The 2021 water year ends September 30, and it was another hot and dry year in the western United States, with almost the whole region in drought. Vital reservoirs for farms, communities and hydroelectricity have fallen to dangerous levels.
The biggest blow came in August, when the U.S. government released its very first declaration of water shortage for the Colorado River, triggering water use restrictions.
In response, farmers and cities across the South West are now finding new, often unsustainable, ways to meet their future water needs. Las Vegas has opened a low-level tunnel to Lake Mead, a Colorado River reservoir where water levels have reached unprecedented lows at 35% capacity. Farmers are mobilizing groundwater pumping. Officials in Arizona, which will lose nearly a fifth of its river water allocation under the new restrictions, have even pitched the idea. of water pipes hundreds of miles from the Mississippi River.
These strategies hide a more fundamental problem: the uncontrolled growth in water consumption. The South West is in a “anthropogenic drought”Created by the combination of natural water variability, climate change and human activities which continually widen the gap between water supply and demand.
In the long run, this can lead to “water bankruptcyWhich means that the demand for water invariably exceeds the supply. Trying to manage this by increasing the water supply is doomed to failure.
More than 7,000 miles away, Iran faces water problems similar to those in the southwestern United States, but more serious. One of the driest years in the past five decades, following decades of poorly managed water resources, prompted warnings of water-related conflicts between Iranian provinces this year.
As environmental engineers and scientists – one of us is also a former deputy director of Iran’s environment ministry – we have closely studied the water challenges in the two drought-prone regions. We believe past mistakes in the United States and Iran offer important lessons for future plans in the Southwestern United States and other areas that are increasingly experiencing drought and water scarcity. .
Pumping groundwater: a temporary solution with consequences
As the Colorado River’s water supply dwindles, southwestern farmers are putting no more straws in the already declining groundwater accumulated over thousands or even millions of years. But it is a short-term and unsustainable solution that has been tried. on the other side United States and around the globe – with major consequences. The High Plains Aquifer and Central California Valley are just two examples.
Iran offers a case study of what can go wrong with this approach, as our research shows. The country almost doubled its groundwater extraction points between 2002 and 2015 with the aim of supporting a growing agricultural industry, which has drained aquifers to the point of exhaustion. As its water tables declined dramatically, the salinity of groundwater increased in aquifers to levels that might no longer be suitable for agriculture.
As the water-filled pores in the soil are drained, the weight of the overlying soil compresses them, causing aquifers to lose their water-holding capacity and accelerate land subsidence. The capital of Iran, Tehran, with more than 13 million inhabitants, sagged more than 12 feet (3.7 m) between 2003 and 2017. In the same way, some areas of California are sinking at a speed of up to 1 foot (0.3 m) each year.
Inter-basin water transfer: a Pandora’s box
Another proposal in the Southwest was to bring water elsewhere. In May, the Arizona legislature urged Congress to initiate a feasibility study bring water to the Mississippi River to replenish the Colorado River. But that too has been tried.
In Iran, multiple inter-basin water transfer projects have doubled the flow of Zayandeh Rud, a river in the arid central part of the country. The influx of water supported unsustainable growth, create demand without enough water to support it. In the dry years now, no one has enough water. Many people in Khuzestan – the region that provides water in central Iran – lost their livelihoods as their farms dried up, wetlands disappeared and livestock died of thirst. Residents of central Iran also lost crops due to the drought as the water supply was cut off. Both regions saw demonstrations turn violent This year.
California diverted water from eastern Sierra Nevada to support the growth of Los Angeles in the early 1900s, turn the once prosperous Owens Lake Valley into a bowl of dust. Dust storm mitigation costs now exceed $ 2 billion. Meanwhile, California needs more infrastructure and investment to meet its demand for water.
Another project, the California Aqueduct, was built in the 1960s to transfer water from the Sacramento-San Joaquin Delta in northern California to the Central Valley and the southern part of the state to support agriculture and part of urban demand. It also did not close the gap between water demand and supply and pushed native fish species and ecological systems of economic and cultural significance into the delta. to the point of collapsing.
Looking to the future in light of looming water bankruptcy
As the continuous influx of people into the American Southwest increasing demand for water in the face of dwindling water supply, we have to ask ourselves if the South West is heading for water bankruptcy.
If there is no easy solution, a number of actions are possible.
First, recognize that water shortages cannot be alleviated only by increasing the water supply – it is also important to manage water demand.
Cities can save water by reducing outdoor water loss and excessive water use, such as on ornamental lawns. Californians with success reduces their water demand by more than 20% between 2015 and 2017 in response to severe drought conditions. Replanting cityscapes with native drought tolerant vegetation can help conserve water.
There is also emerging technological solutions that could increase water resources in some regions, especially fog water collection, which uses mesh sheets to trap moisture from fog, and desalination plants that turn seawater and saline groundwater into potable water. A new desalination plant planned for Huntington Beach, California is awaiting final approval. However, the environmental consequences of these measures must be carefully considered.
The southwest monsoon returned this summer after a record drought the previous year and a half in the region, but it was not enough to end the drought there. Forecasts now suggest a a good chance that a La Nina model will develop over the winter, meaning the southwest will likely experience another drier than normal early 2022.
Iran is already bankrupt, with demand exceeding supply. It will take much more than a wet year to overcome its water shortages.
Mojtaba Sadegh, Senior Lecturer in Civil Engineering, Boise State University; Ali mirchi, Senior Lecturer in Water Resources Engineering, Oklahoma State University; Amir Agha Kouchak, professor of civil and environmental engineering, University of California, Irvine, and Kaveh Madani, Dear visitors, Yale University