anchor.diff:  
         this%model_time = forcing%current_time
   
  -      call terrain_delta(this, forcing, options)  ! BK TEST
  +      ! call terrain_delta(this, forcing, options)  ! BK TEST
       end subroutine
   
   
  
positive.code: 
  
              ! Then finally:
              delta_dzdx(:,i,:) = dzdx(:,i,:)  -  dzfdx(:,i,:)  ! 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)
  
negative.code:             ! #------------------------------------------
  
  
          endif    
  
  
          end associate
  
  