Did we already alter the level of our Oceans and Seas?

Question

We have built mighty dams (Hoover Dam) creating a large lake where a lake shouldn't be (Lake Mead). If the Colorado river wasn't damed all that water would have ended up in the Gulf of Mexico. Don't we also control how much water leaves the Great Lakes, with all the locks along the St Lawerence Seaway?

There are also lots of controls along the Mississippi river which would slow down the flow of water to the Gulf of Mexico.

I know there are other major rivers in the world and I'm sure we have put controling mechenisms on them too.

So how much water have we diverted from flowing to our oceans and seas?

Okay I stated the wrong Gulf, but still the Gulf of California is connected to the Pacific Ocean:

"The headwaters of the Colorado River are located in Rocky Mountain National Park in Colorado. From here, at an altitude of 9,010 feet, the Colorado begins it's flow southwestward toward the Gulf o f California and the Pacific Ocean. By the time the river enters the Grand Canyon, at Lee's Ferry, its altitude has fallen to 3,110 feet, dropping over one mile since its beginning. The river will drop another 2,200 f eet before it reaches the other end of the Grand Canyon, the Grand Wash Cliffs, 277 miles away."

http://www.bobspixels.com/kaibab.org/misc/gc_coriv.htm

I'm not sure why I thought it fed into the Rio Grande, but sorry for my small geographical error.

Mark - Good discription of what happens to rivers, but also water in general.

Thanks Trevor for that very informative answer.

Thank you Tomcat and Bob for your contributions to this question. This helps me and hopefully others are at least reading the question and great replies.

Answer 1

If you were to add up the total amount of land based water in the world (lakes, reservoirs, rivers etc) it's a minute amount when compared to the amount of water in the seas and oceans. Of all the water on the planet 97% is already in the seas and oceans, 2.4% is locked as ice in the ice caps and 0.6% is land based water.

Looking at the numbers, the seas and oceans have a surface area of 371 million square kilometres, the average depth is 3720 metres, and the total volume is 1.380 billion cubic kilometres, the equivalent of 50,000 Olympic sized swimming pools full of water for every person on the planet.

To put it another way - if you emptied all the Great Lakes into the sea, the amount of water would be so small by comparison to the water already in the seas and oceans that it would raise sea levels by just 0.5mm.

You mentioned Lake Mead, there are 35 cubic kilometres of water in the lake, it would take 40 million Lake Mead's to equal the amount of water in the seas and oceans. Emptying Lake Mead into the oceans would raise se levels by a minute amount - less than one hundredth of a millimetre.

Somewhere in the order of 0.1% of land based water is held in containment (reservoirs, dams etc), this represents about 0.0006% of the world's total water resources. If all this contained water were to be emptied into the oceans it would raise sea levels by 22 millimetres.

The largest manmade lake in the world in Volta Lake in Ghana, West Africa. The water is retained by the massive Akosombo Dam and the reservoir it has created is a little over 500km long, it has several times the volume of Lake Mead but is still a proverbial drop in the ocean compared to the water in the seas and oceans.

For comparison: 1 inch = 25 millimetres, 1 mile = 1.6 kilometres, 1 sqaure mile = 2.6 square kilometres, 1 cubic mile = 4.2 cubic kilometres.

Answer 2

You've received a lot of good answers. They are right even if the rivers were free flowing this would not affect the amount of water in the ocean due to small amount and the fact that all the water that we do damn ends up in the water cycle. A quick example. We'll use the Rio Grande for example: The Rio Grande has many damns. Ok you have the snow fall in the Rockies which come spring melts and run's down tributaries till it reaches and starts the Rio Grande. The Rio Grande is 70% snow fed. So you have water being damned in certain areas of the Rio Grande. At these damning points you may also have diversions that lead water to crops. During this some water will be lost to groundwater and some to evaporation. Well if it evaporates then it returns to the atmosphere to help form clouds in return may produce rain. The water that goes to groundwater is then used by people in the direction of groundwater flow. So where I live we use groundwater for drinking which is then diverted to water treatment facilities and pumped back into the river. Now during the winter all the water in the Rio Grande is stored in reservoirs keeping a minor part of the river full for the silvery minnow. But where I live in Southern NM the river is dry. If we let the river free flow then we would lose most of the water since the Rio Grande is 70% snow fed we only have one part of the year to most of our water and that is spring. Now most rivers in the county may have damns but are a semi free flowing system, b/c you have to keep a certain amount of water flowing at all times. MS is always full and is always dumping int to Gulf of Mexico. Now there are damns but for the most part all that water still makes it into the ocean except for the part that evaporates which will return as rain. Goes for all river systems. They all eventually dump into the ocean even that water that is being damned, b/c they have to release that water and it has to go somewhere, either to the ocean, groundwater, or evaporation. Which in return all lead back to the ocean in some form or another.

Answer 3

Taylor is an idiot, or an industry shill. If you cut off a 10,000' mountain at sea level and come back in 100,000 years, what will you find? Most likely a mountain 8,000-8,500 feet tall. Mountains, and tectonic plates for that matter ride on a semiliquid mantle on the earth's crust, much like an ice cube in your favorite cold beverage. if you put a penny on that ice cube, you will notice it floats lower. Take it off and it bobs up. Popular press articles like this make no sense and are the real tomfoolery. The people who want to advance a political agenda are the deniers. If you want to know the truth, and are capable of doing it, read the articles in scientific journals, which are refereed by other scientists. I count more than 1000 new lakes in my area of the arctic (about the size of the state of Illinois) in the past 10 years. I am watching fungus infections of fish become ten times as frequent, and thrips advancing from the south. I am also watching satellite tracking data on ice seals and polar bears. And I just ordered an air conditioner (in the arctic). But go ahead and pick at minutiae while your food prices head for the sky. Wonder about tornadoes and weather destroying crops? When you add energy to a system, it is likely to behave more energetically. Mother nature eventually wins all battles, and those who think they can escape the consequences with additional profit by refusing to consider the consequences of their actions will get what they deserve. The rest of us--well mother nature is perfectly willing to let God sort out those who raped the land and those who died as a result.

Answer 4

As most here have reasonably answered your question about ocean levels, I would like to point out that one of the consequences of damming up rivers is the contribution that irrigation has on local and regional climate. Studies have indicated that large areas of irrigation often have a cooling effect on local climate by 1 - 2 degrees C. On another note, I think your confusion about the Colorado dumping into the Gulf of Mexico is because there is a river in Texas called the Colorado that does in fact dump into the Gulf of Mexico.

Answer 5

The water in the Colorado River is pretty much prevented from flowing into the Pacific (via the Gulf of Cal)as it used to do. Most of it evaporates before it gets there. It is used for irrigation, mostly. Once it evaporates it comes down as rain somewhere else. The water is not removed from the overall cycle and in the end has no effect on sea levels.

Answer 6

Damming rivers only slows down the water flow in the short term. Once the reservoir is full, the rate of water coming down the river returns to normal. If you tried to permanently reduce a river's flow, you'd just be diverting the water somewhere else. Eventually it's going back to the ocean one way or another. Even water that's diverted for irrigation or other uses will still re-enter the hydrological cycle again at some point, it's unavoidable.

Here's a simplified example: Water is diverted to irrigate crops, now the water is inside plants. We eat the plants, now it's inside our bodies. We excrete, now it's in the sewage system. The water is treated and released back into rivers or the ocean. (In reality, much water is also lost to processing, evaporation, etc. but this water is never truly lost, it ALL finds its way back into the cycle somehow because it's a closed system.)

Answer 7

That amount in dams is just a drop in the bucket. You couldn't measure the difference from human made reservoirs on the ocean sea level with a micrometer. We don't influence the Great Lakes enough to be measured. Not only do oceans cover about 71% of the surface of the earth, they also averages about 3700 meters or 2.3 miles deep.

Answer 8

An addendum to Trevor's excellent answer.

Most of what we do only slows down the flow of fresh water to the sea. It doesn't eliminate it. So the numbers involved in actually altering sea levels are even lower than Trevor's calculations indicate.

Sorry campbelp2002, scoffing at Jello's mark on a rock is inadequate. It's absurd nonsense. Here's the scientific data on sea level change.

http://sealevel.colorado.edu/

Answer 9

I don't mean to be nit picky, but the Colorado river feeds into the Gulf of California. The water in the Colorado is just a drop in the bucket compared to the Pacific.

Answer 10

You might also look at this claim & view the first graph:
http://scienceandpublicpolicy.org/monckton/goreerrors.html
A raise of about 7" per century starting in 1850 and over half that raise was the 100 years before hydrocarbon usage seriously increased.

Interesting statement by IPCC:
"Finally, the IPCC’s 2007 report estimates that the likelihood that humankind is having any influence on sea level at all is little better than 50:50. "

Where's the Panic?? But I still see the children here running around saying 'the sky is falling'?!?!? Did their loony Teachers tell them that?