How to Dig a Trout Dam
You may want to stock trout on your property. In order to do so you must have a moving stream that can be converted into a dam. According to the Department of Fisheries in Western Australia the best dam for trout farming is a gully dam. And the DOF should know: Australia is known for its inhospitable climate. So, survey your land and find a natural gully in the stream. That's where you'll dig your trout dam. Does this Spark an idea?
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Instructions
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Find a stream gully on your property. Stake markers into the ground where the dam will be built, where the spillway will be cut and mark the height of the water when dammed.
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Walk upstream from the proposed dam with a level. Put the level on the ground near the stream to be sure the grade is not more than 15 percent. If the grade is too steep, the dam will eventually fail.
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Use a shovel, pick ax, saw and hoe to clear the land of vegetation where the reservoir will be.
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Use a shovel to dig a diversion around the dam. Dig the diversion trench around the work site starting below the dam and ending above the work site. Dam the stream with large, hard rocks into the diversion trench to divert most of the water in the stream as you work.
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Use a shovel to remove the topsoil where the reservoir will be. Place the topsoil below the dam to be spread later.
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Drive a bulldozer with rippers to the reservoir site. Excavate soil layer-by-layer, building a reverse pyramid into the ground, moving the soil below the dam for later use. The slope of the reservoir trench should drop approximately one yard down for every three yards out.
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Start building the dam wall by digging a trench. Use a shovel to dig the trench under the middle of the dam wall. The trench needs to be at least one yard wide and 12 inches deep.
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Use dam-grade clay to fill the trench. Compact the clay with a tamp to make a waterproof trench.
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Build the dam wall layer-by-layer with dam-grade clay. Lay the clay on six inches at a time and compact the clay with a tamp. The wall must rise one yard above the water level of the reservoir, be three meters wide at the top and resemble an elongated pyramid with sloped walls. The slope of the dam wall should be one yard up for every 2.5 yards out, mirroring the slope of the reservoir and making a continuous grade to the bottom of the trench.
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Use a shovel to dig a spillway from the outer edge of the dam wall. The spillway is a channel about six inches deep that circumvents the dam wall and controls the water level of the reservoir. Connect the reservoir with the stream below the dam via the spillway.
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Pack dam-grade clay into a level sill at the end of the spillway with a tamp. You'll want the flowing spillway water to sheet-flow over the compact sill to prevent erosion. Use a level to be sure the sill is flat.
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Redirect the flow of the stream by pulling down your makeshift rock dam and plugging your diversion stream. Wait and watch as your reservoir fills up. Be sure the spillway and sill are working effectively and the top of the dam wall is one yard above the water level.
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Tips & Warnings
Trout need natural catchment in order to survive. It is best if the stream flows in from fertilized grazing grasslands. It is best if the shrubbery surrounding the stream is covered by the reservoir. The catchment flow from the grassland and the abundant plant life will feed the trout.
Cover any exposed bedrock with six inches of clay and tamp.
References
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