ارزیابی کارایی روش‌های شتاب‌دهنده یادگیری ماشین به‌منظور تخمین شاخص کیفی آب رودخانه زاینده‌رود

نوع مقاله : مقاله پژوهشی

نویسندگان

گروه علوم و مهندسی آب، دانشکده کشاورزی، دانشگاه صنعتی اصفهان، اصفهان، ایران

چکیده

باتوجه‌به پدیده تغییر اقلیم، گرمایش کره زمین و کاهش منابع آب، کیفیت آب‌های سطحی به‌عنوان یکی از مهم‌ترین منابع آبی در جهان مورد توجه مهندسین رودخانه قرار دارد. ازآنجاکه پرکاربردترین شاخص سنجش کیفیت آب شاخص WQI است؛ هدف و اهمیت این تحقیق مدل‌سازی شاخص کیفیت آب به کمک دو روش شتاب‌دهنده یادگیری ماشین Gradient Boosting و XGBoost در رودخانه زاینده‌رود انجام‌گرفته است. در این تحقیق ابتدا بر اساس داده‌های کیفیت آب، شاخص کیفیت آب (NSFWQI) محاسبه، و در ادامه به‌منظور مدل‌سازی، از داده‌های ورودی شامل ویژگی‌های کیفی آب ۸ ایستگاه در یک دوره ۳۱ساله و همچنین شاخص کیفیت آب محاسبه شده رودخانه استفاده شد. در این تحقیق برای مدل‌سازی در محیط برنامه‌نویسی پایتون کدنویسی شده، و در مرحله آموزش ۸۰ درصد داده‌ها و در مرحله ارزیابی ۲۰ درصد باقی‌مانده مورد استفاده قرار گرفت. بر اساس نتایج معیارهای ارزیابی ضریب تعیین R2، میانگین قدرمطلق خطا MAE، حداکثر خطا ME، میانگین مربعات خطا MSE، جذر میانگین مربعات خطا RMSE و جذر میانگین مربعات خطای نرمال‌شده NRMSE  مدل بهینه انتخاب شد. نتایج تحقیق نشان داد که در تمام ایستگاه‌ها به جز یک ایستگاه از بین مدل‌های استفاده شده، مدل GB باتوجه‌به معیارهای ارزیابی مدل عملکرد بهتری نسبت به مدل XGBoost برخوردار بوده است. همچنین نتایج نشان داد که برای صرفه‌جویی در زمان و هزینه و همچنین مدیریت بهینه ویژگی‌های کیفیت آب، انتخاب سری شماره ۳ که در آن از سه ویژگی به‌منظور برآورد شاخص کیفیت آب (WQI) استفاده می‌شود، بهترین ترکیب بوده است.

کلیدواژه‌ها

موضوعات


عنوان مقاله [English]

Evaluation the efficiency of machine learning boosting methods for estimating the water quality index of the Zayandeh Rood River

نویسندگان [English]

  • Elham Fazel Najafabadi
  • Mohammad Shayannejad
Department of Water Science and Engineering. College of Agriculture, Isfahan University of Technology, Isfahan, Iran
چکیده [English]

Regarding climate change, global warming, and the reduction of water resources, surface water quality is of great interest to river engineers as surface water is one of the most important water resources in the world. Since the most widely used water quality index is the WQI index, the goal and importance of this research are to model the WQI using two machine learning boosting methods in the Zayandeh Rood River, Gradient Boosting and XGBoost. First, based on water quality data, the water quality index (NSFWQI) was calculated, and then, for modeling, input data including water quality characteristics of 8 stations over 31 years and the calculated WQI were used. In this study, the model was coded in the Google Colab environment, and 80% of the data was used in the training phase and the remaining 20% in the evaluation phase. Based on the results of the evaluation criteria of coefficient of determination (R2), mean absolute error (MAE), maximum error (ME), mean square error (MSE), root mean square error (RMSE), and normalized root mean square error (NRMSE), the optimal model was selected. The results of the study showed that in all stations except one station among the models used, the GB performed better than the XGBoost according to the model evaluation criteria. The results also showed that to save time and cost, and also to optimally manage water quality characteristics, the selection of the number 3 series, in which three characteristics are used to estimate the WQI, was the best combination.

کلیدواژه‌ها [English]

  • Water quality characteristics
  • Zayandeh Rood River
  • Machine learning models
  • GB
  • XGBoost

EXTENDED ABSTRACT

 

Introduction

With the increase in population and the decrease in water resources, the pollution of water resources, especially surface water resources, has received more and more attention. The most widely used water quality index is NSFWQI, which has been used and studied in numerous studies (Mahrouyan et al. 2021, Zamani-Ahmadmahmoodi et al. 2021, Aghaee et al. 2020, Khalife and Khoshnazar 2018). Since several quality parameters affect this index, the estimation and calculation of this index have always faced challenges. With the advancement of metadata science and artificial intelligence, the use of machine learning models can be useful in accurately estimating the water quality index, especially when limited data is available. In research, various machine learning methods have been used to provide an optimal model for estimating the water quality index, including Khoi et al. (2022), Rahaman et al. (2024), Lin et al. (2024), and Palabıyık and Akkan (2024) noted. Considering that the Zayandeh Rood River is vital in the central plateau of Iran, it is important to detect and estimate its water quality index. Also, given the unavailability of some data at some stations, the present study can be a solution to this problem by examining the ability of two algorithms, Gradient Boosting and Extreme Gradient Boosting, in estimating the water quality index (WQI).

Method

This research was conducted on 8 stations of the Zayandeh Rood River. The dataset used in this study included water quality data from 8 stations: Shahrokh Castle, Zayandeh Rood Dam, Zamankhan Bridge, Cham-Aseman Dam, Kaleh Bridge, Diziche, Lanej, and Musian, measured monthly over 31 years (1991 to 2022). These data included (EC), (TDS), (pH), (TH), (Cl-), (Mg2+), (Na+), (Ca2+), (SO42-), and (HCO3-) as target features for estimating the water quality index (WQI). To calculate the water quality index in this study, the NSFWQI index was used, which is one of the first and most widely used indices for the overall assessment of water quality status (Alexakis et al. 2016, Sutadian et al. 2016) and is classified into five classes: very bad, bad, moderate, good, and excellent. In this study, Machine learning models (GB and XGBoost) were used to predict the water quality index (WQI) based on selected features, and coding was done in Google Colab using the Python programming language. The evaluation criteria for presenting the best model were R2, MAE, ME, MSE, RMSE, and NRMSE. Uncertainty analysis and cross-validation analysis were also performed.

Results

Since different water quality variables do not contribute equally to forming WQI values, it is possible to identify several determinant variables that reflect the water quality status without losing key information. In this study, the importance of the variables was identified by the SHAP method. Based on this analysis, the importance of the variables was obtained as follows: EC, TDS, TH, pH, HCO3-, Mg2+, SO42-, Cl-, Na+, and Ca2+. Based on this arrangement, six series were defined, and the aforementioned models were used for these series to estimate the water quality index. The results of this study showed that in 7 stations, the GB model, and in only one station, the XGB model, is recommended for estimating the water quality index. Also, among the defined series, series number 3 has the highest frequency in different stations as the optimal series, and this series can be introduced as the recommended series. In this series, three parameters have been used to estimate the water quality index. Comparison with previous research showed that Ejaz et al. (2024) and Sidek et al. (2024) also introduced the GB model as the best model for estimating water quality index in their research. The commonality of the mentioned research with the present research was the use of anions such as Cl-, cations such as K+, and features such as TDS and pH.

Conclusions

In this study, two augmented machine learning models were used to estimate the NSFWQI water quality index. The findings of this study showed that the GB algorithm performed best at seven stations. The coefficient of determination was in the range of 0.999-0.802, and the RMSE index was in the range of 0.112-0.201. The results of the feature importance analysis showed that the features EC, TDS, TH, and HCO3- were the most important, respectively. The study of different series introduced three key features, EC, TDS, and TH, in predicting the water quality index. Therefore, since the goal of artificial intelligence is to reduce time and cost in studies, by replacing 3 features instead of 10 features, a proper prediction of the Water Quality Index (WQI) can be achieved. The findings of this study will help water managers and policymakers in efficiently calculating water quality indices for rivers and streams. This is achieved by reducing computational time, lowering costs, and monitoring polluted stations. However, it is important to acknowledge several limitations of this study, primarily related to the selection of physicochemical variables and limited sampling locations. The research can be expanded with a larger number of sampling locations and a wider range of physicochemical variables to predict the water quality index of the Zayandeh Rood River.

Author Contributions

“Conceptualization, E.F. and M.Sh.; methodology, E.F.; software, M.Sh.; validation, E.F., M.Sh.; formal analysis, E.F.; investigation, E.F.; resources, E.F.; data curation, E.F.; writing—original draft preparation, E.F.; writing—review and editing, M.Sh.. All authors have read and agreed to the published version of the manuscript.”

Data Availability Statement

Data available on request from the authors

Ethical considerations

The authors avoided data fabrication, falsification, plagiarism, and misconduct.

Conflict of interest

The author declares no conflict of interest.

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