ارزیابی تاثیر تغییرات اقلیمی بر کیفیت آب با بهره‌گیری از روش‌های آماری و WQI | ||
| منابع آب و تغییر اقلیم | ||
| دوره 1، شماره 2، تیر 1404، صفحه 1-10 اصل مقاله (954.68 K) | ||
| نوع مقاله: مقاله پژوهشی | ||
| شناسه دیجیتال (DOI): 10.22091/wrcc.2025.12775.1011 | ||
| نویسندگان | ||
| منیژه پورعلی دوگاهه* 1؛ سید محمد شعاعی2 | ||
| 1دانشجوی دکتری، گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه زنجان، زنجان، ایران. | ||
| 2گروه مهندسی عمران، دانشکده فنی و مهندسی، دانشگاه زنجان، زنجان، ایران. | ||
| چکیده | ||
| ارزیابی کیفی منابع آب با استفاده از شاخص‌های کیفی، روشی مؤثر برای مدیریت پهنه‌های آبی و حفاظت از کیفیت منابع آب است. از گذشته، رودخانه‌ها به‌عنوان تأمین‌کنندگان اصلی آب شرب و کشاورزی، نقش مهمی در شکل‌گیری تمدن‌ها ایفا کرده‌اند. در طول نیم قرن گذشته، وضعیت آب‌شناسی رودخانه‌ی دربند که دومین رود پرآب تهران است، به‌دلیل افزایش جمعیت و توسعه‌ی شهری تهران، تحت تأثیر قرار گرفته است. این پژوهش، با هدف ارزیابی کیفیت آب رودخانه دربند در حال حاضر و پیش‌بینی آن برای دوره آتی و تحت سناریوهای RCP انجام پذیرفته است. در این پژوهش داده‌های ماهانه بارش، دما، سختی، TDS، EC، PH، SO4طی دوره آماری 2005-1988 با استفاده از شاخص کیفیت آب (WQI) تحلیل شد. برای بررسی تاثیر تغییرات اقلیمی بر کیفیت آب رودخانه، بین پارامترهای دبی و پارامترهای کیفیت آب روابط رگرسیونی برقرار شد و با توجه به پیش‌بینی انجام‌شده برای دبی در دوره 2047-2030، شرایط کیفیت آب باWQI تحت سه سناریوی RCP2.6، RCP4.5، RCP8.5 محاسبه شد. نتایج بررسی‌های نشان دادند که میانگین بلندمدت سالانه بارش در آینده نسبت به دوره پایه بهازای سناریوی RCP 8.5 بیشترین کاهش را داشت. از طرفی کم‌ترین کاهش میانگین بلندمدت سالانه بارش در آینده نسبت به دوره پایه بهازای سناریوی RCP 4.5 خواهد بود. کیفیت آب رودخانه در دوره زمانی پایه و آینده در شرایط مطلوبی قرار دارند. | ||
| کلیدواژه‌ها | ||
| شاخص کیفیت آب؛ پارامترهای کیفیت آب؛ تغییر اقلیم؛ سناریوهای RCP؛ گزارش پنجم ارزیابی IPCC | ||
| عنوان مقاله [English] | ||
| Assessment of the impact of climate change on water quality using statistical methods and WQI | ||
| نویسندگان [English] | ||
| Manizheh Pourali Dougaheh1؛ Seyyed Mohammad Shoaei2 | ||
| 1Ph.D. Student, Department of Civil Engineering, Faculty of Engineering, University of Zanjan, Iran. | ||
| 2Department of Water and Hydraulic Structure Engineering, Faculty of Engineering, University of Zanjan, Iran. | ||
| چکیده [English] | ||
| Abstract Objective: Qualitative assessment of water resources using water quality indices is an effective approach for managing aquatic systems and protecting water quality. Historically, rivers have played a fundamental role in the development of human civilizations as primary sources of drinking and agricultural water supply. Over the past half-century, the hydrological conditions of the Darband River, the second most perennial river in Tehran, have been significantly affected by population growth and urban expansion. This study aims to assess the current water quality of the Darband River and to predict its future status under different Representative Concentration Pathway (RCP) scenarios. Method: In this study, monthly data on precipitation, temperature, total hardness, total dissolved solids (TDS), electrical conductivity (EC), pH, and sulfate (SO₄²⁻) for the period 1988-2005 were analyzed using the Water Quality Index (WQI). To evaluate the impacts of climate change on river water quality, regression relationships were established between discharge and water quality parameters. Based on projected river discharge for the future period 2030–2047, the WQI values were calculated under three climate change scenarios, namely RCP2.6, RCP4.5, and RCP8.5. Results: The results indicate that the largest reduction in long-term mean annual precipitation in the future period, relative to the baseline, occurs under the RCP8.5 scenario, whereas the smallest reduction is associated with the RCP4.5 scenario. Conclusion: Overall, the findings demonstrate that the water quality of the Darband River remains within acceptable and desirable conditions during both the baseline and future periods across all considered scenarios. English Extended Abstract Introduction Water quality assessment using quality indices effectively manages aquatic systems and safeguards water resource quality. Historically, rivers have played a crucial role in supplying drinking and agricultural water, contributing significantly to the formation of civilizations. Over the past half-century, the hydrological conditions of the Darband River, Tehran's second-largest river in terms of discharge, have been impacted by population growth and urban development in Tehran. This study aims to evaluate the current water quality of the Darband River and forecast its future condition under RCP scenarios. Monthly data on precipitation, temperature, hardness, TDS, EC, PH, and SO4 from 1988–2005 were analyzed using the Water Quality Index (WQI). To examine the impact of climate change on river water quality, regression relationships were established between discharge parameters and water quality indices. Based on predicted discharge during the 2030–2047 period, water quality conditions under WQI were calculated for three scenarios: RCP2.6, RCP4.5, and RCP8.5. Statistical analyses revealed that the river's water quality in both the baseline and future periods is expected to remain in favorable conditions. Method This section discusses the various stages of the research process. After collecting baseline information and data for the Darband River basin (located in Tehran), the performance of climate models from the Fifth Assessment Report of the IPCC is evaluated. To assess the performance of these climate models, simulated climate variable results for the study area during the 17-year baseline period (1988–2005) are compared with observed recorded data. For this purpose, statistical error metrics, including Root Mean Square Error (RMSE), Mean Absolute Error (MAE), Nash-Sutcliffe Efficiency (NSE), and the correlation coefficient (r), were employed. Subsequently, to utilize the output of AOGCM models in simulating qualitative climate variables for future periods, their computational grid cells, which are spatially coarse for the region, need to be downscaled to the station level. In this study, the Change Factor (CF) method was used for downscaling due to its simplicity, computational efficiency, and resulting savings in time and cost. The CF method calculates the climate change scenario based on the ratio of the long-term averages simulated by AOGCMs for the climate change period to the long-term averages simulated for the baseline period. Finally, variations in water quality for both the baseline and future periods will be analyzed using the Water Quality Index (WQI). To examine changes in water quality using WQI, relevant parameters must first be measured, followed by the calculation of the WQI using a mathematical formula typically involving weighted contributions from each parameter. WQI computation will be conducted after collecting data, which includes parameters such as DO, BOD, turbidity, total suspended solids (TSS), nitrate, phosphate, pH, temperature, and fecal coliform. Results Based on the results obtained from evaluating the performance of AOGCM models in estimating precipitation and temperature in the region, the NSE for both climate variables is close to 1, indicating the successful simulation of climate variables by these models. To calculate future climate change scenarios for precipitation and temperature during the 2030-2047 period relative to the baseline period (1988-2005), GFDL-ESM2G and MIROC ESM-CHEM models were employed under RCP 2.6, RCP 4.5, and RCP 8.5 scenarios, respectively. The results indicated that all scenarios (except for RCP 2.6) show a decrease in the long-term annual mean precipitation in future years compared to the baseline period. The greatest long-term annual mean precipitation reduction is projected under the RCP 8.5 scenario. Similarly, all scenarios suggest an increase in the long-term annual mean temperature in future years compared to the baseline. The most significant increase in long-term annual mean temperature is anticipated under the RCP 8.5 scenario. The relationships between water quality parameters and climate variables, including temperature and precipitation, were examined during the baseline period. The results revealed an inverse relationship between precipitation and EC, TDS, and SO4. Additionally, the impact of rising temperatures on water quality is negative. Regarding pH, higher maximum and minimum temperatures, along with increased evaporation, indicate elevated concentrations of dissolved solids in surface waters, thereby negatively affecting this parameter. However, precipitation has a positive relationship, as increased river discharge compensates for the negative impacts of temperature. Subsequently, water quality parameters during the future period were analyzed. The investigations revealed that observed changes are directly influenced by variations in climatic factors, particularly precipitation and, consequently, river discharge. Furthermore, the baseline water quality is in good condition, and projections indicate that under all three scenarios, water quality will also remain in good condition. One key reason for this is the anticipated increase in precipitation and the river's self-purification capacity in future years. Conclusion Projections under various RCP scenarios indicate that despite a relative decrease in precipitation in the future compared to the baseline period, particularly under RCP 8.5, air temperatures are expected to rise significantly. These climatic changes directly impact river systems, as observed in the Darband River basin, where variations in precipitation and temperature influence hydrological dynamics and water quality parameters. Analyses also point to critical links between climatic variables and water quality. Increased precipitation leads to reduced concentrations of dissolved solids in surface waters due to enhanced discharge and dilution capacity. On the other hand, rising temperatures, while triggering snowmelt and increasing discharge, can degrade water quality through evaporation and increased concentrations of dissolved solids, as observed in parameters such as EC, TDS, and pH. Nevertheless, WQI assessments reveal that the water quality of the Darband River remains categorized as "good" both under baseline conditions and future scenarios. This condition is largely attributed to the river's natural self-purification capacity and relative increases in precipitation during certain future periods. | ||
| کلیدواژه‌ها [English] | ||
| Water Quality Index, Water Quality Parameters, Climate Change, RCP Scenarios, IPCC Fifth Assessment Report | ||
| مراجع | ||
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