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The Bengal Water Machine | Earth Wise

October 31, 2022 By EarthWise Leave a Comment

Over the past three decades, the owners of 16 million small farms in the Bengal Basin of Bangladesh have been pumping shallow groundwater during dry seasons to irrigate rice paddies.  By lowering groundwater levels in this way during the dry season, the ability of leakage from rivers, lakes, and ponds to replenish the groundwater was greatly enhanced.   Capturing surface water not only improved the recovery of groundwater levels but only helped to reduce flooding during monsoons.

The net result of this enormous collective groundwater pumping by millions of farmers has been the creation of vast natural reservoirs underground that are comparable to what is contained by many of the world’s largest dams.   This system of sustaining irrigation has transformed what was previously a famine-prone country into a food-secure nation.

The details of this remarkable transformation have been laid out in a study by University College London recently published in the journal Science.  According to the study, over the course of 30 years, more than 75 cubic kilometers of fresh water was captured by this process, which is equivalent to the combined reservoirs of China’s Three Gorges Dam and the Hoover Dam in the U.S.

The authors of the study described the water cycling process as “The Bengal Water Machine” and argue that it can be a sustainable alternative to conventional approaches to seasonal river flow storage for irrigation, which typically involve dams and reservoirs.  Such approaches are difficult to implement in densely populated alluvial plains where sand, silt, and clay are laid down by annual floodwaters. 

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Millions of farmers “replumb” world’s largest delta

Photo, posted February 2, 2010, courtesy of Melanie Ko via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio

A Record Low For Lake Mead | Earth Wise

October 4, 2021 By EarthWise Leave a Comment

The low water level of Lake Mead is causing regional water shortages

Lake Mead is the reservoir that was formed by the Hoover Dam on the Colorado River.  The lake spans the Arizona-Nevada border.  It is the largest reservoir in the United States in terms of water capacity.  The lake is part of a system that supplies water to at least 40 million people in seven states and in Northern Mexico.

As of August 22, this year, Lake Mead was filled to just 35% of its capacity.  This low water level is happening while 95% of the land in nine Western states is under some level of drought conditions and 64% of the land is under extreme drought conditions.  A so-called megadrought has been going on for 22 years and may be the worst dry spell in the region in twelve centuries.

As of the end of July, the water elevation at the Hoover Dam was 1,067 feet above sea level, the lowest it has been since April 1937 when the lake was still being filled after dam construction.  The level has dropped by 132 feet since July 2000.  At maximum capacity, Lake Mead reaches an elevation of 1,220 feet and holds 9.3 trillion gallons of water.

With Lake Mead at 35% of capacity, Lake Powell on the Colorado at 31%, and the entire Lower Colorado system at 40%, water allocations for the coming water year are being cut back. Mexico will see a 5% reduction, Nevada will be cut 7%, and Arizona will lose 18% of its apportionment.   This unprecedented official declaration of a water shortage demonstrates the severity of the drought and low reservoir conditions.

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Lake Mead Drops to a Record Low

Photo, posted August 7, 2018, courtesy of Renee Grayson via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Trouble On The Colorado

April 4, 2019 By EarthWise Leave a Comment

The 1450-mile-long Colorado River begins in the Rocky Mountains and wends its way to the Gulf of California, creating the Grand Canyon along the way, and providing water to some 40 million people.  The amount of Colorado River water promised to users is far more than actually flows between its banks, and that amount is dropping.

An unrelenting drought since 2000 has resulted in the water levels of the two largest reservoirs of Colorado River water – Lake Mead and Lake Powell – being at all-time lows.

Lake Mead, just outside of Las Vegas, is the reservoir of Hoover Dam, which provides power for millions of people in Southern California, Nevada, and Arizona.  The last time Lake Mead was full was in 1983.  It has slowly declined and now is 40% full.

If the lake level drops another 7 feet to 1075 feet above sea level, it will trigger a Tier 1 declaration, mandating cuts to water allocations to Arizona and other states.  If the level drops to 1050 feet, it would reach Tier 2 at which point Hoover Dam would have to stop generating electricity because water levels would be too low to flow through it.  If the lake level drops all the way to 895 feet, it would be below the level at which water can be piped out of it.  This is known as the “dead pool”.

These scenarios are no longer doomsday fantasies.  Water managers in the Southwest see the writing on the wall and are busy making contingency plans and developing ways to use less water from the Colorado River.  The booming city of Phoenix in particular is hard at work finding alternative ways to provide water for its millions of citizens.  On the Colorado, drought in the new normal.

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On the Water-Starved Colorado River, Drought Is the New Normal

Photo, posted October 24, 2016, courtesy of Sharon Mollerus via Flickr.

Earth Wise is a production of WAMC Northeast Public Radio.

Hoover Dam As A Giant Battery

September 7, 2018 By EarthWise Leave a Comment

https://earthwiseradio.org/wp-content/uploads/2018/09/EW-09-07-18-Hoover-Dam-As-A-Giant-Battery.mp3

Back in the 1930s, building Hoover Dam was a public works project likened to the pyramids.  Hoover Dam helped transform the American West, harnessing the force of the Colorado River to power millions of homes and businesses.

[Read more…] about Hoover Dam As A Giant Battery

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