1. Overview

Visualisation of the distribution (by volume) of water on Earth. Each tiny cube (such as the one representing biological water) corresponds to approximately 1,000 cubic kilometres (240 cu mi) of water, with a mass of approximately 1 trillion tonnes (2000 times that of the Great Pyramid of Giza or 5 times that of Lake Kariba, arguably the heaviest man-made object). The entire block comprises 1 million tiny cubes.^[1] https://handwiki.org/wiki/index.php?curid=2084992

Water is an essential resource for all life on the planet. Of the water resources on Earth, only 2.5 percent of it is fresh and most of this is unavailable for immediate human use. Two-thirds of this freshwater is locked up in ice caps and glaciers. Of the remaining one-third, a fifth is in remote, inaccessible areas or delivered as seasonal/ monsoonal deluges and floods that cannot easily be used.^[2] As time advances, water is becoming scarcer; having access to clean, safe, drinking water is limited among countries. At present, only about 0.08 percent of all the world's fresh water^[3] is accessible. And, there is ever-increasing demand for drinking, manufacturing, leisure and agriculture. Due to the small percentage of water available, optimizing the fresh water we have left from natural resources has been a growing challenge around the world.

Much effort in water resource management is directed at optimizing the use of water and in minimizing the environmental impact of water use on the natural environment. The observation of water as an integral part of the ecosystem is based on integrated water resource management, based on the 1992 Dublin Principles (see below). ^[1]

As a limited resource, water supply poses a challenge. This fact is assumed by the project DESAFIO (the acronym for Democratisation of Water and Sanitation Governance by Means of Socio-Technical Innovations), which has been developed along 30 months and funded by the European Union's Seventh Framework Programme for research, technological development, and demonstration. This project faced a difficult task for developing areas: eliminating structural social inequity in the access to indispensable water and public health services. The DESAFIO engineers worked on a water treatment system run with solar power and filters which provides safe water to a very poor community in the state of Minas Gerais.^[4]

Sustainable water management requires a holistic approach based on the principles of Integrated Water Resource Management, originally articulated in 1992 at the Dublin (January) and Rio (July) conferences.^[5] The four Dublin Principles, promulgated in the Dublin Statement are: 1. Fresh water is a finite and vulnerable resource, essential to sustain life, development and the environment; 2. Water development and management should be based on a participatory approach, involving users, planners and policy-makers at all levels; 3. Women play a central part in the provision, management and safeguarding of water; 4. Water has an economic value in all its competing uses and should be recognized as an economic good. Implementation of these principles has guided reform of national water management law around the world since 1992.

Further challenges to sustainable and equitable water resources management include the fact that many water bodies are shared across boundaries which may be international (see water conflict) or intra-national (see Murray-darling basin). Perhaps unsurprisingly, international water conflicts have been the motivation for a large number of international treaties that seek to negotiate and regulate water resource sharing as well as adjudication of responsibilities for pollution or other negative outcomes (see international joint commission) ^[1]

2. Agriculture

Agriculture is the largest use of the world's freshwater resources, consuming 70 percent, though this varies widely between countries and regions.^[6] As the world population rises, it consumes more food (currently exceeding 6%, it is expected to reach 9% by 2050), industries and urban developments expand, and the burgeoning biofuel crops trade also demands a share of freshwater resources, exacerbating water scarcity. An assessment of water resource management in agriculture was conducted in 2007 by the International Water Management Institute in Sri Lanka to see if the world had sufficient water to provide food for its growing population or not.^[7] It assessed the current availability of water for agriculture on a global scale and mapped out locations suffering from water scarcity. It found that a fifth of the world's people, more than 1.2 billion, live in areas of physical water scarcity, where there is not enough water to meet all demands. A further 1.6 billion people live in areas experiencing economic water scarcity, where the lack of investment in water or insufficient human capacity make it impossible for authorities to satisfy the demand for water.^[8]

The report found that it would be possible to produce the food required in future, but that continuation of today's food production practices and environmental trends would lead to crises in many parts of the world. It has become increasingly common to think about agricultural uses of water in terms of the water footprint involved in producing particular food or fodder crops and to argue that richer parts of the world need to reconcile themselves to reprofiling their foodways to achieve a smaller agricultural water footprint.

Regarding food production, the World Bank targets agricultural food production and water resource management as an increasingly global issue that is fostering an important and growing debate.^[9] The authors of the book Out of Water: From abundance to Scarcity and How to Solve the World's Water Problems, which laid down a six-point plan for solving the world's water problems. These are: 1) Improve data related to water; 2) Treasure the environment; 3) Reform water governance; 4) Revitalize agricultural water use; 5) Manage urban and industrial demand; and 6) Empower the poor and women in water resource management. To avoid a global water crisis, farmers will have to strive to increase productivity to meet growing demands for food, while industry and cities find ways to use water more efficiently.^[10]

Scientists have been working to find ways to reduce contamination of food using a method called the 'multiple-barrier approach'. This involves analyzing the food production process from growing crops to selling them in markets and, eventually, consuming them. Then, considering where it might be possible to create a barrier against contamination. Barriers include introducing safer irrigation practices, promoting on-farm wastewater treatment, eradicating pathogens, and effectively cleansing crops after harvest in markets and restaurants.^[11] Alternative irrigation strategies including biosaline agriculture, drip irrigation and wastewater irrigation are increasingly being turned to, to better ensure food security.

3. Managing Water in Urban Settings

The carrying capacity of the Earth is increasing greatly due to technological advances and urbanization. This rapid urbanization is occurring worldwide but is mostly focussed in developing countries. Holding many of the world's megacities (cities or urban areas with more than 10 million inhabitants), China and India are both developing at very high speeds.^[12] The number of megacities is projected to continue rising, reaching approximately 50 in 2025.^[13] Within developing economies, water scarcity is an extremely common and prevalent issue. ^[14][15]

Typical urban water cycle in the United States (POTW = Publicly owned treatment works; a municipal sewage treatment plant). https://handwiki.org/wiki/index.php?curid=1090073

In the areas surrounding urban centers, agriculture competes with industry and municipal users for safe water supplies. Through this competition, traditional water sources are becoming polluted with urban runoff. As cities offer the best opportunities for selling produce, farmers often have no alternative to using polluted water to irrigate their crops. Depending on how developed a city's wastewater treatment is, there can be significant health hazards related to the use of this water. Wastewater from cities can contain a mixture of pollutants. Wastewater from kitchens, toilets, and rainwater runoff usually contain excessive levels of nutrients, salts, and a wide range of pathogens. Heavy metals may also be present, along with traces of antibiotics and endocrine disruptors, such as estrogens.^[16]

Developing world countries tend to have the lowest levels of wastewater treatment, although in some desert cities of developing countries innovative public- private collaboration has increased wastewater treatment to more than local reuse capacity.^[17] Often, the water that farmers use for irrigating crops is contaminated with pathogens from sewage. The pathogens that pose the largest threats are bacteria, viruses and parasitic worms. These pathogens directly affect farmers’ health and indirectly affect consumers if they eat the contaminated crops. Common illnesses include diarrhea, which kills 1.1 million people annually and is the second most common cause of infant deaths. Many cholera outbreaks are also related to the use of poorly treated wastewater. Therefore, efforts to reduce freshwater contamination play a large role in the fight for global health.

The long term solution to urban water shortages involves shifting from a paradigm dominated by seeking new supply towards a water sensitive approach to urban development. ^[18][19]

3.1. Digital Strategies for Better Urban Water Management

Urban Decision Support System (UDSS) – is a data-driven urban water management system that uses sensors attached to water appliances in urban residences to collect data about water usage.^[20] The system was developed with a European Commission investment of 2.46 Million Euros^[21] to improve the water consumption behaviour of households. Information about appliances and facilities such as dishwashers, showers, washing machines, taps – is wirelessly recorded and sent to the UDSS App on the user's mobile device. The UDSS is then able to analyse and show homeowners which appliances are using the most water, and which behavior or habits should be avoided in order to reduce the water usage. This allows people to manage their consumption more economically. The UDSS is based in the field of Management Science, at Loughborough University School of Business and Economics, particularly Decision Support System in household water benchmarking, led by Dr Lili Yang, (Reader).^[22]