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http://www.cleanmpg.com/forums/../photos/data/2/AmericanFlag.jpg Bluish colors indicate more flow, reddish colors less. In many heavily populated regions in the tropics and mid-latitudes, rivers are discharging reduced amounts into the oceans. But in parts of the U.S. and Europe there is an upward trend.
(http://www.msnbc.msn.com/id/30326211/)
http://www.cleanmpg.com/photos/data/501/RiversMap.jpgMSNBC - April 21, 2009

Note that this roughly corresponds to political "Blue states" and "Red states". :D --Ed.

The flow of water in some of the world's largest rivers has declined over a half century, according to a new, comprehensive study whose authors tied the discovery to global warming.

An analysis of 925 major rivers from 1948 to 2004, found significant changes in about a third, according to the study appearing in the May 15 edition of the American Meteorological Society's Journal of Climate. Of those, rivers with decreased flow outnumbered those with increased flow by a ratio of about 2.5 to 1.

The reduction in river flow to the Pacific Ocean alone was about equal to shutting off the Mississippi River, according to the researchers at the National Center for Atmospheric Research in Boulder, Colo....http://www.msnbc.msn.com/id/30326211/

I have a problem with this part:
"Indeed, the researchers wrote that "for many of the world's large rivers" the effects of dams, farming and development "are likely small compared with that of climate variations during 1948-2004."

Dams especially have always had a large effect on river flow. That's one of the reasons they build them for flood control. I can't count the number of ponds I have seen constructed that completely stopped a streams flow. That stream never flowed again unless the pond flooded. Those streams feed into these rivers they are looking at.

Heck, Truman Dam (Truman Lake in Missouri) on the Osage River has reduced flow tremendously. The Osage feeds into the Missouri River, and on into the Mississippi.

Another factor that was barely mentioned was increased human populations drinking extra water (not to mention all the other uses we put it to).

Dams have also changed habitats beyond what many of the river creatures can handle.

During the Civil War there were many references to 300+# blue catfish for sale in St. Louis. Since they have been building dams along the Mississippi and its tributaries, the world record is less than 130#.

In Texas, the Trinty River flows thru Fort Worth, then Dallas, then by Houston to the Gulf.

Fifty years ago, the Trinity River would occasionally dry up by the time it reached Dallas in the Summer...people in Fort Worth would say: "remember to flush - Dallas needs the water". :D :eek:

So we are to believe that the world population went from 2.5 Billion in 1948 to 6.7 Billion today and yet water "extraction" from rivers has remained the same and is not a factor but global warming can be nailed as the culprit. :rolleyes:

Terms like "effect... is likely small" don't have any place in a scientific study, they should know not guess, which is what this report seems to do.

One example: the Colorado river.

It no longer flows to the sea. ALL the water is diverted to other places like agriculture and Las Vegas, before it reaches the sea. Mexico complains about it, because the USA takes most of the water even before it reaches the border.

We have certainly drastically changed some locales by diverting water.

The article mentions that "researchers note the only place to increase in water flow was the arctic, with melting ice caps", etc. But, if you can read the color coded map, that clearly isn't the case. I'm a little confused, anybody else notice that same thing?

The article mentions that "researchers note the only place to increase in water flow was the arctic, with melting ice caps", etc. But, if you can read the color coded map, that clearly isn't the case. I'm a little confused, anybody else notice that same thing?

Oh yeah. With all of the inconsistencies I just tossed this out as spin, junk science, and cherry picking.

I think there are multiple man-made causes for this.

I think there are multiple man-made causes for this.

I very much agree, but this article tries to blame almost all of it on global warming. Sounds like a lot of political whitewashing to me.

Pandering to the Global Warming funding machine.

I have a feeling if the opposite were true (increased flow) it would be blamed on flooding, caused by global warming...

There is also the impact of dams, dumping of sewage, loss of wetlands...

Also changes in the amount of forest cover affects the amount of local rainfall and the amount of water flow in the rivers. The eastern half of the United States were pretty much clear cut for agriculture, lumber, and railroad ties through the course of the 1700 and 1800's, then the forests were able to regrow during most of the 1900's as marginal agricultural land was abandoned and we shifted to coal and petroleum for our energy needs. China and much of the 3rd world are currently in the process of cutting down much of their forest cover, resulting in less river flows.

Ya piqued my interest in factors that might have been underestimated in this study. Unfortunately the AMS website is cranky right now and I can't get the pdf. later on, if it seems like they've actually done a poor job, is anyone interested in preparing a response? Land-use changes, impoundments and water withdrawals are all important to hydrology, and if they've been slighted, a letter to the editor is the appropriate mechanism.

But I cannot comment on the study until having read it. MSNBC's interpretation (fine folks though they may be) means nothing to me.

DAS

........

During the Civil War there were many references to 300+# blue catfish for sale in St. Louis. Since they have been building dams along the Mississippi and its tributaries, the world record is less than 130#.

If you talk to the divers who inspect dams they claim jumbo catfish exist there, but they hang out in areas that are hard to fish. Maybe they're just telling tales. My theory would be that commercial fishing took most of the jumbo catfish out of the Mississippi in the late 19th century and high pollution levels finished off the left overs in the early 20th century.

I won't argue with you that dams are hard on some fish. One of the saddest things I ever saw was the spring spawning season after Truman dam was closed. My father and I visited its spillway below Kaysinger bluff where fish (buffalo carp mostly?) trying to migrate upstream were packed cheek by jowl in their doomed effort to swim upstream into a concrete wall. Probably about 5-10 acres of large doomed fish the day I was there.

Back on topic, Basjoos' theory about changes in river flows being a proxy for changes in forest cover looks to me like it matches the map pretty well.