CCGC Water Harvesting

Water sources at the MLK site community garden of the Carrboro Community Gardening Coalition are being investigated. Water Harvesting information can be found here.

See Also:
 * CCGC Well Water

Water Catchment
Water catchment is CCGC's primary source for water. Our backup is well water. Water is collected off of both shed roofs. There are two gutters on each shed, one for each roof pitch for a total of 4 gutters. A rain barrel catches water from each gutter. Each rain-barrel can be linked with a hose for gravity feed to either 275 gal. cisterns or the 1500 gal. cistern also located at the sheds. Water stored in these cisterns is pumped to the garden cisterns using a battery powered pump.

How to use the Battery powered pump for pumping from shed cisterns to garden cistern

 * 1) The battery powered pump is on a dolly for easy transport to cisterns that need to get pumped.
 * 2) Connect the inlet hose (see arrows on the woodwork) to tank from which water will be drawn.
 * 3) Using an extension hose, connect the outlet to the black pipe (goes to gardens) found on the fence at the northwest corner by the northwest shed. You may need a double female adapter (file cabinet). Open valve and make sure second valve on 'Y' is closed.
 * 4) Check to make sure all appropriate valves are open/closed
 * 5) On cistern to be drawn from make sure:
 * 6) main valve (red big one) is open and
 * 7) also leg of smaller ‘y’ valve to which pump inlet hose should be connected is also open.
 * 8) At ‘y’ by the CCGC garden cistern. (valve turned for pumping either to the CCGC cistern or the OCPYC cistern)
 * 9) For CCGC:
 * 10) place hose end into garden cistern by loosening the cover (key is in shed, but not usually necessary) and dangling the hose in (Remember to replace the cover to keep out mosquito larvae.) or,
 * 11) Fill garden garbage cans.
 * 12) For OCPYC:
 * 13) Turn pump switch on.
 * 14) Check to make sure pumping is happening by opening the unused ‘y’ valve leg of black pipe switch.
 * 15) If pumping is not happening:
 * 16) check lines for kinks,
 * 17) check valves to make sure appropriate ones are open/closed,
 * 18) check wiring to the battery, or
 * 19) recharge the battery.
 * 20) Do not let pump run dry.
 * 21) After transferring of water, reverse the above process making sure that all valves are shut except for between gutter catchment and storage beneath the sheds.
 * 22) Put dolly pump and connecting hoses and adaptors away.

How to use the Battery powered pump for pumping from cisterns to garden beds
The battery powered pump can also be used to water the garden by hose, rather than carrying water in 1 gallon containers. The procedure is simple and will help avoid under-watering.

A. From cisterns at the shed. B. From cisterns in the garden.
 * 1) Use the procedure above, except place a long hose from the shed on the exit 'Y' near the CCGC cistern and water as from a garden hose. You may also attach the black 'soaker' hose to the line to water whole beds at once.
 * 1) The battery powered pump is on a dolly for easy transport to the garden cistern.
 * 2) Connect the inlet hose (see arrows on the woodwork) to tank as above.
 * 3) Connect the outlet to an extension hose, open the valves on the tank.
 * 4) Turn on pump and pump to beds as with a garden hose (see above for procedures and troubleshooting).
 * 5) When finished, close valves and return pump and hoses to shed.

Meeting Minutes

 * CCGC Water Catchment Minutes 9/4/07

Status

 * The town has given us permission to harvest water from both shed roofs.


 * Plans for doing this should be submitted for review to Parks & Rec (Carrboro) before implementation.


 * 3/4 of the gutters are already up, we are poised to install the rest of the system.

Water Harvesting Facts
rainwater catchment coupled with the use of the well will produce ample supply for the garden.
 * Surface area and rain: 1" rainfall on 1,000 sq ft. roof produces 625 gallons of water.


 * Catchment efficiency: 80% of water in an area can be captured.

Annual
47.6" Average. During 2007 Drought year we were at 80% of average rainfall. http://www.nws.noaa.gov/oh/hic/current/drought/rah.htm

Quarterly

 * Summer: June, July, August, : 12.9"


 * Fall: September, October, November, : 10.3"


 * Winter: December, January, February: 11.1"


 * Spring: March, April, May: 12.2"

North Shed

 * West Roof: 404 Feet sq.
 * East Roof: 425 Feet sq.

South Shed

 * West Roof: 432 Feet sq.
 * East Roof: 432 Feet sq.

Ideal Storage Capacity
A simple method of roughly estimating storage capacity popular among professional installers is to size the storage capacity to meet quarterly demand. The system is sized to meet estimated demand for a three-month period without rain.

Garden Demand
The general recommendation is to supply 1" of water per week to a garden. Depending on the weather conditions and the crops being grown, the garden may need 1.5" per week. It takes 625 gallons of water on 1000 sq.ft. to equal 1" of rain.

OCPYC

 * Garden Area: 2400 sq.ft.,
 * Planting area: 1200 sq.ft.
 * Estimate of water needs: 750-1100 gallons per week.
 * 22% of aggregate planted CCGC + OCPYC.

CCGC

 * Fenced in area: 8,611 sq.ft.
 * Planting area: 4,305 sq.ft..
 * Estimate of water needs: 2,690 gal. - 4,035 per week.
 * 78% of aggregate planted CCGC + OCPYC

CCGC + OCPYC
Because CCGC and OCPYC are sharing watering sources calculating demand of both is useful.


 * Planting area: 1200 + 4305 = 5,505 sq.ft


 * 3,440 gal./week - 5,135 gal./week or 13,760 gal./season - 20,500 gal./season


 * Assuming Planting area is constant throughout the year, per three month period garden demand:


 * 3,440 gal./week x 12 weeks/3 months = 13,760 gal./season


 * 5,135 gal./week x 12 weeks/3 months = 20,500 gal./season

Well
Approximately 1,000 gal./ week

Water Catchment
Water catchment water will be prioritized over well water for watering the garden.

West Roof
404 sq. ft.


 * For 1": Gallons per sq. ft. of area:: 404 feet sq. x .625 (gal./sq.foot) = 252.5.
 * Efficiency Factor: = 252.5 gal x .8 = 202 gal.
 * Harvest:
 * Summer: 12.9" x 202 gal. = 2,606 gal.
 * Fall: 10.3" x 202 gal. = 2080 gal.
 * Winter: 11.1" x 202 gal. = 2,242 gal.
 * Spring: 12.2" x 202 gal. = 2,464 gal.


 * Volume from rain on planted garden area (OCPYC + CCGC) per season:
 * Summer: 12.9" x (625 gal./1"/ 1000 sq.ft.) x 5505 sq.ft. 202 gal. = 44,384 gal.
 * Fall: 10.3" x 202 gal. = 2080 gal.
 * Winter: 11.1" x 202 gal. = 2,242 gal.
 * Spring: 12.2" x 202 gal. = 2,464 gal.


 * Harvest during drought:
 * Summer: 10.32" x 202 gal. = 2,084 gal.
 * Fall: 8.24" x 202 gal. = 1,664 gal.
 * Winter: 8.88" x 202 gal. = 1,794 gal.
 * Spring: 9.8" x 202 gal. = 1,980 gal.


 * Volume from rain on planted garden area (OCPYC + CCGC) per season (during 2007 drought year):
 * Summer: 10.32" x (625 gal./1"/ 1000 sq.ft.) x 5505 sq.ft. = 35,475 gal.
 * Fall: 8.24" x 202 gal. = 2080 gal.
 * Winter: 8.88" x 202 gal. = 2,242 gal.
 * Spring: 9.8" x 202 gal. = 2,464 gal.

East Roof
425 sq. ft.


 * For 1": Gallons per sq. ft. of area:: 425 feet sq. x .625 (gal./sq.foot) = 266.
 * Efficiency Factor: = 266 gal x .8 = 213 gal.
 * Harvest:
 * Summer: 12.9" x 213 gal. = 2,748 gal.
 * Fall: 10.3" x 213 gal. = 2,194 gal.
 * Winter: 11.1" x 213 gal. = 2,364 gal.
 * Spring: 12.2" x 213 gal. = 2,599 gal.

West Roof
432 sq. ft.


 * For 1": Gallons per sq. ft. of area:: 432 feet sq. x .625 (gal./sq.foot) = 270.
 * Efficiency Factor: = 270 gal x .8 = 216 gal.
 * Harvest:
 * Summer: 12.9" x 216 gal. = 2,786 gal.
 * Fall: 10.3" x 216 gal. = 2,225 gal.
 * Winter: 11.1" x 216 gal. = 2,398 gal.
 * Spring: 12.2" x 216 gal. = 2,635 gal.

East Roof
Same area as South shed's West roof

Solar Pump Design
A simple mobile solar powered bilge pump will move the water from the water catchment site to the main garden cistern and can also be used to pressurize and move the water from the main garden cistern to the garden.

Gravity Design

 * 1) Takes advantage of the fact that water is captured from raised shed roofs to transport water to garden using gravity.
 * 2) Height is maximized by placing barrels:
 * 3) immediately below the gutters.
 * 4) Placing them Horizontally
 * 5) Barrels are interconnected with tubes coming to the lowest point of each barrel. Interconnectivity effectively provides cistern function.
 * 6) Raised storage water barrel structure has alternative trellis function.

West Half

 * Barrels:
 * Radius = 1'
 * Height = 3.33'
 * Volume/barrel = 10.5 cubic feet = 78.5 Gallons


 * Total Capacity:
 * Total Volume(x10) = 785 Gallons


 * Bearing Weight:
 * Weight of water/barrel = 8.33 lbs./Gallon x 78.5 Gallons = 654 lbs.
 * Weight of Water & Barrel/barrel = 654 lbs. + Barrel weight
 * Total weight: 10 barrels x 654 lbs. = 6,540 lbs.
 * Weight per 4x4 column: 6,540 lbs. /13 = 503 lbs.


 * Garden Distance


 * 135' to water cans
 * 170' to closest fence post



Needs:


 * Barrels: 10 (R = 1', L = 3.33') 78.5 gal.


 * Treated Lumber
 * 6 (4" x 4" x 5') if can use existing shed posts
 * 3 (4" x 4" x 4.75')


 * 2 (2" x 6" x 3.75')
 * 1 (2" x 6" x 4.8')
 * 1 (2" x 10' x 4.2')
 * 1 (2" x 10' x 4.7')


 * 4 (2" x 6" x 4.7')
 * 9 (2" x 6" x 6.3')
 * 6 (2" x 10' x 6.3') or 6 (2" x 4' x 6.3')

Water Pressure
Water gains 1 psi of pressure for every 2.31 feet of vertical rise. At the MLK site, with barrels raised to below the height of gutters on the roof of the shed we can achieve:

5ft. * 1 psi/2.31 feet = 2 psi


 * 2 psi is sufficient for irrigation using blue lined drip tape.

Resources

 * Harvesting rainwater guidelines


 * Urban Rainwater Tanks How To


 * Rainwater Harvesting Manuel


 * Resources


 * Mother Earth News article