The combination of two hydrogen atoms and one of oxygen, H₂O, is the elemental key to life on Earth. Yet global issues related to water — whether too much or too little of it, its quality and its accessibility, along with its impact on gender and geopolitics — have never been more critical to our planet and its 7.3 billion inhabitants.

Earlier this year the World Economic Forum declared water crises the greatest international risk. Worldwide, 2.5 billion people don't have access to safe water. Every day nearly 3,900 children die because of dirty water or poor hygiene, according to the World Health Organization.

Read about 10 hot spots across the globe that are being devastated by the most urgent water crises.

—By Bob Woods, special to CNBC.com
Posted 06 October 2015

Throughout California, its worst-ever drought has dried up lakes, parched farmlands, restricted water usage and contributed to massive wildfires that have incinerated wilderness and property while upending lives. A group of scientists recently published a report stating that along with cyclical weather, global warming has most likely intensified the drought by 15 to 20 percent.

Upon touring smoldering towns in northern California this month, Gov. Jerry Brown made the climate change connection. "There is no doubt that we need to de-carbonize our modern economy," he said. "This will smoke it out. Fires are not political. Climate change is not political. It is real."

This hot spot — comprising nearly 4,500 islands across the southern Pacific Ocean and representing 11 countries, eight territories and Hawaii — has been dubbed by Conservation International as the epicenter of the current global extinction. Twenty-five of its 292 native bird species have gone extinct since European settlers arrived 200 years ago, and today 90 birds are threatened, along with scores of its 5,330 plant, mammal and marine species.

Worldwide, while fresh water holds more than 10 percent of all life, between 1970 and 2000, populations of freshwater species declined by 55 percent, compared with a decline of about 32 percent for both marine and terrestrial species, according to UN-Water, a United Nations agency.

In 2010, unprecedented monsoon rains flooded nearly one-fifth of Pakistan, killing close to 2,000 people and impacting 18 million overall. Since gaining independence from India in 1947, the country has witnessed more than 20 major floods, including last year's, which claimed at least 280 lives following the strongest post-monsoon-season storm ever recorded in Pakistan.

Beyond this fragile hot spot, from 2000 to 2006, a total of 2,163 water-related disasters — floods, tropical storms and tsunamis — were reported globally in the Emergency Disasters Database, killing more than 290,000 people, affecting at least another 1.5 billion and inflicting $422 billion of damage.

In many parts of rural Kenya, women remain traditionally responsible for food preparation, care of animals, crop irrigation, personal hygiene of households, care of the sick, cleaning, washing and waste disposal. Such gendered division of labor, UN-Water states, deprives women and girls from opportunities to escape the vicious circle of poverty and disempowerment.

"Water challenges go beyond questions of access," said U.N. Secretary General Ban Ki-moon. "In many countries, girls are forced to drop out of school owing to a lack of sanitation facilities, and women are harassed or assaulted when carrying water or visiting a public toilet."

Argentina's Matanza-Riachuelo River, which flows 40 miles through Buenos Aires, is one of the world's most polluted waterways, ravaged for years by industrial waste, sewage and everyday garbage, creating a variety of serious health problems for the city's poorest people. A full cleanup, Greenpeace said, could take 30 years.

Access to safe, clean water for drinking, food preparation, agriculture and recreation presents a major global risk. According to UN-Water, every day 2 million tons of sewage and other effluents drain into the planet's waters, and every year nearly 3.5 million people die due to inadequate water supply, sanitation and hygiene.

Nearly half of India's 1.2 billion people don't have access to toilets, especially in rural villages, UN-Water reported. The lack of sanitation there is the cause of 1 in every 10 deaths. The World Bank estimates that more than 20 percent of communicable diseases in India are related to unclean water.

Much of the world has made great strides in recent years to improve water sanitation. Since 1990, almost 1.9 billion people have gained access to an improved sanitation facility. Nonetheless, the U.N. estimates that 2.5 billion people — 15 percent of the world's population — still do not use an improved sanitation facility, and more than a billion practice open defecation.

Although Kuwait is one of the top 10 oil producers in the world, it has the least renewable water resources in the world and has experienced a more than tenfold increase in water consumption since 1970, according to the Kuwait Institute for Scientific Research. Desalination is becoming an unsustainable solution, estimated to cost a third of Kuwait's GDP by 2025 unless new technologies and energy sources reduce costs.

The tiny nation is hardly alone among its neighbors in facing water crises. At the recent World Water Week conference in Stockholm, Sweden, the U.N. Food and Agricultural Organization reported that all countries in the Near East and North Africa currently suffer from severe water scarcity, with extreme consequences for irrigated agriculture and food production.

At this month's World Water Week in Stockholm, Jordanian Prime Minister Abdullah Ensour said that his country — one of the most water-scarce in the world—is now under even more pressure due to the dramatic influx of refugees from its war-torn neighbors Syria, Iraq and Yemen. Solving the problem requires tapping into water sources shared by neighboring countries, not always an easy proposition anywhere.

There are 276 transboundary river basins in the world — 64 in Africa, 60 in Asia, 68 in Europe, 46 in North America and 38 in South America. With contentious issues around water quality and scarcity, so-called hydro-diplomacy is increasingly crucial but achievable. Nearly 450 agreements on international waters were signed between 1820 and 2007.

The ongoing building of megacities throughout China points to the stressful relationship between water and energy, which can lead to conflicts as demands for both intensify, according to research by Washington-based World Resources Institute. For instance, desalination, transferring water over long distances and treating wastewater significantly increase the energy requirements associated with providing fresh water to urban dwellers.

"Because of the strong linkages between water and energy, public- and private-sector decision-makers need to better understand water-energy dynamics and learn how to manage these resources in an integrated manner," WRI stated.

Looking toward the future of water usage, the food-plus-people math doesn't add up. Right now 70 percent of the global water withdrawals go to agriculture. With the world population predicted to rise from 7 billion to 9 billion people by 2050, that equates to a 60 percent increase of the food needed globally and a 19 percent increase of agricultural water consumption.

Northern Ghana's persistent food shortage is exacerbated by recurrent droughts and the deleterious impact on farming in a rural area already characterized by extreme poverty and malnutrition, particularly among children. Ironically, the southern part of the west African nation has lately experienced steady economic growth and poverty reduction, thanks to a U.S.-backed agricultural initiative, Feed the Future, which is now focusing its efforts northward.