More than 30 million Americans could be hit with a water shortage after plumbing issues were found with a major US dam that sits on the Colorado River, officials warn.

Inspectors from the US Bureau of Reclamation found serious pipe damage in the Glen Canyon Dam, which means there will be no spring water release - threatening water supplies downstream.

The pipes in question are called the 'river outlet works,' and they're used to release water down the Colorado River to Lake Mead from the penned up Lake Powell. 

A fall release has neither been scheduled nor canceled yet, leaving residents of California, Nevada, and Utah who depend on water from Lake Mead without answers for now.

The pipes in question are called the 'river outlet works,' and they're used to release water down the Colorado River to Lake Mead from the penned up Lake Powell

The Glen Canyon Dam holds back the waters of the Colorado River, forming Lake Powell. Water released from Glen Canyon Dam makes its way down to Lake Mead, but with no releases this spring water levels could fall.

These four 8-foot pipes are the 'river outlet works,' which release water downstream periodically to help re-nourish beaches with sediment.

A fall release has neither been scheduled nor canceled yet, leaving residents of California , Nevada, and Utah who depend on water from Lake Mead without answers for now 

There are four eight-foot-wide pipes out of the dam that release water downstream, where it flows about 200 miles into Lake Mead. Lake Mead is the US's largest reservoir - when it's full.

But these pipes may be too damaged to release water to Lake Mead consistently, according to an inspection after their most recent tests, according to the US Bureau of Reclamation.

READ MORE: Lake Powell and Lake Mead are unlikely to refill for another 50 years

The lake has been receding due to recent droughts leaving the lake and rivers parched. 

This means that the residents of Nevada, Utah, California, and parts of northern Mexico who depend on Lake Mead for drinking water may continue to deal with existing water shortages this year - shortages they've faced off and on since 2014.

What's more, the unfavorable inspection report suggests that the river outlet works pipes are not up to the task of releasing water.

This is a problem because the Colorado River Compact requires that water continue to flow. 

'In summary, at reservoir levels below the minimum power pool (elevation 3,490 ft), there are concerns with relying on the river outlet works as the sole means of sustained water releases from Glen Canyon Dam,' the memo said. 

Farmers and environmental activists have called for draining Lake Powell for years, restoring the natural flow of the Colorado River in that section and refilling Lake Mead.

That movement had not picked up much steam in the past, but with Lake Mead's supply in danger, the situation has changed. 

Both Lake Powell and Lake Mead have struggled with waning water levels due to drought and reduced snowmelt from the mountain ranges that flow into the Colorado River Basin. 

Lake Mead's water level was at 1,076 feet at the end of February, past the 1,075-foot cutoff indicating water shortage, but its levels have declined through March.

On the Lake Powell side of Glen Canyon Dam, the hydropower penstocks can be seen above the water level. These inlets, situated above the river outlet works, feed water to power turbines.

So the conditions may worsen in the coming months.

After a high flow experiment last year, when a huge amount of water was released to feed Lake Mead, inspectors found significant damage to the pipes involved.

This April, therefore, there will be no such water release.

That means Lake Powell's water level will remain high and safe for those locals. 

But without a release, residents downstream are put at risk of water crisis. 

The river outlet works are situated about 120 feet lower on the dam than the hydropower penstocks.

Water flowing through Glen Canyon Dam's hydropower turbines helps provide electricity to more than five million people in Wyoming, Utah, Colorado, New Mexico, Arizona, Nevada, and Nebraska.

That larger set of pipes funnels water through hydroelectric power-producing turbines on the other side of the dam, providing electricity to more than five million people in Wyoming, Utah, Colorado, New Mexico, Arizona, Nevada, and Nebraska.

Not releasing water from the river outlet works may actually improve power production, leaving more water for the turbines - even though power production at Lake Mead could be hampered if the water levels get low enough.

Completed in 1966, Glen Canyon Dam flooded a section of the canyon with the waters of the Colorado River, creating Lake Powell. 

Because Lake Powell needs to retain enough water to reliably generate power, the river outlet works are not often used.

Only with the twice-a-year 'high flow experiment' do they tend to get a workout.

These tests see millions of gallons flow through the river outlet works in just a few days. 

Part of their reason is to test the pipes, but it's also about feeding Lake Mead and preserving the Colorado River downstream, which both depend on artificial releases from the dam.