subroutine res_nutrient (iob) use reservoir_data_module use time_module use reservoir_module use hydrograph_module, only : resz, ob, ht2, wbody use climate_module implicit none integer, intent (in) :: iob real :: nitrok = 0. ! | real :: phosk = 0. ! | real :: tpco = 0. ! | real :: chlaco = 0. ! | integer :: iwst = 0 !none |weather station number real :: nsetlr = 0. ! | real :: psetlr = 0. ! | real :: conc_n = 0. ! | real :: conc_p = 0. ! | real :: theta ! | !! if reservoir volume less than 1 m^3, set all nutrient levels to !! zero and perform no nutrient calculations if (wbody%flo < 1.e-6) then wbody = resz return end if !! if reservoir volume greater than 1 m^3, perform nutrient calculations if (time%mo >= wbody_prm%nut%ires1 .and. time%mo <= wbody_prm%nut%ires2) then nsetlr = wbody_prm%nut%nsetlr1 psetlr = wbody_prm%nut%psetlr1 else nsetlr = wbody_prm%nut%nsetlr2 psetlr = wbody_prm%nut%psetlr2 endif !! n and p concentrations kg/m3 * kg/1000 t * 1000000 ppp = 1000 conc_n = 1000. * (wbody%orgn + wbody%no3 + wbody%nh3 + wbody%no2) / wbody%flo conc_p = 1000. * (wbody%sedp + wbody%solp) / wbody%flo !! new inputs thetn, thetap, conc_pmin, conc_nmin !! Ikenberry wetland eqs modified - not function of area - fraction of difference in concentrations iwst = ob(iob)%wst nitrok = (conc_n - wbody_prm%nut%conc_nmin) * Theta(nsetlr, wbody_prm%nut%theta_n, wst(iwst)%weat%tave) nitrok = amin1 (nitrok, 1.) nitrok = max (nitrok, 0.) phosk = (conc_p - wbody_prm%nut%conc_pmin) * Theta(psetlr, wbody_prm%nut%theta_p, wst(iwst)%weat%tave) phosk = amin1 (phosk, 1.) phosk = max (phosk, 0.) !! remove nutrients from reservoir by settling !! other part of equation 29.1.3 in SWAT manual wbody%solp = wbody%solp * (1. - phosk) wbody%sedp = wbody%sedp * (1. - phosk) wbody%orgn = wbody%orgn * (1. - nitrok) wbody%no3 = wbody%no3 * (1. - nitrok) wbody%nh3 = wbody%nh3 * (1. - nitrok) wbody%no2 = wbody%no2 * (1. - nitrok) !! calculate chlorophyll-a and water clarity chlaco = 0. wbody%chla = 0. tpco = 1.e+6 * (wbody%solp + wbody%sedp) / (wbody%flo + ht2%flo) if (tpco > 1.e-4) then !! equation 29.1.6 in SWAT manual chlaco = wbody_prm%nut%chlar * 0.551 * (tpco**0.76) wbody%chla = chlaco * (wbody%flo + ht2%flo) * 1.e-6 endif !! check nutrient masses greater than zero wbody%no3 = max (wbody%no3, 0.0) wbody%orgn = max (wbody%orgn, 0.0) wbody%sedp = max (wbody%sedp, 0.0) wbody%solp = max (wbody%solp, 0.0) wbody%chla = max (wbody%chla, 0.0) wbody%nh3 = max (wbody%nh3, 0.0) wbody%no2 = max (wbody%no2, 0.0) !! calculate amount of nutrients leaving reservoir ht2%no3 = wbody%no3 * ht2%flo / (wbody%flo + ht2%flo) ht2%orgn = wbody%orgn * ht2%flo / (wbody%flo + ht2%flo) ht2%sedp = wbody%sedp * ht2%flo / (wbody%flo + ht2%flo) ht2%solp = wbody%solp * ht2%flo / (wbody%flo + ht2%flo) ht2%chla = wbody%chla * ht2%flo / (wbody%flo + ht2%flo) ht2%nh3 = wbody%nh3 * ht2%flo / (wbody%flo + ht2%flo) ht2%no2 = wbody%no2 * ht2%flo / (wbody%flo + ht2%flo) !! remove nutrients leaving reservoir wbody%no3 = wbody%no3 - ht2%no3 wbody%orgn = wbody%orgn - ht2%orgn wbody%sedp = wbody%sedp - ht2%sedp wbody%solp = wbody%solp - ht2%solp wbody%chla = wbody%chla - ht2%chla wbody%nh3 = wbody%nh3 - ht2%nh3 wbody%no2 = wbody%no2 - ht2%no2 return end subroutine res_nutrient