Many
people in south Louisiana are rebuilding their homes as a
result of Hurricanes Katrina and Rita. In many cases, property
owners are borrowing dirt from part of their property to raise
the level of the building site. While homes along the coast
in FEMA’s designated V-zones cannot be supported on
fill material, there are many A-zone properties further inland
where elevation on fill is allowed. This earth-moving for
home construction is resulting in many properties being left
with unsafe and unsightly borrow pits.
There
are several things you can do to turn a useless borrow pit
into an attractive fishing pond once you’ve made sure
that the ground will hold water. Soil with 20 percent or higher
clay content holds water well. Most soils in South Louisiana
have that much clay, but watch out for sand lenses during
the digging. Sandy areas should be dug out and filled over
with clay. Tree roots can also be a problem. Dig them out
and pack extra clay in those areas.
Dig
a fish pond instead of just a hole
Pond size,
depth and side slope are important. Many people try to save
real estate by excavating the maximum amount of soil from
the smallest possible area. The resulting ponds are small,
very deep and have very steep sides – and they are both
unsafe and difficult to maintain.
Safe
side slopes: If livestock or a child or pet falls
into the pond, they must be able to climb out easily. This
means that vertical pond walls are not acceptable –
not even in a few places. If you do not have room on your
lot to slope the pond sides at a 3-to-1 slope (at the steepest),
then you should not dig a pond or pit.
Size:
When it comes to fish ponds, bigger is better. A one-acre
pond will need far less intensive management that a one-tenth
acre pond. Larger ponds can approach the level of self-sustaining
ecosystem – like a small lake. Very small ponds can
provide an attractive landscape feature and a bit of fishing,
but they require careful management – they’re
more like an aquarium than a lake.
Depth:
The ideal depth for fish ponds is about five feet,
or a little more. In most cases, areas over seven feet deep
are little used by fish. Very deep areas can become totally
devoid of dissolved oxygen. If a storm causes the oxygen-deficient
water to mix with the surface layer, the rapid destratification
can cause a fish kill. Too much shallow water can also be
a problem. Large areas of water less than two feet deep are
almost impossible to keep from becoming clogged with aquatic
weeds.
Add
water control features
In some
ponds runoff control is needed. If rainwater moves across
your property where the pond is located, you have two options:
add levees around the pond or add water controls within the
pond. If levees are added to keep the runoff out of the pond
(or if the pond is situated in a dry site), then another source
of fill water is needed. Without any method to add water,
many ponds will get very low during dry weather, with reduced
capacity to keep fish alive. Most people choose to install
a well or run a line from an existing well. Remember that
well water has no dissolved oxygen content: adding lots of
well water without aeration is a good way to kill your fish!
A simple series of splash screens will solve this problem.
In-pond
water controls include drainpipes and spillways. While watershed
ponds in hilly areas need to have both, many ponds on flat
terrain will need neither. Drainpipes are not an option for
borrow ponds that are deeper than adjoining ditches. Ponds
that catch runoff will need a spillway at the lower end of
the property to divert overflow without causing erosion.
Add
water quality features
If you
have or need an area of the pond to be deeper than seven feet,
aerating the deeper areas will solve most of the basic problems.
Pumped-air diffusion or turbulent mixing, or both, can be
used. Aeration will prevent stratification, improve nutrient
cycling and prevent problems from periodic low dissolved oxygen
levels.
Fountain-type aerators don’t generate the most efficient
mixing, but in small ponds they provide an attractive feature
and adequate aeration.
For more
information, go to the LSU aquaculture website:
http://www.lsuagcenter.com/en/crops_livestock/aquaculture/
or the LSU Sea Grant aquaculture site:
http://www.seagrantfish.lsu.edu/aquaculture/index.html
or request publication #2573: Management of Recreational
and Farm Ponds in Louisiana from your parish AgCenter
office.
For more
information about flood risk and flood protection:
http://www.LouisianaFloods.org
Download:
borrowponds.pdf
(372KB)
