Water security has been defined as "the reliable availability of an acceptable quantity and quality of water for health, livelihoods and production, coupled with an acceptable level of water-related risks". It is realised to the degree that water scarcity is non-existent, or has been decreased or eliminated, and to the degree that floods and contamination of freshwater supplies are non-threatening.
"Sustainable development will not be achieved without a water secure world. A water secure world integrates a concern for the intrinsic value of water with a concern for its use for human survival and well-being. A water secure world harnesses water's productive power and minimises its destructive force. Water security also means addressing environmental protection and the negative effects of poor management. It is also concerned with ending fragmented responsibility for water and integrating water resources management across all sectors—finance, planning, agriculture, energy, tourism, industry, education and health. A water secure world reduces poverty, advances education, and increases living standards. It is a world where there is an improved quality of life for all, especially for the most vulnerable—usually women and children—who benefit most from good water governance."
The areas of the world that are most likely to have water insecurity are places with low rainfall, places with rapid population growth in a freshwater scarce area, and areas with international competition over a water source.
Water security is achieved when there is enough water for everyone in a region and the water supply is not at risk of disappearing. According to the Pacific Institute "While regional impacts will vary, global climate change will potentially alter agricultural productivity, freshwater availability and quality, access to vital minerals, coastal and island flooding, and more. Among the consequences of these impacts will be challenges to political relationships, realignment of energy markets and regional economies, and threats to security".
It impacts regions, states and countries. Tensions exist between upstream and downstream users of water within individual jurisdictions.
During history there has been much conflict over use of water from rivers such as the Tigris and Euphrates Rivers. Another highly politicized example is Israel's control of water resources in the Levant region since its creation, where Israel securing its water resources was one of several drivers for the 1967 Six-Day War.
Water allocation between competing users is increasingly determined by application of market-based pricing for either water licenses or actual water.
Water, in absolute terms, is not in short supply planet-wide. But, according to the United Nations water organization, UN-Water, the total usable freshwater supply for ecosystems and humans is only about 200,000 km3 of water – less than one percent (<1%) of all freshwater resources. Usable fresh water includes water not contaminated or degraded by water-altering chemicals, such as sewage or any other harmful chemicals from continuous previous use. In the 20th century, water use has been growing at more than twice the rate of the population increase. Specifically, water withdrawals are predicted to increase by 50 percent by 2025 in developing countries, and 18 per cent in developed countries. One continent, for example, Africa, has been predicted to have 75 to 250 million inhabitants lacking access to fresh water. By 2025, 1.8 billion people will be living in countries or regions with absolute water scarcity, and two-thirds of the world population could be under stress conditions. By 2050, more than half of the world's population will live in water-stressed areas, and another billion may lack sufficient water, MIT researchers find.
The most common threat to water security is water scarcity. There can be several causes to water scarcity including low rainfall, climate change, high population density, and overallocation of a water source. An example of periodic water scarcity in the United States is droughts in California. Another category of threats to water security is environmental threats. These include contaminates such as biohazards (biological substances that can harm humans), climate change and natural disasters. Contaminants can enter a water source naturally through flooding. Contaminants can also be a problem if a population switches their water supply from surface water to groundwater. Natural disasters such as hurricanes, earthquakes, and wildfires can damage man-made structures such as dams and fill waterways with debris. Other threats to water security include terrorism and radiation due to a nuclear accident.
According to Nature (2010), about 80% of the world's population (5.6 billion in 2011) live in areas with threats to water security. The water security is a shared threat to human and nature and it is pandemic. Human water-management strategies can be detrimental to wildlife, such as migrating fish. Regions with intensive agriculture and dense populations, such as the US and Europe, have a high threat of water security. Water is increasingly being used as a weapon in conflict. Water insecurity is always accompanied by one or more issues such as poverty, war and conflict, low women's development and environmental degradation. Researchers estimate that during 2010-2015, ca US$800 billion will be required to cover the annual global investment in water infrastructure. Good management of water resources can jointly manage biodiversity protection and human water security. Preserving flood plains rather than constructing flood-control reservoirs would provide a cost-effective way to control floods while protecting the biodiversity of wildlife that occupies such areas.
Lawrence Smith, the president of the population institute, asserts that although an overwhelming majority of the planet's surface is composed of water, 97% of this water is constituted of saltwater; the fresh water used to sustain humans is only 3% of the total amount of water on Earth. Therefore, Smith believes that the competition for water in an overpopulated world would pose a major threat to human stability, even going so far as to postulate apocalyptic world wars being fought over the control of thinning ice sheets and nearly desiccated reservoirs. Nevertheless, 2 billion people have supposedly gained access to a safe water source since 1990 who may have earlier lacked it. The proportion of people in developing countries with access to safe water is calculated to have improved from 30 percent in 1970. to 71 percent in 1990, 79 percent in 2000 and 84 percent in 2004, parallel with rising population. This trend is projected to continue.
The Earth has a limited though renewable supply of fresh water, stored in aquifers, surface waters and the atmosphere. Oceans are a good source of usable water, but the amount of energy needed to convert saline water to potable water is prohibitive with conventional approaches, explaining why only a very small fraction of the world's water supply is derived from desalination. However, modern technologies, such as the Seawater Greenhouse, use solar energy to desalinate seawater for agriculture and drinking uses in an extremely cost-effective manner.
Based on the map published by the Consultative Group on International Agricultural Research (CGIAR), the countries and regions suffering most water stress are North Africa, the Middle East, India, Central Asia, China, Chile, Colombia, South Africa and Australia. Water scarcity is also increasing in South Asia.
The Israeli Holistic Approach to Water Security draws from 70 years of experience in national security and water management. Nations such as the US, UK, Spain, and others are collaborating with Israeli experts in water security standards.
International competition over water can arise when one country starts drawing more water from a shared water source. This is often the most efficient route to getting needed water, but in the long term can cause conflict if water is overdrafted.
More than 50 countries on five continents are said to be at risk of conflict over water.
China, is constructing dams on the Mekong, leaving Vietnam, Laos, Cambodia and Thailand without same amount of water as before investment. A huge project of reversing the flow of the Brahmaputra (Chinese: Tsangpo) river, which after leaving Chinese Tibet flows through India and Bangladesh. The struggle for water in some afflicted regions has led inhabitants to hiring guards in order to protect wells. Moreover, Amu Daria River, shared by Uzbekistan, Turkmenistan, Tajikistan and Afghanistan, which has been nearly completely dried out, so much so that it has ceased to reach the Aral Sea/Lake, which is evaporating in an alarming pace. The fact that Turkmenistan retains much of the water before it flows into Uzbekistan.
The Snowy Mountains Scheme diverted water from the Snowy River to the Murray River and the Murrumbidgee River for the benefit of irrigators and electricity generation through hydro-electric power. During recent years government has taken action to increase environmental flows to the Snowy in spite of severe drought in the Murray Darling Basin. The Australian Government has implemented buy-backs of water allocations, or properties with water allocations, to endeavour to increase environmental flows.
In India, there is competition for water resources of all inter state rivers except the main Brahmaputra river among the riparian states of India and also with neighbouring countries which are Nepal, China, Pakistan, Bhutan, Bangladesh, etc. Vast area of the Indian subcontinent is under tropical climate which is conducive for agriculture due to favourable warm and sunny conditions provided perennial water supply is available to cater to the high rate of evapotranspiration from the cultivated land. Though the overall water resources are adequate to meet all the requirements of the subcontinent, the water supply gaps due to temporal and spatial distribution of water resources among the states and countries in the subcontinent are to be bridged.
There is intense competition for the water available in the inter state rivers such as Kavery, Krishna, Godavari, Vamsadhara, Mandovi, Ravi-Beas-Sutlez, Narmada, Tapti, Mahanadi, etc. among the riparian states of India in the absence of water augmentation from the water surplus rivers such as Brahmaputra, Himalayan tributaries of Ganga and west flowing coastal rivers of western ghats. All river basins face severe water shortage even for drinking needs of people, cattle and wild life during the intense summer season when the rainfall is negligible.
Water security can be achieved along with energy security as it is going to consume electricity to link the surplus water areas with the water deficit areas by lift canals, pipe lines, etc. The total water resources going waste to the sea are nearly 1200 billion cubic meters after sparing moderate environmental / salt export water requirements of all rivers. Interlinking rivers of the subcontinent is possible to achieve water security in the Indian subcontinent with the active cooperation of the countries in the region.
The United States currently does not have a cohesive domestic water security policy. Water security is projected to be a problem in the future since future population growth will most likely occur in areas that are currently water stressed. Ensuring that the United States remains water secure will require policies that will ensure fair distribution of existing water sources, protecting water sources from becoming depleted, maintaining good wastewater disposal, and maintaining existing water infrastructure. Currently there are no national limits for US groundwater or surface water withdrawal. If limits are imposed, the people most impacted will be the largest water withdrawers from a water source. In 2005, 31% of US water use was for irrigation, 49% was thermoelectric power, public supply 11%, public supply, industrial was 4%, aquaculture 2%, domestic 1%, and livestock less than 1%.
The lack of current national water policy is effective in regions of the United States where there is a lot of water but not effective in regions of water scarcity. In the future, a national water security policy may have to be implemented to move water from regions that are water rich to regions that are water scarce. If new policies are implemented, the major stakeholders will be individual states (both water rich and water poor states), farmers, power companies, and other industries that use a substantial amount of water (such as mining and oil and gas).
According to the United States Environmental Protection Agency (EPA), "Improving the security of our nation's drinking water and wastewater infrastructures has become a top priority since the events of 9/11. Significant actions are underway to assess and reduce vulnerabilities to potential terrorist attacks; to plan for and practice response to emergencies and incidents; and to develop new security technologies to detect and monitor contaminants and prevent security breaches."
One of the most important elements of water security is early and accurate contamination detection. The EPA has issued advisory material and guidelines for contamination warning systems to be implemented in water utilities and supplies. The security challenges that utilities frequently revolve around fast detection, accuracy, and the ability to take fast action when there is a water problem. If contamination is detected early enough, it can be prevented from reaching consumers, and emergency water supplies can be put into effect.
In cases where contamination might still reach consumers, fast and efficient communication systems are necessary. All these factors also point to the need for organized and practiced emergency procedures and preparedness.
More recently, under the Drinking Water Security Act of 2009, the EPA is now required to establish risk-based performance standards for community water systems serving more than 3,300 people.
Cincinnati Water Works, San Francisco, and New York City are among the major water utilities that have taken water security measures at their facilities, such as planning for contamination warning systems.
Security of a water supply involves a range of elements. Prevention and detection systems include some or all of the following: access to public health and customer complaint data, water quality monitoring equipment, sampling and analysis, cyber-security which includes situation management and IT systems hardware and software, and physical security. Crisis management and recovery, for when critical water events occur, includes flow control and security valves, rapid and effective communication systems, and emergency water supply equipment.
Specific technologies involved in water security are SCADA, GIS (geographic information system), online (real-time) water quality monitoring devices, contamination warning systems, intrusion detection systems (IDS), contamination detection devices, security valves, security cameras and fences, situation management/emergency management software, emergency supply tanks, manned (or human) security personnel, personal purification devices, and counter-terrorism intelligence.
The Water Information Sharing and Analysis Center (WaterISAC), is the US water sector's security and emergency response information source. This nonprofit service provides US, Canadian, and Australian drinking water and wastewater utilities with the information they need to heighten the protection of water collection and delivery infrastructure. WaterISAC is also a peer-to-peer, business networking platform. Eligible members of the water sector have access to a clearinghouse of government and private documents, guides, best practices, handbooks, and contaminant databases as well as shared data including analysis of successful and failed security incidents within the water sector. These include cyber incidents, physical incidents, and other security related incidents. Many but not all of these are reported to and tracked by WaterISAC. Together, these resources are can be used by utility managers to identify risks, prepare for emergencies, and secure the nation's critical water infrastructure and the environment. American Water Works Association
Blue Peace is a method which seeks to transforms trans-boundary water issues into instruments for cooperation. This unique approach to turn tensions around water into opportunities for socio-economic development was developed by Strategic Foresight Group in partnership with the Governments of Switzerland and Sweden.
The Blue Peace is an innovative approach to engage political leaders, diplomats and populations in harnessing and managing collaborative solutions for sustainable water management.— Foreign Minister Didier Burkhalter of Swirtzerland, speaking at the UN General Assembly
Blue Peace is part of a larger trend of viewing water as a human right rather than a market commodity. When water is viewed as a human right, it empowers people in water stressed areas to manage their water sources effectively. Part of having effective management of water is ensuring that all socioeconomic groups of people in a region have adequate access to water, not just certain people.
A January 17, 2008, article in the Wall Street Journal states, "World-wide, 13,080 desalination plants produce more than 12 billion gallons of water a day, according to the International Desalination Association." 
The world's largest desalination plant is the Jebel Ali Desalination Plant (Phase 2) in the United Arab Emirates. It is a dual-purpose facility that uses multi-stage flash distillation and is capable of producing 300 million cubic meters of water per year.
However, given the energy intensive nature of desalination, with associated economic and environmental costs, desalination is generally considered a last resort after water conservation. But this is changing as prices continue to fall.
However, not everyone is convinced that desalination is or will be economically viable or environmentally sustainable for the foreseeable future. Debbie Cook, the former mayor of Huntington Beach, California, has been a frequent critic of desalination proposals ever since she was appointed as a member of the California Desalination Task Force. Cook claims that in addition to being energy intensive, desalination schemes are very costly—often much more costly than desalination proponents claim. In her writing on the subject, Cook points to a long list of projects that have stalled or been aborted for financial or other reasons, and suggests that water-stressed regions would do better to focus on conservation or other water supply solutions than to invest in desalination plants.
A novel approach to desalination is the seawater greenhouse, which takes seawater and uses solar energy to desalinate it in conjunction with growing food crops in a specially adapted greenhouse.
It is feasible to divert most of the available fresh water resources for drinking, industrial, hydro power and adequate environmental river flows purposes by reducing water use in agriculture which is consuming more than 80% of the global fresh water use. Without cultivating water intense crops, global food security can be achieved at faster pace by producing protein rich feed for cattle, poultry and fish from the cultivation of Methylococcus capsulatus bacteria culture with tiny land and water foot print using natural gas / biogas.