|NORTHERN WATERS SAVE THE SEA|
|Canals (in red) move water to the Aral Basin|
Why Save the Aral Sea?
To spend somewhere between 25-50 billion dollars to refill the Aral Sea and turn the Aral Basin into a cornucopia of fishing, agriculture, forestry – a new example to the world of the old adage “water, wealth, contentment, health” – does seem like a bargain. And that’s about all it would cost to build two canals to drain water from the Volga and Ob rivers and move enough south to refill the Aral Sea in about 25-50 years. But maybe this international effort could yield additional benefits – saving the banks of the Caspian Sea from rising waters, and removing fresh water from the Arctic Ocean to preserve the gulf stream current? Now would it be worth 25-50 billion dollars?
Each spring these days, the Arctic Ocean must adjust to larger than ever amounts of fresh water from the melting icecap. What if during this same period, some of the freshwater runoff from rivers were diverted south? It is especially Eurasia, with its massive Siberian watersheds, that contributes the most fresh water to the Arctic Ocean. In particular, from the northern flowing Ob-Irtush river on the Central Siberian plain.
The ability to regulate ice-formation appears to be a worthwhile human capacity, whether the Earth is warming or cooling and regardless of why. And at the same time as the Arctic chokes on too much fresh water, the Aral Sea withers away. Up until 50 years ago the Aral was the fifth largest inland sea in the world, nearly 70,000 square kilometers. And the draining of the Aral Sea has adversely affected weather and land quality throughout Central Asia – the Aral basin encompasses seven nations and well over two million square kilometers! The draining of the Aral Sea once was the poster child for environmental destruction, now it is nearly forgotten.
How to Save the Aral Sea:
Saving the Aral Sea will only work if fresh water is drained from the Ob-Irtysh and the Volga Rivers. As the map indicates, canals (in red) would drain water from each of these rivers and move it south to the Aral Sea. At the same time as the Ob river pours a staggering 385 cubic kilometers of water into the Arctic Ocean, the Volga River pours an also whopping 240 cubic kilometers of water per year into the Caspian Sea. This is about 10% above normal and has gone on for years. The Caspian Sea is rising, threatening to inundate cities that have thrived on its banks for centuries.
The table below shows how much water reached the Aral Sea before diversions began in 1950, and how water would get there if new canals were built to divert water south from the Volga and Ob.
|WATER TO THE ARAL SEA – ORIGINAL, TODAY, PROPOSED|
|At this point almost any increase will cause the Aral Sea to expand again|
In 1950, the Aral Sea received about 50 cubic kilometers per year from the Amu Darya and Syr Darya. Because of canal diversions for agriculture, these rivers currently deliver at most 6 cubic kilometers per year into the Aral Sea. It is clear these farms are often growing water-intensive low margin crops. By improving the quality of the canals, including upgrades as basic as concrete lining, by making other water efficiency improvements, and by eliminating growing water intensive low margin crops, the Amu Darya and Syr Darya can at least double their input into the Aral Sea. It is estimated at best the Aral Sea could get as much as 20 cubic kilometers of water per year from its original rivers, while still preserving a viable agricultural economy in central Asia. This would be 40% of the original, but would be a 15x increase over today’s flow. The Aral Sea would immediately begin to expand from its current state.
Since there are no mountain formations or uplands between the Volga and the Aral Basins, a gravity-fed canal can move water from the Volga to the Aral Basin, and a 200 meter wide canal five or more meters deep would be able to move 25 cubic kilometers per year. This could be a highly innovative, possibly navigable canal that would literally siphon water into the Aral Basin. Why did canals once criss-cross Europe, yet none can be built today? Are they all so incorrect? Adding another 20 cubic km of water from the Volga to the Aral Basin per year would get the inflows almost to normal. With water going into the Aral Sea sustaining itself at 80% of normal, the Aral Sea could expand back to as much as 50,000 square kilometers.
Why the Ob Canal is Necessary:
To refill the Aral Sea completely, however, would require building a canal from the Ob river, and this would require costly pumping stations to move the water over the crest that separates the Central Siberian Plain from the Aral Basin. While the cost of such a pumping station would be about 2-3 billion dollars, it would allow inter-basin transfers of truly massive amounts of water. Not only does the Ob-Irtysh drain 385 cubic km of fresh water each year northwards across the low-lying plains of Central Siberia, but just to the east on this same watershed is the Yenisy river, which drains hundreds of cubic km into the Arctic and which could be part of a system of canals to divert excess flow into the Aral Basin.
If there were a compelling need to remove fresh water from the Arctic Ocean, this Ob to Aral canal would be an obvious solution. But developing the Aral Basin could be an international effort, and nations that might harvest fresh water from the sources of these rivers, whether they be the Syr Darya and Amu Darya, or the Volga, Ob, Irtysh or Yenisy, could participate in investment in the new agricultural and fishing industries in the Aral Basin. The Ob canal would make refilling the Aral Sea easy, adding up to 20 cubic km of water per year to the Aral, bringing the total inflow to the Aral Sea 60 cubic km, 20% above normal. After some years, the flow from the Ob canal could be slowed, or the extra water could be used for agriculture in the Aral Basin. Gentlemen, start your bulldozers.
The Ob Pumping Station – How Much Electricity?
To calculate the electric power required to move 20 cubic kilometers of water from Arctic watersheds to the Aral Basin, first assume a “lift” for this water of 1,000 feet, or just over 300 meters. That’s how much altitude the pumps will need to raise that volume of water, year after year. For this calculation it is assumed the pumping station will operate constantly, 365 days per year, but altering those assumptions don’t necessarily affect the power required, although they will affect the amount of generating capacity required (the work one 1.0 GW plant might do all year around would require three 1.0 GW plants operating only during the four month flood season). But only the water volume (20 cubic km/year) and the lift (300 meters) affect the total power calculation. If the electricity were coming from the grid, seasonal power requirement fluctuations might be mitigated.
The next step is to determine what amount of power, expressed in terms of “water horsepower,” would be required to run these pumps at the level of power required based on lifting the water 300 meters, and moving a water volume of 20 km3 through the pumps each year.
On the table below, the goal is to express the power requirement as how many “megawatts per 1.0 km3 per year,” it would take to move 1.0 cubic kilometers of water. So for each calculation the amounts are based on the volumne of 1.0 km3 per year.
|HOW MUCH POWER WILL THE PUMPS NEED?|
|Every km3 of water lifted 300 meters will require 124 MW year-round output|
The formula for how calculating water-horsepower requirements for water lift is as follows: Total dyamic head (TDH, the sum of the lift of the water, measured in feet, plus the friction loss encountered, expressed as additional feet) times gallons per minute, times 3960 (a constant). Rather than vary the constant, we must therefore plug into this formula the gallons per minute required to move a cubic kilometer per year.
The first calculation on the table, therefore, water volume required, converts km3 per year into gallons per miinute. As shown, one km3 per year is 502,607 gallons per minute. By knowing this figure, as well as the lift plus friction (total dynamic head) expressed as 1,010 feet, we can plug in the figures and make the second calculation, the water horsepower requirement.
As the second calculation on the table shows, therefore, it requires 255,051 water horsepower to lift a cubic kilometer of water 1,000 feet (or 300 meters). It is a reasonably safe assumption that the total lift required will not exceed this if the canal proceeds along the headlands of the Tobol (an Ob tributary) and passes into the Aral Basin just south-east of the foothills of the Ural Mountains.
The third calculation on the table determines how many megawatts of electric power are needed to generate the water horsepower with the pumping system. This depends on a constant, kilowatts per horsepower, as well as an assumption regarding the efficiency of the pumps. For very large pumps that run constantly, the efficiencies can get pretty good. In this example we assume a pump efficiency of 77%, meaning that 77% of the electrical energy input into the pumps is returned in the mechanical energy of water horsepower. The rest is lost to heat and friction.
Based on these calculations, it would take a constant input of 124 megawatts to move 1.0 cubic kilometer of water up 300 meters using giant pumps and pipes. As the final calculation shows, this means moving 20 cubic kilomters of water per year up 1,000 feet in altitude would require a 2.5 gigawatt electrical input. This is the equivalent of two Hoover Dams, or about one-sixth the output of the Three Gorges Dam. Put another way, it is the equivalent of about 5 very large nuclear reactors. It is unlikely a power plant of this magnitude could be contemplated using anything other than nuclear power, unless highly efficient transmission lines could be built to import electricty. Figure about 1-2 billion dollars per gigawatt for a nuclear reactor, meaning the powerplant for the pumps could cost up to 5 billion dollars. The cost for the new canals and the costs to overhaul the canals already built brings the total price tag to 25-50 billion.
A Renaissance in Central Asia?
But even if we don’t want to save the Aral Sea, or save the Gulf Stream, or stop the rising banks of the Caspian Sea? So what? After all, what’s the output of the restored Aral Basin worth, when its sea employs 100,000 fishermen, and new agricultural lands and rich deltas beckon the farmer and the tourist? What wealth might we reap?
For more information including references go to Refill the Aral Sea.