Rainwater Catchment to a Gravity Fed

Pond

Jessica Ketchum

Site LocationThe

SenecaTreehouse.org

“Creating sustainable communities and learning centers which model nature to create basic human needs”

Site Location…Current Water Use Approx. 1600 gallons/week

Side-ViewThe water level must be 0.2 ft. above this line at 30 gpm and 1.3 ft. above at 85 gpm to have enough pressure head to move the water into the pond.

Side view of gutter shows 1/16” drop per 10ft.

Rain Collection Data/Calcs

Note: Catchment Area is Roof Footprint

Water (gal) Roof Area (ft2) Depth (in.) CF (in-ft2/gal) Runoff CF Safety CF

63135.6 2500 50.2 0.623 0.95 0.85

Annual Rainfall Data: 30-year Average Monthly Rainfall Seneca, SC at 50.2/year

63,135 gallons Water/Year

Frequency of SupplyTable 1. Calculated Water Supply

MonthMonthly

Avg. Rainfall (in)

Catchment Footprint (ft2) Conversion Factor

Runoff Coefficient Safety Factor

Monthly Volume

H20 (gal)

January 4.4 2500 0.623 0.95 0.85 5534

February 4.2 2500 0.623 0.95 0.85 5282

March 5.3 2500 0.623 0.95 0.85 6666

April 3.5 2500 0.623 0.95 0.85 4402

May 4.6 2500 0.623 0.95 0.85 5785

June 3.9 2500 0.623 0.95 0.85 4905

July 4.7 2500 0.623 0.95 0.85 5911

August 4.1 2500 0.623 0.95 0.85 5156

September 4 2500 0.623 0.95 0.85 5031

October 3.9 2500 0.623 0.95 0.85 4905

November 3.8 2500 0.623 0.95 0.85 4779December 3.9 2500 0.623 0.95 0.85 4905

STEADY IS GREAT!!

Roofing, Gutters and Downspouts

Dry Vs. Wet Conveyance Systems

Dry-Filled with water during a rain event or conveyance. Cons-Extra piping, difficult pipe runs

Wet-Full or partially full of water all of the time. Standing water can also create problems (mosquitos, pathogens, algal growth), freezing

Safety: Drainage of line and cleanout value installation. Also, wet system suitable when not drinking.

Calculating Friction

Using Table below to equate selecting fittings to length in pipe.

Diameter of Fitting

(in.)

90 ⁰ Standard

Elbow

45 ⁰ Standard

Elbow

Coupling-Straight

RunGate Valve

Friction Loss as Equivalent Pipe Length (ft)4 14 8 4 2.7

Quantity Fittings90⁰ 145⁰ 5

Couplings 11Gate Valve 2

Total Friction Loss (ft)

103.4

Calculating Friction Loss

C=140 for New Pipe (PVC Schedule 40)D=4.026 in (Inner Diameter)L=180 + 103.4 ft.Q=85 gpm

SC-Greenville 60-minute Duration 100-year Storm Data: 0.034 gpm/ft2

(0.034)(2500ft2)=85 gpm

Flow Rate, Q (gpm)

Head Loss (ft)

30 0.1940 0.3350 0.5060 0.7070 0.9380 1.1985 1.3390 1.48

Pond Size Considerations

Average monthly rainfall in gallons is around 5000 gallons.

5000/(conversion factor ft3 to gallon)

Approximately 15x15x3ft deep Pond Needed

Design Contributions

Manager at Clemson’s Organic Farm-(2009)

Experienced with Irrigation System Design Urban Permaculture Institute of the

Southeast Founder

Toured his home rainwaterand irrigation system.

Important System Extras Gate Value-useful for cleanout/drainage Emergency Drainage System from Pond Contours of Land to Drain Water from

Pond and irrigate land using gravity

References

http://www.dnr.sc.gov/climate/sco/Publications/max_rain_intensity.php

www.Rainwater%20Harvesting%20System%20Practitioner%20Manual.pdf

BE 322 Hydrology Note-Dr. Orwino (2014)