پديد آورندگان :
قنواتي، عزت‌الله نويسنده دانشيار گروه ژيومورفولوژي، دانشكده جغرافيا، دانشگاه خوارزمي , , خضري، سعيد نويسنده , , طالب پور اصل، داود نويسنده دانشجوي دكتراي ژيومورفولوژي، دانشگاه خوارزمي ,
كليدواژه :
انتقال آب بين حوضه اي , ژيومورفولوژي , فرونشست , حوضه رودخانه زاب , درياچه اروميه
چكيده فارسي :
در سال‌هاي اخير تشديد پديده خشكسالي و مديريت نادرست منابع آب، موجب افت شديد تراز آب درياچه اروميه در شمال غرب ايران و بروز پيامدهاي منفي زيست‌محيطي شده است. لذا به‌منظور پيشگيري از بروز چنين مشكلاتي، طرح انتقال آب رودخانه زاب به حوضه آبريز درياچه اروميه در دست مطالعه و اجرا قرارگرفته است. هدف اين مقاله ارزيابي تاثيرات اجراي اين پروژه بر وضعيت مخازن آب زيرزميني دشت پيرانشهر و مورفولوژي زمين در حوضه مبدا مي باشد. داده هاي مورداستفاده شامل تصاوير GDEM ماهواره ASTER باقدرت تفكيك 15 متر، داده هاي اقليمي، آمار مرتبط با هيدرولوژي آب‌هاي سطحي و زيرزميني منطقه موردمطالعه و داده هاي ساختماني و ليتولوژيكي استخراج شده از نقشه زمين‌شناسي 100000/1 مي باشد. همچنين براي تكميل ساير داده ها و انطباق نتايج با وضع موجود، عمليات ميداني انجام‌شده است. روش تحقيق عمدتاً بر پايه روش تحليلي استوار بوده است. نتايج نشان مي دهد كه روند افت تراز آب زيرزميني دشت پيرانشهر در پايين دست سد سيلوه، در دوره پس از انتقال آب به حوضه درياچه اروميه تشديد خواهد شد. به‌طوري‌كه بعد از اجراي پروژه تراز آب زيرزميني تا 92/2 متر كاهش خواهد يافت. پيش بيني مي شود، ازآنجاكه دشت پيرانشهر بر رسوبات جوان آبرفتي مربوط به دوره كواترنر منطبق است، در حاشيه شمالي و غربي دشت كه منطبق بر راس مخروط افكنه ها و رسوبات دانه‌درشت است، نشست زمين به‌صورت ناگهاني و در پايين‌دست دشت كه منطبق بر قاعده مخروط افكنه ها و رسوبات مارن و رس است نشست زمين به‌صورت تدريجي رخ دهد. همچنين ازآنجاكه گسل هاي فراوان ازجمله گسل سراسري زاگرس از جنوب غربي آبخوان پيرانشهر مي گذرد، پيش بيني مي شود نشست زمين و ايجاد شكاف در اين بخش از حوضه تشديد شود.
چكيده لاتين :
Introduction
In recent years, an increased risk of droughts and mismanagement of water resources, leading to a sever loss and the negative environmental consequences in the water level of Urmiain Lake, northwestern of Iran. Therefore, in order to prevent of such problems, the water transfer project from Zab river basin to Urmia Lake has been studied and implemented. In this study of different of point of view and geomorphological perspective has tried to pay off the consequences of loss of water flow in Zab river basin due to the implementation of national project transfer water from the basin to Urmia Lake and its impact on the Zab river ground water reservoirs and morphology of Piranshahr plain.
Methodology
Methodology mainly is based on the analytical method. Data layers in this research are GDEM image of ASTER satellite with 15 m resolution, climatological data, ground and surface water, lithological and structural. In order to evaluate the relation between discharge of Lavin river and groundwater level of Prianshahr plain, applied of different of bivariate regression models. Data layer that used of this relations are discharge (Silveh station) and groundwater level from 20 piezometric wells in period of 12 years (2002-2014). Groundwater mapping of Piranshahr plain were conducted using IDW and the following function in ArcGIS software (Zabihi and et al., 2012);
In the process of selection and verification of regression models to predict the amount of loss of ground water level, was used of relative error (RE), root mean square error (RMSE), coefficient of determine (R2) and coefficient of efficiency (CE) criteria:
Finally, through the assessment of lithological and structural features of Zab basin and field surveys, the area where are prone to land subsidence recognized.
Result and discussion
Result showed that based on the higher of coefficient of correlation (C.C) and CE and RE and less of RMSE, exponential regression equation was selected as the best regression model to predict the loss of ground water level in Piranshahr plain. Results also showed that after implementing of water inter-basin transfer project, the amount of discharge will decrease from 196.39 to 63.89 MCM, as a result of, the ground water level on average about 2.92 m also will decrease and reach to 1426.42 m.
Based on 2.92 meter loss of ground water level, the land subsidence in the region will happen. This result is in agreement with Ranjbar and Jaefari, 1388. Overall, the Piranshahr plain has some alluvial fans where are located in north, northwest and west of it. In one hand, the top of alluvial fans has composed of coarse particles, as a result, the loss of ground water level led to land subsidence as suddenly. On the other hand, the bottom of alluvial fans has covered of clay and marl sediments in the east and south of plain in which land subsidence will happen as gradually. The south and southwest of Piranshahr aquifer is accordance with the Zagros fault by N130E trend. After implementing of project, predicts that at along the Knick line, tensional longitudinal cracks will create due to land subsidence from the side of high lands into the central of plain. What has concerned is the location of Piranshahr city where is located on the knick line. With land subsidence and cracks on the section of plain, the severe damage to the municipal buildings and facilities will impose.
Conclusion
The results showed that the loss of groundwater level in the Piranshahr plain in downstream of Silveh dam, in the period after transferring water into Urmia Lake will be intensified. So that after the implementation of the project the groundwater level will be reduced to 2.92 meters. Since, one of the natural reactions against loss of ground water level is land subsidence; the Piranshahr plain is accordance on new fluvial quaternary sediments. Therefore, predicts that the top of alluvial fans has composed of coarse particles at north and west of plain, the loss of ground water level led to land subsidence as suddenly and downstream of plain that is located on the bottom of alluvial fans (mainly clay and marl sediments), land subsidence will happen as gradually. Also, with respect to frequency of faults such as Zagros, predicts that the land subsidence and cracks at southwest of Piranshahr aquifer, increases.
