The Impact of Climate Change on Water Quality: A Critical Analysis

Abstract

Climate change affects both the quantity and quality of water resources, amplifying the water crisis, slowing progress toward achieving the Sustainable Development Goals (SDGs), and contributing to the needs of future generations. To address these challenges, this study presents an interdisciplinary synthesis of the literature on the subject, highlighting the impact of climate change on water resources (surface water and groundwater). The escalating global demand for water, driven by factors such as population growth, urbanization, and industrial development, is placing significant pressure on water resources. This situation needs sustainable management solutions to mitigate the environmental impacts associated with increased water consumption and climate change. The methodology included bibliometric analysis using VOSviewer version 1.6.19, a software tool for constructing and visualizing bibliometric networks, and systematic analysis according to the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines. 155 records were used in this review from a total number of 1344 documents searched in Science Direct, Scopus and Google Scholar databases. The results indicate that research on the consequences of climate change on water quality remains in its infancy. This study highlights the effects of climate change on water quality indicators, including physicochemical, microbiological, and micropollutants, as well as the implications for human health and water supply infrastructure. Climatic factors, such as rising temperatures and changing precipitation patterns, are particularly important because they control processes fundamental to sustaining life on the planet. The main conclusions are that climate change accelerates the degradation of drinking water quality and amplifies public health risks. These findings highlight the need for rigorous assessments and the development of integrated adaptation strategies involving collaboration among water operators, decision-makers, the scientific community, and climate change specialists.

1. Introduction

Climate change is one of the most complex and pressing issues of the 21st century, with implications for aquatic ecosystems, freshwater resources, and drinking water treatment and distribution systems, both globally and nationally, and threatens human health, sustainable development, and biodiversity [1,2,3,4]. The consequences of climate change are twofold, affecting both water availability and quality [5,6].

The negative impact of climate change has intensified, manifesting as significant changes in the hydrological regime caused by a decrease in groundwater and surface water flow [6].

The intensification of global warming is considered the main factor affecting almost all physical, chemical, and biological processes of freshwater resources [7]. Thus, high temperatures and decreased precipitation lead to an uneven spatial and temporal distribution of water resources, an increase in the incidence of floods and droughts, increased frequency of transitions from floods to droughts, and changes in biodiversity and seasonal dynamics of microbial communities, causing significant changes in the kinetics of chemical reactions and biological structures [7,8,9]. These changes have generated, amplified, and aggravated existing problems, and simultaneously represent the cause of new vulnerabilities, amplifying the issue of water quality degradation [2]. According to the United Nations, over the past five years, surface water bodies, lakes, rivers, and reservoirs have been subjected to rapid climate change, causing one in five river basins to experience large fluctuations in their surface water levels [5,10].

The most complex problem resulting from climate change is predicted by the chemical composition of water, which is significantly and negatively affected. The most alarming fluctuations are a decrease in the dissolved oxygen concentration, excessive accumulation of nutrients, variations in salinity and alkalinity, and a decrease in the dissolved gas concentration [7]. These changes lead to ecological imbalances, changes in species composition, reduced biodiversity, acidification, and the remobilization of pollutants from sediments [11]. Anthropogenic c pressures, particularly pollution from urban, industrial, and agricultural sources, amplify these risks, threatening the integrity of aquatic ecosystems and, implicitly, public health [1,12,13]. Although significant progress has been made in reducing point-source pollution through the implementation of wastewater treatment plants, these often reach their efficiency limits. In this context, climate change amplifies diffuse pollution, particularly that resulting from urban and agricultural surface runoff [7]. All of these factors have the potential to increase the bioavailability of emerging pollutants with bioaccumulative properties, which increases the risk of transfer in the food chain [14]. These effects are compounded by the increased demand for water and energy, changes in the profile of economic activity, intensified industrial activity, and consequently, increased pollution (as depicted in Figure 1) [8,15,16].

Climate factors represent one of the most significant challenges for the drinking water supply sector in the near future [9]. Thus, increased demand and reduced water availability will increase the pressure on water treatment and distribution systems. This situation requires the adoption of optimization strategies to manage available resources correctly and efficiently. The optimization of water systems can be approached from different perspectives, depending on the scale at which the system is analyzed, with various specific techniques and methods proposed [3,17].

Most countries are exposed to risks associated with anthropogenic climate change both now and in the future. The Fourth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) predicts that freshwater resources will be reduced by 10–30% in many arid and tropical areas of the world. Sea levels are expected to rise by 2080 due to climate change [18,19]. It is estimated that by 2050, 1.7–2.4 billion people will live in areas exposed to water shortages, with developing countries being the most vulnerable [20]. South Asia and Africa will be the most severely affected by climate change, with an estimated 4–5% decline in gross domestic product (GDP) [16].

Groundwater resources are affected by these changes through direct alterations in precipitation and temperature (through evapotranspiration), which are essential factors in the hydrological balance that determines the speed and mechanisms of aquifer recharge and their spatial and temporal distribution [9,21].

From a climatic point of view, there is a global trend towards an increase in average temperature, which has a direct effect on changes in precipitation patterns and intensification in both the frequency and severity of extreme events [1,7].

In Europe, climate projections indicate a temperature increase of between +1 °C and +6 °C by the end of this century, depending on the location and emission scenario considered. Between 2015 and 2024, the global average temperature ranged from 1.24 °C to 1.28 °C, making it the warmest decade on record. During the same period, the temperature increase in Europe was even more pronounced, ranging between 2.19 °C and 2.26 °C. The signatory countries to the United Nations Framework Convention on Climate Change have committed to limiting the global temperature rise to well below 2 °C above pre-industrial levels, with a target of limiting it to 1.5 °C. However, without significant reductions in global greenhouse gas emissions, it is highly likely that the 2 °C limit will be exceeded by 2050 [10,22].

Limiting global warming aims to reduce water shortages and the number of people affected by this problem by up to 50% in the regions concerned [5]. Over the last century, the average temperature in Romania has risen by +1.4 °C, in line with the estimate of +1.2 °C for the period 1882–2024, but it indicates a slightly faster increase in recent decades [12,23]; however, precipitation amounts have decreased by an average of 8% with high spatial and temporal variability [23].

Climate change has both direct and indirect effects on the quality and quantity of surface water [24,25]. Rising temperatures directly intensify evapotranspiration, resulting in reduced water resource availability [26,27]. Higher temperatures can affect interactions between biological, physical, and chemical components, and cause changes in peak runoff by altering the timing of snowmelt, particularly in certain river basins where winter precipitation is dominant and stored in the snowpack [5,6,28,29].

Extreme hydrological events, such as floods and droughts, influence water quality through dual mechanisms: dilution of contaminants during rainfall events and their concentrations during periods of drought [7].

Low flows and high temperatures favor the proliferation of algae and limit their natural capacity to dilute point source pollutants [25]. High temperatures and low flow velocities also stimulate biological self-regulation processes and increase the respiration rates of aquatic ecosystems, which can lead to a decrease in dissolved oxygen concentrations. These changes contribute to the degradation of water quality and ecological status of water bodies [18,24,25,27].

Intensified solar radiation may alter water quality, particularly affecting the properties of natural organic matter (NOM) in freshwater bodies. These changes are mediated by both the thermal and photochemical effects of radiation. In this context, phototransformation is an essential process for accurately predicting the formation of transformation products from emerging organic micropollutants, including pharmaceutical compounds [7,8].

The impact of climate change on water resources is complex and highly significant. This has led to a growing interest from the scientific community and, implicitly, a significant expansion of research dedicated to this field of study. In recent decades, concerns regarding the quality of water resources have become increasingly relevant against the backdrop of changes in the hydrological regime and growing pressure from demand in various sectors of use [11]. In this context, the impact of climate change on available resources is not limited to the quantitative dimension but also concerns the capacity of water systems to meet the needs of different users and ensure a sustainable balance between economic, social, and environmental objectives [5,30].

Recent studies have highlighted the significant changes in the thermal dynamics of lakes and reservoirs. Lewis et al., 2019 [31], assessed the effects of climate change on the temperature and thermal stratification of a reservoir in the southern Rocky Mountains. This study demonstrated that climatic conditions have a significant negative influence on the mixed layers of lakes at high altitudes. Another study by Geneviève et al., 2019 [29], which examined 108 water companies in Quebec (Canada), showed that future variations in temperature and precipitation may increase the likelihood of trihalomethane concentrations in drinking water exceeding the limits, with significant differences between seasons (≈30%) and treatment types (25–40%).

Firoozi et al., 2019 [32], investigated the effects of climate change on the thermal regimes of the Latian Dam in Iran. Five climate models under the Representative Concentration Pathways (RCP) 2.6 and RCP 8.5 were used to forecast climate variables for the period 2020–2039. The results of this study showed a trend of increasing air and water temperatures due to climate change. This phenomenon led to a prolongation of the thermal stratification period, adding up to 52 days to the lake stratification period.

Climate change, through global and regional actions, contributes to the intensification of eutrophication processes in freshwater ecosystems [33]. Increasing water temperatures, changing precipitation patterns, and intensifying extreme weather events contribute to increased nutrient input from river basins, favoring algal blooms. Higher water temperatures also accelerate algal metabolism and reduce oxygen solubility, creating conditions conducive to algal proliferation at greater depths [33,34]. These processes lead to deterioration in water quality and the ecological status of aquatic ecosystems and are associated with a higher probability of algal blooms and increased problems with water supply and treatment [2,35].

Michalak et al., 2013 [36], correlated algal blooms in Lake Erie (located on the international boundary between Canada and the United States) with a series of extreme climatic conditions. These include a massive influx of nutrients during spring, poor water circulation in the lake, extended water residence times, and high temperatures. The combination of these factors creates an ideal environment for rapid algal proliferation, leading to large-scale eutrophication.

Another study by Wilby et al., 2006 in the River Kennet in the United Kingdom indicated that increasing temperatures and climate variability might cause an increase in nitrate and ammonium concentrations [11]. Climate change is expected to significantly affect the availability, seasonality, and variability of river flow regimes.

A study conducted in the river basins of Bosnia and Herzegovina, Serbia, Montenegro, and North Macedonia between 1961 and 2020 recorded a significant increase in the frequency of low flow events in the summer season along with a decrease in events, suggesting an intensification of hydrological droughts and a possible reconfiguration of the seasonal flow regime. These trends highlight the increased vulnerability of river systems in the region and underscore the need to develop adaptive water resource management strategies that ensure the maintenance of minimum ecological flow and the resilience of aquatic ecosystems to climatic and anthropogenic pressures [28].

Legislation and international agreements on climate change have evolved steadily over the past few decades, owing to the growing awareness of the scale and serious consequences of this phenomenon. The United Nations Framework Convention on Climate Change (1992) laid the foundation for climate negotiations and enshrined the principle of common but differentiated responsibility [37]. Subsequently, the Kyoto Protocol (1997) introduced mandatory emission reduction targets for industrialized countries for the first time. The Paris Agreement (2015) involved all countries limiting the rise in global temperatures and strengthening resilience. The latest IPCC Synthesis indicates that there will be rapid and widespread changes in global ecosystems, with unknown and unpredictable impacts on human health and ecosystems [18,38].

Although water availability is frequently analyzed in climate policies, the qualitative dimension, indirectly influenced by greenhouse gas emissions, intensification of extreme hydrometeorological phenomena, and changes in the hydrological regime, continues to be treated marginally, without being recognized as an independent vector in adaptation strategies. The deterioration of water quality has direct consequences for the security of supply services and for the health of the population and functioning of economic sectors that are dependent on water resources. In this context, characterized by rainfall variability and increasing water scarcity, it is essential to overcome conflicts between different categories of users and address existing structural and management issues. Therefore, the sustainability of water services cannot be ensured by quantitative solutions alone but requires integrated management that simultaneously addresses issues of resource availability and quality [17].

This study aims to provide a comprehensive assessment of the literature on the current state of knowledge regarding the impact of climate change on water quality, with a focus on water resources, water supply infrastructure, and, implicitly, human health. This approach is in line with the Sustainable Development Goals (SDGs) set by the United Nations, which aim to build a greener, fairer, and more sustainable world by 2030. Of the 17 goals identified, the study pays particular attention to SDG 6 Clean water and sanitation and SDG 13 Climate action. This correlation highlights the need for a rigorous assessment of the literature and is the central motivation for this study.

To address this complex topic, this study is guided by the following research questions:

(1)

How does climate change influence the quality and availability of surface-water resources?

(2)

What are the main pathways through which these changes affect human health?

(3)

How are water supply infrastructures adapting to the challenges posed by climate variability?

Accordingly, this study pursues three main objectives: (i) identify and synthesize the main trends and findings in the international literature regarding the effects of climate change on water quality; (ii) to evaluate the implications for human health and water supply systems and (iii) to highlight existing knowledge gaps and propose directions for future research that can support the development of resilient and sustainable water management policies.

The conclusions drawn from this analysis provide a clear and comprehensive summary of the main findings, with a particular focus on the gaps identified in previous studies and areas for improvement that can guide future research directions.

2. Methodology

This research is based on both systematic and bibliometric analyses.

Systematic analysis, as a fundamental scientific approach, is an essential tool for organizing and interpreting a large volume of information published in specialized literature. This approach synthesizes existing knowledge and facilitates the identification of trends, gaps, and future research directions. Systematic analyses are used by researchers to identify and clarify hypotheses, highlight and avoid the limitations of previous studies, and substantiate the estimation of sample sizes required for future research [39,40].

Bibliometric analysis is a basic tool for investigating scientific trends, enabling the identification of emerging topics, publications, and researchers with a high impact. Unlike traditional reviews, this method reduces subjectivity by relying on statistical data [39,41].

Systematic and bibliometric analyses allow for a detailed understanding of the field of research while providing an overview of the evolution and development of knowledge.

2.1. Systematic Review of Literature

The systematic review of the literature was conducted in accordance with the Preferred Reporting Items for Systematic reviews and Meta-Analyses (PRISMA) guidelines [42]. The implementation of this protocol will enhance the accuracy and reliability of data obtained from systematic reviews. This generates a four-step control chart: Identification, Selection, Eligibility, and Inclusion, which aims to ensure transparency in the process of analyzing and selecting articles [42].

This study is based on bibliographic data extracted from databases such as: Science Direct (http://www.sciencedirect.com; accessed on 19 July 2025), Scopus (https://www.scopus.com/, accessed on 21 July 2025) and Google Scholar (https://scholar.google.com; accessed on 17 July 2025). These databases were selected for their global recognition, extensive coverage of peer-reviewed publications, and robust citation analysis tools.

The present methodology, PRISMA, was applied to all phases of data collection and systematic reviews as presented in Figure 2. Articles were selected based on their titles, abstracts, and keywords. The following keywords were used in the following combinations: impact AND climate AND change AND water AND quality AND infrastructure AND human impact.

The initial database search (ScienceDirect, Scopus, and Google Scholar) returned 1344 publications for review. To ensure linguistic consistency, only papers published in English were included (criterion 1), resulting in 1241 documents being selected. Subsequently, studies published between 2005 and 2025 were selected (criterion 2), reducing the dataset to 882 documents. In the next stage, only publications in the field of environmental science were retained, whereas those primarily focused on agriculture, hydrology, medicine, social sciences and economics were excluded (criterion 3). This filtering resulted in 486 documents, comprising 369 journal articles, 63 conference papers, 47 reviews, and 7 book chapters. A full-text eligibility assessment was then performed, leading to the exclusion of 119 articles that either lacked full-text access or did not provide sufficient methodological information (criterion 4). Consequently, 367 studies were retained for detailed analysis, of which 143 met all the inclusion criteria and were incorporated into the final systematic review and bibliometric analysis. The bibliographic data for this analysis was limited to 155 articles.

2.2. Bibliometric Analysis Using the VOSviewer Program

Bibliometric analysis is an essential tool for investigating scientific trends in a particular field, allowing the identification of emerging issues, journals, researchers, and research centers with a major impact in a specific area of study [7,41,43]. In recent years, the VOSviewer program has been increasingly used in environmental engineering. Bibliometric analysis offers the possibility of illustrating the results in the form of maps [43]. VOSviewer allows the selection of elements of interest, such as authors, organizations, countries, and keywords, and the configuration of indicators necessary for generating analyses and visual networks.

In this study, the VOSviewer software version 1.6.19, developed by Leiden University (https://www.vosviewer.com/, accessed on 11 August 2025), was used to construct and visualize bibliometric networks. This software uses bibliographic data extracted from scientific databases to generate graphical representations of the analysis results in the form of connection networks, overlay visualizations, and density visualizations. This approach facilitates rendering bibliographic analysis results in a transparent and interpretable manner [41,43]. In a network graph, the size of the nodes reflects the importance of the analyzed elements, and the thickness of the lines connecting them expresses the intensity of the relationships.

VOSviewer uses the association strength indicator as a basis for calculation, which is used to construct a similarity matrix derived from the co-occurrence matrix [41,43,44]. A bibliometric map is generated by applying the mapping technique to this matrix. In the next step, the obtained map was adjusted by translation, rotation, and reflection.

The formula used to determine this indicator is as follows [43]:

$$S_{xy}={\displaystyle \frac{C_{xy}}{n_x\times n_y}},$$

(1)

where

C_XY—number of co-occurrences of elements x and y;

n_x—number of occurrences of element x;

n_y—number of occurrences of element y.

Figure 3, Figure 4 and Figure 5 illustrate the results of bibliometric analysis performed using VOSviewer version 1.6.19. Figure 3 shows the co-occurrence network of keywords related to the impact of climate change on water quality. Each keyword is represented by a circular node, and its size increases proportionally with its relevance and importance in the network. They were grouped into four distinct clusters, represented by red (cluster 1), green (cluster 2), blue (cluster 3), and yellow (cluster 4). A short distance between nodes indicates a closer link between keywords, and the lines drawn between them highlight existing connections. The thickness of the lines reflects the frequency of co-occurrence of the two keywords in publications.

Cluster 1 brings together 285 occurrences, 71 connections, and a total link strength of 2245. Keywords such as water quality, seasonal variation, drought, evapotranspiration, sustainability, and risk assessment highlight the concept of hydrological resources and climate pressures while integrating the management dimension.

Cluster 2, with 83 publications and a total link strength of 744, generating 83 distinct links, brings to the fore the phenomenon of eutrophication and pollution. Key terms such as nutrients, algal bloom, lakes, phytoplankton, nitrate, and nutrients highlight a growing concern about biological processes and their impact on biodiversity. Thus, the link between climate change and water quality indicates that water pollution and its effects on aquatic ecosystems are amplified by climate change.

In Cluster 3, the keyword “climate change” had the highest total link power (2539), appearing in 345 publications and creating 71 links. The keywords associated with Cluster 3 indicate the research direction focused on the relationship between water quality, water management, river pollution, hydrology, watersheds, river basins, and climate models. This cluster highlights the global dimension of climate change on water quality and its implications for water quality.

Cluster 4 has a total link strength of 942, appearing in 102 publications and creating 70 links each. Keywords such as land use, catchments, surface water, and seasonal variation related to this cluster reflect concerns regarding how climate variations affect biochemical processes and water quality, indicating the importance of integrating climatic and anthropogenic factors into water resource management strategies.

A chronological analysis of publications showed that the initial research directions (2005–2010) were outlined using keywords such as sediment, organic carbon, aquatic environment, nitrogen, and phosphorus. Subsequently, terms such as ecosystems, precipitation, water temperature, land use, and surface water were frequently used in the literature, marking the consolidation of interdisciplinary studies.

In recent years (2018–2025), researchers have focused on emerging topics, reflected in keywords such as climate change, water quality, water management, river basins, climate models, hydrology, and watersheds, indicating a dominant research focus on the impact of climate change on water resources and strategies for sustainable management.

An analysis of the average number of citations highlights that the central themes, represented by the keywords’ climate change and water quality, dominate the specialist literature, enjoying high visibility and being associated with a significant number of citations. Simultaneously, there is a recent trend of increasing publications addressing topics such as water supply, climate effects, river basins, water management, and climate models, as illustrated in shades close to yellow.

In contrast, terms such as sediment, organic carbon, aquatic environment, nitrogen, and phosphorus appeared in darker areas (blue green), suggesting a concentration of scientific interest at an earlier stage and a relatively lower rate of recent citations.

3. Results and Discussion

The bibliometric analysis performed in Section 2.2 and graphically represented in Figure 3, Figure 4 and Figure 5 highlighted several dominant research groups that define the current state of scientific knowledge on the impact of climate change on water quality. Cluster 1 focuses on hydrological variability and extreme events (e.g., floods and droughts), cluster 2 addresses eutrophication and nutrient dynamics, cluster 3 examines pollutant transport, watershed processes, and hydrological-climatic modeling, while cluster 4 addresses the influence of land use, watershed characteristics, and biogeochemical processes on water quality, including their implications for ecosystem and infrastructure resilience.

These groups provided an analytical framework for structuring the discussion in this section. The analysis of eutrophication and nutrient accumulation processes directly reflected cluster 2, while the examination of hydrological variability and pollutant transport corresponded to clusters 1 and 3. The subsection on implications for ecosystem health, human well-being, and infrastructure resilience is based on cluster 4, integrating bibliometric trends with conclusions from the analyzed literature.

3.1. The Impact of Climate Change on Water Quality Indicators

Aquatic ecosystems currently face extensive and complex challenges owing to global warming and eutrophication. In many parts of the world, surface water sources are important and often the only source of water for the population [45].

Thus, it has been found that the response of aquatic systems to climate change is complex and is not only associated with individual changes in climate variables but also induces a combination of factors that govern the heat budget, such as air temperature, humidity, short and long wave radiation, wind speed, and precipitation [46,47].

Surface water resources (rivers, lakes, and reservoirs) are subject to changes in water quality indicators owing to changes in climate variables, such as rising temperatures, extreme hydrological events (floods and droughts), evapotranspiration, and vegetation fires [7,8,48,49].

The main chemical indicators of water affected by climate change are temperature, pH, dissolved organic matter, dissolved oxygen, organic and inorganic micropollutants, nutrients, and biological indicators with pathogens (as presented in Figure 6) [7,48].

The research highlights how climate change affects water quality, how water systems work, and how long they last, as well as health safety, showing how water resources, public services, human health, and sustainable development goals are all interconnected. Climate change can influence the source, migration, and transformation of pollutants in aquatic environments [50].

3.1.1. Temperature

The consequences of rising surface water temperatures are numerous, ranging from alterations in aquatic biota, increased toxicity of heavy metal ion contaminants and some persistent organic substances, increased concentrations of pathogenic microorganisms in surface waters, decreased dissolved oxygen solubility, and the promotion of pH reduction [5,6,51,52,53,54,55,56,57,58]. Water temperature is an essential water quality parameter because it directly affects other indicators, such as the metabolic function of aquatic life, photosynthesis, compound toxicity, dissolved oxygen (DO), conductivity, salinity, alkalinity, pH, and density [59]. Numerous studies have demonstrated that rising surface water temperatures alter the structure and functioning of aquatic ecosystems by modifying reaction kinetics, gas and mineral solubility, and biochemical cycles within lakes and rivers [7,47]. Decreased river flow, saltwater intrusion, and atmospheric sulphate deposition influence the alkalinity and salinity of surface waters [51,60]. However, the literature presents contrasting findings regarding both the magnitude and direction of these processes. Most studies indicate a consistent increase in surface water temperature, whereas deeper water layers display higher variability, with some lakes showing cooling due to altered stratification or groundwater inflows. It has been found that decreasing flows reduce the dilution capacity of rivers and cause alkalinity and salinity to increase [60]. Studies have demonstrated that reduced flows diminish dilution capacity, leading to higher salinity and alkalinity, while decreased atmospheric sulphate deposition has been linked to alkalization trends [60]. According to Kaushal et al., 2016, increasing alkalization and salinization with higher corrosion rates in water distribution systems, which enhance the release of metals into drinking water, thereby elevating public health risks and necessitating more complex and energy-intensive treatment processes [61,62]. This interaction between thermal and chemical processes shows how climate change affects both natural water and infrastructure.

It is predicted that the average surface water temperature will increase by approximately 3.4 °C by 2090 compared to 1990. Surface water temperatures are expected to increase by 3.8 °C and hypolimnion water temperatures by 2.8 °C. High water temperatures lead to a decrease in carbon dioxide (CO₂) concentration and a decrease in dissolved oxygen solubility, reflecting a lower solubility [7,10,58,63]. Increased water temperature also reduces the viscosity of surface water, amplifying the rate of nutrient diffusion to the cell surface [33,34,64]. These findings are consistent with the bibliometric results obtained in this study, where cluster 2 highlights eutrophication, nutrient enrichment, and cyanobacterial proliferation as major research focuses related to temperature-driven processes.

Climate change and prolonged droughts are often accompanied by an increased frequency of vegetation fires [49]. Vegetation fires amplify soil erosion, leading to increased total suspended solids (TSS) concentrations and turbidity in surface waters, resulting in enhanced transport of organic matter into aquatic ecosystems [49,65]. The combined effects of warming and fire-induced erosion demonstrate the interconnectedness between climate extremes and deteriorating water quality.

Global warming of lake surface waters during summer results in a 20% increase in algal blooms, a 5% increase in toxic blooms, and a 4% increase in methane emissions from lakes over the next century [66,67]. Studies have shown a direct correlation between such temperatures and cyanobacterial dominance, with accelerated growth compared to green algae and diatoms [64,68]. These findings, also clustered under Cluster 2 in the bibliometric analysis, confirm that temperature-driven eutrophication represents one of the most consistent and extensively studied impacts of climate change on aquatic systems. Water eutrophication is a global problem that is becoming an increasing concern under climate change, causing major problems in water resource management, particularly in small and stagnant water resources, fishponds, and reservoirs [18,27,34]. Recent studies have shown a high risk of water pollution, which can lead to eutrophication of large river basins because of increased pollution and climate change [64].

The thermal stratification of a lake and the length of the stratification period are key elements in determining the transport and distribution of gases and nutrients within a lake aquatic system [47]. Multiple studies have shown that global warming significantly affects stratification patterns. In Europe and North America, the stratification period has lengthened by an average of 2–3 weeks, accompanied by temperature increases of 0.2–1.5 °C [7,31,58]. This extended stratification reduces vertical oxygen exchange, promoting anaerobic conditions and enhancing the release of nutrients and contaminants from sediments processes that further reinforce eutrophication feedback loops. Increased evaporation associated with water warming can lead to a decrease in lake water levels, with implications for water security and serious economic consequences, including the loss of aquatic ecosystems [7]. While surface water temperatures show a clear global upward trend, deeper waters exhibit high variability in both direction and magnitude of change [58,69]. This indicates that the warming of aquatic systems is not uniform and depends strongly on stratification stability, local climate, and hydrological connectivity.

Subsurface environments also respond to rising temperatures. Studies have shown that in porous and unconfined aquifers in Germany, variations in groundwater temperature are correlated with previous positive changes in regional air temperature [70].

Variations in groundwater temperature can alter aquifer ecosystems and associate biogeochemical processes, accelerate mineral weathering and ultimately causing changes in water chemical composition. Thus, water warming favors certain microbial activities (intensification of organic matter degradation or redox reactions), which can lead to the mobilization of inorganic and organic chemical species in solution and alteration of groundwater quality indicators [70,71,72,73,74,75]. Although the thermal effects on stratification and algal growth are well established, quantitative thresholds governing temperature oxygen nutrient interactions remain poorly constrained, particularly in groundwater-fed or mixed systems, representing a significant research gap.

The combined effects of rising temperatures, hydrological variability, and anthropogenic pressures reinforce the need for long-term monitoring at different depths and integrative modeling approaches to better understand and predict the cascading impacts of climate change on aquatic ecosystems [26,47,58,76,77,78,79,80,81]. The correspondence between the dominant bibliometric clusters and the main mechanisms identified in the recent literature confirms that temperature rise acts as a central driver linking physical, chemical, and biological processes, influencing both the natural environment and water management infrastructure.

3.1.2. Nutrient Dynamics and Biogeochemical Processes

Changes in precipitation and runoff, as well as temperature increases, lead to an increase in the nutrient load in surface water bodies, undermining the effectiveness of policies aimed at reducing nutrient input [82,83]. Temperature rise can affect nutrient cycles both directly, by altering reaction rates and decomposition, and indirectly, through its influence on oxygen availability and stratification patterns [57,84]. High temperatures increase the rate of release of nitrogen (N), phosphorus (P), and carbon (C) from organic matter. As the oxygen concentrations in the bottom waters decrease, stratification is expected to increase because of phosphorus release from sediments [7,85]. The response of lakes to warming depends strongly on morphometric parameters such as mean depth, surface area, and volume, which control the persistence and intensity of stratification [84].

Thermal stratification over long periods often causes hypoxia, dissolved oxygen < 2 mg L⁻¹, in deep waters [7,57,86]. Low oxygen levels promote the release of dissolved ammonium, carbon, and phosphorus from sediments into the water column while reducing nitrate concentrations through denitrification [87]. Thus, temperature indirectly increases nutrient concentrations by accelerating mineralization and sediment release, yet under certain conditions it can decrease concentrations by stimulating phytoplankton uptake and growth [57,87]. This dual effect illustrates the non-linear nature of nutrient responses to warming and the dependence on both oxygen status and biological activity.

Excessive nitrogen and phosphorus inputs from agricultural runoff promote eutrophication and harmful algal proliferation, particularly cyanobacteria [88]. These indicators, N and P, are essential in determining the variation in the phytoplankton community, as they are limiting nutrients for phytoplankton growth in freshwater [86]. Spatiotemporal variations in temperature and precipitation affect the transport and transformation of N in lakes [7,89]. Periods of drought during summer can lead to the mobilization of nitrogen from soils, which then flows into rivers, contributing to increased nitrate concentrations. Moreover, rainfall–runoff events following these dry periods can generate sharp nutrient pulses in surface waters, thereby amplifying eutrophication risks, particularly in catchments influenced by agricultural and anthropogenic pressures [84,90].

Water quality indicators, such as ammonia and pH, are closely linked to precipitation [91]. An increase in pH causes the transformation of ammoniacal nitrogen in surface waters into non-ionized ammonia, a toxic form that can be lethal to aquatic organisms, whereas an increase in pH and basic cations can reduce the toxicity of metal traces [62,92].

However, scientific literature presents contradictory results regarding nutrient concentrations under high- and low-flow conditions. During floods, high runoff levels can dilute nutrient concentrations in some systems, whereas in others, they can increase nutrient exports from agricultural land. In contrast, droughts tend to increase nitrate accumulation in soils, leading to a sudden increase in nitrate concentration after the first heavy rainfall. These conflicting conclusions highlight the complexity of nutrient dynamics, which are controlled by the combined effects of temperature, hydrology, and biogeochemical reactions. The observed cause-and-effect relationships indicate that prolonged stratification and hypoxia facilitate the release of phosphorus and ammonium from sediments, while oxygen depletion alters the nitrogen cycle by intensifying denitrification. However, the interactions among nutrient availability, algal proliferation, and light limitation remain a subject of debate, particularly in shallow or turbid systems where nutrient limitation and kinetic conditions vary seasonally and spatially. Within cluster 2, identified in the bibliometric analysis, these interactions between climate factors, nutrient enrichment, and eutrophication represent one of the most critical and explored pathways through which climate change degrades water quality and undermines ecological integrity. The link between scientific findings and bibliometric trends confirms that nutrient dynamics, particularly nitrogen and phosphorus transformations, are essential for understanding the cascading biogeochemical responses of freshwater systems in a warming climate.

3.1.3. Dissolved Organic Matter (DOM) and Carbon Cycling

Dissolved organic matter (DOM) is the largest global carbon reservoir in natural aquatic systems [93]. DOM negatively impacts aquatic ecosystems through its influence on acidity, heavy metal ion transport, light absorption, photochemistry, and energy and nutrient input, while also affecting water treatment processes [93,94].

Aquatic DOM originates from both autochthonous sources, such as microbial activity, phytoplankton, and macrophytes, and allochthonous sources, derived from decomposing terrestrial vegetation and soils [93,94,95,96]. In surface waters, the main source of DOM is soil leaching [7].

Numerous studies have demonstrated that temperature and nutrient levels modulate DOM concentration and composition. High nutrient levels have been found to have a direct impact on autotrophic DOM because they promote phytoplankton biomass [7,97]. At the same time, high temperatures have been found to accelerate the decomposition of DOM, altering its sources and inducing photochemical degradation in the aquatic environment during transport, preferentially removing chromophoric DOM (CDOM) over dissolved organic carbon (DOC) [97]. Nutrient excess and climate change have been shown to favor cyanobacterial dominance, resulting in the accumulation of algal biomass in surface waters, which in turn can increase the accumulation of indigenous DOM [95,97]. These processes illustrate the strong coupling between temperature, nutrient enrichment, and organic matter cycling, which aligns closely with the bibliometric cluster 2 identified in this study, emphasizing eutrophication and biological productivity as central research themes.

Hydrological variability further modulates DOM dynamics. During drought conditions, there is a decrease in DOM, which in most cases is followed by a significant increase with the onset of precipitation, and DOM remains high in the aquatic environment for a long period of time [98]. Storms and episodes of heavy rainfall can influence the chemical composition of dissolved organic matter, which is associated with an increase in the proportion of humic compounds [99]. This alternation between drought-induced depletion and rainfall-driven enrichment exemplifies a nonlinear cause–effect dynamic that is typical of climate-driven systems.

The rapid increase in DOM and changes in water quality can cause problems for water treatment; therefore, increased water demand and reduced processing should mean that allochthonous DOM will dominate over autochthonous forms during flood periods. As allochthonous DOM is hydrophobic and can be easily removed, this problem can be addressed through monitoring, process optimization, and rapid response to changes in DOM quality [96,97,98]. It has been found that integrated studies linking the optical properties of DOM to climate variables are still rare, limiting the predictive capacity for treatment optimization in future climate scenarios [100,101].

This topic corresponds to cluster 4 in bibliometric analysis, which emphasizes the interaction between land use, catchment hydrology, and the biochemical transformation of organic matter under changing climatic conditions. Together, these findings highlight that DOM cycling is a key pathway through which climate variability reshapes carbon fluxes, water quality, and treatment performance in freshwater systems.

3.1.4. Organics and Inorganics Micropollutants

Human activities and climate change together shape the occurrence, mobility, and persistence of emerging pollutants, including both organic and inorganic micropollutants, in aquatic environments. Elevated temperatures and intense rainfall events increase the concentrations of dissolved organic matter, pathogens, and micropollutants, while occasionally decreasing certain organic compounds through dilution or degradation.

These contaminants, which include pesticides, pharmaceuticals, persistent organic pollutants (POPs), per- and polyfluoroalkyl substances (PFAS), and microplastics, represent a major concern for aquatic ecosystems and water supply safety [50,91,102].

High concentrations of natural organic matter (NOM), associated with increased temperatures, can intensify microbial growth and compromise the microbiological stability of water in distribution networks by generating biofilms [103]. Increased temperature and salinity can increase the toxicity of persistent organic compounds and other pesticides in aquatic biota [62]. The most consistent cause–effect relationship is the increase in contaminant mobilization during high temperatures and intense rainfall, when dilution and sediment resuspension coexist [104,105]

Although research on the effects of climate change on organic micropollutants remains limited, existing studies reveal important patterns. According to a study by Osorio et al. (2012), high concentrations of pesticides and pharmaceuticals were found in surface waters during periods of low flow compared to periods of high flow [106]. Temperature increases can also enhance the mobilization of organic contaminants from reservoirs, such as natural waters, and can alter accumulation, degradation, and sorption rates. At the same time, these changes can have indirect effects on long-range transport and deposition patterns [107]. These changes can indirectly influence long-range transport and deposition patterns, while high temperatures may trigger the release of persistent organic pollutants (POPs) from sediments or ice matrices [108].

Increased flooding, runoff, and changes in density further affect the fate and transport of microplastics in aquatic environments. Changes in climate variables are expected to reshape the distribution patterns of plastics in aquatic environments, intensifying the problem of microplastics [109].

Similarly, pharmaceutical, pesticide, and PFAS concentrations are affected indirectly by increased water stress and wastewater discharge [110]. Higher temperatures can influence the distribution of contaminants in water bodies and reduce their concentration by promoting the volatilization and degradation of pollutant residues. Low flow during summer can offset this effect. Decreased flow reduces the dilution capacity of water, leading to higher pesticide concentrations in the event of agricultural runoff or spraying [18].

In the study by Petrovic et al., 2011 [108], 72 pharmaceutical compounds were analyzed in the Llobregat River at its mouth in the Mediterranean Sea. They demonstrated that the variation in the concentration of these chemical pollutants is of the same order and magnitude as that of the river flows. Therefore, the interaction and variation of climatic factors can have a major influence on the transformation and migration of environmental contaminants within aquatic systems.

Climate change also affects the dynamics of inorganic pollutants, such as nutrients and heavy metals, through direct and indirect mechanisms [7,18]. Short-term extreme weather events, such as periods of strong winds and storms, can reduce algal blooms by dispersing phytoplankton; however, they also have a negative effect on water resources by increasing the input of sediments and nutrients into the water body, compromising the quality of drinking water sources [111]. A study conducted by Wu et al., 2014 [112], found that arsenic and fluoride levels in most urban lakes were positively correlated with temperature and precipitation.

Collectively, these observations correspond to Cluster 3 from the bibliometric analysis, which integrates research on climate drivers, pollutant behavior, and adaptive water management. This cluster underscores the growing need for predictive models capable of linking meteorological variability with contaminant transport and transformation to support risk mitigation strategies.

3.1.5. Microbiological Contaminants and Pathogen Dynamics

Extreme weather events, such as heavy rainfall and flooding, intensify water pollution by increasing surface runoff, which carries sediments, nutrients, pathogens, and industrial pollutants [82,100,101,102]. In addition, rising temperatures can influence the widespread proliferation of harmful algae, particularly cyanobacteria, contributing to algal blooms and accelerating their metabolic rates [113,114].

Climate variations, such as changes in water temperature and salinity, alter the spatial distribution of pathogens and associated infections [115].

Temperature directly affects microbial population dynamics, while salinity influences ecological niches [116]. Pathogenic microorganisms can spread in freshwater ecosystems due to contamination with anthropogenic or zoogenic effluents, a phenomenon exacerbated by discharges following heavy rainfall that overloads sewage systems [115,116].

Under high-temperature conditions, several pathogens, such as cyanobacteria and Vibrio cholerae, can spread rapidly and proliferate [116]. In warm waters, there is a dramatic increase in the metabolic rates of microorganisms, leading to an increased frequency of outbreaks of microbial diseases [114]. The genus Vibrio includes 140 species, 12 of which are pathogenic to humans. They thrive in aquatic environments with low to moderate salinity (1–25 g/L) and high temperatures above 12 °C.

The adaptability and ubiquity of this genus make it an optimal indicator for highlighting the effects of climate change on aquatic ecosystems [114,115,116,117]. With global warming, cyanobacteria of the genus Microcystis, which can produce microcystin, present an increased risk of becoming invasive species in aquatic ecosystems [118].

The frequency of cyanobacterial blooms in lakes and rivers has increased, particularly in eutrophic environments. Climate change exacerbates this trend by intensifying extreme weather events, such as heavy rainfall, which increases nutrient runoff from agricultural land into water bodies. This increased nutrient load, combined with rising temperatures, stimulates cyanobacterial proliferation [113,114,118].

Building on the growing body of evidence linking climate variability to microbial proliferation, several studies have specifically examined how temperature and hydrological extremes modulate pathogen abundance and distribution in aquatic ecosystems. The most robust evidence concerns the temperature dependence of Vibrio spp. and cyanobacteria, whose proliferation correlates strongly with warming and eutrophication. However, contrasting findings exist on whether rainfall mitigates or amplifies contamination depending on sanitation infrastructure and catchment characteristics.

Climate change also fosters harmful algal blooms by increasing nutrient runoff during heavy rains and accelerating cyanobacterial metabolism under high temperatures. These mechanisms link Clusters 1 and 2, illustrating how hydrological variability and nutrient enrichment interact to amplify microbiological contamination.

Overall, these processes destabilize aquatic ecosystems and amplify public health risks, including the spread of waterborne diseases and antibiotic-resistant pathogens.

The literature confirms that climate change affects both surface and groundwater resources through complex mechanisms, including prolonged droughts, extreme precipitation, temperature increases, and saline intrusion. These cause-and-effect relationships are summarized in Figure 7.

3.2. Implications for Drinking Water Production

Climate change increases the difficulty of water treatment by influencing the quality of the water resulting from the process. However, the impact of these changes on drinking water quality has been insufficiently explored [49].

Climate change has been found to indirectly impact the design and operation of water treatment plants. Surface water treated by conventional processes (coagulation-flocculation, filtration, disinfection, and distribution) is the main source of drinking water, and climate change influences its quality through gradual and continuous changes [7,119]. Coagulation and flocculation are essential steps in water treatment, whereby the addition of aluminum and iron-based salts destabilizes and aggregates suspended particles, thus facilitating their sedimentation and improving water quality [120].

Climate change influences this process by altering the characteristics of raw water, particularly by increasing the concentration of natural organic matter, variations in turbidity, and temperature fluctuations, which require adjustments to the dosage, coagulant type, and operating conditions to maintain treatment efficiency [7,119,121]. This leads to increased infrastructure and operating costs, affects service continuity, and causes system interruptions [49,119,121].

Water disinfection is an essential step in obtaining potable water. The formation of disinfection byproducts (DBPs), resulting from the reactions of chlorine with NOM and inorganic constituents, is influenced by several factors, including temperature, DOC concentration, pH, and operational indicators such as chlorine dose and contact time [122,123].

Numerous studies have reported that rising surface water temperatures promote the rate of DBPs formation [65,122,124]. According to a medium-term projection scenario, a temperature increase of 1.8 °C could lead to an approximately 39% increase in trihalomethane (THM) concentrations by 2050 [103]. A robust cause–effect relationship was established between rising surface water temperatures and DBP formation.

Valdivia et al., 2016 [125], analyzed seasonal trends in surface water quality and trihalomethanes over a year at five technologically unmodified treatment plants. The results showed significant seasonal variations, with THM peaking at the end of summer and low values at the beginning of spring. Positive correlations between ambient temperature and raw water chemical oxygen demand (COD) indicate the sensitivity of drinking water quality to climate change.

However, contrasting findings have emerged regarding the overall impact of warming on treatment performance. Some studies report that higher temperatures improve coagulation efficiency by accelerating floc formation, while others indicate deterioration due to NOM variability and increased microbial activity. These discrepancies likely reflect local variations in raw water characteristics and treatment design.

This section aligns with Clusters 3 and 4, linking climate-driven variations in raw water quality with operational challenges in treatment processes and the necessity for adaptive technology-based responses.

3.3. Impacts on Water Supply Infrastructure

Water supply infrastructure is an essential component in ensuring a reliable supply of clean water for consumption and industry and ensuring the sustainable functioning and development of urban and rural communities [126].

Water supply systems have many functions such as water abstraction, supply, transfer, treatment, wastewater collection and treatment, treated wastewater management, and flood defense [126,127].

The role of water supply systems is crucial, but they need to be redesigned to ensure resilience and adaptability in the face of climate change, population growth, and rapid urbanization [128,129]. High pH and water temperature have been shown to increase the risk of microorganism proliferation in the distribution network, leading to deterioration of water quality [7].

Climate change, represented by rising/falling temperatures and precipitation deficits, directly impacts the maintenance and reliability of functional components, whereas extreme events require constant updates to emergency response plans and long-term changes to projects and operations [127,129,130]. The effects of climate variation on pipelines depend on the pipeline material and geographical region [129,131].

Consistent evidence indicates that temperature fluctuations are the key determinants of pipe failure. Numerous studies have shown that temperature variations are the main cause of pipeline failure during the winter [132,133,134]. According to Wols et al., 2019 [132], who analyzed the influence of weather conditions on pipeline failures, materials such as cast iron, silicon dioxide, polyvinyl chloride (PVC), and asbestos cement show varying degrees of correlation with low temperatures. PVC pipes have a higher failure rate in summer owing to higher temperatures, with most failures occurring owing to joint breakage [135].

A robust cause–effect link is also observed between increased salinity and corrosion rates, accelerating the deterioration of metallic components and reducing the service life.

It was noted that polyethylene pipes (PE) have been shown to have very low failure rates because they are resistant to corrosive soils, ground movements, weather conditions, and pressure changes caused by operational management [131].

Simultaneously, it has been found that high salt concentrations have a corrosive effect on the water supply infrastructure, particularly in pipes, tanks, and pumping equipment. This process promotes leaks, cracks, and structural degradation, significantly reducing the service life of installations [73]. Climate change, through changes in temperature and precipitation patterns, generates both droughts and floods, affecting surface and groundwater bodies differently, depending on their hydrological and morphometric characteristics. These phenomena cause variations in the content of organic matter, nutrients, and micropollutants, promote the proliferation of cyanobacteria and pathogens, and induce a series of problems in the processes of collection, treatment, and distribution.

These findings reinforce cluster 1’s focus on hydrological stress and risk management, emphasizing the importance of infrastructure adaptation and preventive maintenance to ensure resilience under climate variability.

3.4. Implications for Human Health

Climate change threatens human well-being and health [136]. This has led to an increase in temperature, and the frequency and intensity of both droughts and heavy rainfall, which have consequences for waterborne diseases.

High temperatures can influence the survival, multiplication, and virulence of pathogens, whereas heavy rainfall can facilitate their mobilization and affect the functioning of the water supply and sanitation systems [114,115,116]. Rainfall is also associated with microbiological contamination [137]. Drought periods also contribute to the concentration of pathogens in water resources [138,139,140].

According to the IPCC report (https://www.ipcc.ch/report/sixth-assessment-report-working-group-ii/; accessed on 29 August 2025), there is very high confidence that waterborne disease risks will rise significantly under projected climate scenarios. Annually, approximately 1.8 million people die from contaminated water, and 3900 children perish daily due to poor sanitation [141]. Studies have reported that up to 80% of diseases in developing regions, such as Pakistan and Bangladesh, are water related [142].

The most robust evidence concerns the temperature dependence of Vibrio spp. and cyanobacteria, whose proliferation correlates strongly with warming and eutrophication.

Increased aquifer temperature and changes in salinity cause the development and proliferation of numerous Vibrio spp. such as Vibrio cholerae. Therefore, it is essential to emphasize that temperature variations can substantially alter host–pathogen interactions, leading to a series of gastrointestinal infections [116,117,140,143]. The spread and development of microorganisms such as bacteria (Salmonella, Escherichia coli, Vibrio cholerae), viruses (Rotavirus, Norovirus, Adenovirus), and protozoa (Giardia, Cryptosporidium and Cyclospora) are influenced by extreme weather events, such as floods, droughts, and hurricanes, which significantly influence the quality of drinking water in rural and urban areas, generating an increased risk to public health, manifested by the increased incidence of waterborne diseases [140,141,144].

Waterborne diseases include a wide range of infections caused by pathogens belonging to various taxa (viruses, bacteria, protozoa, and helminths). These etiological agents are responsible for a wide range of clinical manifestations, including diarrhea, fever, flu-like symptoms, neurological disorders, and liver damage [136,140].

According to a study by Bhandari et al., 2020 [144], there was a significant positive association (p < 0.05) between infant diarrhea and increases in maximum temperatures and rainfall in Kathmandu, Nepal. Another study conducted in Vietnam established a link between the impact of flooding, consumption of contaminated water, dengue fever, pink fever, and skin problems [145].

A study conducted in Beijing (China) showed that water samples collected after a flood were of unsuitable quality for human consumption. Both flooding and drought can compromise the chemical characteristics of water, generating major effects on public health and amplifying the risks associated with water use [146].

Climatic factors, combined with social factors, exacerbate their impact on health. Climatic factors can affect communities where social factors, such as poverty, population density, living conditions, and lack of health services, including inadequate water supply and sanitation, are prevalent. These consequences are expected to worsen, leading to increased morbidity and mortality in the future [141,143,144,147].

Climate change exacerbates existing social vulnerabilities such as poverty, population density, and inadequate sanitation, amplifying health risks. This corresponds to Cluster 2, which integrates ecological and epidemiological perspectives, underscores the urgency of water safety and public health adaptation strategies.

3.5. Future Research Directions

Climate change is amplifying problems related to water quality, and the effects of rising temperatures and more extreme weather events are becoming increasingly apparent. Although existing research has identified important milestones, many gaps remain in our understanding of how these processes will evolve in the future.

In this context, new research directions are needed to provide practical answers and support sustainable water resource management, such as long-term monitoring of quality indicators to capture hydroclimatic variability and the effects of recurring extreme events [148,149], assessing water quality resistance to rising temperatures and extreme climate events [150,151], studying the relationships between water quality and higher trophic networks, with a focus on the availability of trace elements and potential limitations [152], continuous development and validation of integrated river basins, and receiving water models capable of predicting the future impact of climate change on water quality [56,153,154,155], studying the potential impact of climate change on the occurrence and fate of micropollutants, and changing the behavior of water consumers under the influence of climate change.

4. Conclusions

Climate change is expected to have a significantly negative impact on water quality in many regions of the world. This study clearly illustrates several important aspects of climate change and its negative impact on water quality, examining the interconnections between climate variables and the stages of the water cycle from collection to treatment to distribution, and the impact this has on human health.

The results of this analysis highlight that temperature changes, uneven rainfall distributions, and extreme weather events cause significant changes in the structure and dynamics of water resources. These processes intensify eutrophication, salinization, and contaminant mobilization, favoring the development and spread of pathogens. In this context, water treatment and distribution systems are under additional pressure, and the risks to public health are increasing significantly.

Based on these findings, a better understanding of how climate change affects water quality is needed to develop effective strategies to prevent and manage its impact on public health. Trends highlighted in the literature confirm the gradual deterioration of water quality as a result of climate change, leading to increased risks to human health and the water supply infrastructure. Extreme events, such as torrential rains, storms, hurricanes, and droughts, directly influence pollutant loads, making surface waters more vulnerable to contamination. The persistence of emerging pollutants, such as pharmaceutical compounds, per- and polyfluoroalkyl substances (PFAS), and microplastics, is one of the greatest challenges for modern water treatment technologies. These substances, which are difficult to remove and are sensitive to climate variations, can compromise the efficiency of treatment processes and the quality of drinking water. Increasing temperatures and salinity also accentuate corrosion processes, biofilm formation, and the generation of disinfection by-products.

Climate change also affects groundwater, altering the rate of surface pollutant infiltration, changing the chemical composition of aquifers, and causing saltwater intrusion in coastal areas. Overall, rising temperatures and extreme weather events alter the physical, chemical, and biological indicators of surface and groundwater, particularly affecting sensitive parameters, such as nitrates and dissolved organic carbon.

The results confirm the close relationship between climate change and the UN’s sustainable development goals, in particular, SDG 6—Clean water and sanitation—and SDG 13—Climate action. To mitigate these effects, it is necessary to implement integrated adaptation strategies that combine modern technological solutions, with nature-based solutions and more effective governance.

• Technological innovation through the adoption of advanced treatment processes (membrane filtration, advanced oxidation, and adsorption), continuous monitoring of water quality, and adaptation of operating parameters to variable climatic conditions.
• Ecosystem measures through the restoration of wetlands, protection of riparian strips, and exploitation of natural nutrients and sediment retention processes.
• Strengthening governance through collaboration between authorities, operators, and researchers so that adaptation policies are integrated and consistent with European directives and national legislation.

Despite progress, significant knowledge gaps remain. Future research should focus on the following aspects:

• Developing complex models that correlate hydrological, chemical, and biological processes under the influence of climate change;
• Expanding long-term monitoring programs, especially for emerging pollutants and pathogenic microorganisms;
• Assessing the socio-economic impact of water quality degradation and risks to public health.

Existing research on the link between climate change and the behavior of persistent organic pollutants, emerging pollutants, and disinfection byproducts is still limited, although these substances pose a major threat to the effectiveness of treatment processes and public health. Further research is needed to identify methods for reducing the risks associated with these compounds in water sources. Studies on the impact of climate change on waterborne diseases and water supply infrastructure also remain insufficient, although existing data indicate multiple vulnerabilities, from changes in the quantity and quality of resources to variations in consumption and system operation.

Given the interdependence between climate change and sustainable development, ensuring access to safe drinking water in the context of climate change requires a holistic and preventive approach. Protecting water quality in the face of climate change requires integrating scientific research, technological innovation, and political responsibility into a unified framework for sustainable water resource management.