Children sit on a bed in a flooded house following heavy rain in a village in Yemen's Red Sea province of Houdieda April 15, 2016. (Photo by Abduljabbar Zeyad/Reuters)

An Afghan girl carries water on her back as she climbs a hill in Kabul, Afghanistan February 20, 2017. A growing population is straining water supplies in Afghanistan's capital, forcing those who can afford it to dig unregulated wells ever deeper to tap a falling water table. Finding water in arid Afghanistan is virtually always a challenge, but a drop in the groundwater level in Kabul caused by overuse and drought is making it even more difficult for residents, especially the poor. (Photo by Omar Sobhani/Reuters)

A girl plays in the Eshash el-Sudan slum in the Dokki neighbourhood of Giza, south of Cairo, Egypt September 2, 2015. Residents of the slum clashed with police in late August, when about 50 ramshackle huts were destroyed and at least 20 people were injured by teargas, local media reported, as authorities attempt to clear the area and rehouse residents. The slum dwellers, some of whom have called Eshash el-Sudan home for 50 years, say there are not enough apartments built nearby to house them. The residents of the slum eke out a living by disposing of rubbish or baking bread. Schooling is too expensive for most of their children, who play with salvaged rubbish amid shacks made out of discarded wood and leather. (Photo by Amr Abdallah Dalsh/Reuters)

Participants from Newar community in traditional attire, takes part in the parade to celebrate Newari New Year that falls during the Tihar festival, also called Diwali, in Kathmandu, Nepal November 12, 2015. The Newar community observes the start of their Newari New Year 1136, in accordance with their lunar calendar, by worshipping their spiritual selves in a ritual known as "mahapuja". (Photo by Navesh Chitrakar/Reuters)

A security personnel plays with a girl in the compound of a health and rest centre which serves as a temporary accommodation for refugees from eastern regions of the country in the town of Korostyshiv, Zhytomyr region, Ukraine, July 30, 2015. More than 400 people who left eastern Ukraine due to a military conflict have arrived at the sanatorium in Korostyshiv since the summer of 2014, according to representatives. (Photo by Valentyn Ogirenko/Reuters)

A group of women dance in a pool in Callao, Peru, Sunday, February 22, 2015. One of centers for the front-doorstep, pool-party phenomenon is Lima's port city of Callao. People hold parties in them and sometimes entire blocks chip in to buy a pool, which can be had in local department stores for a bit over $100. (Photo by Martin Mejia/AP Photo)

Cattle are the most important way of livelihood for the Karamojong: they provide milk, meat, blood and money when sold, Karamoja, Uganda, February 2017. (Photo by Sumy Sadurni/Barcroft Images)

A truck carrying gold miners across the Sahara desert to far northern Niger drives outside Agadez, Niger, May 9, 2016. (Photo by Joe Penney/Reuters)