Tuesday, May 10, 2011

Something To Consider: A Front Range Bypass

Heavy rains in the Midwest this spring have pumped historic volumes of water down the Mississippi River, headed for the Gulf of Mexico. The U.S. Corps of Engineers in May opened floodgates into Louisiana's Morganza Spillway for the first time since 1973 to prevent flooding in New Orleans and other riverside cities.

Now, folks in the Missouri River basin, where the Dakotas, Iowa, Nebraska and other states are either under water or bracing for flooding from record rains and melting snow in the northern Rocky Mountains. The Corps is urging people living along the river to once again make evacuation plans.

It's a dance that's been repeated for centuries. But, as cities grow along their banks, the consequences grow as well. Everyone wants a view of the water, just not in their living rooms.

Much of the problem is not with the Mississippi River itself, but with her tributaries. They cannot discharge their regular flows into the Mississippi because the water level of the Mississippi is so high, so streams back up into urban neighborhoods and overflow their banks.

Meanwhile, western Oklahoma and Texas continues to suffer from drought and fire danger. Is there a way to bring balance to this natural imbalance?

The Mississippi River is the world's third-largest watershed, funneling runoff from 41% of the nation's land area from the Continental Divide to the Appalachian Mountains. The Corps has spent decades trying to understand it, and speculating on what combination of factors would create the greatest calamity downstream. As levees are built, and rivers (including the North Canadian River through Oklahoma City) are channelized and developed, the Corps' challenge is constantly changing. Add global warming and amazing climate fluctuations, and the best-made plans of these engineers are questioned and reviewed.

Three-fourths of the basin's land area is between the Mississippi and the Continental Divide. The Great Plains have fed the nation, and the water to grow those crops in the semi-arid plains has often come from water wells tapping the Ogallala Aquifer, one of the largest underground water sources in the world.

Runoff from the Rocky Mountains either flows above ground, to the Mississippi, or below ground into the Ogallala Aquifer. It's essentially a massive lake ranging from a few feet to more than a thousand feet deep, depending on the depth of the ancient surface below. As the Rocky Mountains eroded, sediment washed into the ancient lakebed to the east, filling in the valleys with more porous material burying the water. We have mined, in effect, over 250 million acre-feet of water from the Ogallala in less than two centuries. At the rate we're going, some estimates indicate it will dry up in the next couple of decades.

The U.S. Geological Survey reports that about 27% of the irrigated land in the United States lies over the aquifer, which yields about 30% of the nation's ground water used for irrigation. The aquifer also provides drinking water to 82% of the people who live above it. When you fly from Oklahoma City to Denver, you can see round circles of green; those are fields watered by center-pivot irrigation wells tapping into the Ogallala.

So, is there a way to detour floodwaters bound for the mighty Mississippi, and store that precious liquid in the Ogallala?

The Rocky Mountains, of course, form a spine running from Canada into Mexico; rainfall on the east side of the Continental Divide flows toward the Mississippi, through rivers like the Missouri, the Arkansas, the Canadian and the Red. The terrain gradually slopes from Denver, a mile above sea level, toward the Mississippi. If you look at a topographic map, the gradient lines run evenly from north to south. Lubbock in the south at 3,241 feet is as high above sea level as Rapid City, some 850 miles to the north.

So what would happen if we did what our grandfathers used to do, but on a grander scale, and terrace the Great Plains? What if we carved a huge trench, running 1,200 miles from South Dakota's Black Hills down to the Pecos River in Texas, which flows into the Rio Grande? Through a series of gates, water flow could be controlled and diverted into the myriad of rivers that cross the Great Plains, including the North and South Canadian, the Arkansas and the Red that flow through Oklahoma. With smart engineering, excess water flow from the Rockies can be redirected into drier territory, bringing new life to the western Great Plains and providing a source of replenishment for the Ogallala.

What's neat about this concept is that forecasters have considerable lead time in which to act. If the Rockies receive above-average snowfall, engineers can detour some of the melting snow in the spring so the east-bound rivers can maintain an appropriate flow of water. Or, if North Dakota is hit with heavy rains causing flash flooding, water flowing into the Platte River in South Dakota can be reduced so that, by the time the two meet around Omaha, flooding can be minimized from that point downstream.

Such a huge venture wouldn't be impossible. The Suez Canal and the Panama Canal were massive engineering projects over relatively short distances. The California Aqueduct which waters southern California is over 700 miles long, pumping water over numerous mountain ranges. They're all much more sophisticated than this overflow canal would need to be.

Instead, think of China's Grand Canal. It was begun over 1400 years ago to transport grain to Beijing and control flooding. Instead of flowing downhill, it connects five river systems parallel to the coastline, with an elevation change of about 100 feet over its 1,115 mile length.

At the north end, the American canal could begin in the natural basin created between the Black Hills of South Dakota and the Laramie Mountains of Wyoming, along the North Platte River. At the south end in Texas, the canal could feed into the Colorado River or Pecos River, both of which are important water supplies for both agriculture and urban centers in south Texas.

One of the beneficiaries would be the 48,000-acre Lugert-Altus Irrigation District in southwestern Oklahoma. Begun during World War II, the project includes more than 300 miles of concrete canals that bring water from Lake Altus-Lugert to cotton, peanut and alfalfa farmers in the region, as well as municipal water for Altus. During times of drought, the lake level drops so low that visitors can see the foundations of buildings of the old town of Lugert in the lakebed.

Usually the lake builds up water reserves through July 4, which begins the irrigation season in the region. But western Oklahoma's drought is taking its toll; as of May 11, the lake was less than 48% full, 20% below where it was this time a year ago. It could be argued that some of the water that could be filling Lake Altus-Lugert is flooding homes and farms in Memphis at this very moment.

The canal wouldn't be intended to carry freight; it wouldn't become a noodle of a lake, either. The main purposes would be to move water north and south when the need is greatest, and to recharge the Ogallala Aquifer whenever possible.

The cost? I have no idea. But it would be less than the cost of the damage being done along the Mississippi River today. It would bring new life to the western Great Plains, which would stimulate economic productivity. And, it would employ a lot of people who need jobs as we struggle to recover from this recession.

Smarter people can come up with the details. But it's a project worth considering.