Below appear a series of formulas that can be used to spec out materials for your water garden. These formulas have been derived from our professional experience and are intended to provide very rough suggestions. Every pond project is completely unique, so you might find you will need more or less materials than what these formulas suggest.

## Rocks and Gravel Approximations

**Quantity of boulders for a pond:**

Length x Width (in feet) / 40 = Tons of boulders

For every 1 ton of 6-12" boulders, use 2 tons 12-18" boulders and 1 ton of 18-24" boulders.

**Quantity of boulders for a stream:**

1 1/2 tons for every 10' of stream using a 1:2:1 ratio as above

**Quantity of gravel in a pond:**

Pond gravel = 25% of total tons of boulders used in pond

**Quantity of gravel in stream:**

Stream Gravel = 25% of total tons of boulders used in stream

**Quantity of boulders for face of waterfall box:**

22" - 1 ton of mixed boulders

30" - 1 1/2 tons of mixed boulders

40" 3 tons of mixed boulders

**Quantity of Boulders for retaining wall:**

1 ton of 12-18" boulders will cover 10 linear feet

1 ton of 18-24" boulders will cover 5 linear feet

**Quantity of stone used in a bog filter (per 10 sq ft of bog):**

900 lbs 1 1/2-2" Washed River Gravel

900 lbs 1/2-1" Washed River Gravel

**Quantity of boulders used around the perimeter of a bog filter**

1/2 ton of 6-12" boulders will cover 20 linear feet

1/2 ton of 12-18" boulders will cover 10 linear feet

## Volume Approximations

See also our Calculating Water Volume in Ponds article for more a more in-depth discussion of methods to calculate volume of a pond.

**Approximate gallons of water in a pond**

Length (ft) x Width (ft) x 0.80 x Average Depth (ft) x 7.48 = Total Gallons in Pond

**Approximate gallons of water in a stream**

Length (ft) x Width (ft) x 0.25 x Depth (ft) x 7.48 = Total Gallons in Stream

(Length = measurement down the middle of the stream plus the rise)

**Approximate gallons required in a pond-less basin**

Total Gallons in Stream x 2.5 = Total Gallons Required in Basin

**Approximate gallons of water in a pond-less basin**

With stone/gravel: Length (ft) x Width (ft) x Depth (ft) x 2.2 = Gallons in Basin

With Large Matrix: Number of Matrix x 32 = Gallons in Basin

With Small Matrix: Number of Matrix x 17 = Gallons in Basin

**Basin Matrix capacities**

Large Matrix (4.3 cu. ft.) holds 32 gallons

Small Matrix (2.3 cu. ft.) holds 17 gallons

**Suggested stream flow rates**

Sheet falls: 1,500 gph per foot width

Bouldering falls: 3,000 gph per foot width

## Other Helpful Data

**Pipe and Tubing Flow Chart**

Inside diameter of pipe | Optial flow rate (gph) |

1/2" | 350 |

3/4" | 750 |

1" | 1,200 |

1 1/2" | 2,900 |

2" | 4,600 |

two- 2" | 9,200 |

3" | 12,000 |

4" | 18,500 |

**Bog Filter Sizing Chart**

Note: These are basic guidlines and can change based on site conditions.

Surface area of pond (sq. ft.) | Bog size (sq. ft.) | Flow rate (gph) | Plants |

350 | 70 | 2,000 | 12-18 |

700 | 140 | 4,000 | 24-36 |

1,400 | 250 | 7,500 | 42-62 |

2,800 | 400 | 10,000 | 65-100 |

5,600 | 800 | 24,000 | 130-200 |

11,200 | 1,600 | 40,000 | 260-400 |

**Pond and Stream Plant Selections**

Pond size | Marginal plants | Waterlilies | Floaters | Submerged plants | Lotus |

6'x8' | 6 | 1 | 3 | 8 | - |

8'x11' | 9 | 1 | 5 | 15 | - |

11'x16' | 12 | 2 | 7 | 29 | - |

16'x21' | 15 | 3 | 15 | 91 | 1 |

21'x26' | 21 | 5 | 25 | 91 | 1-2 |

Stream per 10' | 3-6 | - | - | - | - |