TWO POND VARIATIONS

Note marsh grasses and water lilies growing in this pool.

     Back in March I wrote a bit about ponds in the home landscape. Today I thought I would mention two recent permutations on the modern pond. The first began in Austria and has spread through Europe and reached Canada and the West coast of the US. This is the environmentally correct natural swimming pool. No chlorine and other chemicals here. Instead, the pool uses a more elaborate variation of the system of physical and biological filters used by the fish ponds I described earlier. Pumps keep the water aerated and move it over and through gravel colonized by beneficial bacteria as well as through the roots of water plants that absorb nutrients that would otherwise turn to waste.

     In addition to private pools like that shown above, Europe sports large public pools that service hundreds of swimmers at a time -- all without chemicals. A similar public pool is scheduled to open in the Twin Cities next summer.

     At the other end of the spectrum is a water feature designed for those who prefer less "biology." You can have the sights and sounds of running water and a completely landscaped falls and stream without a body of standing water. Instead of a pond, the stream feeds into a mass of river pebbles and sinks out of sight. Beneath the pebbles lies a hidden reservoir and a pump that recirculates the water.

This sketch shows the secret of a "pondless" waterfall.

          I personally would never give up the joys of having fish and a full ecosystem (in which, by the way, fish eat mosquito eggs). But for those who want the sights and sounds of water without worrying about the health of other creatures, a pondless waterfall may be just the ticket.

This long stream vanishes into the rocks at the bottom of the hill.