A drought is a period of drier-than-normal conditions. A drought can last for days, months or years. Drought often has large impacts on the ecosystems and agriculture of affected regions, and causes harm to the local economy. Annual dry seasons in the tropics significantly increase the chances of a drought developing and subsequent wildfires. Periods of heat can significantly worsen drought conditions by hastening evaporation of water vapour, drying out forests and other vegetation and increasing fuel for wildfires.
Groundwater is the water present beneath Earth's surface in rock and soil pore spaces and in the fractures of rock formations. About 30 percent of all readily available freshwater in the world is groundwater. A unit of rock or an unconsolidated deposit is called an aquifer when it can yield a usable quantity of water. The depth at which soil pore spaces or fractures and voids in rock become completely saturated with water is called the water table. Groundwater is recharged from the surface; it may discharge from the surface naturally at springs and seeps, and can form oases or wetlands. Groundwater is also often withdrawn for agricultural, municipal, and industrial use by constructing and operating extraction wells. The study of the distribution and movement of groundwater is hydrogeology, also called groundwater hydrology.
Water reclamation is the process of converting municipal wastewater (sewage) or industrial wastewater into water that can be reused for a variety of purposes. Types of reuse include: urban reuse, agricultural reuse (irrigation), environmental reuse, industrial reuse, planned potable reuse, and de facto wastewater reuse. For example, reuse may include irrigation of gardens and agricultural fields or replenishing surface water and groundwater. Reused water may also be directed toward fulfilling certain needs in residences, businesses, and industry, and could even be treated to reach drinking water standards. The injection of reclaimed water into the water supply distribution system is known as direct potable reuse. However, drinking reclaimed water is not a typical practice. Treated municipal wastewater reuse for irrigation is a long-established practice, especially in arid countries. Reusing wastewater as part of sustainable water management allows water to remain as an alternative water source for human activities. This can reduce scarcity and alleviate pressures on groundwater and other natural water bodies.
Water politics, sometimes called hydropolitics, is politics affected by the availability of water and water resources, a necessity for all life forms and human development.
Water supply and sanitation in Mexico is characterized by achievements and challenges. Among the achievements is a significant increase in access to piped water supply in urban areas as well as in rural areas between 1990 and 2010. Additionally, a strong nationwide increase in access to improved sanitation was observed in the same period. Other achievements include the existence of a functioning national system to finance water and sanitation infrastructure with a National Water Commission as its apex institution; and the existence of a few well-performing utilities such as Aguas y Drenaje de Monterrey.
Water resources in India includes information on precipitation, surface and groundwater storage and hydropower potential. India experiences an average precipitation of 1,170 millimetres (46 in) per year, or about 4,000 cubic kilometres (960 cu mi) of rains annually or about 1,720 cubic metres (61,000 cu ft) of fresh water per person every year. India accounts for 18% of the world's population and about 4% of the world's water resources. One of the proposed solutions to solve the country's water woes is the Indian rivers interlinking project. Some 80 percent of its area experiences rains of 750 millimetres (30 in) or more a year. However, this rain is not uniform in time or geography. Most of the rains occur during its monsoon seasons, with the northeast and north receiving far more rain than India's west and south. Other than rains, the melting of snow over the Himalayas after the winter season feeds the northern rivers to varying degrees. The southern rivers, however, experience more flow variability over the year. For the Himalayan basin, this leads to flooding in some months and water scarcity in others. Despite an extensive river system, safe clean drinking water as well as irrigation water supplies for sustainable agriculture are in shortage across India, in part because it has, as yet, harnessed a small fraction of its available and recoverable surface water resource. India harnessed 761 cubic kilometres (183 cu mi) (20 percent) of its water resources in 2010, part of which came from unsustainable use of groundwater. Of the water it withdrew from its rivers and groundwater wells, India dedicated about 688 cubic kilometres (165 cu mi) to irrigation, 56 cubic kilometres (13 cu mi) to municipal and drinking water applications and 17 cubic kilometres (4.1 cu mi) to industry.
Water scarcity is the lack of fresh water resources to meet the standard water demand. There are two types of water scarcity namely physical and economic water scarcity. Physical water scarcity is where there is not enough water to meet all demands, including that needed for ecosystems to function. Arid areas for example Central Asia, West Asia, and North Africa often experience physical water scarcity. Economic water scarcity on the other hand, is the result of lack of investment in infrastructure or technology to draw water from rivers, aquifers, or other water sources. It also results from weak human capacity to meet water demand. Much of Sub-Saharan Africa experiences economic water scarcity.
Peak water is a concept that underlines the growing constraints on the availability, quality, and use of freshwater resources. Peak water was defined in 2010 by Peter Gleick and Meena Palaniappan. They distinguish between peak renewable, peak non-renewable, and peak ecological water to demonstrate the fact that although there is a vast amount of water on the planet, sustainably managed water is becoming scarce.
Water resources management is a significant challenge for Mexico. The country has in place a system of water resources management that includes both central (federal) and decentralized institutions. Furthermore, water management is imposing a heavy cost to the economy.
Farm water, also known as agricultural water, is water committed for use in the production of food and fibre and collecting for further resources. In the US, some 80% of the fresh water withdrawn from rivers and groundwater is used to produce food and other agricultural products. Farm water may include water used in the irrigation of crops or the watering of livestock. Its study is called agricultural hydrology.
California's interconnected water system serves almost 40 million people and irrigates over 5,680,000 acres (2,300,000 ha) of farmland. As the world's largest, most productive, and potentially most controversial water system, it manages over 40 million acre-feet (49 km3) of water per year. Use of available water averages 50% environmental, 40% agricultural and 10% urban, though this varies considerably by region and between wet and dry years. In wet years, "environmental" water averages 61%, while in dry years it averages 41%, and can be even lower in critically dry years.
The aim of water security is to make the most of water's benefits for humans and ecosystems. The second aim is to limit the risks of destructive impacts of water to an acceptable level. These risks include for example too much water (flood), too little water or poor quality (polluted) water. People who live with a high level of water security always have access to "an acceptable quantity and quality of water for health, livelihoods and production". For example, access to water, sanitation and hygiene services is one part of water security. Some organizations use the term water security more narrowly for water supply aspects only.
Greater Mexico City, a metropolitan area with more than 19 million inhabitants including Mexico's capital with about 9 million inhabitants, faces tremendous water challenges. These include groundwater overexploitation, land subsidence, the risk of major flooding, the impacts of increasing urbanization, poor water quality, inefficient water use, a low share of wastewater treatment, health concerns about the reuse of wastewater in agriculture, and limited cost recovery. Overcoming these challenges is complicated by fragmented responsibilities for water management in Greater Mexico City:
Beginning early in the 20th century, Monterrey, Mexico began a successful economic metamorphosis and growth pattern that remains an exception in Mexico. This all began with increased investments in irrigation that fueled a boom in agriculture and ranching for this northern Mexican city. The economic growth has fueled income disparity for the 3.86 million residents who live in the Monterrey Metro area (MMA). In addition, the rapid urbanization has taken a large toll on the water resources. In addressing many of this challenges, the city of Monterrey has become a model for sound and effective Integrated urban water management.
Water scarcity in Africa is predicted to reach dangerously high levels by 2025 when it is estimated that about two-thirds of the world's population may suffer from fresh water shortage. The main causes of water scarcity in Africa are physical and economic scarcity, rapid population growth, and climate change. Water scarcity is the lack of fresh water resources to meet the standard water demand. Although Sub-Saharan Africa has a plentiful supply of rainwater, it is seasonal and unevenly distributed, leading to frequent floods and droughts. Additionally, prevalent economic development and poverty issues, compounded with rapid population growth and rural-urban migration have rendered Sub-Saharan Africa as the world's poorest and least developed region.
Namibia is an arid country that is regularly afflicted by droughts. Large rivers flow only along its northern and southern borders, but they are far from the population centers. They are also far from the country's mines, which are large water users. In order to confront this challenge, the country has built dams to capture the flow from ephemeral rivers, constructed pipelines to transport water over large distances, pioneered potable water reuse in its capital Windhoek located in the central part of Namibia, and built Sub-Saharan Africa's first large seawater desalination plant to supply a uranium mine and the city of Swakopmund with water. A large scheme to bring water from the Okavango River in the North to Windhoek, the Eastern National Water Carrier, was only partially completed during the 1980s.
Water scarcity in India is an ongoing water crisis that affects nearly hundreds of million of people each year. In addition to affecting the huge rural and urban population, the water scarcity in India also extensively affects the ecosystem and agriculture. India has only 4% of the world's fresh water resources despite a population of over 1.4 billion people. In addition to the disproportionate availability of freshwater, water scarcity in India also results from drying up of rivers and their reservoirs in the summer months, right before the onset of the monsoons throughout the country. The crisis has especially worsened in the recent years due to climate change which results in delayed monsoons, consequently drying out reservoirs in several regions. Other factors attributed to the shortage of water in India are a lack of proper infrastructure and government oversight and unchecked water pollution.
Water scarcity in Iran is caused by high climatic variability, uneven distribution of water, over exploitation of available water resources,and prioritization of economic development. Water scarcity in Iran is further exacerbated by climate change.
The Cape Town water crisis in South Africa was a period of severe water shortage in the Western Cape region, most notably affecting the City of Cape Town. While dam water levels had been decreasing since 2015, the Cape Town water crisis peaked during mid-2017 to mid-2018 when water levels hovered between 14 and 29 percent of total dam capacity.
Sudan is a country that is half desert and much of the population suffers from a shortage of clean drinking water as well as a reliable source of water for agriculture. With the Nile river in the east of the country, parts of Sudan have substantial water resources, but those in the west have to rely on wadis, seasonal wells which often dry up. These imbalances in water availability are a source of hardship, as well as a source of conflict. While storage facilities are limited, many local communities have constructed makeshift dams and reservoirs, weirs, which help in stabilizing farming communities. Farmers also utilize hafirs to store rain water which falls in the rainy season, but groundwater remains a vital source of water for over 80% of Sudanese people. For decades, political instability has led to terrible conditions and thwarted many projects and relief efforts, but aid is making its way through. Several water infrastructure projects have been enacted in recent years, with both domestic and international sources of funding. Funding from the UN has provided 9,550 local farmers with better access to water and fertile soils. A project which also plans to replant forest cover in the wadi to reverse desertification.
