~ ~ ~ PURPOSE ~ ~ ~ this subroutine routes the daily flow through the reach using a variable storage coefficient
~ ~ ~ INCOMING VARIABLES ~ ~ ~ name |units |definition ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ch_d(:) |m |average depth of main channel ch_n(2,:) |none |Manning"s "n" value for the main channel ch_s(2,:) |m/m |average slope of main channel chside(:) |none |change in horizontal distance per unit |change in vertical distance on channel side |slopes; always set to 2 (slope=1/2) pet_ch |mm H2O |potential evapotranspiration ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ OUTGOING VARIABLES ~ ~ ~ name |units |definition ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ rcharea |m^2 |cross-sectional area of flow rchdep |m |depth of flow on day rtevp |m^3 H2O |evaporation from reach on day rttime |hr |reach travel time rttlc |m^3 H2O |transmission losses from reach on day rtwtr |m^3 H2O |water leaving reach on day sdti |m^3/s |average flow on day in reach ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~ ~ ~ LOCAL DEFINITIONS ~ ~ ~ name |units |definition ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ det |hr |time step (24 hours) c |none |inverse of channel side slope jrch |none |reach number p |m |wetted perimeter rh |m |hydraulic radius scoef |none |Storage coefficient (fraction of water in |reach flowing out on day) topw |m |top width of main channel vol |m^3 H2O |volume of water in reach at beginning of |day wtrin |m^3 H2O |amount of water flowing into reach on day ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
~ ~ ~ SUBROUTINES/FUNCTIONS CALLED ~ ~ ~ Intrinsic: Sqrt, Min SWAT: Qman
~ ~ ~ ~ ~ ~ END SPECIFICATIONS ~ ~ ~ ~ ~ ~ Modified by Balaji Narasimhan Spatial Sciences Laboratory, Texas A&M University
Find average flowrate in a day
Find maximum flow capacity of the channel at bank full
If average flowrate is greater than than the channel capacity at bank full
then simulate flood plain flow else simulate the regular channel flow
taking floodwater to wetlands
find the crossectional area and depth for volrt
by iteration method at 1cm interval depth
find the depth until the discharge rate is equal to volrt
find the crossectional area and depth for volrt
by iteration method at 1cm interval depth
find the depth until the discharge rate is equal to volrt
calculate top width of channel at water level
Time step of simulation (in hour)
adjusted by Ann van Griensven Feb 2018 / losses are independent of residence time.
calculate velocity and travel time calculate volume of water leaving reach on day calculate amount of water in channel at end of day
Add if statement to keep rchstor from becoming negative transmission and evaporation losses are proportionally taken from the channel storage and from volume flowing out
calculate transmission losses Total time in hours to clear the water calculate evaporation