Getting Water from the Mississippi River to the Lower Colorado River Basin PART 2 of 2

Importing Water to Augment the Supply of Water in the Lower Colorado River Basin

People have recommended a number of ways to increase the supply of fresh water to the Colorado River Basin (CRB). These range from tried-and-true technologies such as desalination to less practical ideas such as towing glaciers south to harvest fresh water.

Desalination

Desalination of Pacific Ocean water is one approach that's received consideration. This is definitely a possibility - as we know from many nations in the Middle East and Eastern Africa who rely on desalination to meet their need for fresh water. However, it's a fairly expensive prospect that generates a residual that requires disposal. Also, any focus on desalination would concentrate freshwater production in one CRB state.

The Great Lakes

People have proposed an aqueduct to move water from Lake Superior to the CRB. Proponents of this plan recommend the construction of a 900-mile pipeline from Lake Superior to the Green River watershed in southwest Wyoming. The Green River ultimately feeds the Colorado River in Utah. Since half of the water in Lake Superior belongs to Canada, this proposal was a non-starter.

Towing Glaciers

Others have considered towing glaciers down along the coast of California to harvest freshwater. The impracticability of this idea seems to have been recognized and this proposal has largely been abandoned.

River Diversion

Among the river diversion ideas, the Mississippi River has received increasing attention from groups and individuals - including the Arizona State Legislature.

“… A new water source could help augment Colorado River supplies. One promising possibility involves piping water that is harvested from Mississippi River flood waters. Diverting this water, which is otherwise lost into the Gulf of Mexico, would also help prevent the loss of human life and billions in economic damages when such flooding occurs. …” - Representative Tim Dunn, AZ State Legislator and cosponsor of AZ House Concurrent Memorial 2004 (May 11, 2021).

The westward diversion of water from the Mississippi River has actually been considered a number of times in the past. In 2012, the US Bureau of Reclamation (USBR) studied this along with a range of other alternatives. They found that this idea would have a long time horizon (30+ years), would be cost-prohibitive, and would face significant political opposition.

Despite the known limitations and pitfalls associated with this proposal, in 2021, the Arizona legislature petitioned the US Congress to conduct a study on the diversion of Mississippi River water to the Lower Colorado River Basin.

How much water is available to "harvest" from the Mississippi?

The same drought that affects the Colorado River Basin also impacts the Mississippi River Basin. In 2012, drought was more severe in the MRB than it was in the CRB.

In October 2022, the level of water in the Mississippi River was so low that barges have run aground. In Memphis, TN, the Mississippi River reached the lowest level on record. Further downriver near Vicksburg, MS, long lines of barges were visible from NASA satellite imagery. These trends are attributed to low rainfall in the Upper Mississippi River and the Ohio River Basins. Other recent low water conditions occurred on the Mississippi River in 2012, 2000, and 1998.

For the proposal to work, the Mississippi River would have to flood on a year-round basis. Otherwise, it would take many more than 624 [continuous] days to refill Lake Mead and Lake Powell. The Mississippi River doesn't flood every year. Likewise, it doesn't flood uniformly.

The proposed 250,000 gps water diversion was based on a Mississippi River discharge of 4.5 MILLION gps at the Old River Control Structure, downriver from Vicksburg, MS. In fact, 4.5 MILLION gps corresponds to the highest discharge observed over a 20-year period (August 2002 - August 2022) based on data from the US Geological Survey. This is 36% more than the 20-year average discharge. During low flow conditions, the proposed diversion rate is around 17% of the Mississippi River discharge. This is close in magnitude to the 21% mandatory water reduction that the people in Arizona are facing in 2023.

Getting Water to the West - a Water Superhighway?

We need to consider how we might get water to the west. There's a practical limit to the speed at which water can be moved through any water conveyance structure - including aqueducts and pipes. A typical value is 5.5 ft/s. At a rate of 250,000 gps, we would need a channel with a cross-sectional area of nearly 6,100 square ft.

That seems like a large area, but how does it relate to the size of an actual channel or pipe?

• One channel that's 100 ft wide and 61 ft deep
• One channel that's 1,000 ft wide and 6.1 ft deep
• Ten channels that are 100 ft wide and 6.1 ft deep
• One 88 ft diameter "pipe"

These dimensions exclude foundation work and a right-of-way. Likewise, factors such as frictional losses in the conveyance system were neglected in this estimate. These considerations would further increase the size of the conveyance system.

For perspective, an interstate highway with two lanes in each direction is at least 126 ft wide.

• 12 ft lane width x4
• 4 ft left shoulder x2
• 10 ft right shoulder x2
• 50 ft median x1

In this case, it might be tempting to view this as building just another interstate. However, the finished dimensions of this interstate would be a 61 ft deep channel that traverses between 1,200 and 1,600 miles, and four to six states, depending on the final construction alignment.

Invasive Species

The Mississippi River contains more than just water. Invasive species - including silver and bighead carp - are a force to be reckoned with! The best way to manage the adverse ecological and economic consequences of an invasion of non-native species is to avoid it in the first place.

Nutrients

Nutrients - especially nitrates - will also be sent to the west. In fact, under average conditions, filling Lake Mead with water from the Mississippi River will increase the nitrate concentration in the Lake by more than 5 times. While the nitrates in Mississippi River water could be treated, the scale of such a project would be time-limited and cost-prohibitive.