The first table is a listing of river data at different stations along the Mississippi river from Venice to Cairo Illinois. These are not the only river stations that are monitored, these are just selected stations. The second column is the Water surface elevation at the station based on NAVD88 (North American Vertical Datum) 2004.65. the third column is the same information that has been adjusted to NAVD. NAVD is using the DATUM or zero point) as Mean Sea level with 0.0 being the elevation at sea level taking into account high and low tides. As you can see from Venice to Knox Landing (at the ORCS). The values go up as you would expect. Stations above Knox Landing have an asterisk because they are not based on NAVD the number is arbitrary. So according to todays report the water level is 64.4 feet above sea level at Knox landing. I will get back to this later. The final column is the 24 hour deviation. In one row you will see discharge at 1,355,000 CFS. This appears to be the flow rate of the river at Red River landing (could be Baton Rouge) with a deviation of -7000 cfs from the previous 24 hour period.
The second table is the same information for the Atchafalaya River. The Latitude discharge is shown at 1,951,000 cfs. This could be for both the river itself and the Wax Lake outlet I am not sure. That's a lot of water and is more than the Mississippi river.
The final chart is the information at the three ORCS structures, showing the water surface elevation on each side of the structure. The delta head is the difference between the river side and the channel side. Todays values are 19.8, 19.0 and 21.0 feet. This corresponds to about 9.0 psi at the bottom of the structure. That doesn't sound like much but it is about 1300 pounds per square foot. Considering the size of the structure and number of square feet involved it adds up pretty quick.
Getting back to the water surface elevation at knox Landing being 64.4 feet. This is at mile 313.5 (give or take) this corresponds to a slope of 0.205 feet per mile. The distance from the mouth of the Atchafalya river to the same location is about 155 miles. This corresponds to a slope of 0.415 feet per mile. That means that the slope of the water surface going down the Atchfalaya is twice the slope of the Mississippi River. The common understanding is water flows down hill, MORE ACCURATELY water flows in the DIRECTION OF THE DOWNSLOPE OF THE ENERGY GRADE LINE. ANY river monitoring station will provide the guage reading which is a measure of the WATER SURFACE ELEVATION. This is a very important piece of information along with the average velocity of the water. These two pieces of information will allow a computation of the potential energy (water surface elevation ) and kinetic energy (velocity squared divided by 2 times the acceleration due to gravity). Without getting into detail, AND VERY SIMPLIFIED everything is based on an energy balance using Bernoullis theorem along with Mannings formula (to calculate energy losses due to friction) to perform open channel flow calculations.
IF you REALLY REALLY REALLY want to study some more about this subject I suggest this book
https://www.amazon.com/Open-Channel-.../dp/1932846182
It is the bible of open channel flow and the same book I used when I took CIVE 454 in college. Some say it is a substitute for a sleeping pill. Others say it is the best text book ever written. It can be both.
Re: OT: Mississippi River Aquapocalypse 2019
Originally Posted by HelmutVII
The first table is a listing of river data at different stations along the Mississippi river from Venice to Cairo Illinois. These are not the only river stations that are monitored, these are just selected stations. The second column is the Water surface elevation at the station based on NAVD88 (North American Vertical Datum) 2004.65. the third column is the same information that has been adjusted to NAVD. NAVD is using the DATUM or zero point) as Mean Sea level with 0.0 being the elevation at sea level taking into account high and low tides. As you can see from Venice to Knox Landing (at the ORCS). The values go up as you would expect. Stations above Knox Landing have an asterisk because they are not based on NAVD the number is arbitrary. So according to todays report the water level is 64.4 feet above sea level at Knox landing. I will get back to this later. The final column is the 24 hour deviation. In one row you will see discharge at 1,355,000 CFS. This appears to be the flow rate of the river at Red River landing (could be Baton Rouge) with a deviation of -7000 cfs from the previous 24 hour period.
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