Here come those dastardly dams! In Asia, Africa and the Middle East, nations are building new hydroelectric dams, seemingly heedless of the potentially disastrous effects on the countries downstream.

Laos broke ground on a new Mekong River dam that’s causing concern bordering on fury in Cambodia and Vietnam. India is enraged about a new Chinese dam going up on the Brahmaputra River. And Ethiopia’s new dam on the Nile is angering Sudan, while Egypt has threatened war.

The rivers have provided sustenance for millions of people for millennia, and dams threaten that. Because of this, in some places multinational commissions were set up to arbitrate such disputes.

But it’s not working.

As climate change advances and growing populations demand more water and power, many upstream nations are ignoring their responsibilities to their downstream neighbors — and the guidelines of commissions they helped establish.

Perhaps the most egregious example is Laos, which broke ground on a new hydroelectric dam on the Mekong last year, ignoring complaints downstream. Just south in Cambodia, the Mekong provides the livelihood for much of the population because of an unusual natural phenomenon.

Cambodia’s Tonle Sap River is a Mekong tributary that flows southeast from a lake of the same name. Each spring, the Mekong swells and its current grows so strong that it forces the Tonle Sap River to reverse course, carrying tons of rich, fertile mud and millions of young fish back to the lake. The lake floods, depositing new, rich soil on thousands of acres around its perimeter. The fish provide meals for Cambodians through the year. By potentially restricting the river’s flow, the Laotian dam threatens all of that.

But it gets even worse. Breaking ground, Laotian officials said they hoped the new dam would help vault their nation from its status as one of the world’s poorest. Many Lao have never even seen a light bulb. But a short time later the government signed a contract to sell most of the electricity to Thailand.

Still, Laos is subject to a perverse form of dam justice. Now those same leaders are angry about a dam China is building on the Mekong north of the Laotian border.

China recently made public its plans to build more than 60 new hydroelectric dams, potentially setting off multiple disputes. One is already under construction on the Yarlung Tsangpo River, which originates in Tibet and flows south to Bangladesh and India, where it’s called the Brahmaputra.

In the Middle East, Egypt has asserted full control over the Nile River since 1929, when the British colonial government prepared a treaty reserving 80 percent of the Nile’s water for Egypt and Sudan. Ever since, Egypt has insisted that the treaty’s provisions are still relevant and threatened to attack neighbors who dared breach it.

For all of time Egyptians have lived off the river, catching fish and using river silt as crop nutrients.

But now, Egypt is locked in foment over the Muslim Brotherhood’s faltering attempts at governance, and its upstream neighbors don’t seem to fear it any longer.

So Ethiopia is building what it calls the Grand Renaissance Dam, a $4.8 billion hydroelectric behemoth.

Ethiopia plans to create a vast reservoir behind the dam to assure a constant flow of water.

But hydrologists say it could take five years to fill, “drastically affecting agriculture, electricity and water supply downstream,” Haydar Yousif, a Sudanese hydrologist, told Middle East Magazine last month.

What’s more, he added, 3 billion cubic meters of water will evaporate from the dam’s reservoir each year.

Late last year, WikiLeaks made public a memo in which the Egyptian government threatened to deploy fighter-bombers to destroy Ethiopia’s dam.

The government protested that the memo was written in 2010, before the revolution, and was not relevant now. But if the Nile begins drying up because of that dastardly dam, Egypt may change its mind.