## Introduction

Water is equal to life. Freshwater resources mainly mean drinking, cooking, and hygiene. Water resources represent vital input for many human activities and industries, examples involve the construction industry and many other industries. The state of the Arab fresh water resources (WRs) reflects the hyper aridity of the Arab climate. The Arabsphere contains 5% of the world’s population with only 1% of its freshwater resources. The majority of the twenty-two Arab countries suffer from water scarcity. The Arabsphere’s climate is getting warmer, drier and more variable. Millions of people could be displaced. Climate change causes uncertainty to water related decisions, increase temperatures, shorten growing seasons and is likely to change precipitation patterns. More intensive droughts may lead to a reduction in crop production and put more stress on available water resources. Sea level rise could affect many cities and large regions of the most populated zones, especially, in Arabic rivers deltas.

Nowadays, Arab countries are also exposed to coronavirus pandemic which has negative impacts on Arab people’s well-being. Various forecasting and prediction models for COVID-19 have been applied to make appropriate control measures. So, only some examples may be cited. The coronavirus disease 2019 outbreak in China, Italy and France has been analyzed1. Forecasting of COVID-19 spread in Brazil, India, Peru, Russia and the USA has been modeled2. Forecasting the death rate of COVID-19 in the world using time series models has been modeled3.

There is a need for systematic categorization to facilitate recognition and wise preparation for possible future drivers to achieving sustainable development goals (SDGs) in the Arabsphere. The prime objective is to build a robust water vision to pave the road by enabling a SWF. Foresight science and discipline could be considered a protective tool in guiding future-oriented strategies. Foresight studies are used in designing science, technology, and innovation (STI) policies. This work investigated one of the most promising foresight techniques to be utilized to foresee and guide a complicated and cross-disciplinary Arabic water vision. Three Horizons is a method developed to be applied in future studies and has much strength when utilized for “emerging issues” applications4. As a pathway for transformation, Three Horizons could be applied to uncertain futures and complex problems. The characteristics and opportunities of “Three Horizons” have been discussed. “Three Horizons” could explore how Global environmental change, climate change, and other transformations could be achieved5.

Future technological impact and challenges have been provided relating to (STI) policies for the Future6. The techniques utilized for HS and scan horizons have been outlined with special emphasis on Trends, Drivers, Weak Signals, Wild Cards, and Discontinuities. Significant tools for scan horizons and HS have been presented and focused in terms of Reviewing, Brainstorming, Surveys, Network Analysis, Big Data, Bibliometrics, and Semantic Analysis7. “HS” has been implemented to foresee the radical innovation breakthroughs as preparation for policy intelligence and implementation of Horizon Europe’s research and innovation programs8. An example that represents the Russian experience in Foresight has been described9. HS could be an approach for exploring new S&T opportunities10. The example has focused on Russian Foresight in the science and technology (S&T) field which could be useful for other states with similar features, priorities, constraints, and barriers. Foresight activities and how to be designed for Creative Futures and future repositioning focused have been reported11.

Nature-based solutions focuses on sustainable pathways, green growth, sustainable urbanization, infrastructure (blue and green) and ecosystem (mitigation and adaptation), resilience and future societies12. Nature-based solutions could be a pathway to circular economy (CE), strengthen equitable future, support water security, establish maximum advantage for green and grey infrastructures (investments) and achieve sustainable water development for all13. As a pathway to sustainable development (SD), circular economy (CE) could support sustainable, equitable efficient and reasonable resources utilization14.

## Methods

### Study area

The Arabsphere includes any member country of the Arab League. The Arabsphere has four sub-regions (Arab Gulf, Horn of Africa, Maghreb (western Arabsphere), and Mashreq (eastern Arabsphere). Arab Gulf States include Bahrain, Emirates, Kuwait, Oman, Qatar, and Saudi Arabia. Maghreb States include: Morocco, Algeria, Tunisia, and Libya. Mashreq States include: Egypt, Palestine, Lebanon, Jordan, Syrian, and Iraq. The least developed countries (LDCs) include: Mauritania, Sudan, Somalia, Djibouti, the Comoros and Yemen.

### Sustainable development goal on water and sanitation (SDG 6)

SDG 6 is focusing on the sustainable water resources, used water and ecosystems. There are many global indicators to assess progress towards the targets of SDG 6. The global indicators are drinking water, sanitation, hygiene, used water, water quality, water-use efficiency, water stress, Integrated Water Resources Management (IWRM), transboundary, ecosystems (water-related ecosystems), cooperation and participation. There are four key components of IWRM implementation: (I) Enabling Environment, (II) Institutions and Participation section, (III) Management Instruments, (IV) and Financing. The latest year of reporting is 2017 for Country (or area), regional and world data. Based on UNEP data source, and defined by a score (0–100), [Units = %] the Arabsphere status of IWRM has been indicated. Degree of IWRM implementation and Final water resources management (WRM) Score are shown in Table 1 for Arabsphere, and for geographical regions and the whole world are shown in Table 2. Among the 19 IWRM reporting Arab countries, 63% are improbable to meet the global IWRM target unless progress is considerably improved15.

### Water use efficiency

Water-use efficiency (WUE) can be defined as the economic value added per volume of water withdrawn, by an activity. Examples of economic activities include agriculture, fishing, forestry, mining, quarrying, manufacturing, constructions and energy. Agriculture, industry, municipal water and energy sectors have high water use. According to16, WUE is an indicator defined to measure the value added per water unit, for an economic sector over a time, and expressed in USD/m3. Based on16, WUE is shown in Table 3 for the Arabsphere.

The main economic sectors (ES) related to this concept are agriculture (A), industry (I) and services (S). WUE is the sum of water-use efficiency of economic sectors [(AWUE), (IWUE), (SWUE)], weighted to the ratio of water used by each sector over the total uses (Ar, Ir, Sr), using the formula:

$${\text{WUE}} = A_{{{\text{WUE}}}} \times A_{{\text{r}}} + I_{{{\text{WUE}}}} \times I_{{\text{r}}} + S_{{{\text{WUE}}}} \times S_{{\text{r}}}$$
$${\text{Knowing that}},{\text{ Water Efficiency for an economic sector }}\left( {ES_{{{\text{WUE}}}} } \right)\, = \,ES_{{{\text{WUE}}}} \, \times \,ES_{{\text{r}}}$$

where ESWUE is the WUE for the economic sector (ES) index, ESr is the ratio (weight) of water utilized by an economic sector (ES) over the total water.

WUE is a key water indicator in the set of SDGs17. WUE is the core of SDG goal 6, target 6.4, and indicator 6.4.1. It is hoped that WUE will be increased by 2030, as a promising step to mitigate water scarcity, especially, in water-scarce countries such as Arab countries. WUE could provide an analytical instrument for assessing the uncertainty and future water trends in changing environments, climates, and socioeconomic. For Time Interval of First Horizon, Water Withdrawals (Agriculture, Industries, and Municipalities) and Incremental evaporation, from irrigation, over wetlands, over open water, and Reservoir evaporation, could be assessed. To proceed towards other Time Intervals, corresponding to both Second Horizon and Third Horizon, all Demographics, Ecological, Environmental, Political, Economic, Social, and Technological (DEEPEST) dimensions should be investigated.

From WRs discipline perspective, normally rigorous scientific bases should be followed, then specialized knowledge could be applied. The rigorous scientific rule could be “the total quantity of Water Resources should be greater than (or equal) the total quantity of consumed Waters, in the same time period”. In each country or geographic region, Water Resources, Users, and consumers should be clearly identified within the specified time frame. As an example, although Desalination could be a sustainable water resource in many geographic regions, it is not a feasible water resource in Landlocked Countries.

### DEEPEST holistic framework feasible and future water resources

A sustainable water future (SWF) necessitates an interdisciplinary, transdisciplinary, and multidimensional vision. SWF environs Demographics, Ecological, Environmental, Political, Economic, Social, and Technological (DEEPEST) dimensions. The study attempted to simplify the methodology as much as possible.

In this study, a holistic framework is suggested to be wide applicable, especially in Hydrosphere discipline. An acronym "DEEPEST" has been suggested to refer to Demographic, Ecological, Environmental, Political, Economic, Social, and Technological drivers (or domains). This study defines DEEPEST holistic framework as a foresight tool for deepening the future vision, deciding dimensions of future assessment, foreseeing innovative future solutions, and enhancing future developments. DEEPEST holistic framework domains are displayed in Fig. 1. The purpose of Fig. 1 is to shed the light on "DEEPEST" road map domains. The key idea is that a Sustainable water future (SWF) could be considered as a function of Demographic, Ecological, Environmental, Political, Economic, Social, and Technological (DEEPEST) dimensions. "DEEPEST" holistic framework could be considered as a modified version of PESTEL, PESTLE, SLEPT, STEPE, STEEPLE, STEEPLED, PESTLEE, DESTEP, SPELIT, PMESII-PT, STEER, and TELOS frameworks. "DEEPEST' holistic framework has been designed to suit the “Futurology” science and discipline.

DEEPEST holistic framework may be considered as a modification for PEST (political, economic, socio-cultural and technological) analysis to adapt with freshwater challenges and hydrosphere sustainability. Recently, many researchers have used different forms of PEST assessment to analyze academic and practical applications. The Coronavirus Pandemic and higher education developments has been examined based on PEST methodology18. Sustainable management of healthcare waste due to COVID-19 outbreak has been identified based on PESTEL (political, economic, socio-cultural, technological, legal and environmental factors) assessment19. A future transport by means of suborbital flight has been studied using PESTLE (political, economic, social, technological, legal and environmental) analysis20. The urban sustainability has been assessed using STEEP -or PESTE- (social, technological, economic, environmental and political) framework21.

### Horizon scanning process (HSP)

In this century, the HSP has been highly developed, in particular, stakeholder analysis, interrelationships, interactions, impacts, and crossing effects investigation. The methodology that has been chosen for this research “HS” is one of the well-accepted Foresight methodologies. “Foresight” could be considered as the ability to foresee the future wisely. HS is mainly about identifying possible futures, possible signals, and trends. The verb “foresee” has been used rather than the verb “predict”. The verb “foresee” is a transitive verb that means to see (project, development, potential, consequences … etc.) beforehand, and the noun “Foresight” means to act, process, or result of “foreseeing” or “foresighted”.

Foresight techniques are used mainly for strategic planning, developing visioning, and optimizing future priorities. HSP is an emerging framework that could be utilized in the Foresight process. HS is a technique to foresee about future, anticipate probable and possible future visions and explore how the future could be designed and shaped. Some useful definitions for “HS” have been suggested. Definition introduced by22 explains that “horizon” scanning implies it goes beyond probable or even plausible into the whole scope of possible futures. Another feature is considering that “Horizon Scanning” is equivalent to “Environmental Scanning”, the main concern is to explore opportunities, change, challenges, and future developments. Another perspective for “Horizon Scanning” is introduced by23 where the concentration is on the change and its early warning signs. The idea of developments and detecting its early signs has been investigated24. The perspective of “Horizon Scanning” introduced by25 is focusing on the idea of foresight and the thinking in the range of medium and strategic future. Some definitions of horizon scanning, the concentration is on the policy-making process (emerging issues, uncertainties, opportunities, risks, threats, decision making, mitigation and exploitation) have been provided26.

Several horizon scanning (HS) procedures have been applied by International organizations23,24,25,26, and some academic scholars [27,28,29,30,31]. Flow diagram of the HS generic process is displayed in Fig. 2. The flow diagram in Fig. 2 facilitates the idea of the Horizon scanning process for audiences from the non-futurology disciplines such as water resources, environment, and engineering disciplines. Main functions of HSP are exploring innovative ideas, and patterns of future changes. Comparable to the key concepts in geometry, (Points, Lines, Curves, Planes, and Surfaces), the important axioms in HSP are Signals, (data points), Trends (Lines or Curves), Drivers, Emerging issues (EIs), and Uncertainties (Planes and Surfaces). Main concerns of HSP are weak signals, misleading signals, unconscious biases due to narrow vision, high-impact low-probability events, predictable events, and not-expected extreme events.

The practical application has been implemented based on Three Horizons methodology. The first Horizon (H1) represents the current environs as if remains in future. The second Horizon (H2) is a transition interval in which innovative future opportunities are generated. The third Horizon (H3) is when idealistic and innovative ideas concerning the future emerge. Three Horizons methodology implies a dynamic situation composed of three paths move forward in time to future. These paths can harmonize complexity of the emerging issues (EIs) by impacting each other. The concentration of foresight process is the mid-term (H2) to long-term (H3). Engineering Perspective of HSP is displayed in Fig. 3.

The HSP has been initiated by desk research and reviewing the literature and outputs of available sources. Surveying publications of experts, specialists, and stakeholders, for collecting, Clustering, and Listing ideas has been a fundamental stage. Then, generating ideas and motivating creativity for HS based on a “DEEPEST” framework. Wild ideas have been generated by scanning new perspectives and assumptions. Then, a Matrix has been created to identify Themes and Emerging Water Technologies for the purpose of formulating the HSP. The activities have been tailored to suit the contents of the WRs discipline. The new reality could prove that COVID-19 lockdown, the Russo-Ukrainian war, and Grand Ethiopian Renaissance Dam (GERD) (construction and failure) and their related impact on the Water-Food-Energy-Nexus are good new examples of wild cards in the context of sustainable water future (SWF) in the Arabsphere.

Barriers and limitations have included inadequate resources, absence of stakeholders, misconception, uncertainty, fuzzy and cognitive and cultural barriers, forecast-based dominant culture, future illiteracy, cognitive biases, and difficulty to assess the impact or benefits of HS. The most important limitation is the uncertainty and fuzzy nature of HS.

## Results

The DEEPEST holistic framework is a process of systematic categorization to facilitate recognition and intelligence of possible future drivers for specific context. DEEPEST holistic framework establishes an integrated framework of macro-future factors applied in the HS component of foresight process. DEEPEST holistic framework of macro-future factors applied in the FP is presented in Table 4.

In the context of Arabsphere's Water, the main Drivers categories in the future included Demographics, Ecological, Environmental, Political, Economic, Social, and Technological components. Key Factors of each category have been presented in Table 4. From a regional perspective, the “DEEPEST” road map shed light on both primary Water Resources (Rivers water, groundwater, Rains & Floods, Desalination, Reuse of wastewater, and Non-Traditional Water Resources) and Water Users and consumers (Drinking, Industry, Agricultural and Evaporation). By identifying macro-future factors, the road could be paved to procedure toward the HSP.

From water resources engineering perspective, it is not suitable to omit or summarize the factors in Table 4. When ignoring some drivers that formulate water resources needs, could cause a serious and negative impact on the ability to provide vital water resources for all potential consumers. The macro-future factors presented in Table 4 could be considered the most important drivers which affect the sustainability of the water future, and in turn, achieve sustainable development goals (SDGs) in the Arabsphere.

Three Horizons process is used to foresee Water Vision in the Arabsphere. The time intervals for first horizon H1, Second Horizon H2 and Third Horizon H3 are Less than 5 Years, within 5–10 Years and within 15–25 Years, respectively. The Theme for H1 is Water conservation WC, H2 is Circular Water CW, and H3 is Emerging Water Technologies EWTs. Examples for WC, CW, and EWTs are given in Table 5. Table 5 displays examples of possible water solutions corresponding to each horizon. The Theme for H1 is Water conservation (WC), H2 is Circular Water (CW), and H3 is Emerging Water Technologies (EWTs). Examples for WC, CW, and EWTs are given in Table 5.

Water Vision has been presented based on Three Horizons for the Arabsphere in Table 5. The main idea is to utilize the Three Horizons framework to classify freshwater resource availability as a function of cost, effort, and technical complexity, as defined in the WRs discipline. From the WRs discipline perspective, the items in the Water conservation (WC) category are “Safe” solutions which could be considered negative actions. The main idea is to save water. On the other side, the items in the Circular Water (CW) category are “Risky” solutions that require positive actions. The main idea is to treat water. Also, the items in the Emerging Water Technologies (EWTs) category are “Truly Innovative Ideas” which require positive and very complicated actions. The main idea is to harvest any drop of water. Another important issue, the Water conservation (WC) category deals with water resources acceptable for all water resources customers (drinking, hygiene, irrigation, agriculture, and industry), but in the Circular Water (CW) category different water quality parameters should be determined, and according to the actual water quality and the potential customer (drinking, hygiene, irrigation, agriculture, and industry), the cost, technology, and other significant factors could be assessed.

Designed Characteristics of Water should be identified [Physical: Turbidity, Color, Taste, Odor, Temperature, and Specific Conductivity; Chemical: Total Solids, Suspended Solids, Alkalinity, pH value, Hardness, Chlorides, Nitrogen, Phosphorus, Sulphur, Metal, chemical substances, Dissolved gases, Oil and Grease, Dissolved Oxygen (DO), Biological Oxygen Demand (BOD), Chemical Oxygen Demand (COD), Total Organic Carbon, and Adsorbable Organic Halides; Biological: Parasitic organisms (Bacteria, Protozoa, Algae, Viruses, Worms and Fungi)].

In general, industrial water could be classified into three grades according to comprehensive water-quality parameters: pH, BOD, COD, Total nitrogen, Total phosphorus, Total suspended solids (TSS), Total dissolved solids (TDS), Conductivity, Alkalinity as CaCO3, Calcium hardness as CaCO3, Chlorides, Sulfates, Iron (Fe), Silica, Dissolved oxygen and Fecal coliforms. In industrial sector, the technologies most commonly used include Physical, Chemical, Biological, Membrane, Equilibrium, Advanced chemical, Nature-based and Miscellaneous-based treatment. A comprehensive summary about Circular water based on 5Rs approach for WRs [reduce (losses), reuse (no treatment), recycle (treated), restore (return) and recover (other resources from used water)] has been presented32. Circular water technologies have been summarized in Table 6.

### Emerging water technology matrix

The building of the “Emerging water technology matrix” necessitates exploring all possible and probable domains that could be significant water future opportunities. Emerging Water Technology Matrix could be constructed when focusing on the specific water resources in HSP. The grading system has four components; Excellent (E), Good (G), Pass (P), and Fail (F). The Excellent (E), Good (G), Pass (P), and Fail (F) represent Plenty, Sufficient, Vital and Deficient cases of water resources, respectively. Emerging Water Technology Matrix is shown in Table 7.

## Discussion

“Futurology” has been classified as one of the Social Sciences disciplines and focused on the future of people. Now, holistic “Futures studies” are expanding to include environmental trends, S&T, and technological advancement. HS is devoted to researching water signals and their future impacts. Many new research techniques and instruments are being could be utilized in Foresight discipline. Promising examples included Big Data Analysis, Bibliometrics, Semantic Analysis, Data mining, Text mining, Technology mining, Scientometrics, and visualization (displays of the large data). Among the most significant are computer science, social science computing (SSC), computational social science (CSS), artificial intelligence (AI), business intelligence, natural language processing, machine learning, cloud computing, and application programming interfaces (APIs). Computationally, Big data sets could be analyzed to reveal trends, and patterns, relating to human consumption, behavior, production, and interactions. As an example, A future orientation index is proposed to assess the correlation between a country’s Gross domestic product (GDP) and the tendency of seeking information about the future among Internet users33.

### Water vision

Water Vision is a process that facilitates societies, civilizations, and countries in achieving SDGs and could be considered the backbone of an integrated water strategic framework for action. The Water vision should be a result of a huge amount of knowledge, extensive experience, long-term practice, Water wisdom, and foresight skills. Arabsphere's Water Vision for 2050 is tailored to lead to a sustainable water future, mitigate the disastrous threats, enhance coordination, cope with the future growth constraints, reduce poverty, motivate innovative water solutions, optimize value for all consumers, and stimulate social well-being and life decent. The Water Vision is devoted to the Arabsphere, water-scarce countries, countries, societies, and civilizations facing serious water challenges. From an economic perspective, Water resources could be used as a final product for vital activities such as Water, sanitation, and hygiene (WASH), or as raw and input material for cooking, irrigation, agriculture, and many industries.

The world is far from achieving SDG 634. Based on the country data extracted from34, the 2021 status and trend of SDG 6 in the Arabsphere have been shown in Tables 8 and 9, respectively. In fact, these data show a clear picture of the existing water status which is mandatory for foreseeing Arabsphere's Water Vision. The latest data depend on collection cycles. The trend signifies a ( +) positive, ( =) no change, and (−) negative changes with regard to a specific global target. In both Tables 8 and 9, columns I, II, III, IV, V, VI, VII, VIII, IX, X, XI, and XII represent drinking water, sanitation, hygiene, domestic wastewater, industrial wastewater, water quality, water stress, integrated water management, ecosystems, transboundary water cooperation, international water cooperation, and water participation, respectively. For both Tables 8 and 9, the following Legend could be applied.

### Water drivers of future changes

Significant drivers in Arabsphere are water vision, sustainable and climate-resistant water management, irrigation, agriculture and food (plant, animal, hunger, food, and agricultural reclamation projects), herbicide, chemical contaminants, pesticides, veterinary drug residues, infectious diseases in fish and animals, food traceability, food authenticity, anti-biotic residues, illegal and unregulated fishing, eradication of fish species, taking areas out of food production, irrigation, water quality challenges, bioinformatics, sustainable food production, food safety, food security, aquaculture products, sustainable fishing and marine resources, responsible fisheries, water policies, water use, water pollution, water reuse, drought tolerance, flood control, rainwater storage, water control methods, innovative hydraulic structures, protection of deltas, river widening, water systems, water shortages, disaster mitigation, sustainable systems, systems innovations, sustainable society, salinization, animal, plant, weed, invasive alien species, risk maps and flood risk management plans, reforestation, weather control and modification, biofuels, clean water and sanitation, water scarcity, water bill, drinking, hygiene, hand washing, used water, automatization, diagnostic technologies, integrated surveillance, innovative sensors, remote control, lab testing, risk assessment, nanomaterials, nanotechnologies, non-conventional water resources and good health.

### Circular water

Circularity (Circular economy) principle could be applied to improve water management. Used water could be the pathway to SWF and environmental sustainability. Water Circularity in the perspective of CE is the most significant emerging research topic. Water could be a main pathway to CE. Water and used water utilities can lead the pathways to SDGs, in particular SDG6 (concerning sustainable water) and SDG12 (concerning circular economy)35. Circular-Economy could strength sustainable water resource and recovery36. Combined sewer approach could improve combined sewer quality and mitigate water pollution and flooding problems, especially in crowded urban areas. Combined sewer system components are grey [flush tanks (FTs)], green [constructed wetland] and blue [receiving water body (RWB)] infrastructures37. Interpenetrating hydrophilic (hydratable polymeric) polymer networks have been utilized to purify water by solar energy (solar vapor generation). A durable and stable hydrogel solar evaporator could extract water from complex contaminants including heavy metal, detergents and salts components38.

The circular economy could enhance sustainable water management and mitigate water scarcity and nutrients shortage. Drinking water resource recovery using thermal process, chemical precipitation and reverse osmosis has been successfully examined in a pilot plant39. Water Circularity approach has been proposed considering economic and ecosystems and their interdependencies40. Used water could be a sustainable water source, nutrients, and energy resources41. The used water as an economic resource could support water utilities which operating sustainable water supply and sustainable sanitation systems. The World Bank initiative of concerning resource recovery devoted to transfer used water to resource has been highlighted42.

### Water color

Many species of water exist. Precipitation is the main freshwater source on the Earth. Pure freshwater is colorless. The color of water is a good detector for biological, chemical and physical characteristics. Impurities, suspended, particulate and dissolved materials result in discoloration. The color of water can used to diagnose the water quality status.

In case of drinking water, blue, red, green, black colors can be related to specific physical, biological and chemical drivers. Diagnosing water quality based on color spectrum analysis can make solving water problems, especially industrial used water, is a simple and straightforward process.

From irrigation perspective, green water is the precipitation consumed by non-irrigated agriculture, whereas blue water is the precipitation consumed by irrigated agriculture. Green water represents the quantity of freshwater available directly for the ecosphere (biosphere). Blue water is the quantity of freshwater available in surface water (rivers, canals, channels, etc.) and groundwater aquifers. Both “green water” and “blue water” be considered as a productive rainfall.

From domestic used water perspective, grey water is the quantity of domestic used water used at home, except urinals, bidets and toilets. Yellow water represents human urine. Brown water represents human feces without human urine. Black water represents all toilet used water, i.e. yellow water (human urine) in addition to brown water (human feces).

From industrial used water perspective, there is a spectrum of color patterns. In some conditions, all rainbow colors, Variable-colored and iridescent may be existed. The most common are white water (milky white, and whitish to greenish, blueish or brownish), green, yellow, orange, reddish-orange, red, violet, purple, yellowish to brownish, brown, dark brown, grey, and black water. The water general appearance may be quite different. Most common phenomena are Water swirls, filmy, plates, lumpy, cloudy, chalky, foamy, sudsy, scum, gelatinous, shades, dull sheen, dark, fluorescent, and rainbow sheen.

From non-conventional waters perspective, the main idea for defining the colors of domestic used water is to facilitate used water as a valuable water and economic resource. Used water as a resource may be separated into grey water, and black water (yellow water and brown water). Grey water may be reused to irrigate the gardens and green walls. Yellow water can be a source for plant nutrition as urine fertilizers. Brown water can be used to alleviate soil degradation, consequently, enhance irrigation environment.

### Non-conventional waters

In dry regions, water future necessitates application of non-conventional waters which considered base of the circular economy43. Non-conventional waters include desalinated water, reclaimed used water, reuse of agricultural drainage, urban or industrial used waters, fog harvesting and cloud seeding. Emerging sustainable water technologies should be environmentally compatible, socially acceptable, economically feasible and technically promising. Innovative nature-inspired water technologies include atmospheric water harvesters, biomimetic membranes, and biosaline agriculture.

Harvest icebergs could be acquired by hauling the icebergs to a suitable site in the path as an ice, where the ice converted to water, then towing this freshwater to the Arabsphere. From foresight point of view, iceberg towing to Arabsphere from Arctic or Antarctica could be a feasible solution to alleviate water stress and provide freshwater in the Arabsphere. DEEPEST holistic framework could be applied to icebergs hauling scenarios.

Advances in many scientific disciplines, engineering branches, innovation fields and technologies lead to success, achievement and superiority. Engineering fields such as Ocean engineering, Offshore engineering, Mining, Mechatronics, Power, Thermal, Mechanical, Manufacturing, Industrial, Vehicle, Materials, Electronic, Structural, Transport, Information, Safety, Reliability, Systems engineering, Supply chain engineering, Quantum engineering, applied engineering, project engineering, and Engineering management are promising in this vision. Technological advances in fields such as artificial intelligence, computer modelling and simulation, computer-aided design, automation, robotics, artificial satellites, control systems, and super powerful rig towing tug can make a difference. Financial institution, insurance companies, and investment banks could support scenarios of icebergs hauling and offer palatable economic risk-free mechanism. Greenhouse gas and carbon footprint should be mitigated to allowable international standards.

### Atmospheric water harvesting (AWH)

One of the most promising Emerging Water Technologies is Atmospheric Water Harvesting (AWH). Recently, many scholars have made significant contributions in this optimistic field. AWH is emerging technology to mitigate the global water scarcity. AWH is constructed to extract water. Arid Air Water Harvesting by using composite sorbent made of hygroscopic salt and Metal–Organic Frameworks is an emerging water technology44. AWH using Metal organic frameworks as adsorbents is a promising device in the light of temperature and pressure responses, and working capacity45. Atmospheric water could be harvested from air by nano sorbent. Multiple water harvesting cycles could be achieved for effective applications by nano-carbon shell46. Hydrogels are emerging materials for atmospheric water harvesting. Water could be absorbed and evaporated within hydrogels. Hydrogels have tailor-made physiochemical characteristics.47. Atmospheric water could be harvested by nano biopolymer hygroscopic aerogel have high-capacity water storage using lyophilization (freeze-drying/cryodesiccation) process in dry, cool, and nature sunlight severe environmental outdoor conditions48.

Adsorption Water Harvesting systems could be effective by applying Advanced Metal–organic frameworks49. Atmospheric water could be harvested by water sorption process. Polymeric sorbent, which enhance performance and productivity, and free of metal and halide has been proposed50. The water harvester has been provided by non-toxic and bio-degradable desiccant51. Hygroscopic, Inorganic porous materials and Organic sorbents have successfully been used in atmospheric water harvesting. Sorbent-based water harvesting systems have significant design properties such as absorbency, stability, host materials, quantity, regeneration, relative humidity, maximum water harvesting, cost, safety, life cycle and technique52.

Recently, solar‐driven AWH has been emerged as an innovative discipline. Extraction of water vapor could be effective process to purify and produce freshwater when applying solar energy53. AWH is developed by inspiring the biological adaptability of some plant species that could absorb moisture using hygroscopic photothermal organogel powered by solar technique54. AWH is developed by desiccant-based, solar-driven model to reduce energy requirement55. AWH in arid regions is developed by Solar-Driven Dual-Stage Device utilizing advanced performing adsorbents to maximize water production and minimize heat losses56.

### Humidity harvesting systems

Humidity Harvesting system utilizing a porous framework has been suggested. The system could purify moisture captured from contaminated air environment or atmospheric environment57. Advanced dehumidifiers could be effective devices for sustainable freshwater production, dehumidification and raising the thermal comfort. High humidity could be utilized as a freshwater resource to alleviate water scarcity.58. Humidity Harvesting systems depends on successful water adsorption. Emerging Water adsorbents involve porous organic polymers, metal–organic structures, hydrogen-bonded organic structures, covalent organic structures, bioinspired nanostructures, nano-porous water-absorbent gels, controlled morphologies nanomaterials, nanofibers, nanorods, and two-dimensional nanosheets materials. The physicochemical characteristics of merging Water adsorbents for water capture by dehumidification such as hydrophilicity, stability, binding enthalpy, surface areas, water uptake and tunable functionalities are extremely significant when designing such porous organic polymers materials59.

AW irrigation process using solar-powered for sustainable farming has been proposed. Super Moisture Absorbent Gels could harvest AW and irrigate the plants. Atmospheric water irrigation process causes the agriculture in drought and arid areas could overcome distant and/or remote water supplies60. AWH could be applied to enhance the performance of Green Roofs. Integrated green roof with fog harvesting (FH) and dew harvesting (DH) systems to enhance the performance of Green Roofs has been proposed61. AW in island regions could be harvested by air-cooled water device62.

Practical considerations are extremely important. The water source could be precipitation, fog, dew, or humidity. The innovative system could be manufactured, fabricated, installed, built, constructed or implemented in the site. Of course, the main concern is the WH capacity of technology, i.e. the total volume of water could be supplied per day. DEEPEST holistic framework could be applied to investigate challenges and sustainability aspects. Water sources, water treatment if any, community needs, target users, market price, design specifications, technical support, life cycle, safety, performance, spare parts, materials, energy requirement, hazards, quality systems and environmental conditions are significant elements.

### Shared waters

The majority of the Arabsphere’s fresh water originates outside their political borders. Shared waters are serious to Arabsphere and must be cosidered as a tool for building cooperation and peace. Equitable allocation of WRs and exchange benefits through dialogue and negotiations are the key for active regional cooperation among countries in the Arabsphere and their neighbors. The Arabsphere needs to examine how to enhance cooperation and integration. The Arabsphere should develop innovative schemes for conflict resolution. Water balance should be explored at shared basins including both green and blue waters. Utilization of all waters including rivers, surface water, groundwater, blue-water, and green water, should be equitable and reasonable. IWRM, WUE and Water Nexuses should be monitored and supported.

### Water's horizons

The category of Water conservation techniques is the cheapest, easiest, and technologically simplest, so it is most suitable to be applied in the First Horizon. Comparably, the category of Circular Water techniques is more costly, harder, and technologically more complex, so it could be suitable to be applied in the Second Horizon. Similarly, the category of Emerging Water Technologies is the costliest, hardest, and most technologically complex, then it is hoped to be suitable to be applied in the Third Horizon. So, the decision-maker in the WRs discipline could emphasize technologies related to Water conservation in First Horizon (less than 5 years), technologies related to Circular Water in Second Horizon (within 5–10 years), and technologies related to Emerging Water Technology in Third Horizon (within 15–25 years). The items in the Emerging Water Technologies (EWTs) category are “Truly Innovative Ideas” which require positive and very complicated actions, the main idea is to harvest any drop of water.

## Conclusions

Availability of water resources is the most complicated challenge facing sustainable development in the Arabsphere. “Foresight” could be considered as the ability to foresee the future wisely. The application of “Futurology” principles and methodologies in the WRs discipline, which mainly belongs to civil and environmental engineering discipline leads to an interdisciplinary study, which in turn necessitates paving the road, and bridging the knowledge gap between Social Sciences and engineering disciplines, and practicing some sort of common language. The present study focused on United Nations SDGs—in particular, SDG 6 and SDG12—to achieve the strategic visions of the Arabsphere. From water resources engineering perspective, there are many opportunities to provide water resources. It is a common-sense practice to prioritize criteria for choosing the most suitable alternative, in terms of all Drivers, and in particular, Demographics, Ecological, Environmental, Political, Economic, Social, and Technological. From the WRs discipline perspective, there is some sort of analogy between Water conservation (WC), Circular Water (CW), and Emerging Water Technologies (EWTs) from one side and “Safe” solutions, “Risky” ideas, and “Truly Innovative Ideas”, from another side. Although the individual brainstorming started with “Safe” solutions, it continued with “Risky” ideas, hoping to achieve “Truly Innovative Ideas”. The wild ideas have guided the survey of future water developments and suggested more water resource opportunities and explored innovative water resource solutions. Some examples of wild ideas have been deep offshore groundwater, Unified Super Smart Water Grid (USSWG), and Antarctic and Arctic icebergs Harvesting. Now, some emerging water technologies which successful at the laboratory scale could be insignificant as a water resource for the Arabsphere water balance. In the future, those emerging water technologies could perfectly support the Arabsphere's Water Vision. Actually, achieving the SDGs necessitates successful integration between foresight methodologies and the decision-making process. Although the HSP is not a magic wand to create precious freshwater resources, Hopefully, HSP is a base for a wise Water Vision in the Arabsphere. The Proactive vision of this study is to promote Foresight discipline in academia, technology, industry, and business. The outcomes of the application of the HSP to foresight emerging issues in Arabsphere's Water Vision could be a pioneering example for other areas of Sustainable Development and other United Nations SDGs. The successor examples could emphasize achieving no-regrets futures, avoiding extreme weather and disruptions, and mitigating Climate Change. From a future-relevant perspective, similar assessments could be implemented for other SDGs. Food (SDG 2), energy (SDG 7), and cities (SDG 11) could be obvious and straightforward applications. Similar approaches for resources, especially, climate, water, food, energy, and land nexus could be applicably fruited to enable sustainable pathways and the furtherance of the SDGs for the future.