The Role of Water Bodies in Climate Regulation: Insights from Recent Studies on Urban Heat Island Mitigation

Abstract

Urban heat islands (UHIs) pose a significant challenge in cities worldwide, exacerbating energy use, air pollution, and health risks. This paper reviews the role of water bodies in mitigating UHI effects, which is vital for informed urban planning and climate adaptation. We analyze how water features, particularly when combined with green spaces and strategic urban design, can significantly cool urban environments. The effectiveness of water bodies in reducing temperatures is influenced by their size, shape, surrounding land use, climatic conditions, and vegetation. Empirical research and case studies indicate that larger and well-shaped water bodies, due to their extensive surface area and continuous evaporation, are more effective. Furthermore, the integration of water bodies with green spaces enhances cooling through increased evapotranspiration and shading. This review highlights the strategic placement and design of water bodies within urban landscapes as crucial for maximizing their cooling benefits. By integrating water features with other urban cooling strategies, such as tree planting and expanded greenery, cities can effectively counter UHI effects, leading to more sustainable and resilient urban environments.

1. Introduction

Urban heat islands (UHIs) are characterized by elevated temperatures in urban areas compared to their rural surroundings, primarily due to anthropogenic activities and the concentration of heat-absorbing infrastructure [1,2,3,4,5,6]. This phenomenon exacerbates the effects of heat waves, increases energy demand for cooling, and poses significant public health risks [7,8,9]. To mitigate these challenges, urban planners are exploring the cooling potential of water bodies, including rivers, lakes, and artificial ponds, through mechanisms such as evaporative cooling and modification of local wind patterns.

Water features can effectively lower urban temperatures by utilizing natural processes like evaporation and convection. As water evaporates, it absorbs latent heat from the surrounding environment, resulting in localized cooling. This process is particularly effective in hot, arid conditions where the atmosphere can accommodate higher moisture levels. Empirical studies have demonstrated that water bodies can significantly reduce land surface temperatures (LSTs). For instance, research conducted in Wuhan, China, revealed that water features could reduce daytime surface temperatures by up to 3 °C, with the cooling effect extending up to 800 m from the water’s edge [9,10].

The cooling efficiency of water bodies is influenced by their size and shape. Larger water bodies generally provide more substantial cooling effects due to their expansive surface areas, which facilitate greater heat absorption and evaporation. Additionally, the geometric configuration of water bodies plays a crucial role; regularly shaped features, such as those of circular or square water bodies, tend to deliver more consistent cooling compared to irregularly shaped ones, as uniform shapes promote balanced evaporation and airflow dynamics [11].

Surrounding land use and the extent of impervious surfaces also impact the cooling effectiveness of water bodies. Areas with adjacent green spaces experience synergistic cooling effects, as vegetation enhances evapotranspiration and provides additional shading. Conversely, high concentrations of impervious surfaces, such as concrete and asphalt, can diminish the cooling effect by reflecting and retaining heat [12].

A comprehensive review by Taylor et al. (2022) [11,12] on urban water features across Canadian cities underscored the importance of strategic urban planning. The review concluded that integrating water bodies with green infrastructure, such as urban forests and green roofs, can create synergistic cooling effects. This integrated approach not only enhances cooling potential but also improves overall urban resilience to heat waves.

Further research has explored the cooling benefits of smaller urban water features in Canadian cities. For example, a study in Montreal demonstrated the advantages of incorporating artificial ponds and fountains into urban parks. Lemieux et al. (2021) [13] found that these features could reduce surrounding air temperatures by up to 2 °C during peak heat wave periods. Similarly, in Calgary, the Bow River has been identified as a natural cooling source, with Smith and Chen (2018) [14] noting that the river’s cooling influence extends up to 500 m from its banks.

These findings highlight the critical role of water bodies in regulating urban climates and emphasize the need for continued research and innovative urban planning strategies to maximize their benefits. By incorporating both natural and artificial water features, Canadian cities can effectively mitigate the UHI effect, contributing to more sustainable and livable urban environments. As climate change accelerates and urban populations grow, the strategic integration of water bodies into urban planning will be essential. Optimizing the cooling mechanisms of water systems will enhance urban resilience to heat waves, reduce energy consumption, and improve residents’ quality of life.

The following section outlines the research design, detailing the keywords, search strategy, and the review roadmap. Section 3 summarizes the cooling effects of water bodies. In Section 4, an analysis of reviews are presented, along with a discussion of the factors that influence the cooling efficiency of water systems. The concluding section highlights the key findings, identifies research gaps, and outlines future research needs. It also provides guidance for policymakers and urban planners on mitigating the adverse impacts of heat waves in urban environments. Figure 1 outlines the comprehensive roadmap of the structure of this paper and the logical relationships among water bodies’ effects on the UHI.

2. Research Design

This literature review examines research on the impact of municipal water bodies on the UHI effect, with a focus on Canadian cities. The review examines the range and intensity of the cooling effects provided by water bodies, the factors that influence these effects, and the implications for urban planning. By integrating findings from a variety of studies, this paper offers a comprehensive understanding of how water bodies contribute to cooling urban areas and provides insights for urban planning and policy development. A systematic approach was employed to ensure thorough coverage of relevant studies, identifying key themes and trends within the literature as outlined below.

2.1. Keywords and Search Strategy

To identify relevant literature, a comprehensive search strategy was formulated using the following keywords and phrases:

• “Urban Heat Island” AND “Water Bodies” AND “Water Systems”;
• “Cooling Effect” AND “Urban Planning”;
• “Municipal Water Features” AND “Bluespaces”;
• “Urban Climate Regulation” AND “Canada”;
• “Lake Ontario” AND “Urban Heat”;
• “Vancouver Water Features” AND “Urban Cooling”;
• “Urban Heat Island Mitigation” AND “Canadian Cities”;
• “Urban Trees” AND “Cooling Effect”;
• “Urban Green Spaces” AND “Temperature Reduction”.

These keywords were combined using Boolean operators to refine the search results. The search was conducted across several academic databases, including Google Scholar, PubMed, Web of Science, and JSTOR. The inclusion criteria were: (1) peer-reviewed journal articles, (2) studies examining the impact of water bodies on urban temperatures, and (3) research conducted in Canadian cities or studies offering relevant comparative analysis. Articles published between 2000 and 2023 were included to ensure the review captured the most current and pertinent studies.

To illustrate the trends in research related to Canada, a flowchart was developed (Figure 2). This flowchart maps the progression of research topics and findings over time, showing the evolution from general studies on the UHI effect to more focused analyses of the role of water bodies in urban cooling.

The process of reviewing the literature on this topic presented several challenges due to the volume, diversity of methodologies, inconsistent terminologies, and geographical and contextual variations of the studies involved. The extensive number of articles necessitated the implementation of stringent criteria to refine the selection while preserving essential insights. Different methodologies across studies complicated the synthesis and comparison, requiring careful evaluation to ensure valid and meaningful comparisons. Additionally, inconsistencies in terminologies across the literature demanded standardization for accurate analysis. Many studies’ geographic and contextual diversity sometimes limited their direct applicability to our specific focus, necessitating a critical assessment of each study’s relevance. Furthermore, challenges related to publication bias, where certain types of studies or outcomes were more frequently published, required a careful balance in article selection to maintain a comprehensive and unbiased review. These factors combined to create a complex landscape for conducting a thorough and applicable literature review. Despite these challenges, we were able to curate a robust set of articles that provided valuable insights and a solid foundation for our study.

2.2. Data Collection and Analysis

The PRISMA (Preferred Reporting Items for Systematic Reviews and Meta-Analyses) methodology was adapted to ensure a systematic and transparent selection process for the articles included in the review. This widely recognized framework helps maintain a comprehensive and unbiased approach to literature reviews.

The process began with a comprehensive search of relevant databases, yielding 2350 articles through keyword searches, reference lists, and consultations with subject matter experts. After identifying the articles, duplicates and non-relevant studies were removed during the initial screening, where titles and abstracts were reviewed to exclude those that did not meet the inclusion criteria, such as studies unrelated to the research focus or lacking empirical data. Next, full-text articles were assessed for eligibility based on predefined criteria, including relevance to the research question, methodological rigor, and the quality of data presented. Articles that failed to meet these standards were excluded. Ultimately, more than 70 high-quality articles were selected for inclusion in the final review, chosen for their strong relevance and robust evidence in addressing the research questions.

By employing the PRISMA methodology, the selection process was conducted systematically, transparently, and with careful consideration, ensuring the review’s credibility and rigor.

As such, each article was meticulously analyzed to extract pertinent information, including the following:

• Study location and context;
• Type and size of water bodies studied;
• Methodologies used (e.g., empirical analysis, modeling);
• Key findings on the cooling effects of water bodies;
• Factors influencing the cooling effects (e.g., climatic conditions, integration with green spaces);
• Implications for urban planning and policy recommendations.

The extracted data were synthesized to identify common themes, patterns, and gaps in the literature. A narrative approach was utilized to summarize the findings, emphasizing the role of water bodies in mitigating the UHI effect and identifying factors that enhance or limit their effectiveness. However, in this paper, we focus on summarizing the 76 most relevant articles that illustrate the impact of water bodies on UHI and their role in moderating urban climates.

Accordingly, the efficiency of cooling provided by water bodies is influenced by various factors, including size, shape, depth, distance from water bodies, surrounding land use, and climatic conditions. Understanding these factors is essential for optimizing the cooling potential of urban water bodies and effectively integrating them into urban planning strategies. Figure 3 shows a summary of the factors affecting the cooling efficiency of water bodies. In the following sections, a summary of the effects of each parameter is provided.

3. Physical Characteristics of Water Bodies

The size and shape of water bodies can affect the ambient and surface temperatures. Larger water bodies generally provide more substantial cooling effects due to their greater surface area, which facilitates significant heat absorption and evaporation. Regularly shaped water bodies, as noted by Gunawardena et al. (2016) [15], tend to enhance cooling efficiency by promoting uniform evaporation and airflow patterns. Research conducted by Sun et al. in Beijing, China, demonstrated that wetlands also have significant cooling effects, particularly in areas with high levels of evapotranspiration. Their study found that air temperatures within 1 km of the wetlands could be reduced by up to 4 °C [16].

Similarly, Du Hongyua et al. (2016) [17] found that lakes in Shanghai had a more substantial cooling impact than rivers, with average air temperature reductions of 3.3 °C for lakes and 2.3 °C for rivers. This study highlighted that both the size and depth of water bodies influence their cooling capacity, with larger and deeper lakes providing more pronounced air and land surface temperature reductions. Li et al. (2016) [18] found that deeper lakes in urban areas provided more prolonged cooling compared to shallow ponds. As such, deeper water bodies can store more heat and release it gradually, contributing to sustained cooling effects, particularly at night.

In Colombo, Sri Lanka, Gunawardena et al. (2017) [19] observed that urban lakes could reduce ambient air temperatures by up to 3 °C, with the cooling effect extending approximately 500 m from the water’s edge. This study utilized both remote sensing data and ground-based temperature measurements to confirm the cooling patterns. In another study, Zhi Cai et al. (2018) [20] found that water bodies in Chongqing, China, exhibited lower land surface temperatures (LSTs) compared to their surroundings, with cooling effects extending up to 1 km. The cooling effect was particularly pronounced during summer, with temperature reductions of up to 4 °C near large water bodies.

Overall, these studies consistently demonstrate that areas with water features exhibit lower temperatures compared to their surroundings, with the cooling effect most pronounced within 500 m of the water bodies and gradually diminishing beyond this range. This pattern aligns with previous research, reinforcing the potential of water bodies to mitigate UHI effects. Figure 4 shows the temperature reduction at various distances from water bodies.

To further illustrate the cooling effects of water bodies, remote sensing data and temperature measurements from previous studies were analyzed for various Canadian cities. The land surface temperature (LST) in urban areas, both with and without significant water bodies, was examined. Geographic Information System (ARCGIS Pro 3.3) software was employed to map temperature variations and identify cooling patterns associated with the presence of water bodies. The analysis consistently revealed that areas near water bodies exhibited lower temperatures compared to their surroundings. The cooling effect was most pronounced within 500 m of the water bodies and gradually diminished beyond this distance (Figure 5). This pattern aligns with findings from previous research, underscoring the potential of water bodies to mitigate UHI effects. The first graph (Figure 5a) shows the change in LST with increasing distance from water bodies, and the second graph (Figure 5b) displays the correlations between mean LST and distance from water bodies.

4. Climatic Interactions

The cooling efficiency of water bodies is influenced by various climatic factors, including, but not limited to, humidity, wind patterns, and ambient temperature. In hot and arid climates, the cooling effect is typically more pronounced due to the accelerated rates of evaporation. Conversely, in humid environments, this cooling effect may be less significant as the high moisture content in the air inhibits evaporation. A study by Oke et al. (2017) [21,22] demonstrated that urban water bodies in Mediterranean climates provided substantial cooling during the hot, dry summer months, although this effect diminished during the more humid winter season.

Wind patterns also play a critical role in modulating the cooling effect of water bodies. In regions with strong and consistent winds, the cooling influence can extend further inland, providing thermal relief to larger urban areas. Wind aids in the distribution of cooler air from the water body to the surrounding environment. Research by Stewart and Oke (2012) [23] highlighted that in coastal cities, variations in wind direction and speed could significantly alter the extent and magnitude of cooling provided by adjacent water bodies.

The ambient temperature establishes the baseline from which the cooling impact is measured. In regions with higher ambient temperatures, such as deserts or subtropical zones, the cooling effect of water bodies becomes more noticeable. For instance, a study by Chow and Roth (2006) [24] conducted in Singapore, a tropical city-state, revealed that even small water bodies could reduce the surrounding air temperature by up to 2 °C, particularly during the hottest parts of the day.

Wei et al. (2024) [25] investigated the effects of anthropogenic activities and climate change on ecological sensitivity (ES) within the Yangtze River Economic Belt (YREB). The study highlights the importance of understanding how these factors interact to affect ES, an area that has been underexplored. From 2001 to 2021, ES in the YREB showed fluctuations, with an overall increase of 2.2%, primarily due to declines in biological abundance and water network density. Spatially, ES was higher in the north and lower in the south, with nearly 50% of cities in 2021 exhibiting relatively high sensitivity [25].

In European cities, lakes and rivers have been shown to substantially contribute to urban cooling. Völker et al. (2013) [26] found that in Berlin, Germany, water bodies were most effective in lowering nearby air temperatures by 1.5–2.5 °C during hot summer days. This study utilized a combination of empirical measurements and numerical simulations to assess the cooling effects and their implications for urban planning.

Similarly, in North America, water bodies offer considerable cooling benefits. For example, Jansson et al. (2007) [27,28] observed that urban lakes and ponds in Phoenix, Arizona, could reduce local air temperatures by up to 2.5 °C, with the cooling effects varying depending on the size and configuration of the water bodies. This research suggested that strategically positioning water bodies could mitigate the urban heat island (UHI) effect and enhance urban microclimates.

Canadian cities experience a wide range of climatic conditions, from temperate to subarctic, providing a comprehensive understanding of how water bodies influence UHI across different climate zones. The urbanization patterns in Canadian cities are unique and offer a valuable case study for examining the interplay between natural water bodies and urban development, which can differ significantly from other regions. In addition, given the growing emphasis on climate resilience and sustainable urban planning in Canada, understanding the role of water bodies in mitigating UHI effects is particularly relevant for developing targeted policies and strategies. By also focusing on Canadian cities, this study aims to contribute to both the scientific understanding of UHI mitigation and the development of practical strategies that can be applied both within Canada and potentially in other regions with similar climatic and urban characteristics.

In Toronto, Canada, the cooling influence of Lake Ontario extends several kilometers inland, contributing to lower temperatures in adjacent neighborhoods. Broadbent et al. (2020) [12] demonstrated that Lake Ontario’s cooling effect can reduce peak summer temperatures by up to 3 °C in nearby urban areas. Similarly, Vancouver’s numerous water features, including its extensive coastline, play a vital role in regulating urban temperatures. A study by Oke and Maxwell (2019) [22] found that the presence of water bodies such as False Creek and Burrard Inlet could reduce local temperatures by approximately 2–4 °C, thereby influencing the urban microclimate. This research further suggests that urban planning should prioritize the preservation and integration of water bodies to enhance thermal comfort in cities.

Overall, the cooling effects of water bodies vary significantly across different climatic regions due to differences in evaporation rates, humidity levels, solar radiation, wind patterns, and seasonal temperature fluctuations. For instance, in tropical regions, where humidity is already high, the cooling effect of water bodies is often more pronounced in terms of moderating temperature rather than drastically lowering it. The presence of water bodies can enhance local humidity, which may provide relief from extreme heat but can also make the air feel more humid. Due to the relatively stable temperature patterns throughout the year, water bodies in tropical climates tend to provide a consistent cooling effect, helping to reduce heat stress during both day and night.

On the other hand, in Mediterranean climates, the cooling effects of water bodies are more seasonal, with a stronger impact during the hot, dry summers. The cooling effect is particularly valuable during heat waves, providing a local microclimate that is cooler and more comfortable. As such, the cooling effect in Mediterranean climates is often more noticeable during the day, as the contrast between the warm air and the cooler water surface helps moderate daytime temperatures. At night, the cooling effect continues but may be less pronounced compared to arid regions.

In arid climates, where daytime temperatures can be extremely high and humidity is low, water bodies provide a stark cooling contrast. The cooling effect is typically more intense in these regions, as the dry air allows for more effective evaporative cooling. Water bodies in arid climates often contribute significantly to nighttime cooling, as the dry environment allows heat to escape rapidly. This can create a much cooler microclimate around the water body, offering significant relief from the daytime heat.

Accordingly, in tropical climates, the cooling effect is moderated by high humidity and consistent solar radiation, whereas in Mediterranean climates, the effect is more pronounced during hot, dry summers. In arid climates, the cooling effect is substantial but localized, driven by high evaporation rates and extreme diurnal temperature variations. Understanding these regional differences is crucial for optimizing the design and placement of water bodies in urban environments to maximize their cooling potential.

5. Diurnal and Seasonal Variations

The cooling effects of water bodies are not only influenced by location but also exhibit significant seasonal and temporal variations. These fluctuations are shaped by factors such as solar radiation, atmospheric conditions, and the thermal properties of water. Research indicates that the cooling effect of blue spaces is most pronounced during the daytime, especially in warmer months, while at night, particularly towards the end of summer, a warming effect is more likely due to thermal inertia [29]. These diurnal changes occur because, during daylight hours, water bodies typically absorb heat and gradually release it at night. This diurnal pattern results in substantial cooling during the day when solar radiation is most intense. However, at night, the retained heat in the water can lead to a warming effect in the surrounding areas.

A study by Zhao et al. (2018) [29] on the diurnal cooling effects of urban lakes in Beijing revealed that during the daytime, temperatures in areas adjacent to the lakes were reduced by up to 3 °C compared to non-water body areas. At night, however, these same areas experienced a slight temperature increase, approximately 1–2 °C higher than their surroundings, due to the gradual release of stored heat from the water. Similarly, Völker et al. (2013) [26] examined diurnal temperature variations around urban water bodies in Berlin, reporting that water bodies could reduce daytime temperatures by up to 2.5 °C, while at night, the cooling effect diminished, and in some cases, a warming effect was observed. This study highlighted the importance of considering the timing of cooling benefits in urban water features planning.

Seasonal variations in the cooling effects of water bodies are also significant. During summer, water bodies provide the most substantial cooling benefits due to higher evaporation rates and increased solar radiation. In winter, the cooling effect is less pronounced as the temperature difference between the water and the surrounding environment narrows. Hathway and Sharples (2012) [30] investigated the seasonal cooling effects of ponds and lakes in Sheffield, UK, and found that in summer, temperature reductions near water bodies could reach up to 4 °C, while in winter, the effect was minimal, with a reduction of only about 0.5 °C. Their study emphasized the role of water bodies in mitigating heat stress during the hottest months.

Similarly, Li et al. (2020) [31] analyzed seasonal cooling patterns of wetlands in Guangzhou, China, and found that the cooling effect was most significant during late spring and summer, with temperature reductions of up to 5 °C. In contrast, during autumn and winter, the cooling effect diminished to around 1–2 °C. Figure 6 shows the seasonal temperature variations close to water bodies.

Deeper water bodies also contribute to sustained nighttime cooling through a combination of thermal storage capacity, heat flux dynamics, temperature stratification, and prolonged evaporation. These processes ensure that the heat absorbed during the day is released gradually, preventing rapid temperature drops and maintaining a moderated and cooler urban microclimate throughout the night [32].

For instance, deeper water bodies have greater thermal inertia, meaning they can absorb and store more heat during the day compared to shallower water bodies. This stored heat is released slowly, helping to moderate temperatures and sustain cooling effects throughout the night. In addition, because of their depth, these water bodies experience less drastic temperature changes between day and night [33]. This stability helps maintain a cooler microclimate in the surrounding area, as the gradual release of heat from the water prevents sharp increases in nighttime temperatures.

Moreover, deeper water bodies tend to have a longer cooling period because of the greater volume of water that needs to release stored heat. This prolonged-release process extends the cooling effect well into the night, providing a more consistent and sustained temperature reduction [34]. Similarly, the gradual release of heat from deeper water bodies during the night can also influence the temperature of surrounding air masses, helping to maintain cooler air temperatures in the vicinity, which is especially beneficial in urban areas where nighttime heat retention is a common issue [29]. As such, understanding these mechanisms is essential for urban planners and environmental engineers aiming to leverage water bodies for UHI mitigation and enhance thermal comfort in cities.

The diurnal and seasonal variations in the cooling effects of water bodies suggest that urban planners need to consider complementary cooling strategies to address different times of the day and year. For instance, integrating water bodies with green spaces that provide shade during the day and additional cooling through evapotranspiration can optimize the overall cooling effect. Additionally, planning for nighttime cooling can involve using materials with low thermal inertia around water bodies to minimize the warming effect.

6. Synergistic Effects with Green Infrastructure

The cooling efficiency of water bodies is influenced by the surrounding land use. Areas with a higher proportion of green spaces (e.g., parks, trees, forests, green roofs, etc.) adjacent to water bodies (blue spaces) benefit from synergistic cooling effects, as vegetation enhances evapotranspiration and provides additional shading. Conversely, the presence of impervious surfaces, like concrete and asphalt, can reduce this cooling effect by reflecting and retaining heat.

Integrating water bodies with other forms of green infrastructure, such as urban forests, green roofs, and permeable surfaces, can amplify their cooling efficiency. The combination of water features and vegetation can create cooler microclimates and improve urban thermal comfort. Bowler et al. (2010) [12] found that cities strategically combining water features with extensive green spaces experienced greater reductions in urban temperatures compared to those that did not. Zhang et al. (2017) [35,36] demonstrated that urban parks with integrated water bodies and abundant vegetation exhibited a more pronounced cooling effect compared to water bodies surrounded by built-up areas. Similarly, Hathaway and Sharples (2012) [30] observed that the cooling effect of rivers in Sheffield, UK, was more significant in open urban forms with high vegetation levels. Jacobsa et al. (2020) [34] also emphasized that small urban water bodies might not provide substantial cooling unless combined with other strategies, such as shading and vegetation.

Wang et al. (2023) [37] emphasize the need to manage land and artificial water bodies better, highlighting their role in mitigating UHI effects and promoting sustainable use. Studies have also analyzed the impact of resource extraction on counties along rivers, emphasizing water-based services and their role in supporting sustainable riverine development [38,39].

Tan et al. (2021) [40,41] conducted a comprehensive study comparing the cooling effects of water bodies and green spaces in a tropical urban environment. Their findings indicated that water bodies could lower surrounding air temperatures by up to 4 °C, while green spaces achieved a temperature reduction of around 2–3 °C. The study also noted that water bodies provided more stable cooling effects throughout the day and night, unlike green spaces, which primarily offered cooling during the day due to evapotranspiration [40,41,42,43]. Trees and plants absorb heat during photosynthesis and release moisture into the air, cooling the surrounding environment.

Bowler et al. (2010) [9] reviewed multiple studies on urban green spaces and found that parks and urban forests could reduce local temperatures by up to 3 °C [9]. The effectiveness of green spaces varied significantly based on factors such as plant species, density, and canopy cover. The study highlighted those larger green spaces with diverse vegetation types offered the most substantial cooling benefits when integrated with water systems [43,44,45,46].

The integration of both green and blue spaces in urban areas has been shown to yield the most substantial cooling benefits. The synergistic effects of water bodies and vegetation can create cooler microclimates and improve urban thermal comfort more effectively than either type of space alone. Norton et al. (2015) [44] investigated the combined cooling effects of green and blue infrastructure in Melbourne, Australia, and found that areas with both water features and dense vegetation experienced temperature reductions of up to 5 °C. This combination enhanced evapotranspiration and provided more comprehensive shading, leading to greater overall cooling. Bowler et al. (2010) [9] also highlighted those urban areas incorporating both green and blue spaces could benefit from a combined cooling effect, suggesting that the integration of these spaces should be a key consideration in urban planning to effectively mitigate the UHI effect.

Another factor that needs to be considered is the impact of impervious surfaces surrounding urban water bodies. Materials like asphalt, concrete, and buildings prevalent in urban settings absorb and store substantial amounts of heat during the day, which is released slowly at night. This stored heat raises ambient temperatures, diminishing the natural cooling effects of nearby water bodies by reducing the temperature gradient necessary for effective heat exchange. The integration of impervious surfaces also disrupts natural airflow patterns around water bodies, which can hinder the dispersal of cool air. Additionally, these surfaces reduce evaporation rates—a crucial process for cooling—by increasing local temperatures and decreasing humidity. The absence of vegetation exacerbates this issue by limiting transpiration, which could otherwise contribute to cooling.

Increased runoff from impervious surfaces not only carries pollutants but also raises water temperatures, reducing the water bodies’ ability to cool the surrounding air. This runoff, warmer from surface contact and solar exposure, leads to thermal pollution, further diminishing the water’s cooling capacity and disrupting aquatic ecosystems. Impervious materials’ high thermal inertia means they change temperature slowly, maintaining elevated temperatures longer into the night and reducing water bodies’ effectiveness in nighttime cooling. This sustained warmth necessitates higher energy use for cooling in nearby structures and impacts thermal comfort. Moreover, the presence of these surfaces creates localized heat islands, particularly during intense solar radiation periods, and disrupts local microclimates by making the air consistently warmer and drier. Such conditions override the cooling effects provided by water bodies, especially in densely built areas with limited green spaces.

To counter these effects, urban planning should focus on integrating permeable materials, augmenting vegetation near water bodies, and designing landscapes that promote natural ventilation and evaporation. Addressing the impact of impervious surfaces can significantly enhance the cooling potential of urban water bodies, leading to more sustainable and comfortable urban environments.

As such, the integration of water bodies with green spaces in urban areas will offer a wide range of environmental, social, and economic benefits. These benefits are increasingly recognized as critical components in sustainable urban planning, particularly in mitigating the UHI effect, enhancing biodiversity, improving air and water quality, and providing recreational opportunities for urban populations. The synergistic effects of combining water bodies (blue infrastructure) with green spaces (green infrastructure) are well-documented in the scientific literature [29,47,48,49,50,51,52,53,54,55].

The blue and green integration improves air quality, as green spaces absorb pollutants and produce oxygen, and water bodies help capture particulate matter. The overall enhancement in air quality can lead to better health outcomes for city residents. Furthermore, the presence of both green and blue spaces creates diverse habitats, supporting a variety of plant and animal species, which enrich urban biodiversity. This biodiversity is crucial for ecological services such as pollination, pest control, and soil health maintenance.

Additionally, these integrated spaces play a significant role in stormwater management by absorbing and filtering runoff, helping to reduce flooding risks and mitigate the impacts of heavy rainfall, which is particularly vital in urban settings prone to flash floods. From a social perspective, these spaces provide recreational and leisure opportunities, promoting physical and mental well-being through activities in aesthetically pleasing environments. They foster social interaction and contribute to the community’s quality of life.

Economically, integrating water bodies and green spaces can elevate property values, attract tourism, and lower energy costs by reducing reliance on air conditioning in surrounding buildings. This holistic approach addresses critical urban challenges, such as extreme temperatures and flood management, while also boosting urban resilience against climate change.

These findings underscore the importance of a holistic approach to urban planning that integrates both green and blue spaces. Urban planners should consider the spatial arrangement, size, and type of these spaces to maximize their cooling benefits. The strategic placement of water bodies and green spaces can significantly enhance urban resilience to heat waves [56,57,58,59,60]. The consistent findings across different studies and geographical locations emphasize the importance of integrating water bodies into urban design, as they not only provide immediate cooling benefits but also enhance the overall urban microclimate, contributing to improved thermal comfort and reduced energy consumption for cooling.

7. Urban Sustainability through Green and Blue Infrastructure

Incorporating green and blue infrastructure into urban design is increasingly recognized as a critical strategy for mitigating urban heat island (UHI) effects, improving public health, and enhancing environmental sustainability. These infrastructures encompass a broad range of natural and semi-natural systems, including parks, green roofs, permeable pavements, wetlands, rivers, and artificial lakes, which work in synergy to cool urban environments, enhance biodiversity, and improve the overall quality of life in cities [55].

A key element in urban design is the strategic placement of green and blue infrastructure to maximize its benefits. Studies suggest that the cooling potential of these infrastructures can be optimized by placing them in areas where the UHI effect is most severe, such as densely populated neighborhoods, commercial zones, and areas with limited vegetation [61]. Additionally, urban planners should consider the layout of these elements in relation to prevailing wind patterns, topography, and sun exposure, which can significantly influence cooling effectiveness. Research has shown that incorporating tree canopies and water features in key locations can reduce surrounding temperatures by 2–5 °C [62]. Moreover, aligning green spaces with natural airflow corridors can enhance ventilation and contribute to cooling effects across a broader urban area.

Zoning laws and land use policies can ensure the successful integration of green and blue infrastructure into urban environments. Urban renewal projects and new developments should be mandated to incorporate these elements into their designs. Policies should also focus on protecting existing natural features, such as rivers, lakes, and wetlands, from urban encroachment [63]. Furthermore, incentives for developers, such as tax reductions or subsidies, can encourage the creation of sustainable urban landscapes [64]. By embedding green and blue infrastructures into urban policy frameworks, cities can become more resilient to the impacts of climate change, reduce energy consumption, and enhance the quality of urban life.

Additionally, the adoption of green and blue infrastructure contributes to climate resilience, a critical factor as cities face rising temperatures due to climate change. These infrastructures not only help reduce the immediate impacts of extreme heat events but also lower the associated health risks, such as heat-related illnesses, by providing cooler, more livable urban environments [65].

Stormwater management and flood mitigation is one of the primary benefits of incorporating water bodies and permeable green areas in urban landscapes. These elements help reduce surface runoff and lower the risk of flooding, especially in cities experiencing increased rainfall due to climate change [66]. Urban planning policies can mandate the inclusion of stormwater retention features, such as artificial ponds, wetlands, bioswales, and green roofs, which not only absorb rainwater but also enhance biodiversity. These features can be integrated into both new developments and retrofitted into existing urban areas [67].

In addition, sustainable drainage systems (SuDSs) are increasingly being implemented in cities to manage stormwater sustainably. SuDSs combine green infrastructure with traditional drainage systems to reduce runoff, filter pollutants, and improve water quality [68]. For example, SuDS features such as permeable pavements, rain gardens, and constructed wetlands work to naturally slow and treat stormwater before it reaches the drainage system. This method not only mitigates urban flooding but also contributes to long-term water management strategies by promoting groundwater recharge and reducing the burden on sewage systems during heavy rainfall [69].

The cooling and aesthetic benefits of green and blue infrastructure significantly impact public health and well-being. As mentioned before, the thermal comfort provided by shaded green spaces and the cooling effects of water bodies help reduce heat stress and mitigate heat-related illnesses, especially during periods of extreme heat [70]. This has particular relevance for vulnerable populations, such as the elderly and children, who are more susceptible to heat exhaustion and other related health issues. In addition, these infrastructures foster active lifestyles by encouraging outdoor activities like walking, cycling, and playing, further contributing to public health improvements [51].

Moreover, recreational spaces created by the integration of water bodies with green areas provide essential mental health benefits. Access to natural environments has been shown to reduce stress, improve mood, and foster social interaction [71]. Urban parks and water feature also provide vital spaces for community gatherings, exercise, and relaxation, enhancing the quality of life in densely populated urban areas where access to nature is often limited [72]. These benefits underscore the importance of developing urban policies that prioritize green and blue infrastructure to promote both physical and mental well-being among urban residents.

Integrating green and blue infrastructure into urban design can drive both economic and environmental sustainability. One key benefit is energy efficiency, as the cooling effects of green spaces and water bodies reduce the demand for air conditioning during hot periods, leading to significant energy savings. Research shows that this can result in a noticeable reduction in energy consumption, especially in cities where extreme heat increases energy demand [7]. This not only cuts energy costs for residents and businesses but also helps lower greenhouse gas emissions, contributing to global efforts to mitigate climate change.

Additionally, the presence of green and blue infrastructure can enhance property values, as proximity to parks, water features, and green spaces is often associated with higher property desirability. Homebuyers and developers are increasingly recognizing the value of these spaces for both aesthetic and functional purposes, such as flood protection and pollution control. Policies that encourage or mandate the integration of these elements in new developments can further drive economic growth and urban regeneration Furthermore, municipalities can benefit from increased tax revenues due to rising property values in areas with green and blue infrastructure.

The integration of green and blue infrastructure also enhances urban biodiversity and ecosystem services. Creating habitats for a variety of species within urban environments can support diverse flora and fauna, fostering ecosystems that provide essential services such as pollination, carbon sequestration, and natural cooling [70]. Policies that promote the design of biodiversity-friendly urban spaces can help counter the habitat loss caused by urbanization, contributing to the health and resilience of urban ecosystems.

Another significant benefit of integrating water bodies and green spaces is their ability to improve water and air quality. Vegetation can naturally filter pollutants from the air, while wetlands and other water features can remove contaminants from stormwater before it enters larger bodies of water or the sewage system. This contributes to healthier urban environments and reduces the burden on artificial water treatment systems [72]. Overall, green and blue infrastructure helps cities address environmental challenges while supporting economic development.

8. Key Findings and Future Research Needs

Water bodies possess significant potential to mitigate the urban heat island (UHI) effect in urban environments, offering substantial cooling benefits. These benefits are influenced by various factors, including the size, shape, and depth of the water bodies, surrounding land use, and local climatic conditions. Research suggests that larger and more regularly shaped water bodies tend to deliver more consistent and pronounced cooling effects. Moreover, green spaces adjacent to water bodies can amplify cooling through synergistic processes, while impervious surfaces, such as concrete, can diminish these benefits. The cooling effect of water bodies is often more pronounced in hot and dry conditions due to higher evaporation rates. However, while water bodies provide significant cooling during the day, they may exhibit a warming effect at night, especially late in the summer. Seasonal variations also impact these effects, with more substantial cooling observed during warmer months.

Despite these insights, several research gaps remain that need to be addressed to fully harness the cooling potential of water bodies. There is a need for long-term studies that monitor the cooling effects of water bodies across various seasons and over multiple years. Such research would enhance our understanding of the temporal dynamics and sustainability of these effects. Additionally, further research is necessary to explore how water bodies interact with other urban microclimates and their combined impact on urban thermal comfort. Understanding these interactions could lead to more effective UHI mitigation strategies.

Although integrating green and blue spaces shows promise for enhanced cooling, there is a lack of quantitative studies that accurately measure these synergistic effects. Research in this area could provide valuable insights for urban planning. In addition, more research is needed to assess the direct impact of cooling provided by water bodies on human health and well-being, particularly during extreme heat events. This is especially crucial for vulnerable populations such as the elderly and infants.

Research focused on optimizing the placement, design, and maintenance of water bodies within urban landscapes is crucial for maximizing their cooling efficiency. Such research could inform urban planning and policymaking to better utilize water bodies for UHI mitigation.

To inspire and guide future research, studies should prioritize several areas. Advanced modeling techniques should be utilized to simulate the long-term impacts of water bodies on urban climates, including the effects of climate change, which will provide deeper insights into their role in urban resilience. Additionally, developing urban planning strategies that integrate water bodies with other green infrastructure, such as green roofs and permeable pavements, could significantly enhance urban resilience to heat waves.

Furthermore, formulating and promoting policies that encourage the inclusion of water bodies in urban development projects is essential. This should include guidelines for the effective maintenance and management of these features. Lastly, raising public awareness about the benefits of water bodies and promoting community participation in maintaining and protecting these urban assets will be key to their long-term success.

The potential of water bodies to mitigate the UHI effect is substantial, but fully realizing this potential requires a holistic and multidisciplinary approach. By addressing the identified research gaps and focusing on the outlined future research needs, urban planners, policymakers, and researchers can develop more effective strategies. These strategies will not only enhance the cooling benefits of water bodies but also contribute to the creation of more sustainable, livable urban environments and improved public health and well-being in the face of rising global temperatures and increasing urbanization.