The 2021 Water year ends September 30th and it was another hot, dry year in the western US, with almost the entire region in drought. Reservoirs vital for farms, communities and Hydropower have fallen to a dangerous low.
The biggest blow came in August when the US government released its first edition Declaration on water scarcity for the Colorado River, which triggers water use restrictions.
In response, farmers and cities around the world have southwest are now finding new, often unsustainable, ways to meet their future water needs. Las Vegas opens a deeper tunnel to Lake Mead, a reservoir on the Colorado River where water levels hit unprecedented lows 35% of the capacity. Farmers lend a hand Groundwater pumps. Officials in Arizona, which will lose nearly a fifth of its river water allocation under the new restrictions, even brought the idea to market from tap water hundreds of miles from the Mississippi.
Behind these strategies lies a more fundamental problem: the unchecked growth in water use. The southwest is located in a “anthropogenic drought“Is created by the combination of natural water variability, climate change and human activities that continuously widen the gap between water supply and demand.
In the long run, this can lead to “Water bankruptcy“Which means that the demand for water inevitably exceeds the supply. Any attempt to cope with this by cranking up the water supply is doomed to failure.
More than 7,000 miles away, Iran is grappling with water problems similar to, but more severe, to the US southwest. One of the driest years in the last five decades, behind several decades of poorly managed water resources, this year brought warnings of water conflicts between Iranian provinces.
As environment Engineers and scientists – one of us is also the former deputy head of the Iranian Ministry of the Environment – we have carefully investigated the water problems in both drought-prone regions. We believe that past mistakes in the US and Iran provide important lessons for future plans in the US Southwest and other regions of increasing drought and water scarcity.
Groundwater pumps: a temporary solution with consequences
As the water supply from the Colorado River decreases, farmers are settling in the southwest more straws in already sinking groundwater that have accumulated over thousands to millions of years. But that’s a short-term, unsustainable solution that has been tried above the USA and around the world – with serious consequences. the Plateau aquifer and California’s Central Valley are just two examples.
Iran offers a case study of what can go wrong with this approach, as our research shows. The country its groundwater extraction points almost doubled between 2002 and 2015 to support a growing agribusiness that drains aquifers to the point of exhaustion. When the water table dropped dramatically, the salinity of the water table in the aquifers rose to a level that may no longer be easily suitable for agriculture.
When water-filled pores in the soil are drained, they are compressed by the weight of the soil above, causing the aquifers to lose their water-holding capacity and accelerate land subsidence. Iran’s capital Tehran with more than 13 million inhabitants dropped by more than 3.7 m between 2003 and 2017. Similar, some areas in California are sinking at the rate of up to 1 foot (0.3 m) per year.
Water transfer between the pools: A Pandora’s box
Another suggestion in the southwest was to draw water from elsewhere. In May, Arizona lawmakers asked Congress to initiate a feasibility study to bring water from the Mississippi to replenish the Colorado River. But that too was tried.
In Iran, several inter-basin water transfer projects have doubled the Zayandeh Rud, a river in the arid central part of the country. The water inflow supported unsustainable growth, Creating demand without enough water to support it. In dry years nobody has enough water anymore. Many people in Khuzestan – the region that supplies central Iran with water – lost their livelihoods when their farms dried up, wetlands disappeared and cattle died of thirst. In central Iran, too, people lost harvests due to the drought, as the water was cut off. Both regions saw Protests become violent this year.
California diverted water from the 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. The cost of mitigating dust storms there now exceeds $ 2 billion. Meanwhile, California needs more infrastructure and investment to meet its water needs.
Another project, the California Aqueduct, was built in the 1960s to divert water from the Sacramento-San Joaquin Delta in northern California to the Central Valley and southern parts of the state to support agriculture and certain urban needs . As a result, the water demand-supply gap was not closed and economically and culturally important native fish species and ecosystems in the delta were promoted to the point of collapse.
Looking ahead in view of the threat of water bankruptcy
As the continued influx of people into the southwestern United States As water demand increases in the face of shrinking water supplies, we must ask ourselves whether the Southwest is heading for water bankruptcy.
While there is no simple solution, a number of measures are possible.
First, realize that not just increasing water supplies can help alleviate water scarcity – managing water needs is also important.
Cities can save water by reducing water leakage outdoors and excessive water consumption, for example on ornamental lawns. Californians successful reduced their water requirements by more than 20% between 2015 and 2017 in response to severe drought conditions. Replanting urban landscapes with native, drought tolerant vegetation can help conserve water.
There are also new technological solutions This could increase water resources in some regions, including Fog water collectionthat uses mesh to catch moisture from fog, and desalination plants that convert seawater and salty groundwater into drinking water. A new desalination plant is planned in Huntington Beach, California waiting for final approval. However, the impact of these measures on the environment should be carefully considered.
The southwest monsoon returned this summer after one Record dry previous year one and a half in the region, but it was not enough to end the drought there. Forecasts now suggest a. before high probability that a La Nina pattern will evolve over the course of winter, meaning there is likely another one to the southwest drier than normal start by 2022.
Iran is already in water bankruptcy, with demand exceeding supply. It will take much longer than a wet year to alleviate the water shortage.
Mojtaba Sadegh, Junior professor for civil engineering, Boise State University; Ali Mirchi, Junior professor for water management, Oklahoma State University; Amir AghaKouchak, Professor of Civil and Environmental Engineering, University of California, Irvine, and Kaveh Madani, Visiting scholar, Yale University