I don’t understand something but it’s going to be hard to explain. Rivers. I don’t understand rivers. Let’s take the Mississippi for instance. It “starts” at Lake Itasca in the Minnesota North Woods and flows 2,350 miles down through the mid continental United States to the Gulf of Mexico. It starts 20 feet wide and 3 feet deep and reaches as wide as 4 miles wide at Lake Onalaska (due to damming) in Wisconsin and 200 feet deep at Algier’s Point in New Orleans. Purely as a point of interest, a raindrop landing in Lake Itasca will arrive in the Gulf of Mexico in roughly 90 days.
What don’t I understand? Well, where the fuck does all this water come from?? Don’t get me wrong, I understand all about rain and gradients. I can talk until everyone is asleep in the room about elevations (it starts at 1,475 feet above sea level and ends a 0 in New Orleans more than half of that drop happens in Minnesota), watersheds and floodplains. My problem is that I watch the rain on my driveway and about 2 minutes after it stops all the rain has trickled down to the street and my driveway is dry. The rainwater in the streets makes its way down to the local stream in about 5 minutes tops. I’m on board so far, all the little streams make a bigger stream until you have one big one feeding into whatever river is nearby. Fine. All clear on that. BUT if it doesn’t rain for 2 weeks where the fuck is all the water coming from then? Ever seen the Mississippi? It’s the same friggin’ size whether it’s rained or not! It should be giant the day after a rain and just a trickle after a 2 week drought. Nope. I lived in Iowa, sure it dropped a foot or flooded a bit but day after day it was the same big-ass river of water. You’re gonna tell me that all of the feeder tributaries just happen to provide it the same amount of water whether it has rained or not?! I’m not buying it. Sure at Lake Itasca the average flow rate is only 6 cubic feet per second, which doesn’t sound like very much, but if you consider that a cubic foot of water is 7.489 gallons you have to start doing the math in your head when you hear that the flow rate has increased to 12,000 cubic feet per second by the time the mighty Mississippi has reached Upper St. Anthony’s Falls in nearby Minneapolis. That’s almost 90,000 gallons of water PER SECOND. You’re going to try to sit there with a straight face and tell me that if it hasn’t rained in 2 weeks in Minnesota that there should be 90,000 gallons of mystery liquid shooting over the falls in downtown Minneapolis?! It should be bone-fucking-dry with fish gasping and flopping along the banks like something out of National Geographic! Is it just me? I’m trying to figure this out. I won’t even begin to tackle the 600,000 cubic feet per second of water that flows along in New Orleans. That’s 4 and half MILLION gallons EVERY SECOND!!! Fuck that.
Water falls from the sky. What isn’t absorbed by the soil or sucked up by thirsty plants & animals then trickles down to streams and such and carried to the river. Once there it moves at a rate of somewhere between 1.2 and 3 miles per hour downstream. Given that the river basin extends from the Allegheny Mountains in the eastern United States to the Rocky Mountains, including all or parts of 31 states and 2 Canadian provinces, that would mean that the river basin measures approximately 1,837,000 square miles. Hmmm. Now what? I guess I could look up the precipitation data for the Mississippi River Basin but given the diverse hydroclimatological applications I would need to develop a rainfall estimation based on a Z-R conversion algorithm that involved an optimization technique to determine the parameters for the transformation of radar-reflectivity to rainfall. But wait, knowing I would want to track not only precipitation but where and when this precipitation occurred to build my case that all rivers are breaking the most basic rules of physics I would have to integrate to an hourly 4 Ã— 4 km2 resolution and then visually inspect the final numbers for each region. I think it would be much easier to build a scale model of the Mississippi River Basin in my backyard. Give me a moment for this one. I WILL prove once and for all that 2 days after it stops raining that rivers should run dry.