Water use is a concept that combines the substance of water with the human act of using it. We propose R & D strategies to be implemented to manage risks in water use. Currently, there are unresolved various risks in water use worldwide and in Japan. In addition, over a medium- to long-term timeframe such as 2030 or 2050, environmental and social changes will further increase risks in water use. To better understand the risks in water use, it is necessary to broaden the consideration about individuals left behind in detail. There is potential neglected demand in this area. After studying and analyzing these issues, we describe the strategies to promote science, technology and innovation.

Water is regarded as human basic rights for human survival and health. And, wide variety value of water includes culture value in any part of the world. However, because of spatial and temporal uneven distribution, the amount of freshwater that can be used by human beings has limited. There are also safety issues in terms of water quality. In the natural environment, water is a carrier of muds, sands, substances, microorganisms, temperature, energy and the like. There are also factors such as accessibility to water, sanitation, economy, and energy for treatment and transportation. These factors combine to form risks in water use.

There remains the serious problem, base of the economic pyramids peoples (BOP) cannot afford safety water at a reasonable price in the world. BOP means individuals with an annual income of less than $ 3,000. It is estimated over 4 billion population. Furthermore, there remains the problem of water fetching that makes children and women negative influence. Due to global population explosion and economic growth, global water demand will continue to increase and risks in water use will further increase. For example, due to food supply, the use of groundwater for irrigation is rapidly increasing in the world, and groundwater will be disappeared in each place. This is not a problem limited to other countries far away from Japan. Japan relies on food imports and any parts of those are made by unsustainable water. Other words, Japan also relates the problem through using indirectly unsustainable water unconsciously. So, visualizing indirect water use, we should create a scenario for a sustainable regional / global water cycle system.

Regarding domestic, there is the problem about aging of the water infrastructure developed some decades ago. In addition, the risks of water use in rural areas is increasing seriously compared to metropolitan areas. In rural areas, depopulation, aging, discontinuity and widening of agriculture field are remarkable. Compared to centralized water treatment technology suitable for metropolitan areas, decentralized water treatment technology suitable for rural areas is less mature.

In addition, climate change has a significant impact on risks in water use. Due to the frequent occurrence of extreme precipitation phenomena such as localized heavy rain, heavy snow, drought, etc., the risks in water use will increase further both in the world and in Japan.

Based on these backgrounds, we regard promoting inclusive innovation as effective. Inclusive innovation includes radical technology, disruptive technology, incremental technology, and traditional technology. It is desired to establish and maintain a sustainable water use system by grasping and controlling various variability of water resource supply and demand. Specifically, we propose to promote the following R & D themes.

• (1) Integrated understanding for the water cycle system:
  

  R & D to understand the circulation of water resources in the world, domestic and local watersheds. In addition to the elemental processes of the natural water cycle such as evapotranspiration, precipitation, and groundwater infiltration, it is important to evaluate social system influences such as dams, embankment, land use change, and groundwater pumping. By showing the variability and sustainability of water sources and the value of water, it also plays a role in visualizing guidelines for the other R & D themes.

• (2) Water treatment:
  

  A variety of water treatment technologies to safely control raw water from variable water sources in response to demand for water use. Depending on the removal target and application, suited water treatment technology is different. So, there are complicated many needs for problem solving type R&D. About R&D themes of materials, there are such as reverse osmosis membranes, flocculants, adsorbents and photocatalysts. Also, there are optimization of ultraviolet disinfection, water treatment equipment and so on. And there are systematic R&D themes such as decentralized water treatment system, reuse water system and the assessment of and life cycle costs and energy and so on.

• (3) Practical visualization and diagnosis technology of risks in water use:
  

  This theme means monitoring and analysis technology for water quality and quantity, and visualization technology for efficient and effective water use. Research on various technologies for detecting impurities in water related to water quality. Technologies that enable to visualize pathogen microorganisms with rapidly, high sensitivity, comprehensively, simply, or in the spot is expected. To develop those, there are some R&D applying such as MEMS and next-generation DNA sequencers. Furthermore, there are challenging themes such as visualization of the diffusion or behavior of pathogen microorganisms. Recently, there are noticed R&D themes about water quantity control that applied information and communication technology. For examples, there are remote and automatic control of agricultural water using IoT, prediction and detection of vulnerability of water supply pipes and sewage pipes using AI, and energy efficiency improvement of water treatment equipment using machine learning and so on. In addition, there is accumulation and utilization of data resources for sustainable and equitable water use.

• (4) Collaborative and narrative dialogue interactive R&D for social implementation:
  

  Since risks in water use also involve diverse values of people, it is impossible to separate the elements of humanity that have both rationality and irrationality. In the case of cutting-edge R & D such as treated sewage reuse, it is difficult to implement socially with only the lack of knowledge provision model of accumulating scientific analysis results and explanation in plain terms with objective facts. Economic values, social values, environmental values, etc. is based on the subjectivity of various people. So, co-creation model is more hopeful than the lack model. In co-creation model, communicating and sharing of each various sense of values, resonance and trust relationship forms as a community. There are aspects related to each of the above R & D.

Risks in water use is an area of R & D closely related to society and economy. In addition to examining sustainable water use scenarios based on accumulation of scientific analysis and technological development, R & D efforts aimed at social implementation in response to various water subjective values and social acceptability are extremely challenging. However, R & D aimed at establishing a sustainable water use system in the medium to long term has been regarded as leading and high academic value. Additionally, risks in water use is essentially an issue in a hybrid discipline. Therefore, the demand for integrated cross-disciplinary and beyond-disciplinary R&D promotion is inevitable and cannot be ignored. This trend is remarkable in world-leading water research.

Although some good practices have been made in Japan as well, considering the world and domestic situation where risks in water use are increasingly increasing, it is desirable to encourage tactics and policy to increase and expand such efforts.