Monday, August 12, 2013

American Rivers

I came across this map of American rivers where river symbols are proportional to the “gage-adjusted flow.” The rivers on the map drawn here have widths proportional to the square root of the rivers’ estimated average annual discharge. Only rivers with discharge above 1,000 cfs are shown.

The original map and an article about it can be found at American Rivers: A Graphic on the Pacific Institute Insights blog and the authors are Peter Gleick, President and Matthew Heberger, Research Associate.

How big is your local river?  Does anything surprise you about this map? How would the Amazon look on the same scale?

I am sharing this work under a Creative Commons License.


Mitch Zeissler said...

I like that graphic. Interesting how there isn't much water flowing away from the Rocky Mountains.

Tillerman said...

Yes, it is a little strange that there seems to be so little water flowing out of the Rockies, apart from the Missouri, the Columbia and the Colorado rivers. The note at the top of the original blog post implies that the first version of this map showed more rivers in the West but that this was old data and that many of those rivers are now very small or dried-up because of "dams and diversions." I bet Pat of the Desert Sea blog will be able to tell us more about that.

A few things I found surprising...

I had never realized before how significant the Ohio RIver is. I have seen it at Pittsburgh but never knew that it is the largest tributary by volume of the Mississippi, providing more flow than the Mississippi and Missouri combined where it joins the Mississippi.

Also what happens to the Colorado? I think I read that its flow becomes very small as it reaches the sea, but is the map reflecting that or does it just not show any data for the river after it crosses the Mexican border?

Pat said...

The Colorado River system appears to have had its water over-allocated, with the allocation based on data from what now appears to be a wetter-than-average few decades. In the meantime, the population whose thirst it tries to satisfy has grown hugely. Population movement, the advent of air conditioning, and improvements in transportation and especially the big western water projects, have brought millions of people to cities such as Phoenix, Las Vegas (NV), and southern California. So much water is diverted for agricultural and urban/suburban use that precious few drops ever make it to the Sea of Cortez.

Pat said...

While some cities such as Tucson and Albuquerque are doing pretty well in encouraging water conservation, there is still much do be done and learnt. Golf courses are often as not supplied by recycled gray water, and cities offer bonuses for installation of low-flow bathroom appliances. Individuals debate the trade-off between water use and electrical consumption in considering the choice between evaporative cooling and refrigerated air. Agricultural canals are often unlined and open to both transpiration through the dirt and evaporation to the hot sun. Artificial subsidy still makes it feasible to use increasingly scarce water to produce relatively low-value crops.

The Rio Grande system is also heavily used and probably over-subscribed. Shortly after its origin in southern Colorado, communities in the densely populated areas between Taos, Espan~ola, Santa Fe, and Albuquerque take water. By the time this is done, sometimes especially during early summer, the river will entirely dry up in some segments between Albuquerque and El Paso.

Elephant Butte Lake, once New Mexico's largest reservoir with a capacity of 2 000 000 acre feet of water, was reduced to about 60 000 acre feet early this summer -- only about 3 per cent of capacity -- and farmers were given a minimal irrigation allotment. This is the lake where I need to figure out how to schedule regattas this fall -- it will be a challenge, even though the lake has now ceased making irrigating releases and is rising again thanks to some summer monsoonal showers.

As for further north in the state, the situation is little better. This summer, for the first time in nearly a decade, the Heron Lake marina, owned by the New Mexico Sailing Club, didn't open and won't open this year. It is now sitting on the dirt, about six feet above the level of the lake, which is reduced to less than a quarter of capacity and will likely end the year as low at a tenth of capacity, with all the paved boat ramps unusable and ending well above lake level. What are club members doing during the relative absence of water? Well, in a couple of weeks some club members will be going to a minor league baseball game.

Pat said...

As a whole, the state of Colorado is doing better; it had a decent snow pack. Dillon Reservoir, home of the Dillon Yacht Club's big open regatta, is only about four feet below its maximum level of 9017 feet above mean sea level. I'll probably be up there next weekend.

But, all of the West, and especially the southwest, has much with which to concern itself. If global warming is an actual trend, then wildland fires are likely to take more severe advantage of dry, overgrown forests and rangelands and burn intensely. That could cause a decrease in forest canopy, and make more lands vulnerable for water runoff and erosion when rain does fall.

Pat said...

And, zeroing in on Heron Lake,

Tillerman said...

Thanks Pat. i knew you would have all the info on water trends in your part of the world.

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