code: def calc_qv_v1(self):
      
      con = self.parameters.control.fastaccess
      flu = self.sequences.fluxes.fastaccess
      for i in range(2):
          if (flu.av[i] > 0.) and (flu.uv[i] > 0.):
              flu.qv[i] = (con.ekv[i]*con.skv[i] *
                           flu.av[i]**(5./3.)/flu.uv[i]**(2./3.)*con.gef**.5)
          else:
              flu.qv[i] = 0.
docs: Calculate the discharge of both forelands after Manning-Strickler.
  
      Required control parameters:
        |EKV|
        |SKV|
        |Gef|
  
      Required flux sequence:
        |AV|
        |UV|
  
      Calculated flux sequence:
        |lstream_fluxes.QV|
  
      Examples:
  
          For appropriate strictly positive values:
  
          >>> from hydpy.models.lstream import *
          >>> parameterstep()
          >>> ekv(2.0)
          >>> skv(50.0)
          >>> gef(0.01)
          >>> fluxes.av = 3.0
          >>> fluxes.uv = 7.0
          >>> model.calc_qv_v1()
          >>> fluxes.qv
          qv(17.053102, 17.053102)
  
          For zero or negative values of the flown through surface or
          the wetted perimeter:
  
          >>> fluxes.av = -1.0, 3.0
          >>> fluxes.uv = 7.0, 0.0
          >>> model.calc_qv_v1()
          >>> fluxes.qv
          qv(0.0, 0.0)