There are a few main points to consider when you have decided to construct a dugout that will contain fish:
- site selection
- dugout size
- construction methods
- other water uses
- aeration systems
- maintenance of the dugout
Site selection
Before dugout construction begins, proper planning and
design must take place. The intended dugout site should
be thoroughly investigated. First, the location should be a
safe distance from all possible contamination sources as
shown in the following table. Excess nutrient loading from
farmstead practices contributes to problem weed growth
and fish die-off in dugouts.
Local bylaws can affect where dugouts are to be
constructed. Always check with your municipality on their
regulations for dugout construction. Overhead and
underground utility lines and right-of-ways could play a
factor in the placement of the dugout. Always have the
utilities located and marked before starting any
construction.
Good wind exposure is a benefit, as it helps circulate water
during the summer while keeping snow off in winter.
Avoid coulee bottoms or ravines with little wind action.
Although they ensure plentiful water supply through
drainage and snow trapping, they tend to have problems
with low oxygen levels, either from nutrient loading,
excessive snowpack or toxic gas buildup from plant
decomposition.
Be careful of slough or bog areas containing high organic
matter, such as peat moss. Maintaining water quality is
difficult in these areas.
Particular attention must be paid to the dugouts water
source. Water can be obtained from four basic sources:
direct precipitation, surface runoff, ground water or from
another water body. If water quality is questionable,
samples should be submitted to a lab and the results
reviewed by a fish biologist.
Surface runoff, originates from snow melt and rainfall.
Because water drains from fields and livestock operations,
the watershed needs to be checked for activities that
contaminate the runoff. If, at any time, the water quality is
questionable, then the addition of berms around the
dugout and the installation of a water diversion will help.
Groundwater is another source of water used to fill
dugouts. This water is naturally available only in high
water table areas. Fluctuations of the ground water table
should be monitored over a 12-month period, prior to
construction. This monitoring helps you decide whether
water levels will be adequate to keep the dugout filled
year-round.
Filling from another water source is the fourth water
option. Water may be obtained from other dugouts, lakes,
wells, canals or rivers. If this option is chosen, consider
distance, topography, land cover (i.e. bush roads, etc.) and
land ownership between source and dugout prior to
construction.1
If the dugout is located near a creek or stream, it should be
located off the main channel. A corrugated metal pipe with
a control gate on the end should be installed to control
water flow into the dugout. This allows the operator to
avoid receiving poor quality water.
In all cases, sample the soil at least one meter below the
proposed dugout floor to determine soil type and moisture
content. Soil conditions will dictate what equipment is
required to construct the dugout, what material will be
used for an impermeable barrier and whether the dugout
should be constructed at all.
Size and capacity
Correct dugout sizing is very important to ensure an
adequate water supply for years to come. The dugout
should store enough water to last for two years, the typical
limits of a severe drought cycle. There may be other
demands on a ponds water supply besides raising fish. The
following table provides approximate guidelines for water
usage.
Other water usage guidelines are listed in the Water Act application package published by Alberta Environment. The size of the dugout will determine the number of fish to stock, although other factors have a bearing. These factors include:
- amount of weed growth
- type of aeration
- water flow
- amount of natural fish food
- size of fish
The licenced Commercial Fish Farmer who sells you fingerlings will help determine an appropriate stocking rate for your dugout. Always start with low trout numbers in a new dugout or dugouts that have never held fish. A 50 metre by 20 metre dugout should be capable of stocking 100 trout in the 20 cm (8 inch) size. More information on fish stocking rates is available from the Aquaculture Section, Alberta Agriculture, Food and Rural Development.
Design and construction
Any shape of dugout is acceptable for fish farming,
although the simple rectangular shape is the most common
(Figure 1). For fish culture, a minimum depth of four
meters is recommended. If a shallow section is required,
sloping the bottom of the dugout is the solution, with the
deepest section being a minimum of four meters.
Side slopes are recommended to be not steeper than
1.5 to 1 on every side of the dugout. If unstable soil
conditions are present or easy access is required (e.g. boat
ramp), slopes may have to be flattened out to 1:4. The
type of construction equipment used may also have a
bearing on the steepness of the slopes. Shallow slopes are
an open invitation to predaceous birds such as great blue
herons. As well, prolific weed growth is normal in dugouts
or ponds with shallow shore edges.
Dugout costs will vary according to each site and its soil
and moisture properties. The average cost for excavating,
landscaping, and installing inlet control on a dugout of
50m x 20m x 5m deep (with a capacity of 2 million litres)
is $4,000 to $7,000.
Make provisions for the installation of aeration systems,
water intake and watering systems. Fence off the dugout to
exclude livestock as they can damage the dugouts integrity
by trampling, causing erosion or indirectly contributing to
water quality problems. For more information on fencing
for livestock, see Agdex 400/716-3 Pasture Water Systems.
Be safe. Fences prohibit access to young children and may
be necessary in some locations. Dugouts with aeration
systems are especially dangerous in the winter as they
usually cause unsafe or thin ice.
Impervious lining
In some instances, you may chose to locate a dugout
where the subsurface soil conditions are not capable of
holding water (i.e. sand and fractured bed rock). In this
case, lining the dugout with an impervious material may
be the only option (Figure 2).
Various types of lining materials are on the market.
Presently, plastic lining (woven polyethylene) is most
popular. Cover the liner with soil, free of rocks, to a depth
of 0.4 - 0.5 meters.
Installing a liner in an area with high groundwater is not
recommended. If the water table is higher than the water
level inside the dugout, the liner will be pushed inward
causing sloughing and eventual collapse of the sides.
Dugout aeration
Many dugouts require aeration to improve water quality
for domestic use, to increase dissolved oxygen in the
dugout for fish and to reduce the likelihood of muddytasting
fish. Air flows of 1.7 m3/hour (1 ft3/min) are
usually sufficient to aerate an average-sized dugout of
2,700,000 litres (600,000 imp gallons).
Basically, two types of air pumping devices can be installed
in a dugout: wind mills or electrically-powered air
compressors. For fish culture, electrically-powered air
compressors are recommended over wind mills as they
allow uninterrupted dugout aeration. The initial cost of an
air compressor is around $400, increasing with pump size.
Annual electricity costs range between $50 and $100 when
using a typical air compressor with 1/8 to 1/4 HP electric
motor.
The compressor should be oil-less and of a diaphragm
type. Compressor suppliers should be able to help you
select the proper pump. Before seeing a dealer, obtain the
basic information about your dugout, such as depth,
length and width. Depth is especially important for sizing
a compressor. Only the most recent measurements should
be used.
Once air is pumped into the dugout, it should be
distributed by a linear or point diffuser located on or close
to the bottom. This method ensures efficient circulation of
water and uniformity of dissolved oxygen. Inexpensive air
stones can be purchased at most farm supply stores.
Dugout maintenance
If the dugout is constructed properly and in a suitable location, very little maintenance is required. If algae, vegetation or suspended solids become problems, then control can be either chemical (copper sulphate, diquat, aluminum sulphate, etc.), mechanical (uprooting weeds with chains) or biological (grass carp). Care must be taken in dugouts used for fish culture, as some of the chemical applications are directly toxic to the fish or result in decomposing plants that ultimately deplete the fishs oxygen.
Useful references
Quality Farm Dugouts, Agdex 716 (B01) is available from
Alberta Agriculture, Food and Rural Development
Publications Office
7000 - 113 Street
Edmonton, Alberta T6H 5T6
Phone toll-free: 1-800-292-5697 or
visit: www.agric.gov.ab.ca/publications
PFRA water quality information is available from any
PFRA district office or by visiting:
www.agr.gc.ca/pfra/water/quality_e.htm
If you require assistance, please contact:
Aquaculture Section
Alberta Agriculture, Food and Rural Development
Agriculture Centre
100, 5401 - 1st Avenue S.
Lethbridge, Alberta T1J 4V6
Phone: (403) 381-5170
Fax: (403) 381-5903
1 When diverting or discharging water, a permit may be
required from Alberta Environment, Water Management
Division, Licencing and Permitting Standards Branch.
Source: Alberta Government - Revised February 2005
