Review Reports - Implications of Water Quality Index and Multivariate Statistics for Improved Environmental Regulation in the Irtysh River Basin (Kazakhstan)

Round 1

Reviewer 1 Report

Comments and Suggestions for Authors

I find the article interesting and the content relates to contemporary water quality issues. The authors presented interesting research supported by a long series of detailed measurements. The whole was enriched with extensive sets of tables. I recommend the article for publication after taking into account the following comments.

1. Please change the order of the figures. The reader should first learn the location of the area in question and only then more detailed information (such as flow rate).

2. Methodology of sampling and their further analysis is described too generally. Please expand this thread.

3. How did the methodology of pollution measurements change over the analyzed period - I assume that a different equipment (accuracy) was conducted in 2011 and a different one in 2020. How does this affect the results obtained?

4. The authors refer to the role of flooding in the context from changes in water quality. Another element is ice phenomena, which isolate water from external factors for a certain period. Please clarify these issues in relation to the research conducted.

5. The numbering of the chapters is incorrect: 3. Results and Discussion, 5. Conclusions. Chapter number 4 is missing.

6. Subchapter 3.4 Discussion is disproportionately short against the background of widely described results. In addition, it should be more expanded with references to other studies conducted on similar topics. Currently, I only find there a citation to five studies.

Author Response

The authors highly appreciate the reviewer for all the time and efforts spent to comment on and improve the manuscript. We have revised the manuscript accordingly, considering the suggestions from the reviewer. Below are answers to the comments and description of actions taken: The black text is comments from the reviewer, and the Red text is our response. Changes in the revised manuscript are also highlighted by Red.

Please change the order of the figures. The reader should first learn the location of the area in question and only then more detailed information (such as flow rate).

Thank you very much for your suggestion. The respective changes have been made with the improvement of the study area map.

Methodology of sampling and their further analysis is described too generally. Please expand this thread. and 3. How did the methodology of pollution measurements change over the analyzed period - I assume that a different equipment (accuracy) was conducted in 2011 and a different one in 2020. How does this affect the results obtained?

Thank you for your questions. Unfortunately, the data provider has not supplied all the details concerning the sampling and analysis methodology. However, the government ensures quality assurance and quality control procedures are in place. This is evidenced by the east-Kazakhstani branch of “Kazhydromet” pursuing accreditation and control from the International Laboratory Accreditation Cooperation (ILAC) (https://ilac.org/). While the methodology itself hasn’t undergone significant changes, there has been a replacement of equipment with instruments of similar characteristics. The inclusion of the new sub-section of the results dedicated to the analysis of seasonal patterns demonstrates that temporal variations remained consistent. Therefore, the results likely remained unaffected throughout the observation period.

The authors refer to the role of flooding in the context from changes in water quality. Another element is ice phenomena, which isolate water from external factors for a certain period. Please clarify these issues in relation to the research conducted.

Thank you for your suggestion. It has been considered and the following text has been added to the sub-section 3.1 Cold seasons (Lines 338-348):

“Figure 5 illustrates the spatial distribution of the Water Quality Index (WQI) within the study area during cold seasons. The key characteristic of the season is river ice covering, which represents a dynamic element in freshwater ecosystems, influencing water quality through various physical and biogeochemical processes [36]. While ice cover can offer temporary benefits, its impact on water quality is multifaceted. Reduced sunlight penetration resulting from the ice cover restricts the primary production by phytoplankton, leading to a decrease in dissolved oxygen levels in the water column [37]. This oxygen depletion can stress aquatic organisms, especially during prolonged periods of ice cover. Moreover, certain pollutants may become concentrated in the unfrozen water as they are excluded during ice crystal formation, posing a particular concern for contaminants with high water solubility [38].”

The numbering of the chapters is incorrect: 3. Results and Discussion, 5. Conclusions. Chapter number 4 is missing.

Thank you for your careful reading. The issue has been fixed.

Subchapter 3.4 Discussion is disproportionately short against the background of widely described results. In addition, it should be more expanded with references to other studies conducted on similar topics. Currently, I only find there a citation to five studies.

Thank you for your suggestion. Now, the discussion section has been expanded, highlighting the impact and response to mining activities in the region, the state of the operation of domestic wastewater treatment facilities, and legislative measures to mitigate the existing risks. Lines 623-690 present the revised text as follows:

“This study highlights the significant impact of mining activities and inadequately treated domestic wastewater on the water quality of tributaries within the Irtysh River Basin. The study underscores the necessity of paying close attention to the potential transfer of toxic elements, as highlighted in a review by Babuji et al., which identifies hazardous substances such as Co, Cu, Mn, Pb, Se, Ni, V, and Zn that can migrate to soils and subsequently enter plants, particularly vegetables [39]. This suggests a critical consideration, especially as the river inundates the floodplain during the spring period, exacerbating water quality issues in the main water body and potentially leading to floodplain contamination in the Basin [40]. Moreover, these elements remain at high concentrations even nowadays, according to the annual bulletin from Kazhydromet [41]. Regrettably, the bulletin fails to clarify the proposed sources of extreme concentrations, offering only a broad reference to the “main attribution to emissions from technological production and the impact of the unique soil composition in the area”. Therefore, Tileugabulov and Madani refer to the active and closed tailings storage facilities as the driving surface water contamination sources since the 1960s [42].

The findings demonstrated a significant impact of ore mining activities on the water quality within the Basin. In 2021, mining companies in Ridder extracted over 17,000 tonnes of zinc and 1,300 tonnes of lead. Production figures for raw materials in the region included over 110,000 tonnes of zinc and 155,000 tonnes of lead produced in Ust-Kamenogorsk, alongside over 107,000 tonnes of raw lead and 55,000 tonnes of copper [43]. Being large taxpayers, mining enterprises within the region might benefit from the prevalence of the Entrepreneurial Code over the Ecological Code. Industrial inspections were conducted every six months, with companies receiving advance notice of at least thirty calendar days [44]. This prior notification allowed facilities to undertake corrective actions in the short term to achieve compliance during the inspection. There is only one known study focused on the water management of a mining company operating in the region. [30]. Despite the company’s increasing water intake, a significant rise in freshwater withdrawal was also identified. The company's withdrawals exceeded their government-issued water permit by up to 30%. This discrepancy underscores the outdated water allocation standards used by governmental bodies, failing to adapt to advancements in mining technology and the growing water demands. The authors recommended that government bodies adopt specialized mining discharge regulations that can progressively mitigate the environmental impact of mining on both water quality and quantity. Additionally, climate change poses a threat to mining industries in the region by affecting water supply and management through changes in precipitation patterns and temperature extremes [45]. This further exacerbates the existing challenges to water quality in the studied region.

Another concern comes from the impact of domestic wastewater treatment facilities. The study [46] claimed that most of the Kazakhstani small settlements rely solely on basic treatment facilities (mechanical and natural systems) that are often outdated and in poor condition, designed and built in the 1960s and 1980s. Moreover, according to a study by Karataev et al., only a small percentage (7%) of industrial wastewater and sewage underwent full treatment before being released back into waterways [5]. This might lead to excessive loads of organic pollutants and biogenic compounds. Thus, these facilities are not operating properly and are likely discharging poorly or even untreated wastewater, with human health [47] and environmental threats [48] consequences.

Until recently, water management practices in Kazakhstan have suffered from a lack of science-based approaches at both governmental and industrial levels. There is an emergency for detailed characterization of wastewater, combined with the implementation of new environmental monitoring tools, such as contamination transport models, can empower environmental agencies to effectively assess and control the impact of industrial activities and associated risks [49]. The implementation of permanent monitoring stations, mandated by the Ecological Code, requires enterprises to maintain automated “real-time” monitoring systems for emissions and pollutant discharges at contamination sources. This data must be recorded and directly transmitted to a government regulatory body [50]. The findings of this study can serve as a guide for installing such monitoring equipment in crucial areas, particularly near the confluence of the Ulba, Tikhaya, and Breksa rivers (based on mining company data), and at locations with outdated wastewater treatment facilities (Krasnoyarka and Glubochanka rivers).

Another critical aspect requiring attention is the continuous update of the list of substances subjected to operational control. While environmental monitoring in developed countries ensures environmental safety and aligns with principles of sustainable development, leading to robust monitoring systems, Kazakhstani industries have often resisted such changes. For instance, there has been industry pushback against the inclusion of sensitive indicators in the list of monitored parameters [49]. These legislative loopholes have historically allowed polluting industries to further contaminate already compromised sites and water bodies. In line with recent legislative updates, it is imperative to prioritize identified hot zones as the primary areas for remediation and restoration efforts in the region.”

Author Response File: Author Response.pdf

Reviewer 2 Report

Comments and Suggestions for Authors

The paper reports the water quality indices of the Irtysh River Basin (Kazakhstan) using the data from twenty six stations. Despite being well-written, the paper is merely a report of different factors with no specific application. Here, I listed some of the main issues of the paper. However, considering these issues, It can be recommend it for publication (Major).

1. The paper has no clear goal. It only collected the reports of the water quality parameters Irtysh River Basin (Kazakhstan) as previously published.

2. The abstract is too vague not presenting the key results.

3. Relation between WQI and assigned quality scale for each parameter in terms of regression diagrams may be developed which may help for indicating contribution of quality scale to WQI.

4. A Two-way ANOVA (P < 0.05) analysis is important to distinguish inter-annual and inter-station variation.

5. Improve the Map (Color) of the River basin and twenty six sites used in analysis.

6. Study area map is not clear and it should be topographical map with detail description.

7. Methodological flow chart of the of River data analysis may be given

8. Trend analysis may be important for this study to see the decadal changes in water quality

9. Analyze and discuss the water quality parameters with their standard acceptable limit.

10. The sources of pollution need justification and explanation.

11. How do anthropogenic factors and natural characteristics influence the river water quality: please explain in the discussion section

12. The reliability of the results is very much lowered and the reader has very difficulty in understanding presented results

13. Most of the values are reported upto three decimal after point. Is it required?

14. Some of these parameters (and every two sets of parameters), may have high or low correlations. The authors should mention what the aim of this correlation study is.

15. The paper's central idea is not novel, and the manuscript does not present any new scientific findings. The manuscript is distinguished by a lack of novelty and a gap in current knowledge: Please include the novelty of the study.

Comments on the Quality of English Language

Extensive editing of English language required

Author Response

The paper has no clear goal. It only collected the reports of the water quality parameters Irtysh River Basin (Kazakhstan) as previously published.

Thank you for your comment. We acknowledge the need to provide a clearer articulation of our research objectives. While water quality assessment is a central component of this study, it serves as a means to a larger goal. Our primary objective is to leverage the assessment findings to inform the development of updated environmental regulations. This will involve highlighting the identified locations and activities of major water polluters, along with their impact on the overall water quality of the Basin. The text has been revised throughout the whole manuscript, including parts of the Intro section, including Lines 96-110:

“While natural purification processes generally maintain satisfactory water quality along the main course of the River, it is essential to prioritize water quality assessments in tributaries, particularly in areas vulnerable to contamination. Current assessment methods and monitoring procedures for the Basin exhibit inefficiencies, leading to an inadequate understanding of the present state and necessitating a reevaluation. Implementing standardized monitoring and evaluation protocols throughout the basin would enable a more equitable and objective evaluation of regional challenges, facilitating targeted remediation efforts. Furthermore, analyzing historical and contemporary water quality data is crucial for effective river management and contamination risk mitigation. This analysis provides a critical baseline for identifying trends, potential pollution sources, and the effectiveness of existing and suggested management practices [13]. A comprehensive understanding of past and present water quality supports proactive environmental management strategies that safeguard these vital ecosystems. Additionally, there is a significant research gap concerning persistent organic pollutants, pesticides, pharmaceuticals, microplastics, and analogous contaminants in the basin’s water bodies.”;

and Lines 129-138: “This work is dedicated to a comprehensive assessment of the health status of the Irtysh River Basin in its East-Kazakhstani part. The authors aimed to pinpoint hotspots and sources of pollution that exert the most substantial influence on water quality in both the mainstream and tributaries of the River. For this purpose, a ten-year dataset of measurements encompassing 26 chemical components at 26 observation points was analyzed utilizing the Water Quality Index (WQI), Geographic Information Systems (GIS), and multivariate statistical tools. The central idea of this study is to uncover specific areas with low water quality and to identify particular sources of contamination that will be targeted for improved environmental regulation in alignment with the updated ecological legislation of Kazakhstan.”.

The abstract is too vague not presenting the key results.

Thank you for your comment, which we have considered. Now the abstract has been revised and now looks as follows (Lines 17-43): “The selection of sites for permanent environmental monitoring of natural water bodies should rely on corresponding source apportionment studies. Tools like the water quality index (WQI) assessment may support this objective. This study focuses on analyzing a decade-long dataset of measurements of 26 chemical components at 26 observation points within the Irtysh River Basin, aiming to identify priority zones for stricter environmental regulations. The WQI tool, integrated with geoinformation systems (GIS) and multivariate statistical techniques, was used in this analysis. The findings highlighted that both upstream sections of tributaries (Oba and Bukhtarma rivers) and the mainstream of the basin are generally in good condition, with slight fluctuations observed during flooding periods. Areas in the basin experiencing significant impacts from mining and domestic wastewater treatment activities were identified. The rivers Glubochanka and Krasnoyarka consistently experienced marginal water quality throughout the observation period. Various contaminant sources were found to influence water quality, with domestic wastewater treatment facilities showcasing elevated levels of chemical oxygen demand (twice the standard), natural factors leading to calcium excess (two-fold the threshold), and mining operations introducing trace elements like copper (exceeding reference limits by 12-13 times at peaks), zinc (exceeding the set limit of 0.03 mg per L by almost 50-100 times), and cadmium (peaking at levels surpassing 1000 times the norm). The adverse impact of mining activities was evident in the Tikhaya, Ulba, and Breksa rivers, showing similar trends in trace element concentrations. Seasonal effects were also investigated. Ice cover formation during cold seasons led to oxygen depletion and the exclusion of pollutants into the stream when ice melted, worsening water quality. Conversely, flooding events led to contaminant dilution, partially improving the WQI during flood seasons. Principal Component Analysis and Hierarchical Cluster Analysis indicated that local natural processes, mining activities, and domestic wastewater discharge were the predominant influences on water quality within the study area. These findings can serve as a basis for enhanced environmental regulation in light of updated ecological legislation in Kazakhstan, advocating for the establishment of a comprehensive monitoring network and the reinforcement of requirements governing contaminating activities.”

Relation between WQI and assigned quality scale for each parameter in terms of regression diagrams may be developed which may help for indicating contribution of quality scale to WQI. and 4. A Two-way ANOVA (P < 0.05) analysis is important to distinguish inter-annual and inter-station variation.

Thank you for your comment. We appreciate the suggestion and acknowledge that your recommendation is reasonable. While the potential value of incorporating other methodologies can be valuable, we believe that our current approach, which combines already used techniques, can effectively and reliably achieve our source apportionment goals.

Improve the Map (Color) of the River basin and twenty six sites used in analysis. and 6.Study area map is not clear and it should be topographical map with detail description.

Thank you for your valuable suggestions, which have been incorporated in the text (Lines 155-176):

“This research focuses on the East-Kazakhstani region of the Republic of Kazakhstan (Figure 1). A total of 26 monitoring sites were selected based on data provided by the National Hydrometeorological Service of Kazakhstan, “Kazhydromet. Eight of these points are located along the mainstem (IR 1 – IR 7), with one positioned at the initial entry point near the Kazakhstan-China border (KI). Five sampling points were established along the primary tributary, the Ulba River (UL 1 – UL 5). The selection of these sampling sites was made considering upstream, within, and downstream positions relative to settlements, and the potential impact of both urban and rural areas on water quality. The same approach was employed when establishing observation points along the Krasnoyarka (KR), Clubochanka (GL), Breksa (BR), Tikhaya (TK), Oba (OB), and Bukhtarma (BU) rivers. Observation points located on the Tikhaya, Breksa, and Ulba rivers (UL 1, UL 2) are situated within the city of Ridder, a major metallurgical center of East Kazakhstan. Points UL 3 - UL 5 and IR 1 - IR 3 are situated within the administrative boundaries of Ust-Kamenogorsk, the central city of the East-Kazakhstani region. Observation points IR 6 - IR 7 are located near Semey city, the administrative center of the Abay region. Observation points on the Krasnoyarka and Glubochanka rivers are situated within the boundaries of large villages with operational domestic wastewater treatment facilities. All sampling points are located at a reasonable distance from the monitored objects, at the regulated boundary of sanitary zones defined as being at least 1000 meters downstream from contamination sources.

Figure 1. Study area.”

Trend analysis may be important for this study to see the decadal changes in water quality. and 8.Analyze and discuss the water quality parameters with their standard acceptable limit.

Thank you for these valuable suggestion, which have been incorporated within the text (Lines 301-336):

“A ten-year retrospective analysis revealed persistent exceeding of established thresholds for trace metals (zinc, cadmium, and copper), calcium, and sulfates, which serve as indicators of natural processes within the river basin., Additionally, chemical oxygen demand levels surpassed acceptable limits, serving as a marker for the influence of domestic wastewater facilities (Figure 3). The highest zinc concentration was observed at the station KR 2 in 2010, exceeding the limit of 0.03 mg/L by nearly 100 times. Similarly, an alarming spike in zinc levels was detected at the GL 2 sampling point in April 2019, reaching a concentration of 2.025 mg/L, nearly 70 times the standard threshold. In September 2019 at UL 2, zinc levels peaked at 1.57 mg/L, surpassing the permissible concentration by over 50 times. Figure 4 indicates a pattern of higher Zn concentrations during the cold seasons compared to the warm seasons. However, even during warm periods, Zn concentrations remained above the recommended limits.

Similar to zinc, cadmium exhibited concerning exceedances of safe limits. The maximum Cd concentration (0.8 mg/L) was recorded in April 2018 at the station KR 2, exceeding the limit by a factor of 1000. Stations GL 2, TK 1, and UL 2 also displayed persistent Cd contamination, with values consistently surpassing the allowable concentration of 0.0008 mg/L. For example, the Cd content at TK 1 in January 2016 reached 0.147 mg/L, exceeding the norm by more than 180 times. Copper concentrations also displayed extreme elevations, with the highest value (0.051 mg/L) observed at the station KR 2 exceeding the limit of 0.004 mg/L by 13 times. At the GL 2 sampling point in 2014, copper concentrations reached 0.046 mg/L, surpassing the reference limit by 12 times. The data depicts distinct seasonal variations, with lower values observed during warmer periods and pronounced peaks during flooding seasons.

Consistent exceedings of recommended calcium levels was noted at the KR 2, GL 2, and GL 3 sampling stations, with tendencies to exceed the specified limit by nearly twice the standard. These exceedances were most pronounced during the cold seasons for all sampling points, with minimal values observed during flood periods likely due to dilution effects. In contrast, chemical oxygen demand (COD) demonstrated peak values during warmer seasons, while registering minimal levels during colder periods. KR 2, GL 2, and GL 3 emerged as the most impacted locations under the influence of this parameter.

Figure 3. Temporal variation of selected chemicals within the studied period in the observation points with Fair and Marginal water quality status.

Figure 4. Average seasonal concentrations of indicative chemicals in the observation points with Fair and Marginal water quality status.”

The sources of pollution need justification and explanation. and 10.How do anthropogenic factors and natural characteristics influence the river water quality: please explain in the discussion section

Thank you for these valuable suggestions. The text has been seriously revised and now the discussion sub-section looks as follows (Lines 623-690):

Most of the values are reported up to three decimal after point. Is it required?

Thank you for your question. As Figure 3 demonstrates, permissible limits and observed concentrations vary across the analyzed chemicals, so three decimals applicable to particular parameters are required.

Some of these parameters (and every two sets of parameters), may have high or low correlations. The authors should mention what the aim of this correlation study is. and 11.The reliability of the results is very much lowered and the reader has very difficulty in understanding presented results

Thank you for your comments. We appreciate your feedback regarding the balance between presenting empirical evidence and providing clear explanations for the identified parameters. While we understand the challenge of achieving both objectives, we have tried to improve our manuscript by (i) extensive language editing to enhance the clarity and conciseness of our writing throughout the manuscript; and (ii) revision of the discussion subsection: This section now more effectively interprets the data, highlighting the exceedances of established limits alongside clear explanations for the identified parameters. We also responded to your question in the methodology section, clarifying that (Lines 203-213): “The research methodology employed the following steps. First, a water quality index (WQI) tool was utilized for a comprehensive assessment of water quality. Second, descriptive statistical analysis was conducted to interpret the WQI scores. Third, the potential sources impacting water quality were identified through the application of multivariate statistical techniques. These techniques included Pearson’s correlation matrices and Principal Component Analysis (PCA). These techniques evaluate the similarities in contaminants’ patterns and group them based on their likely shared source of origin. Fourth, hierarchical clustering analysis was employed to summarize the findings of the source apportionment study and to identify spatial-seasonal patterns in water quality across the entire Basin. This framework was applied to data from all three defined seasons (cold, warm, and flooding).”

The paper's central idea is not novel, and the manuscript does not present any new scientific findings. The manuscript is distinguished by a lack of novelty and a gap in current knowledge: Please include the novelty of the study.

Thank you for your final comment, which summarizes the key point of your valuable suggestions: the need to further emphasize the study’s significance. We have attempted to address this within the text, incorporating most of the suggested revisions as replied above. Additionally, the Conclusions section has also been revised starting with the following Lines (692-703):

“This study is the first known attempt, which successfully identified patterns in the water quality of the Irtysh River Basin in its East-Kazakhstani part in the extensive spatial and seasonal levels. The Water Quality Index indicated good water quality upstream of the Ob and Bukhtarma Rivers and the Basin’s main channel, with slight declines during flood events. However, emerging areas like those influenced by ore mining (Tikhaya, Ulba, and Breksa Rivers) and outdated wastewater treatment facilities (Glubochanka and Krasnoyarka Rivers) exhibited concerning water quality issues. Multivariate statistical analyses supported these findings and highlighted the influence of natural factors, particularly during flooding seasons. These results provide valuable insights for governmental bodies. Prioritizing specific areas for enhanced environmental monitoring and stricter regulations for mining and manufacturing companies is crucial for safeguarding the Basin’s water quality…”

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

Comments and Suggestions for Authors

This paper's authors attempted to assess the water quality dynamics (physicochemical, nutrient) in the Irtysh River Ba- 3 sin. This paper suggests management strategies to protect these river systems. Even after the major revision, the paper has its own drawbacks and requires further modifications to be published in the journal. Please see the following comments:
Abstract: Please check the values of the results are not given properly.
Point-point reply is absent

Methodology: Please make “Multivariate statistics” little small as this analysis is familiar with all.

What was the method adopted to collect the data? It is not mentioned in the method section. The methodology section lacks clarity, and re-writes it for better clarity.

Check the values in the result section and mention in the abstract.

The paper seems weakly drafted (spelling errors, spaces, formatting etc.)…several formatting errors and spelling mistakes. I invite the authors to review the manuscript to correct such errors carefully.

Comments on the Quality of English Language

Minor editing of English language required

Author Response

Abstract: Please check the values of the results are not given properly. and 5.Check the values in the result section and mention in the abstract.

Thank you very much for your suggestions. We have revised the abstract accordingly, and now it looks as follows (lines 26-39): “…The rivers Glubochanka (GL) and Krasnoyarka (KR) consistently experienced marginal water quality throughout the observation period. Various contaminant sources were found to influence water quality. The impact of domestic wastewater treatment facilities was represented by twofold elevated concentrations of chemical oxygen demand, reaching 22.6 and 27.1 mg/L for the KR and GL rivers, respectively. Natural factors were indicated by consistent slight exceedings of recommended calcium levels at the KR and GL rivers. These exceedances were most pronounced during the cold seasons, with average value equal to 96 mg/L. Mining operations introduced extremal concentrations of trace elements like copper, reaching 0.046 – 0.051 mg/L, what is higher than the threshold by 12-13 times; zinc, peaked at 1.57 – 2.96 mg/L, exceeding the set limit by almost 50-100 times; and cadmium, peaking at levels surpassing 1000 times the safe limit, reaching 0.8 mg/L. The adverse impact of mining activities was evident in the Tikhaya, Ulba, and Breksa rivers, showing similar trends in trace element concentrations. Seasonal effects were also investigated. Ice cover formation during cold seasons led to oxygen depletion and the exclusion of pollutants into the stream when ice melted, worsening water quality…”.

Point-point reply is absent

Thank you for this comment. I am so sorry to hear about this misunderstanding, but we have replied to your comments in a respective point-point manner in both an editorial system's box and in an attached doc-file. Your comments during the previous round of revisions were extremely beneficial. While we had not implemented all of them, even rejected suggestions were useful, as inspired us to improve and restructure our manuscript and make it more consistent. The only skipped point during the previous round of revisions was “7. Methodological flow chart of the of River data analysis may be given”. As the tone of this suggestion was optional, we decided to not consider it, as it could be complicated: the resulted flow chart comprised a large amount of information. Another reason to reject this suggestion is that the methodological flow had already been present in the manuscript in the subsection 2.1. Study area, data management, and research flow, lines 210-220: “…The research methodology employed the following steps. First, a water quality in-dex (WQI) tool was utilized for a comprehensive assessment of water quality. Second, descriptive statistical analysis was conducted to interpret the WQI scores. Third, the potential sources impacting water quality were identified through the application of multivariate statistical techniques. These techniques included Pearson’s correlation matrices and Principal Component Analysis (PCA). These techniques evaluate the similarities in contaminants’ patterns and group them based on their likely shared source of origin. Fourth, hierarchical clustering analysis was employed to summarize the findings of the source apportionment study and to identify spatial-seasonal pat-terns in water quality across the entire Basin. This framework was applied to data from all three defined seasons (cold, warm, and flooding)...”

Methodology: Please make “Multivariate statistics” little small as this analysis is familiar with all.

Thank you for this suggestion. It has been considered, and now the sub-section 2.3. Multivariate statistics has been shortened.

What was the method adopted to collect the data? It is not mentioned in the method section. The methodology section lacks clarity, and re-writes it for better clarity.

Thank you for this question. As it had already been stated (in Lines 192-196 and in Data Availability Statement), the data were supplied by the responsible governmental authority. As we did not carry out our own measurements, we did not supply the references for respective acknowledged methods of analysis. However, we highlighted that reputable International Laboratory Accreditation Cooperation (ILAC) permanently controls the governmental lab, which ensures QC/QA and allows generate reliable data: “…The National Hydrometeorological Service of Kazakhstan “Kazhydromet” provided a comprehensive ten-year dataset spanning from 2011 to 2020 for this study. The equipment, laboratory, staff, and analytical methodologies adhered to national and international standards for quality control and quality assurance (QC/QA), accredited and controlled by ILAC (International Laboratory Accreditation Cooperation, https://ilac.org/)...

Data Availability Statement: Data have been provided by The National Hydrometeorological Service of Kazakhstan “Kazhydromet” upon a special request.”

Nevertheless, you were right and our manuscript lacked the description of the data processing. Now we have updated the text, which describes this procedure in Lines 197-203: “…The raw dataset consisted of measurements of 45 hydrological and chemical parameters throughout the entire observation period. Due to uneven measurements frequencies for different parameters, sampling events were selected based on the availability of regular chemical analyses for key contamination indicators. For seasonal fluctuations analysis this dataset was segmented into three distinct periods: cold season (including measurements taken in January and March, once per month), warm season (monthly measurements from June to October), and flooding season (monthly measurements in April and May)…”

The paper seems weakly drafted (spelling errors, spaces, formatting etc.)…several formatting errors and spelling mistakes. I invite the authors to review the manuscript to correct such errors carefully.

Thank you for your careful reading. The authors have revised the manuscript, and we hope that the current version would satisfy your expectations.

Author Response File: Author Response.pdf