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Rain Water Catchment / Irrigation Design

Rain Water Catchment / Irrigation Design

This report is a detailed design description of the RWC/Irrigation system. Each sub-assembly is connected to the sub-assembly above and below it, except for the fences, and follows the path of a drop of rainwater. Below the description is a one-line diagram of the whole system

Project Statement/Scope

The primary objective of this project is to expand the learning opportunity of the students of Ullo by helping them explore new and in-depth agricultural practices. The secondary objective of this project is to show the community members and local farmers how relatively simplistic a rainwater catchment system is to build. This will be achieved by delivering a rainwater catchment system that supplies a sustainable, water-efficient irrigation system at the school’s garden during the dry season that has community buy-in and long-term scalability.

Design Description

  1. Gutters Sub-Assembly: 44 ft of the gutter with a pitch of 1 inch will be nailed along the south edge of the dining hall roof.
  2. Connection to tanks Sub-Assembly: Immediately after the roof ends, a downspout adapter will allow for pipe to be routed at an angle and for the cross-section of the flow to change from square to circular as desired. A coarse filter will catch debris in the gutter flow before it can enter the tanks. A fine filter will be installed within the circular section of pipe to catch any debris that may not have been caught earlier.
  3. Tanks Sub-Assembly: There are four tanks that will be provided by the school. Two of the tanks are 5.5 ft tall with a 5.81 ft diameter that holds 4500 litres and the other two are 6.16 ft tall with a 4.92 ft diameter that holds 3500 litres. The tanks will be lined up along the west side of the building with the 3500-litre tanks further south.
  4. Tank Stand Sub-Assembly: The tank stand for the 3500-litre tanks will have a height of .4575 m, and a width and length of 1.55 m. The tank stand for the 4500-litre tanks will have a height of .4575 m, and a width and length of 1.83 m.
  5. Above ground piping Sub-Assembly: 1-inch HDPE piping will be connected to the holes at the bottom of each tank. These pipes will connect to either a 90-degree elbow or a three-way tee depending on their tank placement. About 20 feet of piping will connect all of these elbows and tees together and a third tee will connect this sub-assembly to the below-ground piping subassembly. A one-way check valve will be placed before the third tee to control backflow caused by the differing tank heights.
  6. Below ground piping Sub-Assembly: About 125 feet of 2-inch HDPE piping will bring the water from the above-ground piping to the drip irrigation system following the path outlined below.
  7. Drip Irrigation System: Includes a system of HDPE piping spanning a total of 300 feet (5 rows of 60 feet). This system would enable irrigation to 100 tomato plants for 80 days. The pipes are connected to one another with elbows. The drip line would likely come with pre-drilled holes for emitters to be placed. The ideal distance between each emitter is 36”, but various distances will also work.
  8. Temporary Fence: There will be a temporary fence while the living fence is becoming established. This fence will serve the purpose of keeping animals out of the garden and projecting the irrigation system from damage. It will be made of barbed wire wrapped around large poles along the perimeter of the garden.
  9. Living Fence: The living fence will be planted via seeds around the perimeter of the garden before the rainy season. This allows for the seeds to be watered naturally and less maintenance during the early stages of growth. The fence would keep out humans and small animals when it is mature. Pruning will need to be done during the first few years to establish a shrub-form. The branches that are removed in the process can be used for firewood among other things.

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