ارزيابي ويژگي‌هاي هيدروديناميكي آبخوان‌هاي كارستي با استفاده از آناليز سري‌هاي زماني(مطالعه موردي آبخوان‌هاي كارستي گيلانغرب و خورين در استان كرمانشاه)

Karst Aquifers Hydrodynamic Characteristics Assessment by Using Time Series Analysis (Case Study: Gilangharb and Khorin Karst Aquifers- Kermanshah Province)

آبخوان‌هاي كارستي داراي ناهمگني بالا و تنوع فضايي از نظر توسعه كارست بوده، كه اين امر واكنش آبخوان‌هاي كارستي به ورودي و تغييرات آن در سيستم كارستي را كنترل مي‌كند. ژيومورفولوژي كارست با تعيين نوع و ميزان تغذيه، واكنش آبخوان ها را به بارش كنترل مي كند. ارزيابي سري هاي زماني ورودي و خروجي در سيستم هاي كارستي اطلاعات جامعي را در زمينه رفتار هيدروديناميكي آبخوان ها ارايه مي دهد. هدف از اين پژوهش ارزيابي و شناخت ويژگي هاي هيدروديناميكي آبخوان هاي گيلانغرب و خورين با استفاده از توابع خودهمبستگي و چگالي طيفي و مشخص كردن عوامل موثر در ويژگي هاي هيدروديناميكي آبخوان ها است. در اين پژوهش از داده‌هاي دبي و بارش ايستگاه‌هاي هيدرومتري و بارانسنجي وزارت نيرو جهت محاسبه تحليل سري‌هاي زماني تك متغيره و آناليز منحني فرود هيدروگراف استفاده شده است. نتايج نشان داد سيستم كارستي آبخوان خورين نسبت به آبخوان گيلانغرب توسعه يافته تر است. آبخوان خورين داراي رفتار هيدروديناميكي چندگانه و اينرسي كم و آبخوان گيلانغرب داراي رفتار هيدروديناميكي نسبتا پايدار و اينرسي بالا مي باشد. معادله منحني فروكش در آبخوان خورين، چندگانگي رفتار سيستم كارستي را نشان داده و نتايج بدست آمده از توابع سري زماني را تاييد مي كند. اما معادله منحني فروكش هيدروگراف در چشمه گيلانغرب وجود جريان سريع در آبخوان را كه توسط توابع سري زماني نشان داده، تاييد نمي كند. توسعه ژيومورفولوژي كارست سطحي و وجود فروچاله ها عامل اصلي رفتار هيدروديناميكي چندگانه در آبخوان خورين مي باشد. نبود فروچاله ها و توسعه كم ژيومورفولوژي كارست و ويژگي هاي فيزيوگرافي همچون كشيدگي حوضه تغذيه كننده آبخوان گيلانغرب باعث نوسان كم در رفتار هيدروديناميكي آبخوان گيلانغرب گرديده است. در نهايت مي توان گفت كه توابع سري زماني كاركرد قبل قبولي در ارزيابي رفتار هيدروديناميك آبخوان هاي كارستي دارند.

Introduction Karst systems structure is complicated and the relationship between its components is heterogeneous (JEMCOV and PETRI?, 2010). Karst development level is the reason of hydraulic conductivity heterogeneity in karst aquifers (Manjin 1985). Padilla and Pulida-Bosch Believe that it is difficult to do the hydrogeological studies due to environment heterogeneity and complexity in karst systems. Time series can use the exiting data, less time usage and cheapness. In addition, time series present useful data about time model, hydrological process variability and pressure response characteristics in karst aquifers(Duffy and Gelhar;1986). Recognition of spring discharge spatial-time variability in karst systems results in hydrologic processes and aquifer structure recognition, water consumption management and aquifer vulnerability of aquifer to pollutants (Liu et al, 2011). Time series analysis by using single variable method specifies the particular structure of hydrograph (Goldscheiderand Drew, 2004) and the cyclic changes. Karst water resources are the main water supply resources in Kermanshah province. Karst water resources play a critical role in formation and continuity of civilization in Kermanshah. So hydrodynamic features recognition of karst aquifers has an important role in province policy making in order to have a water resource optimal management in terms of quantity and quality. The aim of this study is to assess the hydrodynamic characteristics and to recognize the effective factors in hydrodynamic behavior of karst aquifers in Gilan Qarb and khor by using time series analysis with emphasis on karst geopmorphological features. Methodology This study is a developing-functional study based on library methods, site visits, autocorrelation analysis, spectral density and hydrograph recession curve analysis. In this study, discharge, hydrometric stations rainfall and pluviometry data of Energy Department have been used. The presented method is based on Karimi et al method (2003) which has been used to calculate the area of spring catchment. Hydrograph recession curve analysis has been used to assess the flow type system in karst aquifers. Finally the obtained results from time series analysis, obtained result from hydrograph recession curve analysis and geomorphologic characters of aquifer karst have been assessed and the hydrodynamic characters of the aquifer have been identified. Results and Discussion The charge type of case study aquifer is autogenic. The area of the Gilangharb and Sabzali catchments are respectivelt 101 and 41 square kilometer (Table 2). discharge coefficient of variation in Gilangharb is 1.38 and in sabzali spring it’s 4. Springs water type is bicarbonated. Conclusion The results show that Khorin aquifer has multiple hydrodinamic behavior and low inertia. It also represents that Gilangharb aquifer has a relatively stable hydrodinamic behavior and high inertia. The comparison between the autocorrelation function ans spectral density show the developement of Khorin aquifer karst system compared to Gilangharb aquifer. Decline curve equation in Khorin aquifer shows the multiplicity in karst system behavior and confirms the obtained result from time series but hydrograph decline curve of Gilangharb doesn’t confirm the rapid flow in the aquifer which has been showed by time series before the analysis. This is due to the stretch of Gilan gharb feeding basin. Surface geomorphologic development has an important role in aquifers hydrodynamic behavior. Surface geomorphologic karst development and sinkholes are the main reasons of multiple hydrodynamic behaviors in Khorin aquifer. Absence of sinkholes, low development of karst geomorpholy and Gilangharb feeder basin physiographic features are the reasons of low swing in Gilangharb aquifer hydrodynamic behavior.