subroutine hydro_init !! ~ ~ ~ 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 !! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ !! ~ ~ ~ OUTGOING VARIABLES ~ ~ ~ !! name |units |definition !! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ !! lat_ttime(:)|none |Exponential of the lateral flow travel time !! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ !! ~ ~ ~ SUBROUTINES/FUNCTIONS CALLED ~ ~ ~ !! SWAT: Ttcoef !! ~ ~ ~ ~ ~ ~ END SPECIFICATIONS ~ ~ ~ ~ ~ ~ use hru_module, only : hru, sdr, dormhr, ihru use soil_module use plant_module use climate_module use plant_data_module use pesticide_data_module use basin_module use channel_module use time_module use organic_mineral_mass_module use hydrograph_module, only : sp_ob, ob use constituent_mass_module use output_landscape_module implicit none integer :: j = 0 !none |counter integer :: l = 0 !none |counter real :: scmx = 0. !mm/hr |maximum soil hydraulic conductivity real :: xx = 0. !none |variable to hold calculation result real :: tsoil = 0. ! | integer :: iob = 0 ! | integer :: iwst = 0 ! | integer :: iwgn = 0 ! | real :: sffc = 0. ! | integer :: nly = 0 !none |end of loop integer :: k = 0 !none |counter integer :: ipl = 0 !none |counter integer :: isdr = 0 !none |conversion factor to convert kg/ha to g/t(ppm) real :: sd = 0. real :: dd = 0. real :: sdlat = 0. real :: hlat = 0. real :: daylength = 0. real :: rock = 0. do j = 1, sp_ob%hru ihru = j iob = hru(j)%obj_no iwst = ob(iob)%wst iwgn = wst(iwst)%wco%wgn !! calculate composite usle value rock = Exp(-.053 * soil(j)%phys(1)%rock) hru(j)%lumv%usle_mult = rock * soil(j)%ly(1)%usle_k * & hru(j)%lumv%usle_p * hru(j)%lumv%usle_ls * 11.8 !hru(j)%lumv%usle_mult = 1.586 * (hru(j)%area_ha) ** 0.12 * rock * soil(j)%ly(1)%usle_k * & ! hru(j)%lumv%usle_p * hru(j)%lumv%usle_ls tsoil = (wgn(iwgn)%tmpmx(12) + wgn(iwgn)%tmpmx(12)) / 2. !! should be beginning month of simulation and not 12 (December) !! set fraction of field capacity in soil if (bsn_prm%ffcb <= 0.) then sffc = wgn_pms(iwgn)%pcp_an / (wgn_pms(iwgn)%pcp_an + Exp(9.043 - & .002135 * wgn_pms(iwgn)%pcp_an)) !!S-curve equation Jeff made up. else sffc = bsn_prm%ffcb end if !! set initial soil water and temperature for each layer nly = soil(j)%nly soil(j)%sw = 0. soil(j)%ffc = sffc do k = 1, nly soil(j)%phys(k)%tmp = tsoil soil(j)%phys(k)%st = sffc * soil(j)%phys(k)%fc soil(j)%sw = soil(j)%sw + soil(j)%phys(k)%st end do !! set day length threshold for dormancy and initial dormancy dormhr(j) = wgn_pms(iwgn)%daylth sd = Asin(.4 * Sin((Real(time%day) - 82.) / 58.09)) !!365/2pi = 58.09 dd = 1.0 + 0.033 * Cos(Real(time%day) / 58.09) sdlat = -wgn_pms(iwgn)%latsin * Tan(sd) / wgn_pms(iwgn)%latcos if (sdlat > 1.) then !! sdlat will be >= 1. if latitude exceeds +/- 66.5 deg in winter hlat = 0. elseif (sdlat >= -1.) then hlat = Acos(sdlat) else hlat = 3.1416 !! latitude exceeds +/- 66.5 deg in summer endif daylength = 7.6394 * hlat do ipl = 1, pcom(j)%npl if (pcom(j)%plcur(ipl)%gro == "y" .and. daylength - dormhr(j) < wgn_pms(iwgn)%daylmn) then pcom(j)%plcur(ipl)%idorm = "y" else pcom(j)%plcur(ipl)%idorm = "n" end if end do !! set maximum depth in soil to maximum rooting depth of plant soil(j)%zmx = soil(j)%phys(nly)%d !! compute lateral flow travel time if (hru(j)%hyd%lat_ttime <= 0.) then scmx = 0. do l = 1, soil(j)%nly if (soil(j)%phys(l)%k > scmx) then scmx = soil(j)%phys(l)%k endif end do !! unit conversion: !! xx = m/(mm/h) * 1000.(mm/m)/24.(h/d) / 4. xx = 0. xx = 10.4 * hru(j)%topo%lat_len / scmx if (xx < 1.) xx = 1. hru(j)%hyd%lat_ttime = 1. - Exp(-1./xx) else hru(j)%hyd%lat_ttime = 1. - Exp(-1. / hru(j)%hyd%lat_ttime) end if isdr = hru(j)%tiledrain if (hru(j)%lumv%ldrain > 0 .and. sdr(isdr)%lag > 0.01) then hru(j)%lumv%tile_ttime = 1. - Exp(-24. / sdr(isdr)%lag) else hru(j)%lumv%tile_ttime = 0. end if end do return end subroutine hydro_init