Engineered water pulse ‘greens’ Colorado delta

Water being released from Morelos Dam in the first environmental release of water to the Colorado River Delta Water being released from Morelos Dam in the first environmental release of water to the Colorado River Delta Rebecca Lester, Deakin University, Australia
05 Jan
A controlled water release from the Morelos Dam has revived vegetation on the Colorado River delta 

An engineered flood has brought vegetation back to the lower Colorado River delta. The water pulse from the Morelos Dam took place last March after an agreement between the US and Mexican governments and results just released by the US Geological Survey and US Bureau of Reclamation show that it has had an overwhelmingly positive effect.

Between 23 March and 18 May around 130 million cubic metres of water was released into the dry riverbed below the Morelos Dam. The dam straddles the US-Mexican border west of Yuma.

‘The groundwater was recharged, vegetation got greener than previous years and the water helped germinate new native vegetation,’ says Karl Flessa, a University of Arizona professor of geosciences. ‘As a bonus, the river reached the sea.’

People living along the river course also benefited. For many it was the first time they’d seen the river.

The water eventually soaked into the ground 37 miles below the dam, but the surface flow expanded further than had been hoped.  The new studies show that the increase in groundwater revived vegetation along the 83-mile route to the sea. This allowed willows and cottonwoods to germinate.

‘So long as the roots get down into the permanent water table, then you have established a new bunch of trees that will live for 20, 30, even 40 years,’ Flessa says. ‘Those trees will attract birds.’

Scientists have already noticed an increase in the number of birds along the watercourse. Farmers will also benefit from an increase in the water table, which can be pumped to irrigate fields.

The pulse flow came about under the Minute 319 agreement between the US and Mexico. This agreement helps to regulate water surpluses and flows on the Colorado River for benefit of both countries. ‘Another pulse flow would require a new agreement, because Minute 319 calls for only one pulse flow within the five-year term of the minute,’ Flessa says. ‘We hope the results of this pulse flow encourage the negotiators to make this happen again.’

Share this story...

Submit to FacebookSubmit to Google PlusSubmit to Twitter

Related items

Leave a comment

ONLY registered members can leave comments and each comment is held pending authorisation before publishing. Please login or register to voice your opinion.

Geographical Week

Get the best of Geographical delivered straight to your inbox every Friday.

Subscribe Today


Aberystwyth UniversityUniversity of GreenwichThe University of Winchester




Travel the Unknown


Like longer reads? Try our in-depth dossiers that provide a comprehensive view of each topic

  • National Clean Air Day
    For National Clean Air Day, Geographical brings together stories about air pollution and the kind of solutions needed to tackle it ...
    REDD+ or Dead?
    The UN-backed REDD+ (Reducing Emissions from Deforestation and Forest Degradation) scheme, under which developing nations would be paid not to cut dow...
    The true cost of meat
    As one of the world’s biggest methane emitters, the meat industry has a lot more to concern itself with than merely dietary issues ...
    Long live the King
    It is barely half a century since the Born Free story caused the world to re-evaluate humanity’s relationship with lions. A few brief decades later,...
    London: a walk in the park
    In the 2016 London Mayoral election, the city’s natural environment was high on the agenda. Geographical asks: does the capital have a green future,...


NEVER MISS A STORY - follow Geographical

Want to stay up to date with breaking Geographical stories? Join the thousands following us on Twitter, Facebook and Instagram and stay informed about the world.

More articles in PLACES...


The next stage in autonomous vehicles is hoping to transform…


Geographical’s resident data cartographer presents a true picture of the…


What impact could an unprecedented incident of ‘river piracy’ have…


Norway is to undercut a mountainous peninsula to create the…


Benjmain Hennig explores global mortality with maps


Last winter’s cold conditions contributed a further influx of road…


As one of America’s biggest cities, supplying clean drinking water…


Cape Town’s Foreshore Freeway Bridge has been left unfinished for…


An interactive map highlights the shocking number of ongoing conflicts…


Repurposed NASA maps show the racial diversity (and segregation) of…


Benjamin Hennig maps Europe's public train networks


A new map of global landslide susceptibility reveals vast geographical…


For decades, scientists have been divided over how these eerily…


The first count of global tree species reveals how many…


The new ‘world’s longest flight’ now spans a distance of more…


For the Swiss, the iconic yellow postbuses are much more…


After years of inaction, could the clean-up of the Venice lagoon…


Following the recent success of New Zealand’s Whanganui river, India’s…


The UN-backed REDD+ (Reducing Emissions from Deforestation and Forest Degradation)…


Where are Europe's earthquakes located? Benjamin Hennig maps the answer