Reservoir

Reference for constructing Martin Crawford’s gravity filtered reservoir

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

• Dimensions of reservoir w-3.5m x l-20m x d-1m = 70m³
• Calculate size using pond calculator
• Dimensions of liner w-6m x l-22.5m = 135m²
• Quality Firestone PondGarde Liner 1.02mm £1200
• Pond underlay £200
• Subtotal £1400

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.