anchor.diff:  
   
               ! Then finally:
  -            delta_dzdx(:,i,:) = dzdx(:,i,:)  -  dzfdx(:,i,:)  ! use this for w_real calculation.
  +            delta_dzdx(:,:,:) = dzdx(:,:,:)  -  dzfdx(:,:,:)  ! use this for w_real calculation.
   
               ! the same??? without all the above??? could be function in if(use_delta_terrain_for_speedup==True)
               delta_terrain = (terrain - forcing_terrain)
  
positive.code: 
        this%model_time = forcing%current_time
  
        call terrain_delta(this, forcing, options)  ! BK TEST
      end subroutine
  
  
  
negative.code:             allocate(dzfdy(this% ims : this% ime, &
                            this% kms : this% kme, &
                            this% jms+1 : this% jme) )
  
              allocate(delta_terrain(this% ims : this% ime, &
                                      this% jms : this% jme) )
  