Adaptation strategies for climate change impacts on water quality: a systematic review of the literature

There is consensus between scientists and policymakers that human-induced climate change is occurring, with substantial unavoidable impacts despite future reductions in greenhouse gas emissions (IPCC 2022). The consequences of climate change are geographically complex and are manifesting at regional and local scales. To reduce or prevent these consequences, we must lower our emissions. Such actions are referred to as mitigation strategies. However, climate change impacts are irreversible, and as we experience these effects, we must adapt to the new conditions. The IPCC (2022) describes these measures as adaptation strategies that must work across scales and address both the opportunities and risks arising from climate change. As mitigation responses have so far been limited, adaptation strategies have gained importance to respond to climate change and the impacts that it will have on local communities (Baker et al. 2012).

Water is a complex resource that not only supports human and ecosystem health and is essential for food and energy production and transportation services, but also provides cultural, aesthetic, and recreational values (Miller & Belton 2014). Khaniya et al. (2021) concur that water is central to the wellbeing of mankind and the functioning of sustainable ecosystems, and as such, any variations in climate can negatively impact the quality and availability of water resources. Therefore, as Cross & Latorre (2015) emphasise, it is important to develop necessary response mechanisms to protect public health and the environment.

To date, research has predominantly focused on the climate change impacts on the availability of water rather than its quality, despite the mounting evidence that water quality issues are of equal significance and concern (Coffey et al. 2014). While the availability of water is undoubtedly an important issue, there is also a need to direct attention to impacts on source water quality. Water quality compromised by climate change-related meteorological events can hinder the ability of conventional treatment systems to provide communities with quality drinking water (Levine et al. 2016).

As climate change impacts increasingly stress natural resources, water quality requires additional attention, as long-term strategies for preserving environmental services and public health fail to gain traction. To address this gap in the literature, this research aims to understand how we can better deal with the impacts of climate change on water quality and focuses on best practice adaptation strategies to the impacts of climate change on water quality in the peer-reviewed literature. Water quality is impacted not only by climate change but also by urban development and increasing population; however, it is almost impossible to separate the contribution of each. Regardless, the scope of this research is limited to climate change impacts. As such, strategies developed for holistic water management were excluded from this review in favour of those with a specific focus on water quality.

After briefly describing the methods used in this systematic review, we present the results. To assess adaptation strategies for climate change impacts on water quality, one must first identify the risks posed by climate change. So, we first examined how water will anticipate, absorb, adapt to, or recover from future climate change scenarios. Secondly, we distinguished the broad approaches to building resilience to climate change impacts as coping, incremental, or transformational to determine the level of foresight involved. Then, we studied each adaptation strategy in detail to categorise its approach and identify best management practices for water quality. Finally, we identified the factors that positively and negatively influence the implementation of these strategies to gauge a measure of potential implementation success. We anticipate that the identification of broad adaptation strategies may aid their translation to specific tangible actions at the local level.

The Google Scholar and Scopus online databases were used to search English language, peer-reviewed academic literature, using the keywords ‘climate’, ‘adaptation’, and ‘water quality’ to identify relevant articles. In Google Scholar, the first 120 records of the 284,000 hits were screened for publication type excluding book chapters and grey literature. The contents of the selected records were then skimmed to determine their relevance to the topic, resulting in 39 papers selected for detailed assessment. A second Google Scholar search was undertaken with the same keywords in the title of the articles resulting in five additional papers. The Scopus database search of article title, abstract, and keywords produced 620 hits. The first 160 records by relevance were screened for publication type following the same procedures, resulting in 51 papers. A second Scopus search was undertaken limiting the search to the article title only adding another three papers to the database.

An initial review of the identified records showed that many lacked adaptation strategies. As a result, additional searches were undertaken in both databases using the search string (‘climate’ AND ‘adaptation’ ‘water quality’ ‘(strategies OR measures)’). These searches identified not only relevant literature on how water quality will be impacted by climate change but also adaptation strategies or measures.

After identification, screening, and assessment of eligibility, the records identified through the six different searches were amalgamated and duplicates removed. The resulting 111 records were then assessed in detail with only 78 identified as directly relevant to the research questions. These articles were coded in NVivo qualitative analysis software and are listed in the Supplementary Material.

Discovering research that not only focused on impacts of climate change on water quality, but also recommended adaptation strategies, has proved challenging. At times, it was impossible to separate the impacts of other factors such as urban development and population growth. Furthermore, much research aggregates data on water availability with the quality of the water. In the scant literature that focused on impacts of climate change on water quality, the emphasis was often on the data rather than recommended adaptation strategies. These factors significantly limited the literature relevant to this review. Due to the dearth of literature on the topic, the review was not limited geographically, temporally, or thematically. Water quality was examined holistically without differentiating the physical, chemical, and ecological indicators. The research also did not distinguish between the various types of water bodies and includes surface water, such as lakes, rivers, streams, and reservoirs, as well as groundwater.

The amount of research on climate change impacts on water quality has been gaining momentum in recent years. The SQLR identified the most concerning climatic changes anticipated to impact water quality, the approaches to building resilience to these impacts, and the adaptation strategies being proposed or adopted. Finally, it also discovered some of the barriers and drivers of the implementation of these adaptation strategies that would influence their measure of success.

The 78 articles included in the review were published in 50 different journals, as listed in the Supplementary Material. The majority of the articles were contained in meteorological journals (31%), followed by science journals (28%), environmental studies (12%) and geography (10%) journals. Environment and agriculture journals and environment and sustainability journals published 5% of the articles each, followed by urban planning and mathematics journals with 3% each. Only one article relevant to the review was published in a civil engineering publication.

While the responses to global warming have historically been the mitigation of greenhouse gas emissions through national and international initiatives, the consequences of climate change are manifesting at regional and local levels (Baker et al. 2012). It is anticipated that climate change will affect the quality of water in local and regional areas through a number of different climate-related pathways, including drought, increased rainfall, higher temperatures, and more frequent and severe natural disasters (Bates et al. 2008). The IPCC (2022) notes that climate change will impact water quality through increases in stream temperatures and nitrogen loading in rivers. The articles reviewed indicate that, of the climate impacts, increases in temperature and changes to precipitation patterns will have the most significant effect on water quality.

Because the surface water temperature is largely dependent on ambient air temperature, an increase in temperatures under a warmer climate will result in changes to water temperatures (Palmer et al. 2009; Whitehead et al. 2009a, 2009b; Alam et al. 2013; Coffey et al. 2014; Chang et al. 2015; Anisha & Yunus 2016; Shannon et al. 2019). Bi et al. (2018) state that water temperature changes will result in significant disruptions to the normal aquatic ecological balance through changes in water density, surface tension, and viscosity. The most significant impacts on water quality are the changes to water chemistry and thermal stratification. An increase in water temperature can increase the risk of degraded water chemistry and anoxic conditions (Shannon et al. 2019). This can lead to water contamination through increases in pollutants, microorganisms, and bacteria (Thorne & Fenner 2008; Delpla et al. 2011; Coffey et al. 2014; Boholm & Prutzer 2017; Ekstrom et al. 2017). A degradation of water quality will put additional pressure on water treatment systems to ensure that the public is not exposed to contaminated drinking water (Boholm & Prutzer 2017).

Abdel-Fattah & Krantzberg (2014), Ekstrom et al. (2017), and Magee et al. (2019) agree that more frequent algal blooms can also result from increases in temperatures, complicating water treatment processes and creating toxic conditions for users of the water bodies (Ekstrom et al. 2017) such as recreational users, fish species, and livestock that graze in the area.

Both Chang et al. (2015) and Feldbauer et al. (2020) discuss the thermal stratification caused by rising temperatures and the detrimental impact it has on water quality. Thermal stratification not only increases the probability of oxygen depletion in deeper layers of water increasing the risk of algal blooms (Chang et al. 2015), but can also have a significant impact on drinking water production (Feldbauer et al. 2020). Drinking water reservoirs have outlet structures from which water is withdrawn at different depths and variable rates. Stratification and temperature influence the bio-geo-chemical processes and therefore water quality (Feldbauer et al. 2020).

Research indicates that climate change will also result in subsequent effects on regional precipitation, including the occurrence of droughts and floods (Bi et al. 2018). Water quality will be impacted by changes in precipitation patterns, intensity, and duration (Astaraie-Imani et al. 2012; Jin et al. 2012; Cross & Latorre 2015; Qiu et al. 2019). Not only will heavy rainfall increase contaminants in water bodies (Cross & Latorre 2015), but also droughts can result in reduced dilution of pollutants through lower flow rates (Coffey et al. 2014).

Rodriguez & Delpla (2017) argue that heavy rainfall will have the greatest impact on water quality. Many concur that more intense rainfall and storms result in increased pollutant concentrations (Abdel-Fattah & Krantzberg 2014; Coffey et al. 2014; Staben et al. 2015; Boholm & Prutzer 2017; Rodriguez & Delpla 2017; Bi et al. 2018; Shannon et al. 2019). There is also much evidence to demonstrate that high rainfall will lead to a degradation of water quality due to an increase in surface runoff, sedimentation, and nutrient inflow (Abdel-Fattah & Krantzberg 2014; Bi et al. 2018; Magee et al. 2019; Qiu et al. 2019; Wardropper & Rissman 2019). Coffey et al. (2014), Rodriguez & Delpla (2017), and Staben et al. (2015) emphasise that the impacts of precipitation changes will not only apply to surface water but also to groundwater systems.

The changes in precipitation patterns may result in flood and drought events. During flood events, water treatment facilities can become inundated, contaminating both overland and subsurface water (Coffey et al. 2014; Boholm & Prutzer 2017; Parkinson et al. 2021). Drought events particularly impact groundwater by concentrating contaminants and degrading the water quality (Tung et al. 2012; Coffey et al. 2014; Ekstrom et al. 2017).

Most of the strategies identified in this review fall under short-term coping mechanisms. Often the water bodies and catchment areas are already under stress from the impacts of climate change and the strategies proposed are short-term reactive options such as the adaptation of withdrawal depth (Feldbauer et al. 2020); improving or increasing water treatment levels (Levine et al. 2016; Garnier & Holman 2019); and river restoration projects (Palmer et al. 2009).

Some of the coping mechanisms could be modified to adapt to medium-term climate change impacts as well (Ekstrom et al. 2017; Feldbauer et al. 2020). Ekstrom et al. (2017) recommend changes in organisations and infrastructure to support deeper transformative changes, and Feldbauer et al. (2020) suggest dynamic water withdrawal depth and timing become an integral part of future reservoir management strategies.

Effective adaptation requires proactive strategies that anticipate change and adapt water management to changing circumstances. Despite research indicating extensive use of modelling of future climate change scenarios, the literature reviewed includes few proactive strategies. While the risk management approach put forward by Cross & Latorre (2015) predominantly includes preventative actions, it can be adapted to identify appropriate control measures that respond to long-term climate change impacts affecting the supply chain. The modelling implemented by Chiang et al. (2012) uses future climate mitigation scenarios to determine an optimal suite of best management practices and will benefit water quality goals within the watershed. Similarly, Salerno et al. (2018) use modelling to determine the level of reduction of impervious surfaces required to prevent the future impacts of climate change.

Palmer et al. (2009) recommend modelling to anticipate the implications of climate-related hydrological and land-use changes to enable decision-makers to plan for variable river flows, as this is a fundamental trait of natural systems. They also recommend increasing the adaptive capacity of aquatic fauna species; restoring floodplains and setting back levees to prepare for future drought and flooding; and re-evaluating institutional mechanisms that govern water use and management to ensure they are flexible and have a strong awareness of ecological issues.

Policy and management framework strategies featured prominently in the reviewed articles, constituting 45% of the articles reviewed. Policy, governance, or managerial frameworks that decision-makers use to address water quality in a changing climate often already exist requiring little effort to adopt them, perhaps explaining their prominence among the strategies identified through the review.

The adaptation strategies in the policy and management framework category share common themes of flexibility, participation, regulatory framework, risk management, and social–ecological systems. Modifications or improvements to regulatory frameworks, with the encouragement of a participatory approach were widespread common elements in the strategies identified. Flexibility and social–ecological approaches were mentioned in six articles, while risk management appeared only in four articles.

The majority of policy and management strategies identified proposed new regulatory frameworks or the adaptation of existing ones. This included strengthening licencing arrangements (Palmer et al. 2009; De Smedt 2010; Garnier & Holman 2019); integrating water management policies into other inter-related planning policies and programmes (De Smedt 2010; Boholm & Prutzer 2017); reviewing existing regulations that were drafted under different conditions (Cross & Latorre 2015); and investing in policies and education programmes (Kopprio et al. 2015). Palmer et al. (2009) propose strengthening environmental flow programmes and water use permit conditions in an effort to maintain natural flow conditions, ensuring that flows support ecosystems, protect river health, and promote natural flows under a changing climate. Alternatively, Miller & Belton (2014) propose an approach designed to support climate policy planning by incorporating a multi-criteria decision analysis, enabling a whole system perspective and encouraging the identification of climate policies and measures that are low cost, environmentally effective, and consistent with national development goals. These adaptation strategies are all designed within existing policy and management frameworks.

Numerous articles in the review referred to adaptation strategies that involve a participatory approach and encourage coordination and cooperation between a variety of stakeholders. Abdel-Fattah & Krantzberg (2014), Cross & Latorre (2015), and Staben et al. (2015) all recommend multi-stakeholder strategies, and similarly, Poudel & Duex (2017) suggest an initial multi-disciplinary approach for solving complex water resource management issues. Kumar et al. (2020) propose a transdisciplinary and integrated (top-down and bottom-up) approach for avoiding disconnects and redundancies when dealing with water quality issues.

A number of researchers proposed the incorporation of flexibility in the policy and management frameworks. Cross & Latorre (2015), Kashyap (2004), Miller & Belton (2014), and Peirson et al. (2015) identify the need for flexibility within the strategy to allow for different outcomes and to cope with the challenges of unpredicted climate changes. The multi-criteria decision analysis strategy proposed by Miller & Belton (2014) relies on the ability of the framework to take into consideration various values, vulnerabilities, and ecosystem services that the policy may affect. The governance and management framework recommended by Peirson et al. (2015) relies on flexibility to accommodate the different outcomes resulting from the analysis of the uses, values, and goals of the various stakeholders.

Another common theme within the policy and management category of adaptation strategies reviewed was the interrelationships between society and environmental systems. In particular, Kopprio et al. (2015) identify the importance of building social–ecological resilience for climate change adaption. Peirson et al. (2015) also support this theory through their development of a governance and management framework which recognises integrated social–ecological systems to encourage transformative adaptation to climate change.

The risk management approach addresses the changing climatic conditions as a threat to water quality, and as such, the process involves identifying hazards, assessing risks, and determining appropriate control measures along the supply chain from the catchment to the end use for water. Cross & Latorre (2015) recommend a proactive risk management approach, in which resilience is built into water safety planning in an effort to absorb climate change impacts. This preventative and flexible management framework that evaluates and addresses risks is also supported by Khan et al. (2015) and Rosenzweig et al. (2007). Urama & Ozor (2010) go further in their recommendation of providing training to those involved to increase their skills and knowledge in climate risk management, empowering them to scale up or replicate adaptation strategies as required.

Modelling using climate and land-use data to inform decision-making was mentioned in 22% of the articles reviewed. U.S. EPA (2021a) lists the collation of existing data sets, the development of regional scenarios, the mining of existing data sources, and the use of data to demonstrate historical and future trends as strategies that use climate and land-use data to inform the decision-making process.

One of the main modelling strategies includes the analysis and evaluation of climate and land-use data for monitoring water quality. Approximately one-third of the articles mentioning modelling in the review discussed the gathering and modelling of data to monitor climate change and other stressors on water quality to provide early warning indicators. This can lead to a more resilient decision-making framework and more effective climate adaptation strategies and forecasting (Levine et al. 2016). It can also allow local jurisdictions to respond to specific local needs (Palmer et al. 2009).

The review revealed that a variety of models are implemented to determine the potential effects of alternative actions on water quality. Chiang et al. (2012) and Coffey et al. (2014) both discuss the use of watershed modelling; however, the former used the modelling to comparatively analyse a suite of best management practices and determine the combination that would meet water quality goals, whereas the latter used watershed models for informing pollution control measures. Feldbauer et al. (2020) used hydro-physical models to determine withdrawal strategies in thermally stratified reservoirs. Kumar et al. (2020) reviewed the use of integrated water resource models to address key decision choices and facilitate targeted intervention, and Magee et al. (2019) discussed physical and biogeochemical models that were used to broaden the understanding of uncertainties in responses and mechanisms. Pouget et al. (2012) and Wilby et al. (2006) both highlight the benefits of a flexible modelling system, in which a range of models can be linked and then automatically exchange information. Carnohan et al. (2021) use modelling to facilitate participatory processes.

A commonly used hydrological model is the Soil and Water Assessment Tool (SWAT) (Bi et al. 2018; Rocha et al. 2020; Wu et al. 2021). It is a physically based model capable of simulating the impacts of land management practices on water, sediment, and agricultural chemical yields in watersheds (Arnold et al. 2012). It can be used to simulate different ecohydrological scenarios and responses under both current and future climate conditions to inform decision-making.

As crop production and animal husbandry are prominent land uses in catchment areas, agricultural practices have a significant impact on water quality (Mehdi et al. 2015; Nunes et al. 2017). Strategies involving modifications to agricultural practices were almost as prominent as modelling, mentioned in 21% of the articles in the review. The adaptation strategies in agricultural practices involve crop nutrient management (mentioned in 6% of articles), the use of cover crops or consideration of alternative crops (5% of articles), and improved grazing management in animal husbandry (4% of articles).

Shannon et al. (2019) propose avoidance or reduction in the use of organic supplements, nutrients, and chemical delivery to areas near waterbodies. Many others (Whitehead et al. 2006; Chiang et al. 2012; Ha & Wu 2017; Salila et al. 2020) support crop nutrient management to reduce pollutant loading in the waterways.

The review identified a variety of strategies related to crop management for improving water quality. For example, Ebert et al. (2009) recommend the replacement of vulnerable monocultures with more diverse crops. This not only provides a more sustainable ecosystem service but also benefits grazing and other local industries. Godebo et al. (2021) and Salila et al. (2020) propose improved crop choices, while Whitehead et al. (2009a) recommend crops that are better suited to the climatic conditions. Cherkauer et al. (2021), Wardropper & Rissman (2019), Whitehead et al. (2006), Giri et al. (2020), and Ha & Wu (2017) recommend the use of cover crops which can reduce soil erosion and absorb the nutrients remaining in the soil.

Controlling animal husbandry to reduce the impacts of livestock on waterbodies can be achieved through a variety of strategies. Whitehead et al. (2006) recommend the use of off-stream watering without fencing the livestock to reduce stream bank erosion and pollution from livestock defaecation. Boholm & Prutzer (2017) suggest the protection of water quality by controlling livestock – limiting grazing animals near water supply areas, controlling animal health, and keeping track of the location of the animals.

Natural infrastructure includes the natural physical systems that support life and examples include the planting of trees, controlling stream bank erosion, controlling soil erosion in the watershed, and controlling stormwater runoff (U.S. EPA 2021a). Natural infrastructure strategies were reported in 19% of the articles reviewed. The common natural infrastructure adaptation strategies include the implementation of riparian buffers (two-thirds of the reviewed papers); the restoration of floodplains, wetlands, and river corridors; and the reforestation of critical areas (four articles each).

Riparian buffers were identified as a common strategy for reducing sediments, nutrients, and pesticides from surface runoff and therefore improving water quality (Lukasiewicz et al. 2016; Ha & Wu 2017). These buffer strips adjacent to streams, lakes, and rivers may be vegetated with native grasses (Chaubey et al. 2016), switchgrass (Ha & Wu 2017), and shade trees (Shannon et al. 2019). However, Wilby & Wood (2012) identify potential issues with woody debris, channel roughness, and localised flooding. Wu et al. (2021) conclude that while a riparian buffer will reduce sediment outputs, its reduction is not sufficient to fully offset the impacts of climate change.

Khaniya et al. (2021) define reforestation as the planting of new trees within an existing forest area, whereas afforestation is the planting of new trees in a new or fresh area. Both Khaniya et al. (2021) and Salila et al. (2020) recommend the use of reforestation as a strategy for improving water quality. Additionally, Shannon et al. (2019) and Wilby & Wood (2012) recommend afforestation for the purposes of shading the water to offset warming temperatures.

The restoration of floodplains, wetlands, and corridors are recommended strategies put forward by Ebert et al. (2009), Iacob et al. (2014), Magee et al. (2019), and Palmer et al. (2009). Such restoration work is expected to create more robust and dependable freshwater ecosystem services.

Kopprio et al. (2015) suggest a robust strategy for climate adaptation that uses the principles of ecohydrology. This strategy is based on the use of aquatic biota as water management tools and involves the redesign of wetlands (preservation, restoration, and creation) to protect them from erosion and improve water quality through the removal of excess nutrients and pollutants. Natural and social sciences are complementary, and therefore, the integration of both can represent a powerful climate change adaptation tool in complex human–natural systems (Kopprio et al. 2015).

Building staff capacity through the engagement of new staff with appropriate experience, the provision of staff training, and the encouragement of the use of appropriately qualified contractors and engineers can be an important adaptation strategy (Jun et al. 2010; U.S. EPA 2021a) and was mentioned in 15% of the reviewed articles.

The review identified the need to bridge the gap between the research available and local communities' capacity to address water sustainability and climate change adaptation (Palmer et al. 2009; Poudel & Duex 2017; Magee et al. 2019). Magee et al. (2019) discuss the importance of communication as a key strategy for local communities to address the climate change impacts on water quality for Wisconsin lakes. This includes improved communication between management and stakeholders regarding requirements for high water quality; between businesses and other stakeholders; and between lake associations and local community members. Poudel & Duex (2017) propose comprehensive multidisciplinary research, the development of programmes in coordination with local communities, and the development of community capacity to address water sustainability. Palmer et al. (2009) identify the need for affordable tools in regions with few resources. Technical assistance with modelling that demonstrates potential climate change impacts within specific watersheds can be provided to build human resource capacity. However, small communities may not have the resources to access Geographic Information Systems (GIS) or modelling tools. More user-friendly low-cost tools need to be explored.

Cross & Latorre (2015) and Kalafatis et al. (2015) both hail the merits of the Great Lakes Water Quality Protocol and its ability to integrate knowledge across jurisdictions and decision-making scales. The binational regional network binds parties and shares information in a timely and comprehensive manner. The protocol is implemented and enforced by an International Joint Commission, which works in cooperation with local authorities and the public to build their understanding of the water cycle and the climate change pressures it is under. Kalafatis et al. (2015) propose a conceptual model in which knowledge capacity is built up between climate information at the regional level and specialised networks that function like communities of practice. This will enable the two networks to span the boundary between knowledge production and its use.

Strategies that involve the use of technology including advances in engineering and improvements to water treatment processes and technologies were fewer than anticipated and were mentioned in only 15% of the articles reviewed. The research undertaken did not reveal significant breakthroughs in technology or engineering advancements. The strategies proposed were predominantly short-term coping mechanisms. Abdel-Fattah & Krantzberg (2014), Garnier & Holman (2019), Rodriguez & Delpla (2017), and Staben et al. (2015) mentioned upgrading treatment plants, improvements to water treatment processes and technologies, and increasing chemical dosing to accommodate the anticipated reductions in water quality as a result of future climate change impacts. And similarly, Magee et al. (2019) proposed artificial aeration to prevent anoxic conditions.

Feldbauer et al. (2020) and Shannon et al. (2019) discuss the strategy of dynamic withdrawal to overcome the issues associated with thermal stratification. As rising air temperatures impact the thermal stratification of water bodies, the withdrawal depth within reservoirs will need to be adapted. The differing depths and variable rates of withdrawal will depend on the properties of the reservoir; however, this strategy is not expected to be able to fully compensate for the negative impacts of climate change (Feldbauer et al. 2020).

Alternative water sources were mentioned in 12% of the articles in the review as essentially a risk management strategy and include reducing reliance on one major supply source and allowing the use of different water qualities for different purposes. Alternative water sources can be used for maintaining water quality in future climate scenarios. Boholm & Prutzer (2017) identified the risk of relying on only one major supply source for drinking water and propose a risk management strategy, in which the raw supply is derived from multiple sources. Cross & Latorre (2015) recommend revising the regulations around water quality, allowing different water qualities for different uses to ensure there is a more efficient use of water. Yang et al. (2010), Kim & Chung (2015) and Trinh et al. (2013) all propose the reuse of treated wastewater for uses such as irrigation in the agricultural sector. It is anticipated that the wastewater, when used for agricultural purposes, would not need to be treated in expensive tertiary treatment systems, reducing treatment costs. If the wastewater is reused, and not directed to waterways, this will improve water quality management. The challenge to this strategy is how the wastewater is collected, treated, and then distributed for use, without increasing health risks to the population (Trinh et al. 2013).

The U.S. Water Infrastructure Improvement Act (U.S. EPA 2021b) defines green infrastructure as ‘the range of measures that use plant or soil systems, permeable pavement or other permeable surfaces or substrates, stormwater harvest and reuse, or landscaping to store, infiltrate, or evapotranspirate stormwater and reduce flows to sewer systems or to surface waters’. Green infrastructure includes retention ponds for managing stormwater, bioretention to collect stormwater runoff, blue roof to hold rainwater, permeable pavements, and extended detention wetlands to reduce flood risk (U.S. EPA 2021a). Adaptation strategies involving green infrastructure were identified in only 10% of the reviewed articles.

Green infrastructure mimics natural habitat and is a natural solution implemented to provide ecological, economic, and social benefits (EEA 2014). It can be implemented as a strategy for protecting water quality against the impacts of climate change. Salerno et al. (2018) recommend the implementation of permeable pavements, rain gardens, bioswales, green roofs, and infiltration trenches, as these practices will protect the quality of water in natural water bodies by slowing and filtering the water flows. They anticipate that a 15% reduction in imperviousness would be sufficient to prevent the negative impacts of future climate changes.

Magee et al. (2019) and Ricart & Rico-Amoros (2021) recommend the construction of wetlands to treat wastewater as an alternative to wastewater treatment plants (grey infrastructure). Constructed wetlands are a cost-effective strategy for protecting water quality, with the additional benefits of flood risk mitigation, stormwater management, and additional water supply. Depending on their design, they can also provide recreation, aesthetic values, and landscaping (Ricart & Rico-Amoros 2021).

Stormwater management strategies prioritise and direct the flow of water in catchment areas and were mentioned in only 8% of the reviewed articles. The strategies involved increasing vegetation, implementing permeable pavements (Abdel-Fattah & Krantzberg 2014), and slowing road surface drainage to reduce sedimentation (Shannon et al. 2019). Wilby & Wood (2012) promote the use of low-cost soft engineering solutions, such as runoff attenuation features that slow, store, and filter runoff to mitigate the potential effects of flooding.

Klein et al. (2014) identify eight types of barriers and drivers that can exert a positive or negative influence on the planning or implementation of adaptation actions. These categories have been adopted for this review and include governance and institutional; financial; knowledge, awareness, and technology; physical; social and cultural; human resource; economic; and biological. Acting as barriers, these factors can significantly reduce the range of adaptation options and opportunities. On the other hand, as drivers they can positively influence the success of adaptation measures.

This literature review has identified barriers and drivers in all categories but one: biological factors. The results demonstrate a broad range of factors influencing the success of adaptation strategies implemented to address the impacts of climate change on water quality (Table 2).

The most commonly reported factors were governance and institutional barriers and drivers, followed closely by financial and knowledge, awareness, and technology factors. The physical, social and cultural, and human resource barriers and drivers are also featured in a significant number of the articles reviewed. There were relatively few economic factors identified.

Governance and institutional barriers and drivers were identified in 18% of the articles reviewed. Klein et al. (2014) describe how societal institutions can support or hinder climate change adaptation measures through the mobilisation of resources, decision-making, and the implementation of specific policies. The success of adaptation can also be influenced by the complexities of governance networks, coordination among the various actors who will likely have different objectives, jurisdictional authority, and levels of power and resources. The influence that the inter-related themes of governance and institutions have on water quality adaptation strategies was prevalent in the papers reviewed. The institutional barriers and drivers identified predominantly relate to regulatory systems, while the governance factors relate to the cooperation and coordination of the various players involved.

Regulatory systems can hinder climate change adaptation strategies through their inflexibility, insufficient attention to detail, and the lack of coordination between jurisdictions. Cross & Latorre (2015) and Ebert et al. (2009) both identify issues with flexibility in existing regulatory systems. Strict regulations can prevent timely responses (Cross & Latorre 2015) and thwart individual efforts through the imposition of institutional processes, regulatory structures, property rights, and social norms (Ebert et al. 2009). Cross & Latorre (2015) also acknowledge the risks of too-flexible regulations as the high costs of ensuring compliance and the determination of tolerable risks. Azhoni & Goyal (2018) and Crabbe & Robin (2006) found that existing regulatory systems were insufficient for monitoring and addressing the changing climate patterns. However, the most significant issue with regulatory systems revealed through the review was a lack of coordination between government levels and differing policies. Both Crabbe & Robin (2006) and Jordan (2020) discuss the difficulties with federal intervention or lack of leadership at the local government level. Boholm & Prutzer (2017) mention disparate roles and responsibilities within existing regulatory systems. De Smedt (2010) explains how other policies, such as spatial policies and land-use practices, can interfere with water quality management, making some ecosystems more vulnerable and less capable of adapting.

Governance issues such as the cooperation and coordination between stakeholders, the complexity of the authorities and agencies involved in the decision-making process, political interferences, and interactions with institutional frameworks were also mentioned (e.g. Carvalho et al. 2019). Boholm & Prutzer (2017) discuss the importance of cooperation and positive interactions between public and private actors, including non-government organisations, stakeholders, and the public. This was supported by Ricart & Rico-Amoros (2021). Boholm & Prutzer (2017) also identified the complexity of governance structures as an obstacle to the success of adaptation strategies, admitting that interdisciplinary collaboration and better integration with authorities are not easily achieved. Jordan (2020), Parkinson et al. (2021), and Ricart & Rico-Amoros (2021) all discussed the barriers that institutional frameworks can have on good governance. They identified institutional fragmentation, asymmetric power dynamics, and inadequate human and financial resources as the issues that may hinder effective water governance. The political issues that can disrupt good governance were identified as a lack of political engagement (Boholm & Prutzer 2017) and political pressure that can be exerted by influential stakeholders with short-term interests (Ebert et al. 2009).

Klein et al. (2014) describe financial constraints on adaptation as the impacts that access to financial capital (credit, insurance, tax revenues, and earnings of individual households or private entities) can have on specific adaptation strategies and options. Financial barriers and drivers were identified in 17% of the articles reviewed.

Financial resources can be both an impediment to and a driver of the implementation of water-related adaptation strategies. Almost half of the articles that identified financial resources as a relevant factor in implementing adaptation strategies cited the impact of high costs (e.g. Mukheibir 2008; Nagy-Kovács et al. 2018; Mi et al. 2020). In particular, Cross & Latorre (2015) discussed the low rates of the application of adaptation strategies when there are high costs associated with ensuring compliance. Ebert et al. (2009) found that even when cost–benefit analyses are favourable, there are often hidden financial barriers such as transaction costs and compensatory measures. Adaptation strategies that involve changes to agricultural practices often financially impact farmers unfairly. Particularly in developing countries, farmers do not have access to credit or savings to improve their crop varieties (Godebo et al. 2021). Xu et al. (2019) identified adaptation strategies that would lead to farm-level cost-savings; however, Ricart & Rico-Amoros (2021) argue that such strategies often involve high investment costs and are influenced by unpredictable behaviour of the food market. While the majority of adaptation strategies were impeded by the availability of financial resources, De Smedt (2010) and Khaniya et al. (2021) proposed cost-effective eco-based adaptation strategies. They concurred that water quality strategies that work with nature's capacity to control or absorb impacts can offer consistent financial benefits over the long term.

Knowledge-, awareness-, and technology-related barriers and drivers were identified in 14% of the articles reviewed. IPCC Assessment Report 4 concludes that knowledge gaps and impediments to the flow of information can impede adaptation, yet knowledge itself is not sufficient to drive adaptative responses (Adger et al. (2007) as cited in Klein et al. (2014)). More information can support decision-making processes and build capacity through education, training, and information access to provide valuable opportunities for adaptation. Boogaard et al. (2020) conclude that fundamental change is only possible through knowledge and awareness.

Among barriers to effective adaptation related to the lack of knowledge and information, four articles discussed the impacts of a deficit in climate change data. Azhoni & Goyal (2018) and Godebo et al. (2021) both acknowledge a lack of reliable historical data on projected weather and climate conditions as key challenges. Crabbe & Robin (2006) identify the need for information to be consistent, credible, and downscaled to the local level.

Ricart & Rico-Amoros (2021), Jordan (2020), and Garnier & Holman (2019) all cite the lack of scientific knowledge as a significant constraint on adaptation capacity. Ricart & Rico-Amoros (2021) mention the impacts on farmers, whereas Jordan (2020) discusses the need for up-to-date scientific information to help manage risks and forecast conditions. Garnier & Holman (2019) identify a significant gap between the scientific knowledge of climate change impacts and the adaptation capacity at the local level.

Klein et al. (2014) describe physical factors that can constrain adaptation as the physical environment including the climate itself, geographical features, soil conditions, and anthropogenic land uses. Physical barriers and drivers were identified in only 6% of the articles reviewed.

Of the reviewed articles that identified physical barriers to adaptation strategies, two discussed land-use issues. Kim et al. (2021) claim that Korean farmers were impeded in dealing with climate change adaptation because they feel they have already maximised the productivity of their lands with an intensive input of resources, machine farming, and the use of freely available water. Magee et al. (2019) also discuss challenges with land use, as the restrictions proposed for watershed lands were often controversial and difficult to implement. The only other physical barriers identified in this review were the limited capacity of reservoirs to support climate change adaptation measures (Rocha et al. 2020) and the challenges of capturing sufficient rainwater of acceptable quality (Chan et al. 2020).

The social and cultural factors associated with our values, world views, and cultural norms and behaviours can influence the choice of adaptation options and the perceptions of associated risks (Klein et al. 2014). Social and cultural factors were identified as barriers or drivers of adaptation in 6% of the articles reviewed.

Ebert et al. (2009) and Kopprio et al. (2014) both identify socio-economic factors as barriers to adaptation. While the former points to the challenges of changing the uses of privatised lands, the latter discusses how socio-economic constraints can hinder the use of technology in developing countries. Social and cultural factors can also be used to drive adaptation strategies. Magee et al. (2019) suggest that changes will have more opportunities for success if local community values are used to inform adaption approaches.

Klein et al. (2014) identify humans as the primary agents of change and therefore pivotal in the effectiveness of our efforts to adapt to climate change. Of the articles reviewed, only 5% indicated the influence of human resources as significant barriers or drivers.

Water quality is generally the responsibility of local authorities or municipalities. This level of government often lacks the necessary human resources for developing robust climate change adaptation strategies (Palmer et al. 2009; Boholm & Prutzer 2017; Azhoni & Goyal 2018). Experts from a variety of science fields will be required to contribute knowledge to water, natural resources, urban planning, crises, and disaster management domains, enabling the information to be linked to effective decision-making processes (Boholm & Prutzer 2017). Interestingly, Crabbe & Robin (2006) note that external consultants are often engaged due to a lack of internal human resources. This then leads to an overreliance on technological strategies rather than managerial solutions. While several articles cite the limits of human resources as a significant obstacle to the implementation of adaptation strategies, Palmer et al. (2009) propose adaptation actions that take into consideration the challenges of limited financial and human resources.

Economic factors defined by Klein et al. (2014) as macroeconomic constraints associated with broader macro-level driving forces were identified in only 3% of the articles reviewed. The articles reviewed identified economic factors as both a driver and a barrier for climate change adaptation. Ebert et al. (2009) suggest that the public were more supportive of strategies for improving water quality that improved their livelihoods and strengthened local economies. On the other hand, Parkinson et al. (2021) discuss the challenges of accessing funding for adaptation actions through the various levels of government.

Four key themes have emerged from the review that require further attention due to the anticipated effects of climate change on water quality and the impacts that this will have on local communities. These include (i) the low level of attention given to climate impacts on water quality; (ii) the difficulty of differentiating the cause of water quality degradation; (iii) the reliance on coping approaches to adaptation which are unlikely to be sufficient; and (iv) the significant challenges to the planning and implementation of the adaptation strategies.

There is a large body of literature that focuses on the impacts of climate change on water security. Much research also aggregates data on water availability with that of the quality of water. Identifying studies focusing on climate change impacts on water quality has been challenging.

Water security is undoubtedly a significant issue. The changing climate impacts the water cycle through droughts, floods, melting glaciers, sea-level rise, and storms with consequences on the availability of water in various locations throughout the world (International Union for Conservation of Nature 2022). However, as the IPCC (2022) acknowledges, there have been significant increases in climate-induced water quality degradation due to temperature increases or melting of the cryosphere.

As the number of articles identified for this review shows, the research on climate impacts on water quality is limited. Many studies are context-specific and have limited regional relevance. The review also shows that this limited body of literature often emphasises data accumulation rather than adaptation strategies. Further research is necessary not only on climate change impacts on water quality but also on strategies for developing resilience.

It is evident from the review that climate change is not the only source of water quality degradation. Degradation of water quality may also occur due to many other factors including water pollution resulting from human activities related to population growth and urban development. This degradation can result in environmental, social, and economic impacts on human health, food production, ecosystem functions, and economic growth (UNESCO 2021b).

However, the impacts of climate change on water quality are not insignificant. UNESCO (2021a) argues that policy discussions and scientific studies often overlook the significant links between water quality and climate change and this is supported by the dearth of studies focused on this specific linkage.

While water quality may be affected by regional and localised climatic effects, this review demonstrates that the changing climate patterns worldwide are continuing to shift, increasing the occurrence of extreme weather events, and are modifying the normal balance of water bodies and cycles, leading to the degradation of water quality. Reductions in water quality can not only affect economic and social welfare, but also critical environmental flows, ecosystems, and biodiversity. Further research is needed to understand the impacts that climate change will have on the physical, chemical, biological, and socio-economic systems related to our water resources (UNESCO 2021a).

Studies examining climate adaptation approaches often find most of the current approaches include coping or incremental strategies (O'Neill & Handmer 2012; Torabi et al. 2018; Fedele et al. 2020). The findings of this review are consistent with those. Of the 78 articles reviewed here, all adaptation strategies to water quality impacts fall under coping or incremental approaches on the resilience spectrum. As the loss and damage to water quality due to the impacts of climate change increase, the need for transformational adaptation strategies to provide major or fundamental changes is becoming more imperative for providing long-term benefits and addressing the root causes of vulnerability. The IPCC (2022) projects an increase in water quality degradation under climate change due to warming, enhanced floods, sea-level rise, droughts, and increased irrigation. The IPCC Assessment Report 6 confirms the need for transformational adaptation measures contrary to the many initiatives that prioritise immediate and near-term climate risk reduction reducing opportunities.

As Fedele et al. (2020) identify when social–ecological systems are impacted by climate change, responses tend to be coping and incremental adaptation strategies that aim to maintain the current social and ecological relationship, offering an immediate solution with short-term benefits. These strategies rarely address the root cause of the vulnerabilities and long-term sustainability issues. Transformational adaptation options are seldom considered or implemented, as they impact either the social or ecological system or the system dynamics and have the potential to influence long-term adaptation in other locations.

The IPCC (2022) also defines transformational adaptation in terms of social–ecological systems, stating that it changes the systems' fundamental attributes in anticipation of climate change and its impacts. As transformational adaptation generally includes adaptation at a greater scale or magnitude, it requires the introduction of new practices or technologies, the creation of new systems of governance, or shifts in the location of activities (Dinshaw 2014). While our review did not uncover concrete examples of transformational adaptation, there are a few examples in the broader literature. Kates et al. (2012) describe an ambitious transformational adaptation programme in the Netherlands. The Room for the River flood control programme is a major change from the traditional approaches of building levees and progressively increasing their heights over time. Rather, the extensive short-term projects are designed to adapt to the future impacts of climate change with a planning horizon of more than two centuries and provide an overall 10-fold level of flood protection. While the components of the programme may not all be new, they are considered transformational ‘because of their enlarged scale, intensity, and integrated combinations of adaptations, and novel approaches, like artificial islands, evacuation of some areas, as well as new institutions and funding mechanisms’ (p. 7157).

Many climate-related water quality issues can be traced back to land use in catchment areas. A case study of Canadian agriculture undertaken by Hadarits et al. (2017) examined the circumstances around which transformational adaptation would be adopted. For example, when faced with extreme drought conditions, an agricultural community would consider outmigration. Vermeulen et al. (2018) also identified examples of transformational adaptation in response to climate change, one such example being a Bangladesh farm impacted by the rising frequency and severity of floods reallocating land from crops to aquaculture.

The review identified significant challenges to the planning or implementation of adaptation actions. The barriers identified predominantly related to societal institutions and regulatory settings. Within the category of governance and institutional factors, the majority of issues were mentioned as barriers rather than providing a positive influence to support strategic actions. This finding highlights the importance of having sufficient and adequate regulatory settings, integrated and coordinated responses, and flexibility and sufficiently detailed policies.

This review has systematically evaluated peer-reviewed studies on adaptation strategies for climate impacts on water quality and the barriers and drivers that influence their implementation. At the beginning of this paper, we noted that there has been and continues to be a cautious approach to protecting our water quality from the impacts of climate change. Our review of the literature has confirmed these concerns but also highlighted the lack of attention to studies which focused on climate-impacted water quality adaptation strategies, the challenges in differentiating the sources of water quality degradation, the need for transformational adaptation strategies, and finding ways to overcome barriers to adaptation.

It was anticipated that the climatic conditions threatening water quality would be site-specific. However, while endemic weather patterns will play a significant role in levels of water quality, the review revealed common challenges of rising temperatures and variations in precipitation in a large proportion of the case studies from around the world. Rising air temperatures are intrinsically linked to water temperatures, and thus a warmer climate can lead to significant disruptions to the normal aquatic ecological balance. As a result, water quality is reduced through degraded water chemistry and anoxic conditions, resulting in implications for water treatment processes and increasing risks for users of the water bodies. Regional precipitation changes are increasing the occurrence of floods and droughts. Both of these extreme events lead to increased contaminants in the water, once again impacting water quality and putting increased stress on water treatment processes. While this study examined water quality holistically, there is an opportunity to focus future research on how impending climatic conditions impact the physical, chemical, and ecological indicators of water quality.

It became evident in this review that the literature on climate change impacts on the water is dominated by water security, with much less emphasis on strategies for the protection of water quality. Effective adaptation should be an intentionally planned process that responds to identified climate change impacts and vulnerabilities. The strategies developed need to adjust natural or human systems to minimise the harm from the changing effects of climatic elements (Wardropper & Rissman 2019). The strategies for protecting water quality identified in the reviewed articles include specific responses to local hydrology and ecology and within pre-existing management frameworks. Many are not necessarily significantly new measures or responses, but rather modifications implemented to contribute to an increase in resilience to climate change. Several authors concur that no one strategy can meet all future challenges, rather an integration of adaptation options tailored for different situations is necessary.

The approaches to adaptation for addressing climate-induced water quality challenges are predominantly reactionary, for example, simply altering the withdrawal depth for water treatment processes when thermal stratification occurs in water bodies. Some of the approaches are proactive, aiming to anticipate the changes and implementing preventative measures. The use of modelling to anticipate the implications of climate-related impacts on water quality is an example of incremental adaptation strategies. All adaptation strategies identified in the reviewed articles offer low to medium levels of resilience, with no examples of transformational adaptation necessary for high levels of resilience. Essentially, this lack of long-term adaptation strategies explains the current level of urgency assigned to climate change impacts by the majority of world leaders.

The review indicates the significance of societal institutions, governance networks, and decision-making frameworks on our ability to develop adaptation strategies to cope with the changing climate. As such, governance and institutional factors should be key considerations in determining appropriate strategies. Numerous examples of barriers and drivers in each of the other six categories identified by Klein et al. (2014) are also evident in the literature reviewed. A better understanding of these constraints and drivers can inform the selection of adaptation strategies or approaches.

Access to clean water is one of the most important human needs. Climatic changes are threatening the quality of our precious water resources, making it increasingly challenging to protect public health and water-reliant ecosystems. To date, research has focused on the volume and supply of water threatened by climate change, despite increasing evidence that the quality of water is of equal significance and concern. An improved understanding of the climate factors threatening water quality and the barriers and drivers of adaptation strategies will help unlock the innovative transformational solutions that will undoubtedly be required to protect our water quality in the future.

Data cannot be made publicly available; readers should contact the corresponding author for details.

The authors declare there is no conflict.