Development, weather changes and a lack of conservation have put Iran -- an arid country whose population has doubled to nearly 80 million since 1979 -- on the brink of a crisis.
Iranians use 250 liters (66 gallons) of water per person per day, significantly less than United States residents, who use nearly 400 liters (105 gallons) per day but have access to abundant fresh water. Countries neighboring Iran tend to consume water at similar levels to Iran but have significantly lower populations.
"Our water usage is twice the world standard and considering the situation in our country, we have to reduce this level," said Massoumeh Ebtekar, the head of Iran's Department of Environment.
A study by the World Resources Institute in 2013 called Iran the world's 24th most water-stressed nation. Although it has desalinization plants on the Caspian Sea and the Persian Gulf to convert seawater to drinking water, the costs to transport the potable water are excessive.
Across Iran, rivers and lakes are drying up -- symptoms of a drought caused by six years of below-average rainfall, as well as longstanding habits of Iranians that include public and household water taps that are never shut off, and the practice of hosing down concrete to cool it.
Karaj, a Tehran suburb of 1.6 million people, began a rationing program this summer, and other major cities are likely to begin their own.
"If water consumption in Tehran is managed and controlled we will not need rationing this summer. If people reduce their water consumption by just 20 percent there won't be any need for action," said Seyed Hossein Hashemi, governor of Tehran.
A state estimate claims nearly 60 percent of agricultural irrigation water is wasted.
"In less than 50 years, we've used all but 30 percent of our groundwater supply, which took a million years to gather and it's getting worse and worse due to unsustainable development," said Nasser Karami, an Iranian climatologist.