Globally, more than 40% of the population experiences water scarcity, with over 700 million people lacking access to clean drinking water [1]. Approximately 50% of human-generated wastewater is discharged directly into rivers or oceans without any treatment, causing severe environmental and health consequences. The lack of safe and reliable drinking water may lead to desertification, forced migration, hunger, diseases, and domestic or regional conflicts. For instance, the Atatürk Dam on the Euphrates River has enabled extensive irrigation within Turkey, while reducing water quantity and quality in Iraq and northeastern Syria [2]. It is important to note that the impact of water scarcity in developing countries is more challenging than in Western countries. To create a sustainable water infrastructure, the focus should be on conservation, protecting water sources, and limiting pollution.

Desalination is considered one of the most effective ways to increase water supply and provide clean and affordable water to millions of people. Nevertheless, it is important to recognize that addressing the global water crisis requires a multifaceted approach. In addition to desalination, other measures should be implemented, such as centralized governance, education, improvements in water catchment and harvesting technologies, irrigation, agricultural practices, distribution infrastructure, prevention of leakage, wastewater reclamation, pollution treatment and prevention, investment in innovative technology, and transboundary water cooperation.

2. Essential Measures to Address the Worldwide Water Shortage

2.1. Centralized Governance

Centralized governance is essential for providing guidelines in overseeing all water-related issues to ensure adequate water supply. A key aspect of such a system is a water authority which holds the responsibility of licensing the drilling of wells, desalinating water, treating domestic and industrial wastewater, designing and constructing water infrastructure, and setting water prices ^[3][4][5][4,5,6]. The government must adopt recommendations to achieve progress in water management. However, it is not feasible for the government to accomplish this task solely by itself ^[6][7]. Collaborative water governance can enhance the sustainability, equity, and efficiency of water management by capitalizing on the expertise, knowledge, and resources of all stakeholders. Collaborative water governance is a multi-stakeholder approach involving various entities such as government agencies, non-governmental organizations, community groups, and private sector entities, working in conjunction to manage water resources and supply ^[7][8]. This approach provides a comprehensive understanding of water needs at the national and sub-national levels, considering both present and future needs, as well as considering potential extreme circumstances, such as droughts and floods, which can significantly affect water availability and quality. The development of contingency plans that outline appropriate actions during such events will help to mitigate their impact and ensure the continuity of the water supply.

2.2. Education

It is imperative to raise awareness about the water scarcity issue and encourage individuals, organizations, and governments to take action. Promoting an understanding of the value of water and the significance of its protection at national and international levels through educating children and communities is of utmost importance. Water conservation measures must include both household and industrial water usage, with the latter accounting for approximately 22% of total global water consumption ^[8][9]. Private households can implement various water conservation techniques to minimize water usage, such as using water-saving faucets and toilets, collecting rainwater for garden irrigation, and growing low-water-demanding plants. On the other hand, industrial water conservation measures comprise adopting water-saving manufacturing processes and reusing wastewater. For instance, an effective approach is to replace once-through cooling systems with closed-circuit cooling systems, where only the evaporated water is replenished ^[9][10].

2.3. Water Catchment and Harvesting Technologies

Water harvesting and catchment technologies vary depending on the water source, i.e., surface water, rainwater, floodwater, and groundwater. These technologies are utilized in a multitude of settings, including domestic, industrial, and agricultural sites, as well as wetlands. Some examples of these technologies are rainwater harvesting aquifer recharge, floodwater harvesting systems, and dams ^[10][11]. Rainwater harvesting (RWH) is the most traditional and sustainable method of water harvesting. The key advantages of RWH systems are that they can augment the water supply, provide an alternative to potable water for non-potable uses, and help reduce storm water runoff ^[11][12]. Nevertheless, concerns have been raised regarding its feasibility, primarily due to the quality of rainwater that is dependent on airborne components. As a result, the successful implementation of rainwater harvesting depends on effective treatment to eliminate contaminants ^[12][13]. In addition, RWH systems have limited water supply potential and are substantially more expensive than centralized systems ^[13][14]. Recent review articles on RWH are available ^{[11][14][15][16][17][18][19][20][21]}[12,15,16,17,18,19,20,21,22]. In addition to increasing groundwater levels ^[22][23][24][23,24,25], aquifer recharge can also mitigate soil erosion caused by runoff, and distribute water availability more evenly throughout the year. Moreover, it can reduce the risks associated with hydrometeorological events such as drought and flooding, promote soil moisture, and regulate water tables that support vegetation and biodiversity ^[25][26]. However, the successful implementation of community-based aquifer recharge strategies requires a thorough understanding of the socio-hydrological system in which they are implemented ^[24][25].

2.4. Water Infrastructure

Strong water infrastructure is crucial for ensuring a reliable water supply, reducing waste, improving quality of life, and preventing the spread of water-borne diseases. There are several challenges to water infrastructure including aging, improper maintenance, and cyber-physical threats. As infrastructure and equipment age, they require repairs, overhauls, or replacements. However, establishing a sustainable infrastructure necessitates a significant financial investment to maintain critical parts and networks in operational conditions ^[26][27]. Inadequate maintenance of water infrastructure may cause its components to deteriorate or be damaged over time, which can compromise the quality of water and result in interruptions to service ^[27][28]. Therefore, it is essential to recognize proper infrastructure management and maintenance as a significant issue in water management practice ^[28][29]. In the water management context, Cyber-Physical Systems (CPS) are designed to integrate physical water assets with networked devices, enabling the monitoring and control of various physical processes in water and wastewater treatment plants and distribution systems. The primary objective of CPS in water management is to minimize leakage, guarantee water quality, and optimize operational efficiency ^[29][30]. While CPS technologies offer significant benefits, they also introduce cyber-physical threats that can potentially compromise the safety and reliability of the water supply. Thus, it is crucial to develop effective strategies that can detect and mitigate both cyber and physical threats, which may result in damage to physical components, (pumps, valves, and tanks) as well as the overall water supply and quality ^[30][31].

2.5. Irrigation and Agricultural Practices

The agricultural industry has been recognized as a major consumer of water resources, accounting for 70% of the world’s freshwater withdrawal to irrigate approximately a quarter of the world’s cropland. Due to the combined effects of climate change and population growth, water availability for agricultural production is becoming increasingly scarce. To address these challenges, water management approaches need to be adopted, along with precision agricultural technologies to enhance water use efficiency and satisfy the requirements of agricultural production, despite the diminishing availability of land and water resources ^[31][32]. Precision agriculture and smart irrigation technologies enable farmers to optimize resource use and prevent plant water stress. Smart irrigation involves monitoring and controlling strategies to supply water at the appropriate time, location, and quantity, considering soil moisture, weather patterns, and plant conditions. Traditional irrigation methods can lead to over- or under-irrigation, resulting in nutrient leaching, water waste, and quality and yield loss ^[32][33]. Enhancing irrigation efficiency is crucial for minimizing water usage in agricultural operations while maintaining maximum crop yields and reducing environmental impacts ^[33][34]. Enhanced irrigation can be achieved through the adoption of effective irrigation systems such as drip irrigation or deficit irrigation, improvement in the precision of water application, changes in farming practices such as crop rotation and conservation tillage, and the repair of irrigation system leaks or damages. These strategies can significantly reduce the carbon footprint, limit water consumption, minimize agricultural runoff, decrease energy requirements for water pumping and transportation, and reduce irrigation-related costs for extraction and transport ^[34][35]. Drip irrigation is important in sustainable agriculture for its precise delivery of water and nutrients to plant roots. However, it has challenges such as clogging and soil salinization. Subsurface irrigation is a viable alternative to address these issues, reducing evaporation and weed growth, and increasing safety with reclaimed wastewater. Desalination of effluent also address the problem of salinity buildup ^[35][36]. The injection of fertilizers into the water stream of a drip irrigation system (i.e., fertigation) enables precise applications of nutrients, which can lead to higher crop yields and improved soil health.

2.6. Pollution Control

Water pollution poses risks to ecological and human health. Inorganic and organic pollutants, along with microbial agents, are increasingly seen as harmful to ecosystems and organisms. Therefore, it is necessary to allocate resources to mitigate water pollution. Emerging contaminants (ECs) such as pharmaceuticals, personal care products, plasticizers, surfactants, fire retardants, nanomaterials, and pesticides have received attention in recent years due to their hazardous effects. Physical, chemical, and biological techniques are being explored to remove ECs and reduce their harmful effects. The scientific literature comprehensively reviews these techniques ^{[36][37][38][39][40][41][42][43][44][45]}[37,38,39,40,41,42,43,44,45,46].

2.7. Novel Technologies

Developing effective, low-cost, and robust technologies for water and wastewater treatment is critical for improving sustainable water production and management ^[46][47]. To attain sustainable technological change, it is imperative to recognize that progress in technology alone is insufficient. It is equally important to account for the economic and societal factors that can impact the success and longevity of technological advancements ^[47][48]. Numerous obstacles hinder innovation within the water industry. One such barrier is the high initial costs and long lifespan of existing infrastructure, leaving minimal flexibility for the rapid integration of newer technologies. Additionally, the low cost of water results in less funding for future investments. Moreover, public health risks associated with water systems limits the ability to take risks in the implementation of new approaches. Finally, existing regulations may not facilitate innovation in the water industry, and even when they do, water utilities often do not prioritize research and development efforts ^[48][49]. While novel techniques with promising feasibility on a laboratory scale exist, they often face challenges such as low process efficiency, high-energy requirements, a lack of engineering expertise for scaling up, low economic benefits, and poor infrastructure. There are also gaps in innovation that exist between conceptual ideas and solutions that are ready for scale-up ^[49][50]. In addition, due to their relative specificity, novel technologies often pose a challenge in terms of adaptability to different needs once they have been developed ^[50][51]. To overcome all of the above-mentioned challenges, it is crucial to focus on the organizational culture of water management entities and encourage the integration of innovative solutions. Policies should promote the development of services that prioritize innovation and adaptation to address water-related challenges and stimulate economic growth. Several factors that foster innovation in the water industry include a supportive culture that values innovation, regulations that encourage innovation, adequate financial resources for research and development, and crucially, public support ^[48][49].

2.8. Transboundary Water Cooperation

Due to the intricate interplay of diverse economies, ecosystems, climates, politics, and cultures within watersheds, managing transboundary water resources is essential ^[51][52]. It involves cooperation, coordination, and joint action between countries. Securing the availability of water faces significant challenges, such as concerns about the loss of national sovereignty, misunderstandings about the risks and benefits of collaboration, and a lack of capacity and political will ^[52][53]. Collaboration on transboundary water management has been shown to yield economic, societal, and environmental benefits. These include positive effects, such as expanding activity and productivity in agriculture, mining, and energy; reducing the economic impact of water-related hazards such as floods and droughts; fostering joint initiatives and investments; preserving resources; increasing ecological integrity; creating a shared basin; enhancing environmental sustainability and political stability potentially ^[53][54].  The Jordan-Israel energy and water agreement is a prominent example of transboundary water cooperation. It involves building a large solar farm in Jordan that would supply power to Israel in exchange for water. Additionally, a new desalination plant will be constructed on the north Mediterranean coast of Israel to supply water to both Jordan and Israel. Cooperation also extends to the southern region of the two countries, where a new desalination plant will be built to provide water to both nations. Key components for effective transboundary water management include financing, exchange of information, enforcement ^[54][55], equitable access, responsibility and transparency, stakeholder participation, and inclusiveness ^[55][56].