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bmp_wet_pond.f
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bmp_wet_pond.f
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subroutine wet_pond
!! ~ ~ ~ PURPOSE ~ ~ ~
!! run wet pond processes
!! ~ ~ ~ INCOMING VARIABLES ~ ~ ~ ~ ~ ~ ~
!! name |units |definition
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! wtp_evrsv |none |detention pond evaporation coefficient
!! hhvaroute(2,:,:) |m^3 H2O |water
!! hhvaroute(3,:,:) |metric tons |sediment or suspended solid load
!! i_mo |none |current month of simulation
!! sub_subp_dt(:,:) |mm H2O |precipitation for time step in subbasin
!! wtp_pvol(: |m^3 H2O |volume of permanent pool including forebay
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! ~ ~ ~ OUTGOING VARIABLES ~ ~ ~ ~ ~ ~ ~ ~ ~
!! name |units |definition
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! hhvaroute(2,:,:) |m^3 H2O |water
!! hhvaroute(3,:,:) |metric tons|sediment or suspended solid load
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! ~ ~ ~ LOCAL DEFINITIONS ~ ~ ~
!! name |units |definition
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! ii |none |time step counter
!! k |none |weir stage counter
!! titldum |NA |dummy string
!! ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~ ~
!! ~ ~ ~ SUBROUTINES/FUNCTIONS CALLED ~ ~ ~
!! SWAT: surf_seep,surf_evap,water_depth
!! Intrinsic: Log,exp
!! ~ ~ ~ ~ ~ ~ END SPECIFICATIONS ~ ~ ~ ~ ~ ~
use parm
implicit none
character (len=80) :: titldum
integer :: ii, k, sb
real :: qin,qout,qpnd,sedin,sedout,sedpnd,spndconc
real :: rf,imc,pndwdth,seep,evap,rain,seepa,surfa
real :: a1,b1,qdepth,hdep_ext,usettle,tmpw,mu,qhyd,dp
real :: alpha,beta,vol,hp,tvol,ht,decayexp,qweir,sedweir,coeff_R
sb = inum1
qout=0.; sedout=0.; qdepth=0.
dp = wtp_dp(sb) * 0.1 !cm
if (iyr<wtp_iyr(sb).or.(iyr==wtp_iyr(sb).and.i_mo<wtp_imo(sb)))
&then
return
endif
!! Estimate Pond Volume using Austin Design Manual if not entered by user
!! COA Environmental Criteria Manual Chapter 1.6.6 and Table 1-9
if (wtp_dim(sb)==0) then
imc = subdr_ickm(ihout) / subdr_km(ihout) !fraction impervious cover
rf = 0.5463 * imc ** 2 + 0.328 * imc + 0.0296
wtp_pvol(sb) = 0.162 * rf * (subdr_km(ihout) * 247.11) !ac-feet
wtp_pvol(sb) = wtp_pvol(sb) * 1233.4 !m3
if (wtp_pvol(sb)<3000) wtp_pvol(sb) = 3000. !minimum area 21780ft2 * depth 5ft gives ~3000m3
wtp_pdepth(sb) = 2. !m
wtp_sdslope(sb) = 4. !h:v
wtp_lenwdth(sb) = 2. !l:w
wtp_pdia(sb) = 0.1524 !m (=6inch )
wtp_plen(sb) = 5. !m
wtp_pmann(sb) = 0.012 ! concrete surface
wtp_ploss(sb) = 0.1 !minor loss
call ext_dpth(wtp_extdepth(sb))
end if
alpha = wtp_lenwdth(sb)
beta = wtp_sdslope(sb)
hp = wtp_pdepth(sb)
vol = wtp_pvol(sb)
!pond width at the bottom
a1 = 3. * beta * hp * (alpha + 1.)
b1 = 12. * alpha * (3.* vol / hp - 4.* beta**2 * hp**2)
pndwdth = (- a1 + sqrt(a1**2 + b1)) / (6.* alpha) !m
!surface area of the permanent pool
surfa = wtp_pvol(sb) / wtp_pdepth(sb) !m2,
!pond volume (permanent pool + extended detention
ht = hp + wtp_extdepth(sb)
a1 = 2.* beta * ht
tvol = (alpha * pndwdth **2 + (pndwdth + a1) * (alpha *
& pndwdth + a1) + (pndwdth * (alpha * pndwdth + a1) + alpha *
& pndwdth * (pndwdth + a1)) / 2.) * ht / 3.
!! Get initial values from previous day
qpnd = wtp_qi(sb) !m^3
sedpnd = wtp_sedi(sb) * qpnd / 1.e6 !tons
!! iterate for subdaily flow/sediment routing
do ii=1,nstep
qout = 0.; spndconc = 0.
qin = hhvaroute(2,ihout,ii) !m^3
qpnd = qin + qpnd !m^3
sedin = hhvaroute(3,ihout,ii) !tons
!overflow to emergency outlet
if (qpnd>tvol) then
qweir = qpnd - tvol
qpnd = tvol
sedweir = sedin * qweir / qin
sedpnd = sedpnd + sedin - sedweir
else
qweir = 0.
sedweir = 0.
sedpnd = sedin + sedpnd !tons
endif
if (qpnd>1e-6) then
spndconc = sedpnd / qpnd * 1.e6 !initial sed conc, mg/l
if(spndconc<wtp_sede(sb)) spndconc = wtp_sede(sb)
else
cycle
end if
!! Estimate water depth, m
call wpnd_depth(qpnd,pndwdth,beta,alpha,qdepth)
hdep_ext = qdepth - hp
if(hdep_ext<0) hdep_ext = 0.
!! Calculate outflow
if (hdep_ext>0.) then
!! Use stage-discharge relationship if available
if (wtp_stagdis(sb)==1) then
select case(wtp_sdtype(sb))
case(1) !! 1 is exponential function
qout = wtp_sdc1(sb) * exp(wtp_sdexp(sb) * qdepth) +
& wtp_sdintc(sb)
case(2) !! 2 is Linear function
qout = wtp_sdc1(sb) * qdepth + wtp_sdintc(sb)
case(3) !! 3 is logarthmic function
qout = wtp_sdc1(sb) * log(qdepth) + wtp_sdintc(sb)
case(4) !! 4 is power function
qout = wtp_sdc1(sb) * (qdepth**3) + wtp_sdc2(sb) *
& (qdepth**2) + wtp_sdc3(sb) * qdepth + wtp_sdintc(sb)
case(5)
qout = wtp_sdc1(sb) * (qdepth**wtp_sdexp(sb)) +
& wtp_sdintc(sb) !m3/s
end select
else
!! Discharge out of extended detention storage through inverted PVC pipe
call pipe_discharge(wtp_pdia(sb),wtp_plen(sb),
& hdep_ext,wtp_pmann(sb),wtp_ploss(sb),qout) !m3/s
end if
qout = qout * idt * 60. !m3/s ->m^3
! no outflow from the permanent pool
if (qout>qpnd-wtp_pvol(sb)) qout = qpnd - wtp_pvol(sb)
if (qout<0) qout = 0.
else
!! no discharge from the permanent pool
qout = 0.
end if
!! Seepage, evaporation and rainfall
a1 = wtp_lenwdth(sb)
b1 = wtp_sdslope(sb) ** 2 + 1.
seepa = a1 * pndwdth ** 2 + 2. * (a1 + 1) * pndwdth * qdepth *
& b1 ** 0.5 + 5.64 * qdepth ** 2 * b1 * wtp_sdslope(sb) !m2
b1 = 2.* beta * qdepth !jeong 05/22/14
surfa = (a1 * pndwdth + b1) * (pndwdth + b1) !m2
seep = wtp_k(sb) / 1000. / 60. * idt * seepa !m3
evap = wtp_evrsv(sb) * sub_pet(sb) / 1000. * surfa !m3
rain = sub_subp_dt(sb,ii) / 1000. * surfa !m3
!! Mass balance for flow
qpnd = qpnd + rain - seep - evap - qout
if (qpnd<0) qpnd = 0.
!----------------------------------------------------------------------------------
!! Sediment removal
tmpw = sub_hhwtmp(sb,ii)
! water viscosity (g/cm-s) using 3rd order polynomial interpolation
mu = -3.e-6 * tmpw ** 3 + 0.0006 * tmpw ** 2 - 0.0469 *
& tmpw + 1.7517
mu = mu * 1.e-2
!settling velocity, cm/s
usettle = 0.7 * 981. / 18. * 1.6 / mu * dp ** 2 !ro,s=1.6g/cm3, g=981cm/s
b1 = 2.* beta * qdepth
surfa = (a1 * pndwdth + b1) * (pndwdth + b1) !m2
if(qout>0.) then
!WERF equation
qhyd = qout / idt / 60. / surfa * 100. ! m3/s / m2 * 100 = cm/s
coeff_R = (1.+ usettle /
& (qhyd * wtp_hydeff(sb))) ** (-wtp_hydeff(sb))
spndconc = spndconc * coeff_R ! mg/l
sedpnd = spndconc * qpnd * 1e-6 !tons, amount sediment in the pond at the end of the time step
!sediment conc no less than the minimum value
if(spndconc<wtp_sede(sb)) spndconc = wtp_sede(sb)
else
!SWAT sediment equation for ponds
decayexp = exp(-7.667e-3 * idt / 60. * dp)
spndconc = (spndconc - wtp_sede(sb)) * decayexp +
& wtp_sede(sb)
sedpnd = spndconc * qpnd * 1e-6 !tons
endif
!Sediment coming out of the pond
sedout = spndconc * qout * 1e-6 !tons
qout = qout + qweir
sedout = sedout + sedweir
!! Store flow/sediment out of the pond at the subbasin outlet
hhvaroute(2,ihout,ii) = max(0.,qout)
hhvaroute(3,ihout,ii) = max(0.,sedout)
end do
! Store end-of-day values for next day
wtp_qi(sb) = qpnd !m^3
if (qpnd>0.1.and.sedpnd>0.000001) then
wtp_sedi(sb) = sedpnd / qpnd * 1.e6 !tons
else
wtp_sedi(sb) = 0
endif
if (wtp_sedi(sb)<wtp_sede(sb)) wtp_sedi(sb) = wtp_sede(sb)
end subroutine
!-------------------------------------------------------------------
subroutine ext_dpth(hmax)
use parm
implicit none
real,dimension(40) :: cumrain=(/0.,0.006,0.012,0.019,0.026,0.034,
& 0.043,0.053,0.064,0.077,0.092,0.11,0.134,0.166,0.212,0.287,0.384,
& 0.542,0.802,1.262,1.462,1.587,1.688,1.746,1.784,1.811,1.832,
& 1.849,1.863,1.875,1.885,1.894,1.902,1.91,1.917,1.924,1.93,1.93,
& 1.93,1.93/)
real :: ia, ss, plen,inflow,outflow,pndvol,wdth,pndarea,vtmp,hdep
real :: aa,bb,pdia,hvol,alpha
real, dimension(40):: fa
real, intent(out) :: hmax
integer :: ii,sb
sb = inum1
fa=0; inflow=0.
ss = 1000. / sub_cn2(sb) - 10.
plen = wtp_plen(sb) * 3.2808 !ft
pdia = wtp_pdia(sb) * 3.2808 !ft
!volume of permanent pool
pndvol = wtp_pvol(sb) * 3.2808 ** 3 !ft^3
!pond width at the bottom of the pond
wdth = ((140.3**2 - 4*(5828.2-0.072 * pndvol))**0.5 - 140.3) / 2. ! ft
!pond area at the top of permanent pool
pndarea = (wdth + 187.) * (2*wdth + 187.) ! ft^2
alpha = wtp_lenwdth(sb)
hmax=0.
do ii=1,40
if(hvol<0) hvol = 0.
! calculate surface runoff
ia = 0.2 * ss
if (ia>cumrain(ii)) then
ia = cumrain(ii)
fa(ii) = 0
else
fa(ii) = ss * (cumrain(ii) - ia) / (cumrain(ii) - ia + ss)
endif
if (ii>=2) inflow = fa(ii) - fa(ii-1) !inches
! calculate max water depth in extended detention
inflow = inflow * subdr_km(sb) * 8.97e5 !inch-km2 ->ft^3
hvol = hvol + inflow !ft^3
call wpnd_depth(hvol,wdth,wtp_sdslope(sb),alpha,hdep)
if (hdep>hmax) hmax = hdep
!compute discharge from outlet pipe
call pipe_discharge(pdia,plen,hdep,wtp_pmann(sb),wtp_ploss(sb),
& outflow)
outflow = outflow * 35.31 * 300. !m3/s ->ft^3 per 5 minutes
if (outflow>hvol) outflow = hvol
hvol = hvol - outflow
end do
hmax = hmax / 3.2808 ! meter
end subroutine
!-------------------------------------------------------------------
subroutine wpnd_depth(hvol,width,slp,lenwdth,hdep)
!calculate ponding depth using Newton's method
implicit none
real, intent(in):: hvol,width,slp,lenwdth
real, intent(out):: hdep
real:: dfn,fn,alp,ll
alp = lenwdth
ll = width
hdep = 0.1; fn = 100
do while (abs(fn)>0.1)
fn = alp * ll ** 2 * hdep + slp * ll * (1.+ alp) * hdep ** 2 +
& 4. / 3.* slp ** 2 * hdep ** 3 - hvol
dfn = alp * ll ** 2 + 2. * slp * ll * (1.+ alp) * hdep + 4.*
& slp ** 2 * hdep ** 2
hdep = hdep - fn / dfn
end do
end subroutine
!-------------------------------------------------------------------
subroutine pipe_discharge(pdia,plen,hdep,mann,mloss,outflow)
! calculate discharge from extended detention through pvc pipe,m3/s
implicit none
real, intent(in):: pdia,plen,hdep,mann,mloss
real, intent(out):: outflow
real:: parea,kf,rh
parea = 3.14159 * (3.2808 * pdia) ** 2 / 4. !ft^2
rh = 3.2808 * pdia / 4. !ft
kf = 29. * plen * mann ** 2 / rh ** 1.33
outflow = parea * ((64.4 * 3.2808 * hdep) / (1.+ kf + mloss))
& ** 0.5 !cfs
outflow = outflow / 35.31 !m3/s
end subroutine