anchor.diff:                      dvdt(i,j,k) = dvdt(i,j,k) - 1.0d0*ar*(v(i,j,k) - 1.0d0*v(i,j,k+1))
                   else if (k .eq. layers) then ! bottom layer
                       dvdt(i,j,k) = dvdt(i,j,k) - 1.0d0*ar*(v(i,j,k) - 1.0d0*v(i,j,k-1))
  -                    ! add bottom drag here in isopycnal version
  +                    if (.not. RedGrav) then
  +                        ! add bottom drag here in isopycnal version
  +                        dvdt(i,j,k) = dvdt(i,j,k) - 1.0d0*botDrag*(v(i,j,k))
  +                    endif                
                   else ! mid layer/s
                       dvdt(i,j,k) = dvdt(i,j,k) - 1.0d0*ar*(2.0d0*v(i,j,k) - 1.0d0*v(i,j,k-1) - 1.0d0*v(i,j,k+1))
                   endif
  
positive.code:     call evaluate_dhdt(dhdtold, hhalf,uhalf,vhalf,ah,dx,dy,nx,ny,layers, spongeHTimeScale,spongeH,wetmask)
      call evaluate_dudt(dudtold, hhalf,uhalf,vhalf,b,zeta,wind_x,&
          fu, au,ar,slip,dx,dy,hfacN,hfacS,nx,ny,layers,rho0,&
          spongeUTimeScale,spongeU)
      !if the wind is changed to be meridional this code will need changing
      call evaluate_dvdt(dvdtold, hhalf,uhalf,vhalf,b,zeta,wind_y,&
          fv, au,ar,slip, dx,dy,hfacW,hfacE,nx,ny,layers,rho0,& 
          spongeVTimeScale,spongeV)
  !    These are the values to be stored in the 'old' variables ready to start 
  !    the proper model run.
  
  
negative.code:                     dudt(i,j,k) = dudt(i,j,k) - 1.0d0*ar*(u(i,j,k) - 1.0d0*u(i,j,k+1))
                  else if (k .eq. layers) then ! bottom layer
                      dudt(i,j,k) = dudt(i,j,k) - 1.0d0*ar*(u(i,j,k) - 1.0d0*u(i,j,k-1))
                      if (.not. RedGrav) then
                          ! add bottom drag here in isopycnal version
                          dudt(i,j,k) = dudt(i,j,k) - 1.0d0*botDrag*(u(i,j,k))
                      endif
                  else ! mid layer/s
                      dudt(i,j,k) = dudt(i,j,k) - 1.0d0*ar*(2.0d0*u(i,j,k) - 1.0d0*u(i,j,k-1) - 1.0d0*u(i,j,k+1))
                  endif
  