unit_hyd Subroutine

subroutine unit_hyd(tc, uh)

~ ~ ~ PURPOSE ~ ~ ~ This subroutine computes variables related to the watershed hydrology: the time of concentration for the subbasins, lagged surface runoff, the coefficient for the peak runoff rate equation, and lateral flow travel time.

~ ~ ~ INCOMING VARIABLES ~ ~ ~1 name |units |definition ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ch_n(1,:) |none |Manning"s "n" value for the tributary channels ch_s(1,:) |m/m |average slope of tributary channels gdrain(:) |hrs |drain tile lag time: the amount of time |between the transfer of water from the soil |to the drain tile and the release of the |water from the drain tile to the reach. hru_km(:) |km2 |area of HRU in square kilometers lat_ttime(:)|days |lateral flow travel time slsoil(:) |m |slope length for lateral subsurface flow slsubbsn(:) |m |average slope length for subbasin tconc(:) |hr |time of concentration ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ OUTGOING VARIABLES ~ ~ ~ name |units |definition ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ lat_ttime(:)|none |Exponential of the lateral flow travel time ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ LOCAL DEFINITIONS ~ ~ ~ name |units |definition ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ l |none |counter scmx |mm/hr |maximum soil hydraulic conductivity t_ch |hr |time for flow entering the farthest upstream |channel to reach the subbasin outlet xx |none |variable to hold calculation result ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~

~ ~ ~ SUBROUTINES/FUNCTIONS CALLED ~ ~ ~
SWAT: Ttcoef

~ ~ ~ ~ ~ ~ END SPECIFICATIONS ~ ~ ~ ~ ~ ~

sum 20 points on the unit hydrograph to get sum for the time%step

increment within the time step to get accurate estimates near peak Triangular Unit Hydrograph rising limb of hydrograph falling limb of hydrograph Gamma Function Unit Hydrograph

Arguments