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Reservoir

Reference for constructing Martin Crawford’s gravity filtered reservoir

Greenish water in small reservoir
Small reservoir in Langdale Forest, by Oliver Dixon

Martin Crawford has information about creating a reservoir in Agroforestry News vol 23 no. 2, PDF available online (though pricey)

Key detail

  • Design derives from maximum size of plastic pond liner: 25m x 6m (not sure if this is still the case)
  • Each reservoir 3.5m x 20m x 1m deep = 70 cubic metres
  • Use gravity fed where possible
  • Any water fed into pipes needs to be filtered
  • Circulation requires powerful pump, MC uses 4 x 180W solar panels to power Lorentz pump
  • Filter is an upwards-flow (much easier to clean) stone-gravel-grit system, using upcycled 1200 litre plastic water tank (previously used for transporting fruit juice):
    1. Bottom layer 30cm deep, 40mm stone
    2. Middle layer 30cm deep, 10mm gravel
    3. Top layer 30cm deep, 4mm grit

|        | → clean water out
|--------|
|  grit  |
|--------|
| gravel |
|--------|
| stone  |
|________| ← reservoir water in

Approx pricing

Pond liner - per reservoir

Pump kit

  • Lorentz PS2-100
  • From Wind and Sun
  • Includes solar panels
  • Subtotal £800

Filter

  • 1000 litrew water tank IBC £70
  • Stones, gravel & grit £100?
  • Pipes & fittings £30
  • Subtotal £200

Installation

  • Digger hire £200 1 day
  • Install pond liner £100 1 day
  • Fit pump & pipes £200 1 day
  • Subtotal £500

Totals

  • Liner £1400
  • Pump £800
  • Filter £200
  • Installation £500

Grand total about £2,900

Obviously, cheaper per reservoir for more reservoirs. Cheaper than a borehole (£10-15k)! Can also use cheaper liner and do some of the installation yourself.

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