of locationfinding in fifth scenario were prioritized as follows:First scenario (weights equality of four main criteria) locations: 5, 3, 2, 4, 6, 1Second scenario (priority with water criterion) locations: 5, 3, 2, 6, 1, 4Third scenario (priority with pedestals criterion) locations: 5, 6, 4, 3, 1, 2Forth scenario (priority with fountain criterion) locations: 3, 6, 4, 5, 1, 2Fifth scenario (priority with economicsocial issues) locations: 3, 1, 5, 4, 2, 6As shown in most scenarios, pedestals A and D mostly take first to third place. Furthermore, theses pedestals as the best ones catering for all groups’ opinion to underground dam establishment can be offered.