Design the Hydropower Dam Site
Analyze the watercourse to determine if there is sufficient water flow and drop for a hydropower plant. Micro hydropower plants typically need a 5-foot drop and at least 2-3 gallons per minute to activate the power wheel. The drop can easily be determined from the vertical distance to the planned powerhouse location. Measure the water volume by collecting gallon containers of water over a 60-second time period.
Analyze the potential contenders for the actual site of the dam itself. The closest location above the intended power plant may not be the best location. Another location higher or on another watercourse may be a better choice. There should be enough level space or space that can be leveled for the dam itself. Consider the intended course of the water from the dam outlet to the powerhouse. While typically accomplished by PVC piping, it can also be a combination of piping and lower watercourses.
Consider the total volume of water storage possible. Unless complex power storage is planned, it is advisable that enough water be stored to drive the generator through the dry season at the site. At 3 gallons per minute the water wheel would be consuming over 4,000 gallons of water per day.
Analyze the surface of the intended dam location. Is the ground muddy and soft, or rocks and gravel? A hard-surface location will require a perimeter-only structure; muddy or soft-earth locations will need pond surface lining. Determine also how much of a support structure will be required to accommodate the weight of the water. At 62.4 lbs. per cubic foot, water is heavy. A dam full of water weighs that times the length times the width times the depth. A single wall of concrete block courses will typically support a 10-foot diameter x 4-foot deep micro-dam. Sketch out the design on graph paper.
Build the Dam
Prepare the dam site by diverting water away from or around the dam wall area; constructing a concrete dam in the face of moving water is a problem. This can be as simple as a hand-scraped ditch or as involved as a temporary dam of rocks, plastic sheeting and downspout gutters.
Apply a ground cover of heavy plastic if the ground and/or surrounding earth is muddy or soft. A small dam might be ground-covered with an old plastic shower curtain. Larger dams require landscaping-sized squares of vinyl. Stake the material and allow it to run up the sides of the area if it is an enclosed cut-through the rocks or a mini-valley. Perfect sealing here is not the objective, simply enough control of water leakage so the dam holds enough water to get the job done is.
Create a ring of heavy rocks placed into the ground for the foundation; a tiny dam (6-feet in diameter for 2-3 gallons per minute flow) requires nothing more than this. Follow that up with 12-inch sidewalk pavers stacked on edge inside the forward surface of the rocks. Finish with an in-slanting course of concrete on the water side of the pavers. Be sure to break off one of the corners on one paver to provide and exit space for the outflow line. For this size dam, a 2-inch PVC pipe will suffice. Make it flush with the inside surface with the dam and long enough to allow an outside attachment.
Dig and frame a 1 foot x 1 foot-deep footer around the dam area and tie it into the rock or earth at both ends of the dam; larger dams require a poured concrete foundation and several courses of block. Lay three or four courses of concrete block on top of the footer, and cover the inside of the blocks with tar or roofing cement. Use a brick hammer to cut a hole in one of the first-course blocks, and insert and cement around the outflow pipe. For larger dams, a 4-inch PVC pipe is typically sufficient. For this size dam be sure to install a twist-lock valve on the downside of the outflow pipe.
Engineer and install an overflow system for the dam. For small hand-made dams this may be nothing more than a "V" cut in the top of the dam where the runoff is harmless below the dam. For larger dams this may require an additional inset PVC pipe that is course-directed below the dam and into a safe direction or returned to the watercourse.
Things You Will Need
- Graph paper and pencil
- Tape measure
- Vinyl sheeting
- Chalk line
- Wood stakes
- 12-inch sidewalk pavers
- Ready-mix concrete
- 1-inch x 12-inch common lumber
- Concrete block
- Bricklayer's hammer
- PVC pipe and twist-lock valve
- Roofing tar or cement
- Photograph the dam site for off-site review of plans.