How to..... make a pond
Why make ponds
This century has seen the loss of about
three quarters of Britain 's ponds,
along with the populations of wetland
plants and creatures they supported.
In making a pond you are literally
building an oasis - for frogs, toads,
newts, dragonflies and the like - in our
modern desert. A pond is a feature of
great beauty, which will give you
endless pleasure as you watch its
wildlife come and go. It is also an
invaluable aid to understanding the
workings of nature - no school should
be without one!
What kind of pond?
Natural ponds come in many shapes,
sizes and locations. each suiting a
different plant and animal community,
but your garden, school or nature area
pond will probably be most useful if it is
unshaded and holds water constantly.
Choose a sunny spot, away from trees
and near a water supply.
The most straightforward way of
holding water in is usually to lay a butyl
or other flexible liner. (Advice on using
clay. concrete or other linings can be
given separately.) To work out the size
of liner needed for the size of pond you
have in mind. use this formula: (length
plus twice maximum depth) by (width
plus twice maximum depth).
Digging and lining
Your deepest point need be no more
than one metre - in fact, most of the
pond's wildlife activity goes on in the
shallows Make this point even
shallower in the case of a small pond,
otherwise the sides will be too steep.
Place the deep point off-centre, shaping
the sides with gentle contours, gradual
slopes and perhaps shelves.
Dig the hole a few inches deeper than
the pond to allow for padding -
newspapers, carpet, sand or pond liner
underlay - and remove anything sharp.
Lay the liner on top of the padding,
cover with a two-inch layer of subsoil,
and trickle water into the pond over a
plastic sheet to avoid disturbing the soil.
As the pond fills, the weight of water
will push the liner into the exact shape
of the hole. Now you should bury the
edges of the liner - there's no need to
trim off the excess, as the buried liner
will serve to impede drainage and
encourage damp-loving plants around
the pond.
Stocking
Leave the pond to settle for a few days,
then pour in a bucket of mud and water
collected (with permission) from a good
established pond. This will help to start
off a balanced living community.
Introduce plants at this stage as well,
including species suitable for each
depth. Don't use non- natives - such as
Canadian pondweed, parrot feather,
floating fern (Azollo) and swamp
stonecrop - as they are not as useful to
wildlife and they have a habit of
spreading to other ponds. The Trust can
supply a list of suitable plants.
It's probably OK to move frog spawn to
a new gorden pond from another nearby
gorden pond, but we would discourage
spawn movement in all other cases. The
danger is that undesirable plants,
creatures or even diseases will be passed
around in this way. If your pond is
suitable, amphibians should find it
sooner or later.
Don't introduce fish! They only occur
naturally in very deep (or stream-fed)
ponds, and will reduce the wildlife
value of any pond into which they are
artificially released.
Managing
If you want to top up the pond
(remember that, in nature, pond levels
rise and fall, and that seasonal drying
out of ponds is a good thing for some
species), try to use rainwater.
Otherwise, hold tap water in buckets or
barrels for a few days to allow its
chlorine to escape, or add very small
amounts at a time.
Algal blooms might be a problem at
first, but, if you have followed the rules
above, your pond should soon reach a
natural balance. In the meantime, scoop
the algae out if you can. As with any
weed clearance, leave it on the pond's
edge for a couple of days, to allow
creatures to hop back in, but then
remove it from the site so its nutrients
don't overfeed the water.
Managing your pond should be very
easy. Keep marginal plant cover to
about a third of the pond's surface,
leaving the other two thirds for
submerged weeds and bare mud. Silt
normally takes many years to fill a pond
- you shouldn't need to clear any out
within your lifetime. Don't ever "clean
out" a pond as this will destroy the
wildlife community it has developed.
This guide has been written by Mark
Nicholson, Education Officer of the
Cornwall Wildlife Trust. For further
information, call the Trust on (01872)
73939.
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