# Where could the Mississippi River be dammed to create the largest possible lake? **URL:** \ **Category:** Factual Questions\ **Created:** [September 29, 2011, 5:40pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038 "2011-09-29T17:40:46Z")\ **Posts on this page:** 20\ **Page:** 2
**Author:** ![Telemark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/telemark/32/372_2.png) [@Telemark](https://boards.straightdope.com/u/Telemark)\ **Post date:** [September 30, 2011, 1:56pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/21 "2011-09-30T13:56:20Z")
> [@Boyo\_Jim](#): > > Og knows I’m all in favor of nuking Memphis, but if there’s no outlet to the ocean for water between the two big mountain ranges, it seems the space will eventually fill up, nukes or not. Not if evaporation and absorption into the ground is faster than the incoming water rate. This would eventually happen with a large, very shallow reservoir. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [September 30, 2011, 2:03pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/22 "2011-09-30T14:03:22Z")
> [@boytyperanma](#): > > Except there isn’t enough water in the system to actually fill such an area. What do you mean, not enough water in the system? Have you no patience? Let’s for simplicity’s sake say we want a lake the size of the Mississippi basin, about 3 million square kilometers, with an average depth of 100 meters. That would fill up in a mere 570 years with the average Mississippi flow rate of 16792 cubic meters per second. ---
**Author:** ![Ludovic](https://avatars.discourse-cdn.com/v4/letter/l/7ab992/32.png) [@Ludovic](https://boards.straightdope.com/u/Ludovic)\ **Post date:** [September 30, 2011, 2:08pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/23 "2011-09-30T14:08:45Z")
Does anyone have firm numbers on the evaporation? A back-of-the-napkin…err, spreadsheet calculation shows that taking the average flow of 16000 sq m/sec and an evaporation rate of 1 meter/yr\*, shows that the basin would be around 500000 square kilometers, which is not the entire Mississippi Embayment but is not really just a bunch of small lakes and swamps, either. \*which might be too high, but might be too low for shallow basins in hot climates, I have no clue as I’m not a hydrologist. ---
**Author:** ![BetsQ](https://avatars.discourse-cdn.com/v4/letter/b/fbc32d/32.png) [@BetsQ](https://boards.straightdope.com/u/BetsQ)\ **Post date:** [September 30, 2011, 2:44pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/24 "2011-09-30T14:44:43Z")
IANA Geologist, but thinking back to the 1993 [flood](http://en.wikipedia.org/wiki/Great_Mississippi_and_Missouri_Rivers_Flood_of_1993), I might try just to the south of the Mississippi-Missouri confluence. The south side of Missouri around to the east side of the combined rivers there is on a bit of a bluff (and by bluff, I mean _maybe_ 50 feet). If you extend eastward from there, you might get a back up like we experienced in 1993. That was a lot of water, but it wasn’t very deep. You could see miles and miles of water, with tree tops sticking out the whole way. It was an amazing sight. The wiki page in the link above has satellite pictures. ---
**Author:** ![Spiff](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/spiff/32/9852_2.png) [@Spiff](https://boards.straightdope.com/u/Spiff)\ **Post date:** [September 30, 2011, 3:17pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/25 "2011-09-30T15:17:56Z")
Building a dam at the south end of [Lake Pepin](http://en.wikipedia.org/wiki/Lake_Pepin) might be the biggest bang for your engineering buck. The bluffs around that lake are kinda high (for Midwestern standards). ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [September 30, 2011, 4:15pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/26 "2011-09-30T16:15:28Z")
> [@BetsQ](#): > > IANA Geologist, but thinking back to the 1993 [flood](http://en.wikipedia.org/wiki/Great_Mississippi_and_Missouri_Rivers_Flood_of_1993), I might try just to the south of the Mississippi-Missouri confluence. The south side of Missouri around to the east side of the combined rivers there is on a bit of a bluff (and by bluff, I mean _maybe_ 50 feet). If you extend eastward from there, you might get a back up like we experienced in 1993. That was a lot of water, but it wasn’t very deep. You could see miles and miles of water, with tree tops sticking out the whole way. It was an amazing sight. The wiki page in the link above has satellite pictures. The Mississippi River Flood of 1927 [covered 27,000 square miles of Iowa](http://www.iptv.org/iowapathways/mypath.cfm?ounid=ob_000136). Granted, it wasn’t deep, but it was big. ---
**Author:** ![Boyo\_Jim](https://avatars.discourse-cdn.com/v4/letter/b/87869e/32.png) [@Boyo\_Jim](https://boards.straightdope.com/u/Boyo_Jim)\ **Post date:** [September 30, 2011, 4:16pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/27 "2011-09-30T16:16:01Z")
> [@Telemark](#): > > Not if evaporation and absorption into the ground is faster than the incoming water rate. This would eventually happen with a large, very shallow reservoir. Well, I can be convinced to drop the dam idea so long as we can still nuke Memphis. ---
**Author:** ![boytyperanma](https://avatars.discourse-cdn.com/v4/letter/b/4491bb/32.png) [@boytyperanma](https://boards.straightdope.com/u/boytyperanma)\ **Post date:** [September 30, 2011, 4:16pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/28 "2011-09-30T16:16:07Z")
> [@naita](#): > > What do you mean, not enough water in the system? Have you no patience? > > Let’s for simplicity’s sake say we want a lake the size of the Mississippi basin, about 3 million square kilometers, with an average depth of 100 meters. That would fill up in a mere 570 years with the average Mississippi flow rate of 16792 cubic meters per second. That’s assuming the water never leaves through other means. Take the Caspian Sea for example. It’s surface is below sea level. It has well over 100 rivers that flow into it. I’m just guessing but I think the total flow into the Caspian sea is greater than the Mississippi. It has plenty of room to expand. But in our lifetimes the Caspian Sea is shrinking not growing. If we apply the logic being used in this thread the Caspian Sea should have filled up and turned western Europe into a giant lake. That isn’t happening. ---
**Author:** ![naita](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/naita/32/5862_2.png) [@naita](https://boards.straightdope.com/u/naita)\ **Post date:** [September 30, 2011, 6:16pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/29 "2011-09-30T18:16:31Z")
> [@boytyperanma](#): > > That’s assuming the water never leaves through other means. > > Take the Caspian Sea for example. It’s surface is below sea level. It has well over 100 rivers that flow into it. I’m just guessing but I think the total flow into the Caspian sea is greater than the Mississippi. It has plenty of room to expand. But in our lifetimes the Caspian Sea is shrinking not growing. > > If we apply the logic being used in this thread the Caspian Sea should have filled up and turned western Europe into a giant lake. That isn’t happening. Western Europe? Let’s not guess. (Or at least back our guessing with facts.) Wikipedia says the Caspian Sea has a catchment area of 3 626 000 km[SUP]2[/SUP] to the Mississippi’s 2 981 076. The Caspian sea has a surface of 371 000 km[SUP]2[/SUP]. So supposing similar rainfall and evaporation rates, the Mississipi would be able to support a lake of 300 000 km[SUP]2[/SUP]. Is the rainfall comparable? Well, to use wikipedia data again: Over 130 rivers provide inflow to the Caspian, with the Volga River being the largest. A second affluent, the Ural River, flows in from the north, and the Kura River flows into the sea from the west." The Volga river has an average flow of 8000 m[SUP]3[/SUP]/s, half that of the Mississippi, but the next largest, Ural and Kura, are both around 400 m[SUP]3[/SUP]/s. Comparing catchment and flow the Volga catchment is about as wet as Mississippis, while Ural and Kura are between a third and half as wet. A justified guess IMO would be that the Caspian gets less than or similar inflow to our hypothetical Lake Mississippi. Of course there’s still the question of whether or not the rate of evaporation would be comparable, and how geology would influence the growth of the lake. How deep a 300 000 km[SUP]2[/SUP] Mississippi lake would be is of course a major factor, but I’ll leave that to someone else to figure out. Maybe someone has access to elevation data in a way that can tell us the contours of the lake? But before I leave the issue, with a WAG average depth of 100m, Mississippi lake would fill up in just 57 years (ignoring evaporation). ---
**Author:** ![Saltire](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/saltire/32/553_2.png) [@Saltire](https://boards.straightdope.com/u/Saltire)\ **Post date:** [September 30, 2011, 6:44pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/30 "2011-09-30T18:44:10Z")
A body of water like that would change the weather. It might get increases in rainfall which would do a better job keeping the lake full. You could pitch your idea as a way to mitigate natural disasters. Tornado Alley would almost surely cease to exist. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [October 1, 2011, 4:00am UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/31 "2011-10-01T04:00:40Z")
> [@Spiff](#): > > Building a dam at the south end of [Lake Pepin](http://en.wikipedia.org/wiki/Lake_Pepin) might be the biggest bang for your engineering buck. The bluffs around that lake are kinda high (for Midwestern standards). The other possible area would be at the south end of the Twin Cities, perhaps near Minnehaha Falls outlet or by Fort Snelling. A high dam there would flood up to the top of the Mississippi River Gorge through Minneapolis. This is an area of high cliffs, that could confine a sizable lake, unlike most of the rivers course, which is mostly through very flat land. ---
**Author:** ![JRDelirious](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/jrdelirious/32/9531_2.png) [@JRDelirious](https://boards.straightdope.com/u/JRDelirious)\ **Post date:** [October 1, 2011, 9:04pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/32 "2011-10-01T21:04:21Z")
Er, how about we give up on the Mississippi proper and instead try for the maximum reservoir in the Mississippi BASIN, and thus may place it on the Missouri/Ohio/Arkansas/etc? Or maybe that has already been done for some of the rivers? ---
**Author:** ![Kent\_Clark](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/kent_clark/32/105_2.png) [@Kent\_Clark](https://boards.straightdope.com/u/Kent_Clark)\ **Post date:** [October 1, 2011, 9:34pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/33 "2011-10-01T21:34:12Z")
> [@JRDelirious](#): > > Er, how about we give up on the Mississippi proper and instead try for the maximum reservoir in the Mississippi BASIN, and thus may place it on the Missouri/Ohio/Arkansas/etc? Or maybe that has already been done for some of the rivers? On the Arkansas there’s [Lake Dardanelle](http://en.wikipedia.org/wiki/Lake_Dardanelle). The Missouri is dammed in several places. The largest lake is [Lake Sakakawea](http://en.wikipedia.org/wiki/Lake_Sakakawea), the third largest man-made lake in the U.S. Also, there are a whole buttload of dams and lakes in the Tennessee Valley, which flows into the Ohio. ---
**Author:** ![yabob](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yabob/32/2821_2.png) [@yabob](https://boards.straightdope.com/u/yabob)\ **Post date:** [October 1, 2011, 11:27pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/34 "2011-10-01T23:27:27Z")
The Upper Mississippi itself is already dammed in several places, too, actually. It’s just that none of them create really massive reservoirs: > **[List of locks and dams of the Upper Mississippi River](https://en.wikipedia.org/wiki/List_of_locks_and_dams_of_the_Upper_Mississippi_River)** > > This is a list of current and former locks and dams of the Upper Mississippi River which ends at the Mississippi River's confluence with the Ohio River at Cairo, Illinois. > The Army Corps of Engineers has studied the expansion of some locks on the Upper Mississippi. Since at least 1999, the Corps has considered expanding 600 ft locks 20, 21, 22, 24, and 25 to 1,200 ft. > The inland and intercoastal waterways, with the Upper Mississippi highlighted in red. ---
**Author:** ![Darth\_Panda](https://avatars.discourse-cdn.com/v4/letter/d/ee7513/32.png) [@Darth\_Panda](https://boards.straightdope.com/u/Darth_Panda)\ **Post date:** [October 1, 2011, 11:39pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/35 "2011-10-01T23:39:34Z")
I would just like to add that I think “catchment” is a pretty nifty word. I also like the idea of nuking and/or flooding Memphis. ---
**Author:** ![NinetyWt](https://avatars.discourse-cdn.com/v4/letter/n/cc9497/32.png) [@NinetyWt](https://boards.straightdope.com/u/NinetyWt)\ **Post date:** [October 2, 2011, 4:50am UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/36 "2011-10-02T04:50:48Z")
> [@Polycarp](#): > > Using modern technology, I want to build a dam, plus any needed ancillary construction, somewhere in the world, no more than 3 km in span, which will confine the greatest amount of acre-feet of water. For our purposes, assume no issues of navigability, historical importance, cities needing relocation, etc., are issues – for whatever reason, this dam _must_ be built. Where would it be located to meet the criteria outlined above? You should locate it in the valley which has the greatest depth for that width (3 km). This will yield the biggest volume for your given dam length. This is basically a volume problem. As has been pointed out many times upthread, the Mississippi Valley is much too shallow to be economical. I am a bit surprised at the “make the river flow backwards” comment. The normal way to construct a dam which holds water is to use an outlet structure to regulate the flow. In other words, the water flows \*out of \*as well as in to the lake. ---
**Author:** ![Tim\_T-Bonham.net](https://avatars.discourse-cdn.com/v4/letter/t/46a35a/32.png) [@Tim\_T-Bonham.net](https://boards.straightdope.com/u/Tim_T-Bonham.net)\ **Post date:** [October 2, 2011, 6:19am UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/37 "2011-10-02T06:19:59Z")
> [@Polycarp](#): > > Using modern technology, I want to build a dam, plus any needed ancillary construction, somewhere in the world, no more than 3 km in span, which will confine the greatest amount of acre-feet of water. For our purposes, assume no issues of navigability, historical importance, cities needing relocation, etc., are issues – for whatever reason, this dam _must_ be built. Where would it be located to meet the criteria outlined above? Then you would want a contained area with the largest volume behind it. I’d think likely places are:[ul] [li] the Grand Canyon (but not much water available to fill this volume quickly)[/li][li] the African Great Rift Valley (already contains Lake Tanganyika, the Red Sea, the Dead See, & Lake Galilee)[/li][li] the West Antarctic Rift (but that’s mostly under water/ice already)[/li][li] the Russian Baikal Rift (already home to Lake Baikal)[/li][\*] the NorthAmerican Midcontinent Rift (already containing Lake Superior & some of the other Great Lakes)[/ul] ---
**Author:** ![Spoke](https://avatars.discourse-cdn.com/v4/letter/s/a88e57/32.png) [@Spoke](https://boards.straightdope.com/u/Spoke)\ **Post date:** [October 2, 2011, 3:38pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/38 "2011-10-02T15:38:00Z")
OK, now that we’ve dammed the Mississippi, is there any way to recharge the [Ogallala Aquifer](http://en.wikipedia.org/wiki/Ogallala_Aquifer)? ---
**Author:** ![TriPolar](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/tripolar/32/3008_2.png) [@TriPolar](https://boards.straightdope.com/u/TriPolar)\ **Post date:** [October 2, 2011, 3:41pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/39 "2011-10-02T15:41:53Z")
After we’ve dammed the Mississippi, we just drill a hole in the ground. ---
**Author:** ![Spoke](https://avatars.discourse-cdn.com/v4/letter/s/a88e57/32.png) [@Spoke](https://boards.straightdope.com/u/Spoke)\ **Post date:** [October 2, 2011, 3:43pm UTC](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038/40 "2011-10-02T15:43:27Z")
Piece of cake, then! [Previous page](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038.md?page=1) [Next page](https://boards.straightdope.com/t/where-could-the-mississippi-river-be-dammed-to-create-the-largest-possible-lake/598038.md?page=3)