Dams

Southeast Asia’s Mekong may be the most important river in the world. Known as the “mother of waters,” it is home to the world’s largest inland fishery, and the huge amounts of sediments it transports feed some of the planet’s most fertile farmlands. Tens of millions of people depend on it for their livelihoods. But how valuable is it in monetary terms? Is it possible to put a dollar value on the multitude of ecosystem services it provides, to help keep those services healthy into the future? That’s what my research colleagues and I are trying to figure out, focusing on two countries that hold the river’s most productive areas for fishing and farming: Cambodia and Vietnam. Understanding the value of a river is essential for good management and decision-making, such as where to develop infrastructure and where to protect nature. This is particularly true of the Mekong, which has come under enormous pressure in recent years from overfishi...

A 23-year western drought has drastically shrunk the Colorado River, which provides water for drinking and irrigation for Wyoming, Colorado, Utah, New Mexico, Arizona, Nevada, California and two states in Mexico. Under a 1922 compact, these jurisdictions receive fixed allocations of water from the river – but now there’s not enough water to provide them. As states try to negotiate ways to share the decreasing flow, the U.S. Department of the Interior is considering cuts of up to 25% in allotments for California, Nevada and Arizona. The federal government can regulate these states’ water shares because they come mainly from Lake Mead, the largest U.S. reservoir, which was created when the Hoover Dam was built on the Colorado River near Las Vegas. These five articles from The Conversation’s archive explain what’s happening and what’s at stake in the Colorado River basin’s drought crisis. The Colorado River prov...

Conservationists breathed a sigh of relief when Luiz Inácio Lula da Silva won Brazil’s presidential election in the fall of 2022. His predecessor, Jair Bolsonaro, had opened large parts of the Amazon region to business by crippling enforcement of environmental laws and turning a blind eye to land grabbing. It should come as no surprise that deforestation showed a sharp uptick. However, while Lula oversaw a more than 70% drop in deforestation during his first run as president in the early 2000s, the rainforest’s future remains deeply uncertain. That’s in part because Brazilian administrations, whether of the right or left, have all promoted an ambitious project to boost exports and the economy called the Initiative for the Integration of the Regional Infrastructure of South America, or IIRSA. The initiative focuses on new roads, dams and industry that can threaten the region’s fragile rainforest ecosystem – and harm the world’s climate i...

As Western states haggle over reducing water use because of declining flows in the Colorado River Basin, a more hopeful drama is playing out in Glen Canyon. Lake Powell, the second-largest U.S. reservoir, extends from northern Arizona into southern Utah. A critical water source for seven Colorado River Basin states, it has shrunk dramatically over the past 40 years. An ongoing 22-year megadrought has lowered the water level to just 22.6% of “full pool,” and that trend is expected to continue. Federal officials assert that there are no plans to drain Lake Powell, but overuse and climate change are draining it anyway. As the water drops, Glen Canyon – one of the most scenic areas in the U.S. West – is reappearing. This landscape, which includes the Colorado River’s main channel and about 100 side canyons, was flooded starting in the mid-1960s with the completion of Glen Canyon Dam in northern Arizona. The area’s stunning beauty and unique...

California has seen so much rain over the past few weeks that farm fields are inundated and normally dry creeks and drainage ditches have become torrents of water racing toward the ocean. Yet, most of the state remains in drought. All that runoff in the middle of a drought begs the question — why can’t more rainwater be collected and stored for the long, dry spring and summer when it’s needed? As a hydrogeologist at the University of California at Santa Cruz, I’m interested in what can be done to collect runoff from storms like this on a large scale. There are two primary sources of large-scale water storage that could help make a dent in the drought: holding that water behind dams and putting it in the ground. Why isn’t California capturing more runoff now? When California gets storms like the atmospheric rivers that hit in December 2022 and January 2023, water managers around the state probably shake their heads and ask why they can’t hold...